One thing that I’ve found over the course of the last 4ish years is that there are always new projects that need doing.  This one is The Battery Project, but I also have, Heavy Duty Bumper Supports, Battery Gizmo Upgrades, Bike Rack Install, and Is There a Water Leak Behind the Basement Wall? (and others) lined up already, waiting for timing and opportunity/motivation to get done.  (I’ve finished Bumper Supports and Bike Rack while I was working on this post)

Our battery situation started out like this:

2 Interstate 12v 100AH AGM deep cycle batteries
Wired in parallel
12v and 200AH  (Parallel doubles amp hours to 200AH but voltage stays 12v)
20ish pounds each
Maintenance Free
In theory, can be drained as much as 80% of charge
Recommended to only drain 50% of charge
Approx $100 each
These were dealer installed and came with the rig. In practice, these batteries were quite wimpy.  We boondocked several times with them and with minimal usage, (LED lights, some music/stereo, a small 12v fan) they would be down to nothing in a day or so.  Not enough staying power for the level of boondocking I had in mind.  Also, keep in mind these were in the early days and I didn’t have the hardware to track the voltage, state of charge and amp hour usage amounts that I have now.

Lots of research and internet deep diving on options later, and I went with this:

2 Trojan 6v 225AH T-105 flooded lead-acid batteries
Wired in series.
12v and 225AH (series doubles voltage to 12v but stays at 225AH)
70ish pounds each
NOT maintenance free
Strongly not recommended to drain lower than 50% charge
Approx $250-450 each.  (cost variable depending on where purchased)
1-2 year warranty
200-300 charge cycles
These are heavy duty beasts designed as golf cart workhorses, and they worked very well for many lengthy off-grid stays.  The issue is they are only rated from 3-7 year lifetimes depending on usage, and draining more than 50% and spotty maintenance can affect lifetime drastically.  They were difficult to get to on the rig, so maintenance was a pain, and there were a number of times our “normal” usage had these very much under 50% and at least twice where they were inadvertently drained completely.  (And what’s the benefit of having 225AH if you can only use 50% of it??)  Also, I still didn’t have hardware to verify voltage, state of charge and amp hours used until we’d been using them for quite a while.  After the first year or so, I installed a solar system and a battery monitor and keeping track of battery state was much more reliable and easier.

After 3 plus years of my usage, (I purchased them used, so although they were in great shape, they already had miles on them) the Trojan 6v’s were showing many signs of being on last legs.  Noticeably less punch in heavy operations like electric jacks, significantly less staying power when off the grid.  It was time to replace them, but which way to go?  New Trojans?  Something different?  There are a lot of options and variables to consider for RV batteries, especially if there’s a solar system and significant off-grid time involved.

Finally, I settled on something different/new:

2 12v 100AH Battle Born Lithium-ion LiFePO4 Deep Cycle
Wired in parallel.
12v and 200AH (Parallel doubles amp hours to 200AH but voltage stays 12v)
29 pounds each
Maintenance free. (Yay!)
Able to be drained as much as 98-99% of charge!  (Battle Born actually claims 100%!)
$950 each.  (but wait…)
10-year warranty
3000-5000 charging cycles, and will still charge at 80% efficiency well after the 3000 cycles mark
Lithium-ion batteries have been an up and coming choice in the RV battery world, but there have been some caveats that until recently could be an issue.  A lithium battery upgrade would also require an upgrade of your charger/converter unit, as lithiums require a higher bulk rate voltage charge than a standard charger/converter provides.  (14.7v vs 14.4v)  And there’s some sticker shock as the initial cost of lithium-ions is a big hit, as well as some temperature sensitivity.  Lithiums will no longer accept a charge at 24 degrees F or lower and will shut down at 135 degrees F.

But… technology is always moving, and lithium-ion has some new advances and data to consider when looking at capability and price.  First, the Battle Born brand I chose is a “drop-in” battery, meaning it is designed to work very well in an existing RV charging system.  It will charge successfully at the standard 14.4v to 14.6v bulk rate and 13.6v float rate without needing to upgrade your charger/converter.  Second, when you consider the improvement in charging cycles, although the initial investment is higher, it’s actually less expensive to go with lithium over the lifetime of the batteries.  I’d be on my second set of lead-acid batteries now, and looking at yet another set in 3-5 years at best, and lithiums will still be kicking it for 10-15 years.   On a cost per amp hour basis, lithiums run about $.35 where lead-acids go as high as $1.65. (depending on purchase price)  Maths don’t lie.

Eventually, I’ll add two more batteries for a total of 400AH of off-grid reserve.

“More power!  Aurgh, aurgh, auuuuurgh!”