Keeping LifeP04 Batteries At Optimal Temperature

[Buckworth]

OK. So I've order a bank of Lithium batteries, BMS, Inverter/Charger and balance charger for my new solar setup.

Now, I'm looking for solutions to keep the batteries within the appropriate temperature threshold. My idea was to run a DC thermometer/swtich that would run a dc fan or dc heating pad inside an insulated battery box...right off the batteries...but a guy at a solar shop told me that would be too hard on the batteries. He suggested a thermal block. I don't think that idea is for me as I live in a tiny shack and if my general heating solution fails, the batteries could possibly be exposed to -20+ temperatures for extended periods of time.

 

[nosys70]

first thing is to insulate your battery, because the heat exhausted by the battery could be enough to keep them warm.
then a simple 50W heating pad on an aluminium sheet should be enough if insulation is ok.

 

[snoobler]

Guy at the solar shop is probably full of hooey provided you're using a low power heating element.

Other options include small incandescent bulbs (automotive). Most of what they emit is heat.

Exposure to those low temperatures is less of a concern than charging them at that temperature.

nosys70 has a good point. In addition to that, they are a insulated thermal mass in and of themselves and react much slower to temperature changes.

 

[JoeHam]

Bury them below the frostline in a cooler under your tiny shack?

 

[Bhupinder]

if my general heating solution fails, the batteries could possibly be exposed to -20+ temperatures for extended periods of time.

With possibility of ambient temperatures going that low, you might want to consider putting some mechanism to cut-off batteries from the system first (Charging/Discharging). While news on the internet says they can operate @ sub 0 deg Fahrenheit but many threads on this form would suggest you otherwise. Even Tesla for that reason still maintains a Lead-Acid starter battery in their cars - just in case its stuck somewhere and you got to make a cold start.

You may as well do the same - a small sized Pb battery could be your secondary source to bring your primary LiFePo4 power bank up to the mark ( Use Heating Pad/ Automobile Bulb) before reconnecting them to the system again.
Second - may be an insulated yet ventilated enclosure of some kind could help your purpose.

 

[JoeHam]

Second - may be an insulated yet ventilated enclosure of some kind could help your purpose.

Why ventilated?

I would trust the cell manufacturer spec sheet on discharge below freezing but I doubt it will be an issue. Charging is the only likely problem I see.

And I am assuming LiFePO4 cells. Is this correct @Buckworth ?

 

[Bhupinder]

Why ventilated?

I would trust the cell manufacturer spec sheet on discharge below freezing but I doubt it will be an issue. Charging is the only likely problem I see.

And I am assuming LiFePO4 cells. Is this correct @Buckworth ?

To each his own, but I probably would go with Tesla and wouldn't risk putting expensive batteries to test "Low temp discharge performance of LiFePo4 batteries and its long term detrimental effects" hence the cut-off.

Slight internal ventilation would help heat circulation and distribution across the bank - both in cold and hot temperatures. But yes no air should escape out in winters.

 

[Buckworth]

Bury them below the frostline in a cooler under your tiny shack?

Thank you for the suggestion, but I live on a shale and limestone bed. Nothing gets dug.

 

[Buckworth]

With possibility of ambient temperatures going that low, you might want to consider putting some mechanism to cut-off batteries from the system first (Charging/Discharging). While news on the internet says they can operate @ sub 0 deg Fahrenheit but many threads on this form would suggest you otherwise. Even Tesla for that reason still maintains a Lead-Acid starter battery in their cars - just in case its stuck somewhere and you got to make a cold start.

You may as well do the same - a small sized Pb battery could be your secondary source to bring your primary LiFePo4 power bank up to the mark ( Use Heating Pad/ Automobile Bulb) before reconnecting them to the system again.
Second - may be an insulated yet ventilated enclosure of some kind could help your purpose.

Yeah...I have an extra 2x40w panels and 2 remaining lead acid batteries that are still good from my current/old bank. I could use those, great idea.

And yeah...people keep reminding me to insulate...I appreciate it but building the insulated enclosure is what I'm confident about. I'm after electrical solutions :D

 

[Buckworth]

Why ventilated?

I would trust the cell manufacturer spec sheet on discharge below freezing but I doubt it will be an issue. Charging is the only likely problem I see.

And I am assuming LiFePO4 cells. Is this correct @Buckworth ?

Yeah...lifep04 is in the thread title but not the body.

And yes...the BMS won't charge in the cold...but I don't want my bank to not be charging. Ever.

So far the best idea I have is running a low wattage element off a DC temperature controller I power from some extra panels and lead acid batteries.

 

[Bhupinder]

Yeah...I have an extra 2x40w panels and 2 remaining lead acid batteries that are still good from my current/old bank. I could use those, great idea.

You need not essentially have a parallel "system" for housekeeping of the primary one.
May be those additional Panels could go into the primary setup itself (where they could be utilized most) but just have some way to keep the secondary battery charged via primary bank for emergency use. There are commercial and DIY solutions available.

And yeah...people keep reminding me to insulate...I appreciate it but building the insulated enclosure is what I'm confident about. I'm after electrical solutions :D

Use of heating pads and retaining that heat with thermal insulation is the best you could do to maintain optimal working temperatures.
But more than that, automatic disconnection of LiFepo4 batteries during that period of hibernation is crucial to save them from accidental activity.
TC

 

[Buckworth]

You need not essentially have a parallel "system" for housekeeping of the primary one.
May be those additional Panels could go into the primary setup itself (where they could be utilized most) but just have some way to keep the secondary battery charged via primary bank for emergency use. There are commercial and DIY solutions available.

They are a different rating to my 100w panels, so I can't feed them into the main open voltage setup. They'd need their BMS'. Not worth the expense, IMO. Plus...I'll have 2 perfectly good flooded batteries sitting around that can be single tasked to heating/cooling. When the flooded batteries fail, I'll consider adding those panels them to the main system. That said...thanks a ton for the input.

Use of heating pads and retaining that heat with thermal insulation is the best you could do to maintain optimal working temperatures.
But more than that, automatic disconnection of LiFepo4 batteries during that period of hibernation is crucial to save them from accidental activity.
TC

That's the plan.

What is this "period of hibernation" you are talking about? If you mean extreme cold...isn't that what cold protection on the BMS is for?

Thanks again.

 

[Bhupinder]

Yes, I've heard quality BMS(s) are expected to stop charging at sub zero, but not so sure of the discharge aspect.
May be you can check how your BMS is designed/configured by running some tests initially.

 

[JoeHam]

So far the best idea I have is running a low wattage element off a DC temperature controller I power from some extra panels and lead acid batteries.

Sounds like a viable plan.

 

[toms]

I have a well insulated battery enclosure with insulated ducting connecting the enclosure to my living area. When the temperature in the battery enclosure goes out of range, an exhaust fan turns on and draws air from our living area into the battery enclosure.

I used to use a separate reverse cycle unit in the battery enclosure, but since my living area is kept at a comfortable temperature all the time, it’s more economical to transfer this air.

I use a smart switch that turns on automatically when the temperature is over 30’C, or under 5,C.

 

[DThames]

I have been wanting to do a test of this idea to get some numbers but I have not been able to yet. If you can dig down into the earth 1.5 meters or more, there is heat there that you can bring to the surface. A closed loop liquid system with a tiny pump can circulate the liquid to bring heat into the system, making up for heat lost through less than perfect insulation. The same system can be used to carry heat away from batteries.

 

[Supervstech]

I have been wanting to do a test of this idea to get some numbers but I have not been able to yet. If you can dig down into the earth 1.5 meters or more, there is heat there that you can bring to the surface. A closed loop liquid system with a tiny pump can circulate the liquid to bring heat into the system, making up for heat lost through less than perfect insulation. The same system can be used to carry heat away from batteries.

I wonder how you pronounce your username...

I’m thinking deetemmz...

 

[softdown]

You said your BMS will cut off charging if the cell temperature is below freezing. Excellent.

You made your domicile sound cold! Unfortunately super cold weather is an achilles heel of lithium battery technology.

I'm an old member of another solar board with this consensus that all agree on - Don't do lithium in freezing environs. But that board is not into lithium like this board is.

This is just an idea: Get a used aquarium of the proper size and insulate it as well as possible. Use an aquarium heater set to the desired temperature. Of course your lithium batteries will have to be in a water tight box. This could be a bad idea due to humidity levels though. Have not studied it thoroughly. Some lithium chemistry's react poorly to humidity. You could use a rubber container if the heater didn't make contact. It is easier to keep water warm than air - in some respects.

I abandoned my outdoor lithium cell adventures being in a region where -30F is no surprise. Didn't fancy 20 miles in a 10F blizzard with three dogs. I've done something like that - my fingers turned purple for days and the skin sloughed off. Enough on that.

 

[Bhupinder]

I wonder how you pronounce your username...

I’m thinking deetemmz...

I recon may be 'Dee Thames', like the thames of london ?.

 

[DThames]

I wonder how you pronounce your username...

I’m thinking deetemmz...

Dan Thames (thAmes, like James with TH in front, southern US)