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LiFePO4 heating pad for cold temperatures

just wondering, once you have your heaters installed, whether your own heater or built-in from a manufacture (BB, Renogy, etc.), how well does it actually heat the cell? For example are there cold spots in the cell that could be damaged because its not as warm as other spots?

I see some of you have IR scanners, just wondering if you can scan the cell and see how uniform the heat is but I guess it would be hard to see deep into the cell with a surface technique...its almost like there should be a temp sensor inside the cell but I guess that is not a good idea :)
 
That seems overcomplicated to me but I'm withholding judgements until I try mine out.

I suppose I could get off my arse and go hook it up...

Edit: you're not wrong though about disabling the system at higher temps. My plan though was to just deal with it manually.

Makes me wonder if there's a simple mechanical solution that doesn't require power to cut on at 40F.

I'm sure there is, but it might be pricey or bulky, in the case of an old school mechanical thermostat.
 
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just wondering, once you have your heaters installed, whether your own heater or built-in from a manufacture (BB, Renogy, etc.), how well does it actually heat the cell? For example are there cold spots in the cell that could be damaged because its not as warm as other spots?

I see some of you have IR scanners, just wondering if you can scan the cell and see how uniform the heat is but I guess it would be hard to see deep into the cell with a surface technique...its almost like there should be a temp sensor inside the cell but I guess that is not a good idea :)
If I had more free time I could easily pull my cells out and do this on the bench, and photograph the heat gradient.

But class starts Monday and I'll be busy until summer again.
 
This thing should be a zero power solution to turning it on or off based on ambient temperature but not top of cell temperature. Commonly available.

Screenshot_20211011-103650_Amazon Shopping.jpg

Alternatively and cheaper still is this, or similar.

Screenshot_20211011-103832_Amazon Shopping.jpg

If you really want the remote cell temp you can use a capillary therm but the tube is really sensitive to damage.

Screenshot_20211011-104046_Amazon Shopping.jpg
 
I assume that was directed at me. I'd say one extra thermostat that costs about $10 is not much complication.
Yes. But I agree that it would be necessary for automatic control.

What type of thermostat are you using? I'd prefer the system on/off one to be non-powered so it's not consuming and energy when not needed.

Are you using something like in my previous post.

Downside is the cheap mechanical ones aren't very precise.
 
This thing should be a zero power solution to turning it on or off based on ambient temperature but not top of cell temperature. Commonly available.

View attachment 68430

Alternatively and cheaper still is this, or similar.

View attachment 68431

If you really want the remote cell temp you can use a capillary therm but the tube is really sensitive to damage.

View attachment 68434
Or these, which several people here on the forum have used (you would want the 12V version, but I used this 24V version): https://www.amazon.com/gp/product/B076YD8H19
 
Or these, which several people here on the forum have used (you would want the 12V version, but I used this 24V version): https://www.amazon.com/gp/product/B076YD8H19
Yeah I have similar ones.

I just don't want it to pull any power at all when it's not needed. Even if it's milliamps it's just additional stuff that is powered on, and more time spent on means more chances to burn itself out.

The mechanical bit will shut off the digital bit entirely.
 
I'd prefer the system on/off one to be non-powered so it's not consuming and energy when not needed.
It's been a while, but I did try to measure the current of the thermostat I used, and I think it was pretty small, like maybe 50mA.

In my situation my system is in the mountains with no humans within 50 miles for about 5.5 months per year. However, the solar charge controller will be on and providing power to the heating circuit and the batteries. I also cut off the heating circuit if the battery gets below 26V, and the JBD BMS cuts off charging if the temp gets below 4°C. Anyway, I don't care much about the small current that the thermostat consumes. Won't matter.
 
It's been a while, but I did try to measure the current of the thermostat I used, and I think it was pretty small, like maybe 50mA.

In my situation my system is in the mountains with no humans within 50 miles for about 5.5 months per year. However, the solar charge controller will be on and providing power to the heating circuit and the batteries. I also cut off the heating circuit if the battery gets below 26V, and the JBD BMS cuts off charging if the temp gets below 4°C. Anyway, I don't care much about the small current that the thermostat consumes. Won't matter.
My concern isn't the power drain but the fact that those cheap controllers aren't known for having long lasting components. Last thing I need is to try to use the system and the board is shot. Or worse, NEED it to work and it doesn't.

I've got old capillary thermostats that have been in service since the 1960s at work lol

Constantly being powered on and operating should be fine for most of what's there on those boards with the exception of the display module, however even $100 automation direct controllers I've used over the years have failed on me in just a couple of years of being powered on 24/7.
 
Or these, which several people here on the forum have used (you would want the 12V version, but I used this 24V version): https://www.amazon.com/gp/product/B076YD8H19

That's the thermostat I'm using. Two of them, one on each battery, but in 12v. They work well. I prefer the digital over analog. Knowing you have it set at 35° F rather than 30° F is important. My BMS and BMV-712 agree on the temperature that the other thermostat is seeing, so I know it's accurate.
 
That's the thermostat I'm using. Two of them, one on each battery, but in 12v. They work well. I prefer the digital over analog. Knowing you have it set at 35° F rather than 30° F is important. My BMS and BMV-712 agree on the temperature that the other thermostat is seeing, so I know it's accurate.
Accuracy is important for the actual low temp condition.

Much less so for simply enabling or disabling the heater circuit.

Have you checked the actual temp seen at the heater itself with your setup?
 
This is just my gut but I think 60w might be too much for a battery that size. If it turns out to be too hot it is an easy fix to just wire series pairs and cut the wattage down.
I have similar 15w heaters and plan to run two in series. This cuts the wattage from 60w (4 pads) to 15w of heat. I tested on the bench and the pad was warm to the touch but never hot.
 
just wondering, once you have your heaters installed, whether your own heater or built-in from a manufacture (BB, Renogy, etc.), how well does it actually heat the cell? For example are there cold spots in the cell that could be damaged because its not as warm as other spots?

I see some of you have IR scanners, just wondering if you can scan the cell and see how uniform the heat is but I guess it would be hard to see deep into the cell with a surface technique...its almost like there should be a temp sensor inside the cell but I guess that is not a good idea :)
My conclusions so far is that these cells/batteries won't freeze (or develop cold-spots within them at all) quickly due to their mass.

My trailer is unheated, partially shaded (~50% of the day) and parked outside nearby. The JBD/Overkill has a low temp charging cut-off set for 0 degrees centigrade/32 degrees fahrenheit. It has been set to maintain the battery at ~ 3.45V per cell/13.8V total. Even though the temps are dipping below freezing at night the battery itself hasn't gotten below 6 centigrade. This seems mostly likely due to the batteries density overall and the fact that dense objects retain and lose heat more slowly and evenly. This indicates to me that absent a heavy load or an inherent issue with the batteries integrity itself, there is very little chance of it developing spots within the battery or cells that are much different than the cell/battery overall.
 
It's been a while, but I did try to measure the current of the thermostat I used, and I think it was pretty small, like maybe 50mA.
Just for grins I went and measured it. With the relay off, the thermostat pulls 13mA. With the relay on, it pulls 42mA. I would assume both of those would be two times higher for the 12V version.

I know @Short_Shot you said you didn't care about the power drain, but I thought some folks here would.
 
just wondering, once you have your heaters installed, whether your own heater or built-in from a manufacture (BB, Renogy, etc.), how well does it actually heat the cell? For example are there cold spots in the cell that could be damaged because its not as warm as other spots?

I see some of you have IR scanners, just wondering if you can scan the cell and see how uniform the heat is but I guess it would be hard to see deep into the cell with a surface technique...its almost like there should be a temp sensor inside the cell but I guess that is not a good idea :)
There's quite a bit of thermal mass in one of these cells. It will take a while to warm it up from the outside, but I'm certain the material will get to a uniform temperature soon after. So no, there won't be any cold spots.
 
I have similar 15w heaters and plan to run two in series. This cuts the wattage from 60w (4 pads) to 15w of heat. I tested on the bench and the pad was warm to the touch but never hot.
That was my experience as well.

Good news. I cobbled it all together real fast and plugged it in and the empty fuse location on my fuse block lit up so that's promising.

20211011_115430.jpg
 
Update the second. Turned it on. It's 23c outside right now. Set it to kick on, then set it to 25c.

It reached 25c, coasted to 26, then in less than 2 minutes was back down to 25 where I stopped keeping track because that's pretty much exactly what I expected from it.

Obviously with longer run times you will see a note overshoot but shouldn't be anything in the realm of damage.

I will now disable charge and discharge from the battery (running on external power at the moment) and heat it up a bit farther to see what kind of temperature gradient I get at the bms and battery sense respectively.
 
4E0ED351-9672-4FD3-8795-BC8F7AC55772.jpegFor a temperature controller I think an “inside the battery box” is a better way to go than an external controller, and it’s simpler. I used the following controller to turn the heater pads on and off…if I recall correctly they are about $5 a unit.

HiLetgo W1209, 12V DC Digital Temperature Controller Board Micro Digital Thermostat -50-110°C Electronic Temperature Temp Control Module Switch with 10A One-Channel Relay and Waterproof​

 
Huh. At 30c it only overshot by 0.2c lol

Must have been saturated by the time it reached cutoff.
 
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