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Lithium battery box temps

Evening gents I was wondering if anybody monitors their battery box temps in freezing weather?

Built up earlier this year two 280ahrs each LifePO4 battery's for my AF990 giving me a total capacity of 560ahrs.
So now that it's a bit colder and I plan on being places that will be freezing this winter Im thinking of a good way to help keep them warm during the nighttime.

When I built the battery banks I placed on the bottom of the battery pull-out rack some 3/16" foam board to set the new batterys on. I also installed on all four sides of each battery the same foam board. After I made all my series/parallel connections from them I also made a lid out of , you guessed it, the same foam board.

So my idea is this.

I have good access to the box itself by just removing the two sliding drawers and the cubby storage insert next to them for easy access. Also have access underneath the sink area.

So I just ordered small 12vdc fan (40mm x 40mm x 20mm) which I will drill a hole into the top rear corner of the box and mount the fan directly on top of this.
I also ordered a 12vdc digital temp controller that I will probably mount underneath my Solar Charge Control panel on the wall in back of the sink.

I will set the temp to probably 40 degrees or so to run the fan to circulate the warmer cabin heat in that compartment.
In the back section of the cubby storage insert I will cut/mount a 4" round vent cover to xor heat from the cabin into the space underneath the counter area.
Not sure how much difference this will make if any but total cost for all materials is under $40.
Going to replace the white 4" round vent cover that is currently installed in the step to enter the bathroom.
In back of this vent is already a fan that kicks on when the gas heater runs. I will probably install a switch for that fan also so if Im not using the propane heater and using a 120v model I can still run that fan to circulate in the valve shut off area. Good thing I checked that today as one of the connections was not connected properly and the fan would start/stop if you moved the wires. So much for QC.

Parts and materials should be here in the next week or so so I'll take a few pics and relay any pitfalls or issues that come up and then try to see how much difference this little project makes.
Stay tuned.

I have some LifeBlue batteries with internal temp monitoring. Just remember that the batteries take a long time to change temp, big thermal mass. Meaning, the battery temperature tends to be around the average of the daytime hi and low. So 28 deg low and 50 hi, your batteries are plenty warm. Further I only charge at 10 or 20percent of bank capacity around 40 degrees. As per a truck camper adventure article I installed Facon heating pads ..

This is my heating for my two 280ah LifeP04 batteries. I use a 25 watt silicone heat pad sandwiched between aluminum plate and blow air across it, kept them at 50f at 8f outdoor. They are installed in the rear seat area of my crew cab.

With the battery's already being wrapped in foam board Im sure that will help to some extent.
I also have some insulation on the outside against the exterior door to help a bit too.

Still waiting on the fan to show up but I did receive the temp controller and it's the same one used in the post by Rbertalottos doing kinda the same thing.

I ended up mounting the temp display and on/off switch in my command center switch plate in back of the sink area. There was a hr meter in place which I wasn't using so I just adjusted the hole to accept the controller and switch.I can pick up my 12vdc power from one of my lighting circuits that feed the upper cab area as they don't draw much even when their on and at night everything is pretty much off when sleeping and that's when the temps get the coldest.

Go over to the Tech section and read Rbertalotto's write up on battery box temp controls.
***UPDATE 2006 3500 SRW MegaCab pulling a 2007 fleetwood 5'er

I monitor my two 100Ah Lifepo4 batteries via their Bluetooth and a remote thermometer sensor. But I only check to make sure I’m not charging them when they are below 32F. I accept the lower capacity at those temps too.

The batteries do have low temp sensors but I watch them anyway and don’t charge. This is mainly an issue in storage. When the heater is being used they dont get near freezing.
2005 Chevrolet 3500 SRW 4X4 LB/CC D/A
2006 Bigfoot 25C9.4LB
CEK0515 and a dog

Explorer II
Explorer II
I use YoLink temp sensors (and leak sensors) in a number of places around the RV. This setup may not be for everyone since it requires a YoLink smart hub and WiFi/internet connection, but we are full-time and have an unlimited hotspot on all the time. The YoLink equipment is very affordable but, if WiFi and internet are an issue, there are plenty of good alternatives for weather units with multiple sensors available on Amazon, or at your local home improvement store. The advantage to the YoLink stuff is that there is a phone app and the hub sends me alerts if there are leaks or if the temp drops below my set point near the water utilities in the basement.

I no longer have a temp monitor in the front compartment with the batteries since I have thermostatically-controlled heating pads on two of them and the two newer batteries are the internally heated ones (all Battle Born).

U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015

I would have only insulated the outside door to the battery box cabinet than the inside temps would heat the box while the outside temps would be insulated by foam on door.

than just stick the outside pickup of a cheap inside/outside thermometer in the box and watched it.
2022 Ford F150
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Nomad II
Nomad II
I have 2 200 AH LifeBlue lifepo batteries. I ordered them with internal heating. I don't know if the batteries have activated the warming function or not. The coldest I've seen them via their Bluetooth Interface is at 47 to 54 F degrees this winter so far. Bear in mind d I haven't gone out camping yet and there's shore powered heat on in the TC. I have added 1 inch pink foam board around and under the batteries. I also have 1 inch foam board insulating from the compartment exterior door. My battery box has the back cut away for these larger batteries so they get exposure to warmer inside air. Seems to work well enough.

Explorer III
Explorer III
I don't have any of those batteries, but from what I've heard ... some monitor themselves. I'm sure there are some monitors around.

'10 Ford F-450, 6.4, 4.30, 4x4, 14,500 GVWR, '06 Host Rainer 950 DS, Torklift Talon tiedowns, Glow Steps, and Fastguns. Bilstein 4600s, Firestone Bags, Toyo M655 Gs, Curt front hitch, Energy Suspension bump stops.

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