Lithium Battery Upgrade

[DavisK]

I replaced my 2 deep-cycle AGM batteries this weekend with 2 LiFePO4 300Ah batteries. The lithium batteries are about the same size as the 2 battery boxes that I removed. Since lithium batteries don't give off flammable gases, I no longer needed the battery boxes. Instead, I added brackets and straps to hold them in place. The lithium batteries are each about 15 - 20 lbs. lighter than the group 27 deep-cycle batteries.

Most campers built after 2021 come with auto-detect deck mount converters that can fully charge lithium batteries. The WFCO auto-detect model numbers end with -AD. I checked mine before I installed the new batteries, and it is an WF-9855-AD. I also had to change the battery profile on my solar controller from AGM to LiFePo.

I still have one thing to do to complete my project. Since my batteries are not self heating, I will be installing a heating/cooling system in my basement for the batteries. It will consist of a 12v programmable thermostat that will control 2 high volume computer fans to exhaust warm air and force outside ducted air to the batteries when they reach a programmed temperature. These 2 fans will use the original vent holes that the battery boxes were connected to. I will also have a 12v programmable thermostat that will control a 12v 100 watt heater to warm the basement when the temperature drops to a programmed point.

 

[Wingerdinger]

Nice, well thought out installation.
I haven't looked into Lithium yet, but I wonder, are there heaters for the batteries available, presumably powered by the batteries?
Any disadvantage to going that route, other than the obvious power consumption?

 

[DavisK]

I saw some 10 watt seedling heaters on Amazon today. They are all about 10" x 20.75" (the normal size of a seedling tray), which are too large for my basement. They claim to raise the ambient temperature about 10° F. They are 120v, but that would be okay because the batteries will need heating mainly so they can be charged below 32° F. They can be discharged down to -4° F. Chances are good that I will be connected to shore power if I will be charging them below 32°. In my 12v heater setup I will have a relay that will disconnect the heater if I am not on shore power. Frankly, I would probably be using more energy to warm the batteries than I would be putting in from the solar panels. The BMS will prevent them from charging in freezing temperatures.

 

[Minozzy3]

When I installed my batteries, I thought I had to have heated. And we camp in Canada from April till oct. I have since found that having the inverter in the same compartment as the batteries. It keeps everything nice and toasty. If it gets to the point of the furnace kicking in. well then I find just the ducting going through the compartment heats it warm enough. I have checked numerous times to see if the heaters have turned on.
Not once have I seen the heaters on if we were camping. I have seen the heaters on once when we were plugged into shore power. But the furnace/inverter were not turned on.

Just a thought.... In most situations, heaters will not be required.

 

[DavisK]

When I installed my batteries, I thought I had to have heated. And we camp in Canada from April till oct. I have since found that having the inverter in the same compartment as the batteries. It keeps everything nice and toasty. If it gets to the point of the furnace kicking in. well then I find just the ducting going through the compartment heats it warm enough. I have checked numerous times to see if the heaters have turned on.
Not once have I seen the heaters on if we were camping. I have seen the heaters on once when we were plugged into shore power. But the furnace/inverter were not turned on.

Just a thought.... In most situations, heaters will not be required.

My batteries are in my basement, and my inverter is in the pass-through. It was really cold here in January before I left for the Rolex 24 in Daytona. I turned on my furnace and set the temperature to 50° so I put things in my refrigerator without them freezing. The camper was 50° and the pass-through was 52° (the pass-through is ducted and there is only a thin wall between it and the furnace). The basement was about 35°.

I anticipate that the battery heater will come on only while the camper is parked in my backyard, not while I am camping.

 

[campingcpl]

I built an insulated box for our lithium batteries and added 4 25 watt silicone heating pads to a piece of aluminum sheet metal that the batteries sit on. These are connected to an Inkbird thermostat that has controls for both heating and cooling. I have the pads in a series/parallel configuration one to reduce the amp draw and two to reduce the amount of heat they create. When I tested them, I seen a high temp of close to 170 degrees which was a lot hotter than I wanted. With them being in a series/parallel configuration this brought the temps down to around 100 degrees. This easily keeps the temps in the box at 60 degrees even with temps in the 20's.
As for the draw on the batteries, the draw is small enough that usually the solar more that keeps up and really doesn't draw anything from the batteries. With no solar for more than 24 hours it didn't even make a dent in the lithium batteries. This was with temps in the low 30's and the box temp set to 70 degrees. One of the tests I tried was having the box close to 32 degrees and wanted to see how long it would take to get the box to 70 degrees. This setup only took about 15 minutes and then cycled the heat on maybe once every hour for about 3 to 5 minutes just to warm it back up to the 70 degrees after falling to the 65 degrees start temperature.