LiFePO4 heating pad for cold temperatures

[hour]

This has me thinking. I wonder how complicated and effective it would be to use an aluminium frame to thermally connect all the batteries to heat and/or cooling sources? Heat pad on one side of the bank, finned heat sink with fan on the other?

I don't know if it can be done without cooking the one that's in most direct contact... and it'd be a shame if the fan was mandatory to achieve that and for some reason failed.

That's the same thing I'm dealing with and can't for the life me google an answer to, controlling the temperature of the pack (approximately) without roasting them from a bottom heat source. I can keep the alum floor 70*F all day but I'm not terribly interested in the floor temp, more so the BMS and the temp from its probe. But to apply heat based on that is to make the floor potentially a frying pan

 

[ianganderton]

I don't know if it can be done without cooking the one that's in most direct contact... and it'd be a shame if the fan was mandatory to achieve that and for some reason failed.

That's the same thing I'm dealing with and can't for the life me google an answer to, controlling the temperature of the pack (approximately) without roasting them from a bottom heat source. I can keep the alum floor 70*F all day but I'm not terribly interested in the floor temp, more so the BMS and the temp from its probe. But to apply heat based on that is to make the floor potentially a frying pan

Gentle well dispersed heat won’t cause a frying pan effect. Batteries only need to be above freezing so as long as there is a decent thermostat with a backup it will be fine.
An aluminium plate between the heat pad and batteries will provide the required even heat distribution and eliminate hot spots

 

[offgriddle]

I like the metal ammocan idea because much of the material inside of the can is flammable. For heat disapation during warm, sunny weather I would mount the SCC outside of the can unless I was trying to protect it from damaging physical elements.

 

[ytwytw]

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It says on low settings it’s about 32C
Since it’s power by usb, I think it would be easier to build and use Home Assistant to control

It clams it’s also waterproof, probably it can used in outdoor but definitely some kinda cover is required

 

[offgriddle]

Jeepers creepers making heat is one of the, if not the, number one most energy consumptive functions to perform using electricity. It's too bad that we have to use the electricial energy stored in our lifepo's to warm our lifepo's so they will be capable of receiving and storing electricial charge. It's a a bummer. If they can put a huperson on the moon then ...

 

[brassmonkey001]

Jeepers creepers making heat is one of the, if not the, number one most energy consumptive functions to perform using electricity. It's too bad that we have to use the electricial energy stored in our lifepo's to warm our lifepo's so they will be capable of receiving and storing electricial charge. It's a a bummer. If they can put a huperson on the moon then ...

Yeah, it's very inefficient but I'm hoping that the energy that goes in will outweigh the energy used to heat the batteries up.
I've ordered a heat pad and a temperature controller with the intention of setting them up to keep the batteries between 5-10 degrees C.

 

[offgriddle]

Yeah, it's very inefficient but I'm hoping that the energy that goes in will outweigh the energy used to heat the batteries up.
I've ordered a heat pad and a temperature controller with the intention of setting them up to keep the batteries between 5-10 degrees C.

Good luck, let everyone know what the results if you can, thanks.

 

[hour]

Yeah, it's very inefficient but I'm hoping that the energy that goes in will outweigh the energy used to heat the batteries up.
I've ordered a heat pad and a temperature controller with the intention of setting them up to keep the batteries between 5-10 degrees C.

FWIW I'm not finding it to be that big of a battery drain, though tonight will be a more proper test (low of 24*F and was below freezing at like 530pm)

For days in the 50's with some mediocre winter sun and lows around freezing, I've found my ammo can enclosure with < 1/4" thick foil-foam insulation to not dip below 50 averaged between bms and it's probe, until about 3am.

Then the floor heats til the average of the two sensors is 50*F again or the floor hits 105*F. It'll maintain 105*F in that case until the probes are back up to temp. It runs for just a few minutes at a time and only has run once or twice between 3am - 8am for the last nearly two weeks. And never dropped below set temperature. This is dialed in to only output around 30w, though the heat pad could run at over 120w.

First heat cycle is going to cut on soon tonight, it's 51*F average between two sensors.. the floor is 48*F. So once that 51 hits < 50.5, the process begins. I'm sitting with a full (188.8 of 190ah) battery so it'll be interesting to see what I wake up to with tonight being cold, and cold early.

 

[electric_banana]

I learned about the Battle Born heating pad last summer, before they released it. I was surprised to see it wind up being so relatively expensive. That and the internal bluetooth interface were the reasons I wound up buying a LifeBlue with the built in heater.

 

[Buzzard Bait]

There should be a dump mode so when the bms senses temps below 34F, charge power switches to heating elements to maintain pack temp for charging.

I really like this idea. I was thinking I would disconnect the SCC from the batteries with a thermostatic controlled relay, but switching the power from batteries to heat would be less wasteful. Thank you for this post.

 

[SCClockDr]

Or 2 controls

1. Divert partial power to heat @ say 38°F
2. Disconnect battery @ say 35°F & continue heating if the SCC will tolerate no battery or disconnect the panels period.

 

[Buzzard Bait]

Or 2 controls

1. Divert partial power to heat @ say 38°F
2. Disconnect battery @ say 35°F & continue heating if the SCC will tolerate no battery or disconnect the panels period.

You sir are becoming a very helpful guide. I was hoping I could move the load from batteries to the load of a heat source until a thermostat told the relay to go back to batteries. Now you have me wondering if my SCC could handle the switches. I will be using an Epever 6415AN it has a temp sensor, but I believe the temp sensor works on the upper range of temps to reduce the flow of charge when things get hotter. I do not believe it will stop charging when it gets cold. If you think the switching to a dump load, and back could hurt this SCC I don't think I will risk it.

 

[SCClockDr]

@Buzzard Bait you are correct, the SCC temp sensor is charge current related for LA chemistry.
There is a digital F temperature control with red & blue registers & relay you could program with the mode & temp you wanted. I'd recommend cooling mode with the relay closed above 38°F or your choice. That way if power is lost for any reason you interrupt the PV circuit.

 

[SCClockDr]

LM YN DC 12V Digital Thermostat...

 

[Buzzard Bait]

@Buzzard Bait you are correct, the SCC temp sensor is charge current related for LA chemistry.
There is a digital F temperature control with red & blue registers & relay you could program with the mode & temp you wanted. I'd recommend cooling mode with the relay closed above 38°F or your choice. That way if power is lost for any reason you interrupt the PV circuit.

That was my first plan, but then there was that switching idea that looked sooo good. I don't want to ruin my SCC switching from heating to batteries. So I am back to what you have just suggested, but it is nice to know I am not the only one with this idea. Thank you for sharing.

 

[Stupid Monkey]

Had a read through this as that was one of today's research topics.

It would seem that many have the same questions, and most of these solutions are for keeping either

1) RV water tanks from freezing (generally on at 0/1 degree and off at 5 degrees celcius)
2) Keeping reptiles warm. (Generally thermostatic for 20-30oC 70-85F, therefore needing a controller)
3) Spend silly money on a battle born mat

Are we standing Alu cased Li cells direct on the mats? or wrapping mats round them, or do we need an air gap around the cells, and the mat heating the air for less hot spots and 360 degree heating of the cells ?

Alu cased cells are going to be the most problematic for this, just my luck, but I do wonder if I need to worry although we do have down to -10c sometimes generally winters here are mild. Although March 2018 was consistently below zero I can always have a manual shutoff and if I'm in it and using it for work then there will be heating in the living area. ...... but then it just needs 1 charge at sub zero and the batteries are dead, so as my BMS doesn't have LTD.

Or cancel my Daly BMS order (still verifying my account at Ali Express) and get that other one Will has just found and posted .........

 

[Stupid Monkey]

Or cancel my Daly BMS order (still verifying my account at Ali Express) and get that other one Will has just found and posted .........

Done this instead ....

 

[astronom]

Apart from resistive pads, I have been looking at a heating/cooling system based on Peltier elements, it should hopefully be more efficient than resistive heating (the Peltier element basically acts as a mini heat pump), plus it can do both heating and cooling in one shot to also help keeping the battery fresh during summer. With a well insulated battery case I hope it won't draw too much power. We can start a thread around that if more are interested. Don't have the parts yet but I will try something with some stuff from AliExpress.

 

[Max Bender]

Will,
I just found these lithium ion iron phosphate batteries online. I know "nothing"about them, but was hoping you could do some testing on them and see what you come up with

65Ah 12V (12.8V) Lithium Iron Phosphate (LiFePO4) Smart Battery

Miller Tech lithium batteries are lightweight, non-toxic, and long lasting compared to traditional lead acid batteries. Each battery has a built in battery management system (BMS) which provides safety and proper charging/discharging. Each battery also features a built in state of charge (SoC)...

ldsreliance.myshopify.com

Thoughts?

I'm not speaking on Will's behalf but here's my two cents worth: LDS Reliance lists the general operating temperature of a LiFePo4 but not saying one way or the other if their battery has low temperature protection. And $539 for a 65aH battery?? No thanks... too expensive - not worth buying, especially for just testing the thing.

 

[grizzzman]

Apart from resistive pads, I have been looking at a heating/cooling system based on Peltier elements, it should hopefully be more efficient than resistive heating (the Peltier element basically acts as a mini heat pump), plus it can do both heating and cooling in one shot to also help keeping the battery fresh during summer. With a well insulated battery case I hope it won't draw too much power. We can start a thread around that if more are interested. Don't have the parts yet but I will try something with some stuff from AliExpress.

I picked up a Peltier cooler for cheap to test out. I think performance improvements including insulation will work. In my case, I have heating figured out restive heat under an aluminum plate.