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LiFePO4 heating pad for cold temperatures

What thermostats are you guys using? I got these below but three of the four have failed. Looking for something more reliable.
 

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constantspeed said:
I bought this one as well, but how are people mounting this unit? The other cheap little units come with the case assembled from little jigsaw puzzle pieces of acrylic, but this one is naked.
Click to expand...
I used 1 long screw with 3 nuts per corner (4 screws, 12 nuts) to mount it to an aluminum bracket I made.
 
constantspeed said:
The "Inkbird" is an AC powered unit. The little ones just mentioned are DC powered. Depends on your application situation.
Click to expand...
My apologies.....it wasn't an inkbird.....that is the brand that is used in my Momentum Toy Hauler that controls the freezer compressor on the JC Refrigeration 12VDC twin compressor mod.....so YES, Inkbird DOES make a 12VDC model.

Here is the one that I used on the heating pad install for my battery box heaters.

Here is the 12VDC Inkbird for the 12VDC freezer compressor.
T1Hy2y6.jpg
 
Last edited:
Hi, my apologies if this has been suggested already. After going through about 18 of the 36 pages of replies here, I decided to just go ahead and describe the dead-simple, cheap and effective battery warming system that I used last winter.

I have an off-grid cabin here in Bethel, Vermont. The cabin temperature frequently reaches subfreezing temperatures for several days/weeks in a row.

Electrical system consists of four 360W solar panels, two Growatt SPF 3000TL LVM-ES inverter/charger/MPPT controllers in parallel (120v). Batteries are one Jakiper 48v 100ah lifepo4 running in parallel with four series-connected 12v 200ah AGM batteries.

I built an easily removable enclosure, similar to the engine covers used with inboard speed boats - 2x4 frame, 1/2" OSB and interior lined with 1 1/2" rigid foam.

In the box I have a $20 120v electric baseboard heater thermostat like this one connected to the inverter that controls a 120v socket. Heating pad plugged into that and lying on top of the lithium battery. Alternatively, one or two (for redundancy) low wattage (~15w) light bulbs. Not too close to the thermostat. Have thermostat set to turn on when temperature in box drops below 40°-50°F.

An afternoon's work, $100 or so in parts and materials, simple, reliable. Little technical expertise needed. In the spring, take the box off and stick it in a corner.
 
Markboettcher said:
Hi, my apologies if this has been suggested already. After going through about 18 of the 36 pages of replies here, I decided to just go ahead and describe the dead-simple, cheap and effective battery warming system that I used last winter.

I have an off-grid cabin here in Bethel, Vermont. The cabin temperature frequently reaches subfreezing temperatures for several days/weeks in a row.

Electrical system consists of four 360W solar panels, two Growatt SPF 3000TL LVM-ES inverter/charger/MPPT controllers in parallel (120v). Batteries are one Jakiper 48v 100ah lifepo4 running in parallel with four series-connected 12v 200ah AGM batteries.

I built an easily removable enclosure, similar to the engine covers used with inboard speed boats - 2x4 frame, 1/2" OSB and interior lined with 1 1/2" rigid foam.

In the box I have a $20 120v electric baseboard heater thermostat like this one connected to the inverter that controls a 120v socket. Heating pad plugged into that and lying on top of the lithium battery. Alternatively, one or two (for redundancy) low wattage (~15w) light bulbs. Not too close to the thermostat. Have thermostat set to turn on when temperature in box drops below 40°-50°F.

An afternoon's work, $100 or so in parts and materials, simple, reliable. Little technical expertise needed. In the spring, take the box off and stick it in a corner.
Click to expand...
Simple is best
 
I have been working on something called a GAHT ground air heat transfer system. They tell me that six feet down the ground stays at a pretty constant 60 degrees, so I dug a circular trench to lay some thin-walled corrugated 4" poly pipe from the floor of my well house through the trench back to the well house ceiling. It should have a thermal cycle exchange to moderate the temps warming in the winter and cooling in the summer. This will not only be good for my batteries but help keep the plumbing from freezing. As I near completion of this project I realize If the only thing I wanted to keep at a constant 60 degrees a single shaft for battery storage might have been a better option or at least a lot less digging.
 
I think that I have read every page on this thread on heating batteries. My question is a bit different. I plan to parallel a 17s 280 ah LFP battery with 16 L16 FLA batteries (2p 48v) but that's a subject in a thread on that topic. My question is about long term storage (6 months) of an LFP battery in temperatures as low as -40 degrees C. It is in a remote cabin and is difficult or even impossible to get to during the winter. My plan is dicharge the LFP battery to 50% SOC and then turn it off for the winter. I will leave the charge controller on with the FLA batteries. While I could likely rig up a heating system from the FLA bank, it does introduce some risk to the FLA'S. I have 1500 watts of "winter" panels, meaning tilted at about 75 degrees to shed snow. The batteries have survived 9 winters unattended and they pretty much just sit there and float most days. Their capacity, however, in very cold weather will be very low.
I am interested in any comments and/or ideas from the experts on this forum. Should I just leave the LFP battery off all winter and hope? Should I keep them somewhat warm? Should I keep all the batteries somewhat warm to increase the FLA bank capacity? Has anyone stored a LFP battery for that long and how did that work out? Like I said, just looking for comments and ideas.
 
bfitzgerald said:
I think that I have read every page on this thread on heating batteries. My question is a bit different. I plan to parallel a 17s 280 ah LFP battery with 16 L16 FLA batteries (2p 48v) but that's a subject in a thread on that topic. My question is about long term storage (6 months) of an LFP battery in temperatures as low as -40 degrees C. It is in a remote cabin and is difficult or even impossible to get to during the winter. My plan is dicharge the LFP battery to 50% SOC and then turn it off for the winter. I will leave the charge controller on with the FLA batteries. While I could likely rig up a heating system from the FLA bank, it does introduce some risk to the FLA'S. I have 1500 watts of "winter" panels, meaning tilted at about 75 degrees to shed snow. The batteries have survived 9 winters unattended and they pretty much just sit there and float most days. Their capacity, however, in very cold weather will be very low.
I am interested in any comments and/or ideas from the experts on this forum. Should I just leave the LFP battery off all winter and hope? Should I keep them somewhat warm? Should I keep all the batteries somewhat warm to increase the FLA bank capacity? Has anyone stored a LFP battery for that long and how did that work out? Like I said, just looking for comments and ideas.
Click to expand...
I like the constant 60 degree idea above by storing them in the ground. I would be very concerned if my bank went down to -40c. Not sure if anyone tested storage at that temp, but freezing and thawing the cells would most likely have a negative affect on lifespan.
 
Sanwizard said:
I like the constant 60 degree idea above by storing them in the ground. I would be very concerned if my bank went down to -40c. Not sure if anyone tested storage at that temp, but freezing and thawing the cells would most likely have a negative affect on lifespan.
Click to expand...

There is no water in the cell, so should not be an issue. There is research that shows storing at those low temperatures slows down calendar ageing:

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...
www.solacity.com www.solacity.com

Personally, I've had my pack sit at -20C for months and have not noticed any issues.
 
Last edited:
Markboettcher said:
Hi, my apologies if this has been suggested already. After going through about 18 of the 36 pages of replies here, I decided to just go ahead and describe the dead-simple, cheap and effective battery warming system that I used last winter.

I have an off-grid cabin here in Bethel, Vermont. The cabin temperature frequently reaches subfreezing temperatures for several days/weeks in a row.

Electrical system consists of four 360W solar panels, two Growatt SPF 3000TL LVM-ES inverter/charger/MPPT controllers in parallel (120v). Batteries are one Jakiper 48v 100ah lifepo4 running in parallel with four series-connected 12v 200ah AGM batteries.

I built an easily removable enclosure, similar to the engine covers used with inboard speed boats - 2x4 frame, 1/2" OSB and interior lined with 1 1/2" rigid foam.

In the box I have a $20 120v electric baseboard heater thermostat like this one connected to the inverter that controls a 120v socket. Heating pad plugged into that and lying on top of the lithium battery. Alternatively, one or two (for redundancy) low wattage (~15w) light bulbs. Not too close to the thermostat. Have thermostat set to turn on when temperature in box drops below 40°-50°F.

An afternoon's work, $100 or so in parts and materials, simple, reliable. Little technical expertise needed. In the spring, take the box off and stick it in a corner.
Click to expand...
Are you running 1 inverter for each set of batteries?
 
Sanwizard said:
I like the constant 60 degree idea above by storing them in the ground. I would be very concerned if my bank went down to -40c. Not sure if anyone tested storage at that temp, but freezing and thawing the cells would most likely have a negative affect on lifespan.
Click to expand...
I'm sitting on the Canadian Shield. Mostly granite and anywhere you could dig a hole would probably fill up with water. I like the idea though.
 
upnorthandpersonal said:
There is not water in the cell, so should not be an issue. There is research that shows storing at those low temperatures slows down calendar ageing:

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...
www.solacity.com www.solacity.com

Personally, I've had my pack sit at -20C for months and have not noticed any issues.
Click to expand...
Great article, thanks for bringing it to my attention. With insulation I can probably keep the battery around -30 C as well as reduce quick temperature variations. I think that I'm most likely to shut the battery down and cover it up.
 
Sanwizard said:
I like the constant 60 degree idea above by storing them in the ground. I would be very concerned if my bank went down to -40c. Not sure if anyone tested storage at that temp, but freezing and thawing the cells would most likely have a negative affect on lifespan.
Click to expand...
I think it would be a rare for my part of NW Oklahoma to get down to -40C. Here the late fall winter, and early spring nearly always drop below the safe charging temps. The heat my batteries in are exposed to in the summer is nearing that mean old 113F. The depth of the shaft to accomplish a constant 60F would be different in different areas. What I meant to do in my earlier post was to poke a little fun at myself. Digging that circular trench was no easy project. The part where I dug this huge excavation where a smaller shaft would have been enough to protect the batteries., and that would have been sooo much easier. I do not feel very smart. I should have looked at this project from more than one point of view.
 
S Davis said:
I work in HVAC and radiant floor heating
Click to expand...
I was thinking to make someting like the pictures you posted but I need to make it light enought to not encrease the weight too much (best idea was an heating cable drowned in concrete as box or floor for the cells).
 
Alkaline said:
what was the mode of failure?
Click to expand...
They just let the magic smoke out, I saw one of the two installed start smoking and quit. I replaced it as I purchased four of them and it burned out in short order. I am trying a different one now. The one good thing I figured out is if one of the heaters fail the second one will keep everything from freezing.
 
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