Solar charging of chassis battery

 

Charging chassis battery using 30W solar

We had to leave the Roadtrek at the campground for a few days.  I wanted to keep the chassis (engine starting) battery charged. On July 4 I connected the 30W solar panel.  This has a self-contained solar charger and so I simply plug it into the dash 12VDC accessory jack.  These jacks were originally intended for cigarette lighters.

The chart above shows the daily charging, which I can check with my Android phone via the internet. 

The chart indicates daytime charging and nighttime discharge.   

The solar panel is placed on the windshield and is facing west.  It doesn't get sun until afternoon, but that is adequate.   I placed the solar panel outside the windshield, although it works well on the inside, too.  I tie it down because of storms in the area; I don't trust the suction cup mounting. 

I've used this larger panel for several years and it has performed well.  

30W solar panel charging the chassis (engine) battery

(c) Norman Retzke 2022

Practical Solar

 

Making coffee in the morning in the "Solar powered" Class B
Must turn off the hot water heater before using the burner!
Outside ambient: 20F,  Inside: chilly!

Realistic expectations  

We trek and we have spent up to 100+ continuous days in our Roadtrek.  But first, we rented a "100% electric" solar powered Sprinter coach and took it to the National Parks in Utah.  It was mid-October 2013. Nighttime temperatures were about 20F.  It was a good test of how well a solar powered, electric coach would perform.  That was our purpose in choosing it, and I wanted to see how the BlueTec engine performed, etc. 

From a comfort perspective, it was not ideal, and G had to ask "How is it that one would spend $100K to buy this?" Adequate if the ambient temperature was in the range 50F to 80F and if one wasn't parked in the full sun during the daylight hours.  Otherwise uncomfortable. The Sprinter had sufficient batteries and solar, and a large inverter, but it did have power limitations. For example, we couldn't use the electric cooktop and simultaneously make hot water for bathing or cleaning. For comfort heat it had a 1500 W electric heater, which was not adequate at below freezing, nighttime temperatures. There was no propane. It was a Mercedes camping experience as we slept in sleeping bags.

However, that experience allowed us to make a more realistic list of "must haves" and after reviewing these and discussing the Sprinter and our experience, we purchased a Roadtrek 210P which uses multiple fuels for coach amenities.  After the Roadtrek financial bankruptcy, the 210P is no longer made, which is a shame. 

I'm not going to repeat my earlier posts, in particular the one about our experience and decision to purchase the 210P. I do have earlier posts on solar, batteries, etc. 

Solar Power and Batteries

We purchased a new Roadtrek a bit sooner than would have been ideal at the time. We were both working and had very limited time for trekking. On the other hand, the price in December 2013 was really good, with a steep discount.  So, we purchased it. Because we live in a HOA and our garage cannot accommodate the Roadtrek we had to store it, and the largest issue was keeping the chassis and coach batteries fully charged. I did run the generator monthly.  The 210P did not have solar.

To keep the chassis battery fully charged, I purchased a 50W solar panel and controller. That's documented in a earlier post. I selected a de-sulfating controller. That was in Spring of 2014. 

I mounted the solar controller adjacent to the coach batteries, and I decided I wanted a "portable" panel, because when it is hot it is preferable to park in the shade. My approach allowed us to charge the batteries during the day while we were comfy. The cable connecting the solar panel to the controller is about 20 ft long and is coiled and placed under the passenger seat when we are in movement.

The Coach Solar

The 24"  x 24" 50 watt panel is stored behind the drivers seat when we are travelling. Why only 50 watts?

I had evaluated our DC electrical power needs. Our Roadtrek 210P has a 2.8kW Onan gasoline generator. It also had multiple energy sources. For example, propane is the source for the furnace, hot water and a range top, as well as the third source for the 3-way refrigerator. All of the controls are 12VDC.

We have no interest in living "off the grid" for weeks while running the refrigerator and Air Conditioning or space heat using 3000 watts of batteries and solar panels. In fact, our 210P simply doesn't have enough roof space for all of those solar panels. 200W would be pushing the maximum roof space available. Our interest is charging the coach and chassis batteries, reducing but not replacing the amount of grid electricity we need and so on.  This is because of practical considerations. Those considerations include roof area available or size of portable panels, battery considerations and cost.

What can we get if we maximize the roof panel? For example, 100W solar panels can produce about 5.6A. Depending on the orientation of the panel, the intensity of sunlight and the hours of direct sunlight received in a day, a 100W panel can generate 20- to 30-amp hours (Ah) daily. In fact, the amount of energy may be only half of this because of clouds, panel orientation and hours of daylight. 200W could provide a maximum of about 60-amp hours each day. 

To charge the coach batteries using 120VAC and the Triplite charger-inverter requires anywhere from about 3.6A to 9.3A at 120VAC.  To fully charge 50% depleted batteries can take 12 hours.  At the lower charging rate using the Triplite 120VAC inverter-charger, 3.6A is a minimum used, or about 430 watts. I've measured the AC at the pole with everything off in the coach except charging via the Triplite.  At a typical seasonal campground where we pay $0.14 per kWh; that's $1.45 per day to keep the coach batteries fully charged. 

If the batteries are at 50% the AC required for charging can increase to 9.3A (1,116 Watts).   The 50 watt panel can't do that. It can provide about 4.2A at 12 VDC. 

The 50 watt solar panel is sufficient for my needs to keep the coach batteries fully charged under low load.   If we need more charging current I can run the Onan generator, or run the vehicle.  Running the vehicle will charge the chassis battery and, if the battery separator is closed the coach batteries will also charge. 

If we need more 120VAC than the 750 watt inverter and batteries can provide while off the grid, we run the Onan generator. The generator uses 0.3 gallons of gasoline at half load.  That's acceptable and in this manner we can recharge the coach batteries and run appliances. The Onan can provide sufficient AC for the heat pump/air conditioner. 

Why a Portable (detached) solar panel?

I preferred a portable solar panel because we can park the Roadtrek in the shade and put the solar in the sun, and I can orient the panel for maximum DC energy.  The de-sulfating solar controller I purchased is rated for 180W maximum panels.  I can always upgrade to more solar.  However, if I really want more solar, I'll probably mount a flexible panel on the roof and carry another 100W portable panel.  In that way I could get up to 200W if parked in the sun or, at a minimum 100W if parked in the shade with the portable panel in the sun.

I've written about batteries in earlier posts. I don't like the low temperature charging limitations of Lithium-Ion batteries.  Combined with the high cost, I don't see an overwhelming advantage for us. In my earlier posts I do go into greater detail about this.

50 Watt panel in full sun

Charging at MI campground

Coach battery voltage while charging in MI on 50W solar panel
Current (amperes) is not accurately displayed when charging;
the meter displays current draw (discharge) on the battery. 
While charging the current flow is in the other direction

50 Watt behind the windshield
The glass does reduce the efficiency, however, if facing the sun for half of the day the panel does keep the coach batteries fully charged. 

At the AZ "lily pad" the Roadtrek is under the roof.
  I place the portable solar panel on the roof.

The Roadtrek is in the shade, while the solar panel is directly above,
 on the the roof, in full sun.

Charging the Chassis Battery

The chassis battery also needs to be maintained.  My theft prevention device does increase the 12V DC power needs when the vehicle is stored. With the arrival of thin solar, or flexible solar panels I purchased a 30Watt for that purpose. The 30 watt panel can provide 2.5A at 12VDC.

The 30W panel can also be put inside, on the dashboard and facing outward.  This will charge the chassis battery when the vehicle is stationary and stored. 

Monitoring the batteries. 

I have two DC voltage indicators. One plugs into the accessory socket on the dashboard and it displays the chassis battery voltage. The other I added and is mounted inside. It provides coach battery voltage reading and current draw, when the battery is discharging. I added a power "Off-On" switch for the interior meter so as to conserve DC. I've included photos here. I have an earlier post on the coach battery monitor.

30 Watt solar panel

Chassis battery charging voltage on Solar, 13.1 VDC

(c) 2021 Roadtrek210.blogspot.com.

AGM Batteries, Separator Operation, Charging and Voltmeter

Replacement Battery Separator

December 2019:
I installed a replacement battery separator and it works differently from the old one. See Note 5 in the Battery Separator section, below.

September 26, 2019:
After I installed the digital voltmeter I was able to more closely monitor the coach battery voltage as well as the operation of the separator. Earlier this year I purchased a replacement separator as a "spare".  The old separator seems to work inconsistently or intermittently. For example with the engine running and a 14V chassis battery voltage the separator will connect the chassis and coach batteries. But sometimes it does not!  Go figure. I've decided to install the spare and I'll provide an update after I do.

October 6:  I added information on "clicking" battery separators. This has been reported by owners.
To go to the section on the battery separator, click here: Click here to go to the post section about the battery separator.

June 26, 2019 added the SOC table for the AGM batteries in my 210P. Note, I replaced those batteries and the table for your batteries may differ.

July 3, 2019 clarified separator main and aux connections.
================================================

Read the notes at the end before proceeding! This post is not a recommendation that owners perform their own electrical service. Working with electricity can be dangerous and can result in personal injury, or death or damage to your Roadtrek. 
Sorry if I created a scare, but one does have to be careful if tinkering with electrical systems. Mistakes can be very costly, or can result in personal injury.

My 2013 Roadtrek 210P has:

• 2 x 6 volt AGM coach batteries, about 220Ah
• Tripplite 750W Charger/inverter
• Battery Separator (bidirectional)
• LED 12V display (four round indicators)
• Digital 12V display (added by me)
• Onan generator (2800 watt)
• 50 watt solar panel, for charging the coach batteries (added by me)

2013 Roadtrek 210P display/switch panel
This is the display/switch panel on my 210P. In the photo the Onan generator is running and supplying 120VAC power. The Battery Disconnect is ON and this is indicated by the Battery On blue indicator. As a consequence the batteries are charging:

Charging the coach batteries
It is possible to charge the coach batteries:

• While on 120V "shore power"  and using the Tripplite
• While running the vehicle engine (see the Battery Separator section for limitations)
• By running the Onan generator and using the Tripplite.
• On solar

The limitations of the battery LED indicator

The LED indicator of the Roadtrek is a voltmeter which is somewhat limited. It indicates these battery conditions while the soft BATT button is pressed:

• L - Low
• F- Fair
• G- Good
• C- Charging

Note that the "C" indicator may be on even when the battery is discharging. This may occur shortly after disconnecting the coach from AC or stopping the vehicle engine. The reason is because the coach battery voltage is higher than normal 100% charge. This is what is called a battery "surface charge" and after a few minutes with a small DC load such as the slowly running roof fan, this charge will be dissipated and the true condition of the battery will be indicated. 

In the photo the Battery Disconnect switch BATT is ON as indicated by the illuminated "Battery ON" light. Pressing the Battery button displays the battery situation. The highest (rightmost) illuminated indicator displays the condition, which in the photo is a C for Charging:

Using a Voltmeter to Monitor the Battery Voltage
Monitoring the coach battery voltage is helpful for determining battery capacity. We may want to know how much energy is available in our coach batteries. A voltmeter is useful for doing this.

My Roadtrek didn't have a voltmeter, and the power/switch/display area isn't set up for one. However, there is a 12V "cigarette lighter" style receptacle in the rear overhead compartment, above the DVD player. Unplugging my powered antenna allows me to plug in a voltmeter to check the battery voltage:

12V receptacle

Here's a typical digital plug-in voltmeter. These can be purchased for as little as $7:

Plug-in Digital Voltmeter

What does that voltmeter display mean?
Here's a typical chart for AGM batteries. If we are aware of the voltage at the batteries, we have a rough idea of the "capacity" remaining. For example, if your voltmeter displays 12.50 volts, then you have used about 20% of the capacity or available energy in your batteries. However, I must note that it is not recommended to fully discharge batteries to 0%. That will ruin them.

You will have to decide how low you want to run your batteries. For longest life under moderate temperatures (77F is ideal) some recommend not dropping below 50%, or  about 12.05V.  Dropping to 20% (80% discharge) reduces battery life, but provides energy for a longer time. That's discharging to about 11.66V. Going lower will severely reduce battery life. Fully discharging AGM batteries can damage and ruin them. What does repeatedly discharge below 20% mean? It means severely reducing battery capacity, to the point the batteries cannot provide energy when disconnected from the Tripplite charger (when charging the battery).

Note that you might have poor batteries and be unaware. The 750W Tripplite inverter/charger can provide up to 45A (amperes) of charging current when on shore power. That's about 540 Watts. The Tripplite can not only charge batteries, but also power 12V DC appliances including lights, fan, propane furnace and so on when the Roadtrek is connected to shore power, even with poor batteries.

Having a voltmeter helps to determine just how long your batteries can support your RV when you are disconnected from AC power. For example, suppose you are running your fan, there are interior lights on, the occasional water pump, and your 3-way refrigerator is on propane (some 12V is used). After three hours the voltmeter indicates 12.5V. That means it took 3 hours to use about 20% of your battery capacity. Another 3 hours will use an additional 20% or more. That implies you'll have enough battery power to make it through the night (lights off, pump off and fan on).

This table is typical. Your AGM batteries may vary somewhat.

Typical AGM Battery Table

I replaced my AGM batteries and this is the SOC table provided by the manufacturer.  Your batteries may differ:

What does "reducing battery life" really mean?
AGM and gel lead-acid batteries are chemical devices. They generate electricity using lead plates or mats and an acid liquid. As we repeatedly discharge these batteries, certain deposits form inside them that reduces the capacity. Capacity is the ability to deliver full current for a certain amount of time before the voltage decreases below a useable level. As batteries age, that ability diminishes. For example, a new, fully charged battery can provide a specific amount of current for a specific length of time. Think of this as ability to run your fan, lights, DC for a propane refrigerator and a laptop. With new batteries, you might be able to do that all night. As the batteries age, the length of time decreases and you will find the batteries can no longer do so. And the lights will go out before dawn, whereas before they could be left on all night.

Alternative Voltmeter
I decided to add a digital voltmeter/ammeter. The advantage is I can monitor the amount of current being used and the digital meter provides me with a better idea of the "state of charge" and how much electrical energy might be available. The higher the current, the faster I will drain the batteries. The meter includes a Watt hour counter ("energy"), so I can roughly monitor how much energy is used overnight, should I choose to do so. The meter includes both high and low voltage alarms. This is detailed in another post:

The following data is according to the Tripplite 932768 manual for  750 Watt "PowerVerter DC-to-AC Inverter/Chargers", the Tripplite data sheet and a Roadtrek Manual

Charging the AGM batteries
The batteries can be charged from 120VAC. This is either via shore power or by running my Onan generator. One thing to keep in mind is to turn ON the battery disconnect switch before plugging the RV into AC power or starting the Onan generator. That is per Roadtrek recommendations for my RV.

How long can it take? If the batteries are depleted, it can take 12 hours or longer to fully charge the batteries.

Are there circumstances under which I can't charge the batteries? If  the battery voltage decreases to below 10.0V (+/- 3%, or somewhere between 9.7 and 10.3 volts) a low voltage cutoff will occur. The Tripplite inverter/charger will not charge the batteries if the battery terminal voltages fall that low.   If your vehicle engine is running, the battery may be charged via the standard alternator, if the battery separator allows (see the Battery Separator comments below). A underhood battery separator isolates the chassis battery from the coach batteries when the engine is not running.  However, batteries below 10.5 volts should be checked. They could be damaged.

How can I determine the state of charge? The Tripplite charger/inverter includes a display. However, it cannot be viewed without removing a cover.  Here is a photo with the cover removed. The Tripplite has two rows of LED indicators. One blinks green when on 120VAC and the Inverter switch is "OFF". Otherwise if on 120VAC and the Inverter switch is "ON" then it will be steady green. The switch is located on the Roadtrek display/switch panel near the side entry door. (see the first photo in this post, above).

The other Tripplite indicator goes from off to red to yellow to green depending upon the state of charge of the coach batteries. If charged more than 91% and on AC, one will be blinking green (on AC and inverter off) and the other will be steady green (91% or better charge).

The Tripplite is located in an interior compartment to the left and in front of the powered sofa when you are facing the rear of the RT. The Trippite has a fan and at times you will hear it running. However, there are exposed connectors/wiring so you do need to be careful. If you have any concerns, get a pro to do this.  DO NOT TOUCH ANYTHING.  After you have a pro demonstrate this to you, you can decide if you want to do it yourself in the future.

To reveal the Tripplite, lift up on the top wooden cover at the front and then slide it forward.

Tripplite and DC Electrical Compartment

The next photo is a close-up of the indicators on the Tripplite. The arrow points to a flashing green LED. That means the Tripplite is on AC with inverter OFF. The other indicator which is below the blue cable is the charging indicator. In the photo the bottom LED is green which according to the Tripplite manual indicates "battery capacity charging/discharging 91% - Full"

Here's the table from the Tripplite manual. There are a number of switches for configuring the Tripplite. These LEDs function with Switch in "AUTO/REMOTE" or “Charge  Only” Position. That is how my Roadtrek was delivered.

Approximate Battery Charge Level while charging and discharging (bottom indicator in the photo below):

• Green = 91% to Full Capacity (see the Tip below)
• Green and Yellow = 81%-90%
• Yellow = 61%-80%
• Yellow and Red = 41%-60%
• Red = 21% to 40%
• All three LEDs off = 1% to 20%
• Flashing Red = 0% (Inverter shutdown)

Tip: How can we determine the Battery Charge Level above 91%?  At about 91% the AC power of the Tripplite is about 10 amperes. At about 100% charge it will decrease to 2 to 4 amperes, assuming the inverter function is OFF. Monitoring the AC current consumption of the Tripplite can aid us in determining the battery charge level above 91%. I have a Progressive Industries EMS on my 210P and I can monitor the AC current consumption. If you have a similar arrangement, so can you. However, you do have to avoid running anything else in the coach to get a reliable reading from the AC draw of the coach.

Tripplite Fault Conditions (bottom indicator in the photo below):

• All three flashing slowly (1/2 second on, 1/2 second off) = Excessive discharge (inverter shutdown)
• All three flashing quickly (1/4 second on, 1/4 second off) = Overcharge (Charger shutdown)

The arrow in the photo points to the 120v power "Line green LED":

• Steady Green = Roadtrek inverter switch "ON" and the coach is on AC power (shore power or Onan generator)
• Flashing Green = Roadtrek inverter switch "OFF"
• Yellow = Roadtrek inverter switch "ON" and Coach battery providing power to 120V receptacles via the inverter.
• Red = Roadtrek inverter switch "ON" and power demanded of the inverter exceeds 100% load capacity

Tripplite LED Indicators

Tripplite Operation and Inverter Selector
The Tripplite has a 3-way slide switch for selecting the "Operating Mode". See the photo below:

Left Position - Auto/Remote
Center Position - DC OFF
Right Position - Charge Only

The "Auto Remote" position ensures that the connected equipment receives constant, uninterrupted AC power. It also permits the Inverter/Charger to be remotely monitored and controlled (in my 210P the Roadtrek inverter switch turns on and off the "inverter" operation if the Tripp-Lite slide switch is in this position).

The "DC OFF" position de-energizes the unit and connects AC OUT to AC IN. In my 210P this slide switch position disables the Roadtrek inverter selector.

The "CHARGE ONLY" setting allows the Tripplite to charge the batteries faster by turning off the inverter, which halts battery discharging.

Operation Switch in DC OFF position

Battery Separator.

Battery Separator - Bidirectional
The battery separator is under the vehicle hood. It controls the connection of the vehicle battery and the coach batteries. In my 210P the battery separator is a "bidirectional" 200A module with a relay for 12V systems. You may have a "unidirectional" model and if so, your battery separator operates differently than the following; for a unidirectional separator see the description in the next section.

The [bidirectional] separator monitors the engine ("Main") and coach ("Aux") batteries. The manual states "If either battery bank is above the connect threshold [13.2V], the relay [closes and] connects the two banks together. If either battery is below the disconnect threshold [12.8V] the unit will open the relay." However, once connected both batteries are at the same voltage. Opening the relay disconnects the engine and coach batteries, preventing the draining of both.  "The connect threshold is set to a nominal voltage of 13.2V, which would only be reached when the charging system is operating. The disconnect voltage is set to a nominal 12.8V, which is near the full charge resting voltage of the batteries. " 

I've monitored the separator and it seems to be intermittent. At times, if the coach battery voltage is less than 12.8V the engine battery will not charge the coach batteries because the separator disconnects if either battery bank is below that voltage. When this occurs, the battery must be charged via 120VAC (shore power or Onan generator). Or via solar. In other words, the battery separator in my Roadtrek doesn't seem to consistently connect my vehicle alternator to the coach battery if the engine battery is 14V and the coach battery is less than 12.8V. That's a coach battery that is 90% charged. See note 7.

According to the separator manufacturer:  The connect threshold is set to a nominal voltage of 13.2V, which would only be reached when the charging system is operating. This will cause the relay to close and the charging system can charge both banks of batteries. The disconnect voltage is set to a nominal 12.8V, which is near the full charge resting voltage of the batteries. This will cause the relay to be opened shortly after the engine is stopped, attempting to preserve 100% of the starting battery capacity for engine cranking."

Note 1: In my Roadtrek the terminal labelled "Aux" is connected to the coach batteries. The terminal labelled "Main" is connected to the chassis battery:

Note 2: The vehicle alternator (Main)  will connect to the coach batteries (Aux) if either the vehicle or coach batteries are above the "connect" threshold of about 13.2V, which is 100% charge. After connecting the batteries will remain connected unless one of the batteries falls below 12.8V. This was confirmed with a new battery separator. See Note 5.

Note 3 :  The separator includes a momentary "auxiliary start function".  The start terminal must see at least 3V* to activate. The auxiliary [coach] battery must read at least 10V*." "This is the input for engine start signal override. When power is applied to this input, the relay will close if the Aux. Battery [coach] is no less than 0.85 Volts below the Main battery [chassis]."  In my Roadtrek this is not used.

Note 4:  According to the separator manufacturer, "* = Typical voltage settings have a +/- 2% tolerance".

Note 5:  Update December 2019. I replaced the battery separator and the operation of the new one is different than the old one.  If either the coach or engine battery is above the "connect" voltage threshold of about 13.2 volts  then the separator connects both coach and engine batteries.  I've monitored this for several weeks and the operation is consistent. If the engine is running the engine battery voltage is about 14.0 volts and the separator connects the engine battery to the chassis battery. If the engine is not running and I connect the Roadtrek to shore power, the Tripplite charge voltage rises to above 13.4 V and the chassis batteries and Tripplite are connected to the engine battery. This is not the way the old separator operated and I can only assume that the old separator had a flaw or failure.

Separator Options
The separator includes some options, including a "start signal" but that is not wired on my Roadtrek. The "start signal input" is the input for engine start signal override. When power is applied to this input, the relay will close if the Aux. [coach] Battery is no less than 0.85 Volts below the Main [chassis] battery.


Where is the Separator located?
The battery separator is the device in the center of this photo with the two red rubber boots. In my Roadtrek the terminal on the right is labelled "Aux" and is connected to the coach batteries. The terminal on the left is labelled "Main" and is connected to the chassis battery:

Alternate Battery Separator - "Unidirectional" Type
The battery separator is under the vehicle hood, see the photo above. It controls the connection between the vehicle battery and the coach batteries. In my 210P the battery separator is a "bidirectional" 200A module with a relay for 12V systems.  The following is the description of a "unidirectional" model. These two models operate differently. You need to determine which you have in your RV.

The unidirectional separator is a 200A battery separator modules with an integrated relay for 12V systems. The separator monitors the engine and coach batteries. If the Main battery is above the connect threshold, the relay connects the two battery banks together. If the Main battery is below the disconnect threshold the separator will open the relay. You will have to determine which battery bank, Chassis or Coach is connected to the "Main" terminal.

The connect threshold is set to a nominal voltage of 13.2V, which would only be reached when the vehicle charging system is operating. This will cause the relay to close and the engine charging system can charge both the engine and coach batteries. The disconnect voltage is set to a nominal 12.8V, which is near the full charge resting voltage of the batteries. This will cause the relay to be opened shortly after the engine is stopped, attempting to preserve 100% of the starting battery capacity for engine cranking.

Battery Separator - Bidirectional - "Clicking"
The battery separator is under the vehicle hood, see the photo above.  From time to time, you might hear a "clicking" sound if your hood is open. That could be the relay of the separator opening or closing.

For a bidirectional separator the relay will close as noted above if the vehicle battery/alternator is above 13.2V and the coach batteries are above 12.8V. Or vice-versa. If either of these falls below 12.8V the relay will open. When the relay closes it connects the vehicle battery/alternator to the coach batteries and when it opens it disconnects or separates these batteries.

The bidirectional will connect the vehicle and coach battery systems if the coach rises about 13.2V and the vehicle is above 12.8V.

At rest, my vehicle battery is about 12.6V. Fully charged my coach batteries are about 13.2 volts after dissipating the "surface charge".

If one has a solar charging system for the coach batteries, it would be possible for intermittent connection of the two systems if the solar system rises above 13.2V and the engine battery is above 12.8V.  Depending upon load and sunlight conditions, if the coach battery falls below 12.8V or about 90%, then the separator relay will open, disconnecting the vehicle and coach batteries. If the sun comes out, or solar improves and the coach battery terminal voltage increases to above 13.2V (which will happen while charging) then the separator relay will close, connecting the two battery systems.  As the coach battery discharges, the terminal voltage will decrease. When sunlight increases, then the separator will again close the relay, "click" and the two battery systems will be connected.

Of course, a faulty separator may also close the relay at unexpected moments.

Solar.

Solar:
In 2014 I  added a 50-watt solar panel and a desulfating solar controller.  Using a 50-watt solar panel provides a maximum 4.17 amperes of charging current at 12V during peak sunlight conditions. That's more than sufficient for maintaining or topping off the batteries.

Notes:

1. This post is not a recommendation that owners perform their own electrical service. Working with electricity can be dangerous and can result in personal injury, or death or damage to your Roadtrek. 
2. This information is provided "As Is" and no warranty or claim of accuracy is given. Your Roadtrek and its equipment may be very different than what is portrayed here. 
3. Refer to the Roadtrek owners manual and the Tripplite Owner's Manual for complete information. 
4. The Tripplite inverter/charge includes 120V surge protection. In other words, outlets that are powered by the "invert" mode will have surge protection. Any others in the coach will not have any surge protection unless it is added. In my case, I have an electrical management system (EMS) on the shore power line. I don't have such a thing on the generator power output. 
5. For troubleshooting of the Tripplite, refer to the owners manual. 
6. This post is based on several other posts in this blog as well as recent social media posts by me. I'm providing this so I won't have to write this up again. 
7. My coach batteries exhibited difficulty at about 3 years. I suspect the problem was the model battery separator Roadtrek installed in my 210P. The separator won't connect the vehicle alternator to the coach batteries unless the coach batteries are at 100% charge. 
8. All info on the battery separator is per the manufacturer's data sheet. 

AGM Batteries Sulfation, RV AGM Battery Care and Charging - Part 2

This is part 2 about care of AGM batteries in a "motor home." The previous post is part 1.

After a significant amount of research into the chemistry,  technology and charging of AGM batteries I became concerned about battery damage including sulfation and freezing the battery electrolyte. I want to achieve longer battery life and have 100% rated battery power available when I am off the grid and am not running the generator. I decided I needed to make an improvement and installed a solar panel and solar controller-battery charger for my coach batteries. This post looks more closely at the research that led to my decision. I'll provide in brief the why's, as well as some of the "do's and don'ts." I am not promoting any product here. This describes the issues and the solution I chose, and provides background information about that decision. This may be helpful to others.

I chose a 50 watt solar panel and a "Solar Charger/Maintainer/Desulfator" rated for use with solar systems up to 180 Watts. The solar panel is not used when the vehicle is in motion. I decided on this approach because:

1. The replacement price of the coach batteries would be about $250.00-$400.00
2. The Camper Van may be stored for weeks and sometimes for months
3. It's desired to achieve the maximum life from the coach batteries
4. It's desired to have the batteries provide the maximum rated power throughout their life
5. When stored,  120V shore power is not available. Solar power is the only available power option unless the generator or vehicle motor is running.

The following post provides, in brief, what I have learned on this subject and how what I learned has influenced my decision  Why would I want to do this? I'd like to spare the reader the time to replicate what I have researched.

How to Achieve Full Life and Power from AGM Batteries
That is the goal. Get maximum power and longest life from the AGM coach batteries. Doing so should provide a more pleasurable trekking experience and reduce the annual cost of operating the camper van.

Deep Cycle AGM Batteries require complete charging, but not overcharging to achieve full lifespan, avoid freezing damage and provide the amount of power expected from them.

Roadtrek states in their 2014 210P manual "AGM Battery Warranty....... is voided if AGM batteries are tampered with, topped off with distilled water or allowed to sulfate or freeze due to lack of charge."

Here are the most important things that dictate battery life:

• Preventive maintenance
• Depth-of-Discharge (avoid discharge below 75% charged)
• Charging to a full charge
• Temperature conditions of the batteries (cooler is better). Batteries are designed for an average annual temperature of 77F (25C). If the average annual temperature is 95F (35C) then the battery life will be reduced by about 50 percent. 

What is full life? It varies. 3-5 years is fairly typical according to published information. However, AGM batteries are reputed to achieve up to 10 years if properly maintained, kept cool and if used in such a manner to maximize battery life. I decided I would prefer to replace these batteries every 6-8 years instead of every three years. I also decided I do want the maximum battery power to be available when needed.

Avoiding Sulfation and Extending Battery Life
Sulfation if left unchecked will kill the coach batteries. Sulfation begins when the batteries are not fully charged, and storing them unless "float charged" continues the sulfation process. The RT and most RVs include charging systems for the coach batteries. However, there are periods in which these 120V or engine and generator powered charging systems are not available. That is a problem. So how can I achieve my stated goal of long life at maximum power from these batteries under my actual storage and charging conditions?

Frequent charging while avoiding overcharging of AGM batteries will reduce, but not eliminate sulfation. Sulfation occurs each time a battery is discharged. Storing a battery is reputed to cause self-discharge and sulfation, and this is more serious at higher temperatures, above 75F.  Batteries which are not used weekly may experience sulfation.

Sulfation is the gradual coating of the positive lead plate of the battery with lead sulfate (PbSO4). Simultaneously the battery electrolyte, which is sulfuric acid (H2SO4) on losing SO4 molecules becomes diluted by water. This occurs during battery discharge. The chemistry is oxygen molecules (O2) from the positive lead plate combine with hydrogen molecules (H2) from the battery acid and the result is water (H2O).

Because AGM batteries are chemical devices, cold weather will slow the sulfation process while hot weather speeds it up. In other words, full charging may be more important at higher temperatures. On the other hand, as sulfation occurs battery electrolyte (acid) is diluted by water molecules and will freeze at lower temperatures than the normal electrolyte of a fully charged battery. Such freezing can damage the battery.

Normal charging does not remove all sulfate molecules from the plates. Over time they build up on the plate and ultimately contribute to the demise of the battery. Sulfation, or the formation of lead sulfate can permanently reduce battery capacity. If unchecked it can kill the battery.

Keeping batteries fully charged and reducing sulfation will extend the life of the batteries and provide optimum capacity. Battery life expectancy is directly the result of how well these batteries are maintained and how they are used (or abused). Key points are:

• Don't overcharge.
• Don't undercharge
• Keep fully charged and don't store undercharged.
• Use and keep the batteries at their average design temperature.  
• Apply a periodic full-saturation charge to de-sulfate the batteries.
• Don't over-deplete; reduce the average "depth of discharge." and avoid "deep discharge".
• Reduce the number of "discharge-charge" cycles. 
• Don't charge if over 120F and don't charge if the battery is frozen. 

Some of the above might not be possible. That is why many batteries don't survive for more than 3 years according to some published sources. However, I'm convinced that good care and attention to these details will extend battery life for most users. One manufacturer of battery chargers/maintainers/desulphators claims that certain models of their product "can more than double the useful life of new batteries." I can't verify that. However, it's prudent to ask why some batteries fail within 3 years while others go on for 6 or more years.

It is my understanding there are two types of sulfation: 1) reversible (soft sulfation), and 2) permanent (hard sulfation). Reversible sulfation is normal and can be corrected by a specific charging regimen. When charging, the PbSO4 is converted to lead and the SO4 combines with hydrogen to form electrolyte. Non-reversible sulfation occurs when a battery has been in a discharged condition, or "low state-of-charge" for a longer period, be it weeks or months. In such a state the sulfate crystals become permanent, cannot be reversed by charging methods and the capacity of the battery is permanently reduced and impaired.

Charging and Reducing or Reversing Sulfation
Special charging techniques are reputed to reverse sulfation.  Battery charging states include:

• Bulk (high, constant current)
• Absorption (constant voltage)
• Float (hold at 100% charge)
• Equalization.(controlled absorption overcharge)
• De-sulfation

A microprocessor "smart" charger will include three or four of these states. Special chargers provide a fifth state called "de-sulfation." One charger manufacturer declares "Patented high-frequency pulse desulfation is designed to reverse and eliminate battery sulfation."

There is some controversy about the claims of "reversing sulfation." One critic states "simple, electronic de-sulfation is a one size fits all approach." On the other hand, I've seen no comments or evidence that such pulse desulfation techniques can harm the batteries.

How to Apply a "Full Saturation" Charge
Such a charge is a general recommendation for lead acid batteries. However, some AGM battery manufacturers have specific requirements of this type of charge and if not followed it is possible to damage the batteries. This type of charge is also called an "Equalizing" charge. This is done by a deliberate overcharge of the batteries. The problem with sealed AGM batteries is there is no way to measure the electrolyte condition and so the equalizing charge is guesswork and may be based on terminal voltage. My guess is it's better to use a good 4-stage charger and avoid deep discharges.

Choosing a Battery Charger
The charger included in your RV or camper van is probably a three-stage "smart" charger which includes bulk, absorption and float stages.  "Float" charging is not "trickle" charging; a trickle charger can overcharge batteries!

I decided to add a "Charger/Maintainer/Desulfator" which was designed for use with solar panels. I also selected a solar panel which is overcapacity. This approach compensates for the lowered solar power that is available when daylight is minimized, such as during winter hours or when overcast. It also provides for a higher charging rate when there is optimal sunlight available.

Using a 50 watt solar panel provides a maximum 4.17 amperes of charging current at 12V during peak sunlight conditions. That's more than sufficient for maintaining or topping off the batteries.

Overcharging is to be avoided. I decided to use a solar charger that includes temperature compensation with float charging. The temperature sensor is attached to one of the battery terminals. This permits charging in cold and hot weather. The manufacturer states compensation works over the range 0F to 130F.

The solar charging system is only used when the batteries are not being charged via 120V shore power, generator power or via a running vehicle engine. It is intended to be used at any time the vehicle is stationary. The solar charger is connected directly to the batteries and operates independent of the position of the battery disconnect switch.

How Long Does it Take to Charge the Batteries?
The answer to that question is determined by the amount of sunlight available and the condition of the batteries. The purpose of the solar charger is to take the batteries from a condition of 85% to 90% charged to full charge, or apply a "topping" charge. Once at full charge, the goal is to "float" and desulfate the batteries while avoiding overcharge. Temperature compensation reduces the float charge as the battery temperature increases.

To bring a discharged battery to full charge can take 7 to 10 hours or longer. That is not the purpose of the solar system, but if there is sufficient daylight hours such charging is a possibility.

How Does "Depth of Discharge" Influence Battery Life?
Any AGM battery has a service life which is measured in number of discharges and the "depth of discharge." As a rule of thumb, the less the "depth of discharge" the longer the life of the battery, but it should be discharged to 90% peak when used. In other words, if used the battery should be discharged 10% and  a battery which is repeatedly used and discharged to 50% of its peak capacity and then completely recharged may be usable for 1000 cycles. If one cycle occurs each day, then the battery may have a life of 3 years.

That same battery, if discharged to 75% of its peak capacity each day and then fully recharged may be usable for 2000 cycles. Under such conditions the battery may have a life of 6 years.

Furthermore, that same battery if discharged to 25% of its peak capacity each day and then fully recharged may be usable for 500 cycles. Under such conditions the battery may have a life of only 16 months. Discharging a battery to less than 25% capacity is to be avoided.

What are Battery Storage Choices?
Batteries can be disconnected and then charged if they are not going to be used for long periods of time. It's best to store the battery in a cool or cold place (sulfation is slowed when it is below 75F). Here's a few methods:

1. Turn the battery switch "off" and then connect a 3- or 4- stage microprocessor controlled battery charger and fully charge the battery. If the charger includes an automatic "float" mode it can be left connected to the battery for long periods of time. Check your manufacturer. 
2. If the battery is fully charged connect a "float" charger, again check your manufacturer.
3. Alternately, the battery can be removed in the vehicle and kept above freezing while a float charge is applied. 

Avoiding the Freezing of Batteries
If the electrolyte in a lead acid battery freezes, the battery will probably be damaged. The capacity of such a damaged battery will be reduced. What are the freezing temperatures of a depleted battery? A battery in good condition that is 100% charged has the maximum concentration of sulfuric acid as electrolyte. As the battery discharges, the concentration of the acid is reduced as water molecules replace acid molecules in the electrolyte. Here are typical freezing temperatures for lead acid batteries at different charge states:

100% Charged = (-) 77F, or (-) 67C.
75% Charged = (-) 35F or (-) 37C
50% Charged = (-) 10F or (-) 23C

Other Sources
There are a lot of web based sources on AGM battery maintenance and charging. Enter  "AGM battery maintenance", "AGM battery charging" or "AGM Battery desulfation" in your favorite search engine and you'll get a list.

AGM Coach Battery Issues - Do It Yourself Solar Charging

This post looks at achieving the maximum life and performance from AGM batteries and also the steps an owner who doesn't have access to 24/7 120V charging power can take to keep the batteries in his/her "motor home" at full charge. It includes some of the background information I used to decide on solar power for charging batteries, and it includes a short video.

The Problem
Many motor homes and camper vans include coach batteries. Depending upon how many batteries are included and their capacity, they can be used for powering many things. Typical uses include the water pump, interior and exterior lighting, the refrigerator and small appliances via an inverter. Some motor homes include solar panels for recharging of these batteries. Some do not.

Absorbent Glass Matt batteries, or AGM batteries are very different from the old lead-acid and gelled electrolyte batteries. AGM batteries have a thin fiberglass mat or screen between the lead plates. The fiberglass mat is saturated with acid and is compressed and sandwiched between the plates. This tight packing makes the interior components tolerant of vibration. They are ideal for use in moving vehicles.  Many AGM batteries include bolt-on terminals which are reputed to give a more reliable connection.

AGM batteries are not cheap, but the best ones can last longer than other, less costly batteries. Perhaps 5 to 8 years if given proper attention.

As with all things, there are pros and cons. This post will look into some of these. Part 2 will delve more deeply into batteries. This post addresses the need to keep AGM batteries fully charged.

AGM - Are all Deep Cycle?
Not all AGM batteries are alike. Some are designed to be what is called a "deep cycle" battery and others are not.  So what is a "deep cycle" battery? Such a battery is designed to be discharged and recharged many times. "Deep Cycle" means the battery can be discharged to a lower level of peak capacity and recover. Some manufacturer's state that a deep cycle battery will last three to four times longer than a starting battery under the same conditions.

The batteries I am concerned about are deep cycle batteries.

Advantages of AGM Deep Cycle Batteries
If properly maintained, these are some of the advantages of these batteries:

• Improved resistance to shock and vibration
• Totally sealed
• Reliable
• No acid fumes
• No spilled acid
• No need to add water
• If fully charged can tolerate freezing temperatures (temperatures as low as -40F, but check with your battery manufacturer)
• Longer life as compared to a starting battery

How Do I Maintain a Deep Cycle AGM Battery?
That's a good question and as these are expensive batteries they do need to be properly maintained to achieve their full design life. These are sealed batteries so there is no water to add. Does that mean that the battery is "maintenance free?" No, it does not.

So what do I have to do? Most important is to keep these batteries properly charged! For motor homes or campers which are plugged in each day, this should be rather easy because these vehicles include chargers powered by the 120V shore power. Some vehicles charge the coach batteries when the vehicle engine is running. Others include solar charging systems. Some vehicles include all of the above and a gasoline or propane generator which can also recharge the batteries! However, sulfation remains a problem in lead-acid batteries. More on that later.

The two things to do to achieve long life from AGM deep cycle batteries are:

1. Recharge daily to a full charge.
2. Don't discharge too low. Don't fully discharge.

Is AGM Battery Maintenance Important?
Yes it is. Roadtrek has this statement in the current 210P manual:

AGM Battery Warranty Batteries are warranted by the battery manufacturer for one year from the "In Service Date" of the Roadtrek. 

1. Warranty is voided if AGM batteries are tampered with, topped off with distilled water or allowed to sulfate or freeze due to lack of charge. 

So there you have it. Owners must keep their coach batteries charged. Roadtrek has specific instructions about this for dealers, too. Here's two photos showing the stickers on a 2013 210P. The notice about the "Deep Cycle Gel Battery" is specific (this Roadtrek did have AGM batteries):

Charging AGM Batteries When Storing the Motor Home
For anyone who stores their motor home for long periods of time, there are only three ways to get the power necessary to charge the batteries:

1. Shore Power - 120V plug-in connection.
2. Solar Power.
3. Frequent vehicle or generator use. 

However, not all storage facilities include the necessary 120V power for charging, and not all motor homes include a solar power charging system. If you are like many who store their motor homes, you may not start and use the vehicle for two, four or more weeks. Is this a problem? Yes it is. So what to do? One possibility is to remove the batteries and charge them in your garage. However, that might not be easy as these weigh about 70 lbs. each. I decided the most effective method to allow storing the vehicle outdoors with the batteries inside was to install a solar panel and a solar battery charger. That's what I did, and I place the solar panel inside the vehicle when in use for charging. No rooftop installation required! A video is included in this post.

Solar Power Charger and Sulfation
When the batteries are not being drained by daily use, it's possible to keep them charged if there is sufficient solar energy (daylight) available. For anyone who only has access to solar energy during vehicle storage, this might be the only way for daily recharging.

Will using solar energy and a charger avoid sulfation and are there other issues? In a later post I'll give a more thorough description of what sulfation is. For now, suffice it to say that during battery discharge sulfate molecules (SO4) move from the battery acid (electrolyte) to a lead plate to form crystals of lead sulfate (PbSO4). This is called "sulfation." This interferes with the ability of the battery to perform. It reduces battery capacity, which is simply stated the amount of power a battery can provide. Less power means you run out of power for your camper van electrical devices sooner than expected.

A second problem is as the battery discharges the acid concentration decreases and the electrolyte changes slowly to water. This makes the battery electrolyte more susceptible to freezing. Freezing can damage the battery. Uh, Oh!

What Type of Solar Controller-Charger?
I decided to purchase a controller which the manufacturer states has the following features:

• Full-time automatic battery desulphation
• Uses US Patented pulse battery desulfation technology
• One year unconditional money back warranty and five year "no hassle" warranty on parts & labor
• Plug and run operation - fully automatic easy efficient operation
• Never over-charges - you can keep it plugged in for weeks, months, even a year 
• Temperature compensation - prevents over and under charging from freezing to 130 degrees
• Solar battery charger maximizes battery life and capacity and reconditions weak batteries. Maintains up to 2 batteries at a time. Short circuit, spark and polarity protection. 
• When used as a maintainer....is guaranteed to maximize your battery's life and storage capacity. 

Installation Issues
Finding a convenient place to install the controller and near the batteries can be challenging. The charger manufacturer states "....it is important the controller be in the same general temperature environment as the battery(s)." The temperature sensor lead length is not to be altered and that placed a further restriction. I decided I didn't want  a rooftop mounting of the solar panels at this time. I concluded that a larger wattage solar panel could be put on the dash to charge the batteries via a solar controller-charger. I decided on a 50 watt panel because this would provide sufficient power under lower light and reduced daylight hours, such as in winter or with the windshield not clean. It would allow the controller to charge the batteries even on overcast days. I also wanted simplified controller mounting and wiring.

The manufacturer of the charger-controller says this about mounting the solar controller-charger:

IMPORTANT INFORMATION ON USING PRODUCT OUTDOORS: Weather-tight enclosure. Always mount units in vertical position with cord sets exiting downward to ensure weather tight integrity. Unit must be mounted this way to ensure long term trouble-free life including weatherproof integrity. Mounting in any other manner or using unmounted (parallel to ground) except indoors may cause unit to fail due to water intrusion that is unable to drain correctly to avoid damage. 

Installing a Solar Charging System
So how to go about this? Three things are necesary:

1. Solar Panel
2. Solar Controller - Charger
3. Interconnecting cables

Here is a photo of the battery compartment of a Roadtrek 210P, model year 2013. It shows two AGM batteries. As you can see the battery compartment is very tight:

Here's a brief video of the installation of a Solar Battery Condition Charger and Controller with a 50-Watt solar panel: