Remote Vehicle Diagnostics - Battery Monitor

 

Remote Diagnostic - Battery - Sept 2021

Monitoring a vehicle which is parked off the grid

When I purchased the Roadtrek 210P I stored it at a commercial lot a few miles away.  This was necessary because it could not fit in my garage and the Homeowner's Association I lived in had a rule which prohibits RVs on the property.

I investigated several options and decided to purchase a HUM which is owned by Verizon. This included a OBD transmitter to monitor the vehicle and a "black box" which transmits the information to me via the cellular telephone network. It does include vehicle location monitoring, too

To replace power drained by the onboard vehicle computer I was using a small solar panel placed on the dashboard. This proved to be inadequate with HUM upgrades which increased monitoring frequency transmissions.  So I upgraded to a 30W solar panel with built-in controller. The new panel was able to keep the battery level up and I seldom got a "battery voltage" alert.

However, with the vehicle battery approaching 9 years of age, the battery would not hold a charge.  This resulted in a 12V battery voltage while the solar panel was in the sun.  At night the vehicle battery voltage began dropping off. A couple of weeks ago the battery died and the low voltage declined to about 10.5 Volts. Oh, Oh! That's a dead battery.  I received several days of alerts and I replaced the battery.  I received the alerts because in sun, the solar provided sufficient power to get the battery to about 12.3 VDC, but that is too low a voltage to properly recharge the battery.

There was no indication of an unusual load, but I disabled (turned off) the Battery Separator to be certain it wasn't cycling or powering up. My Roadtrek has two solar panel systems; one for the vehicle battery and another for the coach batteries.  So there is no need to connect the two when the vehicle is stored and stationary.

As can be seen in the photo above, the battery voltage is reported as "stable" and during full sun the battery voltage while charging reaches about 13.5VDC.  On cloudy days the voltage decreases to about 13.2 VDC.  The vehicle was in use until September 14.  It has been stationary and off the grid since September 15.  The chart above shows the battery voltage during solar charge and also during nighttime. The vehicle is pointed easterly and the solar panel gets direct sun in late morning to early afternoon, if it is a cloudless day.  The 12.82 VDC reading above was taken as the sun was rising but obscured by a building to the east. Some solar energy was available, but not full sun.

Overnight the vehicle battery voltage, with no solar available is about 12.75VDC, just before dawn (typical reading 7:00am). A fully charged 12V lead-acid vehicle battery is in the range of 12.5 to 12.7 VDC.

(c) 2021 Roadtrek210.blogspot.com

New Voltmeter-Ammeter-Wattmeter for AGM batteries - Part 2

New Ammeter-Voltmeter-Wattmeter

September 15, 2017: Added short video clip

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Short video:

New Ammeter-Voltmeter-Wattmeter

See Part 1 for the background information about the AGM batteries in my roadtrek 210P:

http://roadtrek210.blogspot.com/2017/08/new-voltmeter-ammeter-wattmeter-for-agm.html

Why add a digital voltmeter-ammeter?
The decision to add a digital meter was easy. Then I proceeded to decide upon the type of meter. I had seen a FMCA Roadtrek Chapter Cyberrally post about how someone added a digital meter and I wanted to do the same.

Finding a meter wasn't all that difficult. A meter which stored "Ampere Hours" would have been ideal, but I opted for a digital voltmeter-ammeter-wattmeter. The selected meter also included adjustable alarm points for high and low voltage. That would be useful for monitoring low battery voltage, or a point at which I wanted to pay closer attention to battery draw.

I ordered the meter ($15.99 at the time) with DC shunt. I wanted to connect it directly to the battery so I could monitor battery voltage even with the battery disconnect "off". A switch and protective fuse was necessary. The parts list included:

1. Meter with 100A shunt
2. Off-On switch
3. Case for meter and switch (Case dimensions: 5-1/2" x 3-1/8" x 1-1/2")
4. 25 ft. 4-conductor cable
5. Automotive fuse holder (I used a fuse from my kit)
6. Miscellaneous connectors.
7. Note: for details, see the parts list at end of this post. 

The most difficult part for me was determining where to mount the meter. I had decided that I wanted a surface mount case, so I could remove the meter in the future and leave no trace. Determining how to run the 4/C cable was also a bit of a challenge. I decided to route it behind the fiberglass side panel, into the coach along side the door, then behind the side panel and exiting just below the 120VAC/12VDC power distribution center. This required the temporary removal of the rear passenger seat. Lots of screws.

Passenger seat removed, propane furnace exposed

With the passenger seat removed, it was possible to remove the side panel, and pull the cable behind the panel. I pulled the cable from the battery compartment to the passenger seat area, and re-assembled the interior panel. I left a foot lomg "pigtail" for connecting the meter.

Cable at Passenger Seat

I then mounted the rear of the meter case to the wall. I used 3M Dual Lock™ General Purpose Reclosable Fasteners. Note the female electrical connectors on the cable from the battery compartment:

Base of Meter Case

I assembled the meter in the case. Marked the case and cut the opening with a Dremel tool and cutting wheel. I used connectors so I can remove this if necessary. The "female" end goes on the cable from the battery compartment. The "male" end is in the meter case. This is so there should not be any exposed live parts if I pull the meter, even if the fuse at the shunt is intact.

Meter and Off-On switch in case

This is the front of the meter and switch, assembled in the case:

Front of meter case with Off-On switch

I mounted the meter to the case mounted on the wall:

Meter case mounted to the wall

This is the shunt, which was supplied with the meter. For the meter I purchased the shunt is connected between the negative battery post and the negative conductor. The shunt is rated 100A/75mV. The shunt is actually a precision resistor and the higher the current flowing through it, the higher the voltage drop across it. The voltage drop is 75 millivolts at 100 amperes.

Shunt

The shunt was installed in accordance with the manufacturer's instructions. A right angle screwdriver is helpful for installing the wiring to the shunt (I used a phillips).

CAUTION - Installing the shunt requires removing the negative battery lead. Exercise great care not to short a tool from negative to the nearby positive terminal. DEATH OR INJURY CAN RESULT. Be sure there is no battery load when doing this procedure.

The shunt is connected directly to the negative battery post. The black (Negative) cable is connected to the other side of the shunt; the yellow arrow points to that connection. Three of the leads of the 4-conductor cable is connected to the shunt. The fourth conductor goes to the red (Positive) battery terminal.  I installed an automotive fuse between the positive battery terminal and the lead going to the meter. That is to protect the wire in the event of a short circuit

CAUTION - A properly sized fuse is necessary to protect the wire in the event of equipment failure or short circuit. Fire, damage,  injury or death can result from an unprotected circuit.

Shunt installation and automotive fuse on positive battery terminal

With the installation complete I threw the "Off-On" switch to the "On" position.

I checked the display using a precision digital VOM. I measured the mV at the shunt and calculated the meter reading. The meter agreed.

Meter Setup
The meter has alarm points and some options:

1. Set backlight off or on. The default is "on".
2. Set voltage alarm threshold. The meter includes both "high" and "low" voltage alarms. These are set independently. The presence of an alarm flashes the backlight alternating "off" and "on". I set the low voltage alarm at the 50% DoD level for my coach batteries.
3. Set the measuring range. This meter will work with a 50A/75mV shunt or a 100A/75mV shunt. I set this to match the installed shunt, which is 100A/75mV.
4. Energy reset. The meter will accumulate and store kilo-watt hours (kWh). This value can be reset to zero.  

Meter Limitations
The meter is a DC meter. This means that the ammeter measurement is polarity sensitive. The meter as connected can only measure discharge current from the battery across the shunt. When charging the meter displays 0.00 amperes. However, by reversing the connections it is possible to measure charging current. I tried this and it works.

It was interesting to watch the Tripplite inverter/charger step through the charging levels. I may add a DPDT switch for this purpose, but it is completely optional. I've monitored the Tripplite by watching the AC current; as the Tripplite throttles back the AC current decreases. However, other 120VAC loads will mask that.  It is also possible to pull the compartment cover over the Tripplite and observe the charge state LEDs:

Green = Full Charge

Detailed Parts list, my cost $36.45 plus tax and any shipping:

1. MICTUNING DC 6.5-100V 0-100A LCD Digital Display Ammeter Voltmeter Multimeter Volt Watt Power Energy Meter Blue with 100A/75mV Shunt, Part No. MIC-DVG-015.
2. Serpac black plastic case, model 151i, BK.
3. Rocker switch, Philmore No. 30-882.
4. 4-conductor shielded cable, 24 AWG. (Use #22-24 AWG; smaller AWG is easier to pull).
5. Insulated terminal disconnects, male and female (from toolbox, not included in price total).
6. Fuse and fuseholder to protect the wire from the meter to the (+) positive battery terminal. Size of the fuse is determined by the size of the wire.