Coach Batteries - AGM versus Lithium Ion Update

AGM Lead Acid batteries in my 210P. Mounted outside. 

Here's an update on lead acid sealed AGM batteries versus Lithium Ion (LiFePo4) as coach batteries in my Roadtrek. If you have a Chevy based Roadtrek, you probably have two 6-Volt 220Ah AGM batteries as I do.

Note: 1. I'll post an article about what we can expect from our batteries and my experience powering the stuff in my Roadtrek with AGM batteries since December 2013.

When we compare batteries, we usually look at these three types:

1. 6V type GC2 golf cart batteries. These lead-acid batteries, are not sealed, and do require addition of distilled water from time to time. They also do vent gasses.
2. 6 V type AGC2 AGM batteries. These are also lead-acid batteries, but they are sealed and require no maintenance.
3. 12V LiFePO4 Lithium-Ion batteries. These are radically different than the golf cart and AGM batteries. 

So which is the best type? That requires considering the trade-offs which depends upon your use, and how much money you are willing to spend, and warranties.  Our 210P has an Onan generator and I added limited solar too.  If we are not on shore power we need battery power to get through the night, and then we recharge. If battery power is low we can run the Onan generator, or the chassis engine. We use the inverter sparingly to give us 120VAC. So we don't need a lot of battery power. We also have propane for the stove top and for the hot water heater. Your situation might be different.

Trick question: Should one invest in LiFePo4 batteries or in Solar Panels?  I won't attempt to answer that in this post.  The answer lies in how much electrical power do you need to get through the night, when batteries are important, or use a generator.

In fact the real issue is making a useful comparison of electrical energy sources when off the grid. These include batteries, my Onan generator, and my solar panels.   This is a somewhat unequal comparison, because my Onan can provide 2,800 watts of continuous power. That's sufficient to run my Air Conditioner and the Onan consumes about 25 ounces of gasoline per hour at low power and 55 ounces per hour at full power.

My point is, we are comparing energy sources, and the costs of those sources.  This post will not compare the cost of solar panels and batteries to other sources.

Here is a quick comparison of batteries. I use Battle Born Battery as the Lithium-ion comparison because they seem to be a well made battery with a "10 year warranty".  These would also work with the TrippLite inverter charger in my Roadtrek, with a change in settings to "Gel", because according to Battle Born "the battery prefers to bulk charge at 14.4 volts and float at 13.6 volts".

1. GC2 and AGM batteries are both lead-acid batteries. One of the characteristics of these batteries is they should not be repeatedly discharged below 50% to get maximum life.  So, my 220 Ah batteries can only really provide about 110 Ah of electrical energy if I want to get maximum life from my batteries. 
2. LiFePO4 type Lithium-ion batteries are radically different technology. So they are significantly lighter in weight than any lead-acid battery of similar capacity. They can be repeatedly discharged 75 to 80% without decreasing the life of the battery. They also can tolerate more charge-discharge cycles than the lead acid batteries. A 200Ah LiFePO4 battery can provide 160 Ah of useful electrical energy. 

So why haven't we all switched to Lithium-ion batteries? It is because even if we consider the advantages, the lithium batteries also have some disadvantages.

1. LiFePO4 batteries cannot be charged if they are below freezing temperatures.
2. LiFePO4 batteries are significantly more expensive than AGM batteries.

Here are some cost comparisons. I'm going to use two different AGM batteries and compare them to a "drop-in" Lithium-Ion battery replacement made by Battle Born Battery company:

1. Amstron AP-GC2 6V AGM Deep Cycle Battery. This is rated 210 AH and is currently available for $209.99 at atbatt.com. List at $299.99. Two required to achieve 12V at list = $599.98.
2. Deka 8AGC2 (8AGC2M) 6V Deep Cycle battery. Made in USA. This is rated 220 Ah and is currently available for $389.70 via Amazon. Two required to achieve 12V = $779.40.
3. Battle Born 12V 100 Ah "drop-in" battery list $949 each. Two would provide 160 Ah of electrical energy versus 110 Ah for lead acid.  This is considering a 80% discharge versus 50%  discharge, which are the recommended maximums for these batteries. Price per battery $949 or $1,898 for two, which is required to achieve 200 Ah.  However, if you are an Escapees RV Club member, you can currently get a 15% discount.

So what are the issues? A couple of years ago, I looked at the replacement of my two 6-V AGM batteries with Lithium Ion batteries.  These were the issues I considered then:

1. Available power. The Lithium-ion batteries can provide more electrical energy and more discharge-charge cycles.  My AGM batteries can provide 110 Ah of useful electricity while Lithium-Ion which occupies the same space can provide 160 Ah. This is not trivial if one wants to boondock and could be an incentive to consider Lithium-Ion batteries.   
2. Temperature Restrictions. When I evaluated Lithium-Ion batteries a couple of years ago, I discovered that they should not be charged if the battery temperature is below freezing 32F (0 C).  My 210P carries the batteries in an outside compartment. Because we do trek when it is below freezing, that was a serious impediment. The Battle Born batteries have a low temperature charging limit of 25F.  The batteries are prevented from charging below 25F. However, they can continue to discharge until they reach a "low voltage limit" which is below 10 volts. 
3. Alternative Location. I even considered moving the Lithium-ion batteries inside of the coach as a means to get them above freezing, but that would displace useful space and add to the installation cost.
4. Cost. Comparing the Deka AGM to the Battle Born the difference is about $1,118. Comparing the Armston the difference is $1,199.96.
5. Weight. The Battle Born batteries are about one-half the weight of the AGM batteries. If weight is an issues, that reduction of about 60 lbs could be a significant factor. 
6. Warranty. Most AGM batteries can be expected to have a life of 5 years, or more. Some Lithium-Ion battery manufacturers offer a 10-year warranty. That means that one set of Lithium batteries is the equivalent of two sets of AGM batteries.  This should be considered when evaluating batteries. 
7. Temperature and voltage affects - AGM. AGM battery specifications are under "ideal" conditions. These include an ambient temperature of about 77F, discharging to no more than 50% and then immediately recharging.  That may not happen in the real world. AGM batteries do experience reduced capacity in cold weather. AGM battery life will also be reduced at higher temperatures. In other words, that 110 Ah available will decrease as the ambient temperature decreases and may be 25% less at 32F and 20 A discharge rate.  Under high discharge rates the capacity is further reduced. There is a lot of data about AGM and other lead acid batteries because there are so many manufacturers and they have been in use for many decades. 
8. Temperature and voltage affects - Lithium ion batteries. Using Battle Born Battery data for their "drop-in" 100 Ah battery, they state that the "Output voltage is flat during most of the discharge cycle". Furthermore can provide "100 Amp Continuous Current".  The company states that the batteries have low and high automatic temperature protection which shuts down the battery if temperature falls to 25F or a high temperature of 135F is reached. 
9. Lifespan. The AGMs in my Roadtrek are designed for about 1200 charge/discharge cycles if they are not discharged below 50%. According to Battle Born the lithium ion batteries "Approximately 75-80% of the battery capacity will remain after 3000 cycles in applications recharging at 0.5C or lower". The recharge "C" rating for a 200Ah battery is 0.5 x 200 A, or a charging rate of 100A. The lithium ion batteries will have much more life remaining than the AGMs after a couple of years of normal use. My AGMs should give good service for about 5 years, or longer. The Battle Born batteries will exceed that. 
10.  "Useful Life". Lead-acid batteries experience a reduction in capacity as they are charged and discharged because of internal changes, primarily sulfation. This reduction can be significant. After a year of use, my AGMs experienced about a 10% reduction. So, my useful 110 Ah decreased to about 99 Ah. Since then my batteries have leveled out, based upon voltage after a moderate period of discharge. The lithium ion batteries retain their capacity for a longer period of time. That can be important if one needs every bit of electricity available in the batteries when new. 

When I looked into replacing my AGM lead acid batteries with Lithium-ion, I also considered space requirements:

1. Inside LiFePo4. I would have to give up some under the bed space, because the Lithium Ion batteries should not be charged if below freezing. In fact, the Battle Born battery internal battery management system prevents charging below 25F.
2. Inside AGM. If I kept my two outside AGM batteries and added two inside, that would provide me with 220 AH of energy versus 160 Ah for the Lithium Ion batteries. In other words, I'd get about 38% more energy from four 6-V AGM batteries. However, those four batteries would weigh about 272 pounds. Two Battle Born batteries would weigh about 62 pounds. 
3. Inside AGM and Battle Born comparison. The above with four AGM batteries provides about 220 Ah at the best case at 272 pounds. If I added one Lithium Ion battery to total of three, that would increase the energy available to about 240 Ah. The weight would be about 93 pounds. 

The show stopper:
When I considered AGM versus Lithium-ion, I had these issues and yours might be different:

1. I wasn't willing to mount the LiFePO4 batteries inside the coach, because I didn't want to give up that space. That would be to keep the batteries above 25F while cold weather trekking. 
2. If I compare the normal life of AGMs (5 years or so) to the Battle Born LiFePo4 (10 year warranty) this changes the costs. To get 10 years of use from AGM batteries would probably require replacement after 5 years. In 10 years the two changes of AGMs is $779.40 each, for a total cost of $1,558.80 for Deka versus $1,878 for Battle Born. 
3. If I needed more overnight DC power, the Battle Born could be worth that extra $319. After all, considering the 10 year "warranty" life of the batteries, that's only about $32 per year. 

For more about Battle Born Lithium Batteries:

https://battlebornbatteries.com/





Copyright (C) 2019 Norman Retzke, "All Rights Reserved"

Original material:  https://roadtrek210.blogspot.com/