4PCS Silicone Heater Mat, Icstation Rubber Heating Mat 12V 25W Electric Blanket Flexible Mat Constant Temperature 80X100mm

Lithium Iron Phosphate (LFP) batteries are terrific but can only be charged when they are above freezing. In cold-weather camping, this can be a problem as well as an RV in storage for long periods in cold climates. I have used these pads with two different thermostats and they work very well. I attach two of them in series because I found they got too hot when used individually. I used a Morningstar Relay driver to drive a small cheap relay for one set up. That relay driver can be set up to run multiple sets of pads so I had one pad set turning on at 42F and the other turning on if the battery temp got to 38F. Usually, only one set turned on and it worked perfectly to keep a large (430Ah) LFP battery comfortably above freezing.A less expensive option (Morningstar Relay drivers are over $100) I've also used are snap disk thermostathttps://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_2?crid=1AKM94LJTK81Q&keywords=snap+disc+thermostat+switch+on+at+35&qid=1671214245&sprefix=snap+disc+thermostat+switch+on+at+35%2Caps%2C189&sr=8-2wired in series with the pads and hooked to the battery that is being warmed. They allow power to flow to heating pads when ambient temp reaches 35F and turn pads back off when temp climbs above 45. For $14 for the thermostat plus around $22 for 4 pads and a bit of wire you get an effective battery warmer that actually works.

Bat(s) in insulation w 4 series heaters, surface temp between heater & bat 123F—OK for bat ABS housing durability. Open air heater test temps are lower. Wiring 1, 2, or 3 in series generate higher temps (be careful!) than 4. Is 165F OK for ABS?Use two methods to control heaters in case one fails on!!! Like 2 snap disc thermostat (clean simple) (Amazon, more options direct from mfgr), go with 40F ON since tolerance is +/-5F. or 1 snap disc (w higher than 40F ON) & temp controller.Nice design: Search for DIY Battery Heater for Li-Ion Batteries, has Test data in replies.

a lil too small but will work. have to do some changes to the wiring design.

I'm heating a NOCO NLP20 LiFePO4 battery that sits on the tongue of my trailer. These four pads are wired in series to get a "low and slow" heat for the battery. I tested three pads in series and measured 88.5°F on a single pad. Adding the fourth pad lowers the temperature to right about where I want it.I paired the heating pads with a Bayite DC 12V Fahrenheit Digital Temperature Controller set to keep the battery in the 40°F to 50°F range.I went with this approach to keep the battery warm, but never hot.

We have had them for awhile now. One developed one small hole. Otherwise all have functioned as claimed.

Purchased the four-pack of 80x100mm 12v 25w heating pads to heat a 200ah lifepo4 prismatic 4s cell pack. They seem well made with 8-10" long silicone wires. Applied the pads, in pairs, directly to the cells on the two largest sides of the pack using aluminum HVAC tape (cell/tape/pad/tape). With the 4 pads wired in parallel, they got too hot (160-170f) and drew too much current (8a) for our particular application. To get the individual pad temps down to 110-120f and total current for all 4 pads down to 2a (24w), we wired them in series/parallel. As a test placed the cells outside overnight for 8 hours inside an uninsulated plastic Group 24 battery box (with a top cover). Temps dropped from 8f to 0f throughout the evening/morning. Surprisingly, the 4 pads produced enough heat to keep the cells at 62f. Very pleased with these pads.

I use these with my solar to keep my shop from getting to cold and they have preformed great

Mostly leaving a review to corroborate what others on here have already said. Took some pictures to get an idea of expected amp draw and temperatures. I am using these with a thermostatic relay to keep a lithium battery warm. I will be using them linked in series. It may seem counterintuitive, but hooking in series reduces the amp draw on the battery as well as reducing the heat output. You can see in the pictures when single these get quite hot 250-260°F, but in series they were averaging 120 to 130°F. They come up to temperature quite fast, just a few seconds and there's a noticeable difference. Also these tests were done in a 30° garage. Only took about 1-2 minutes for them to reach their full temperature. Hooking three in series yielded about 0.7 A draw and a 71.5°F average of the three. One note is all were within a half degree of each other which means internal resistance of these units seems to be very consistent.