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Heating for lifepo4

Shosty

New Member
Joined
Jul 23, 2024
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2
Location
Ukraine
I'm from Ukraine and getting ready to build a 8s lifepo4 battery for backup power supply for my home.
I ordered cheap and loud solar inverter from aliexpress, and because it's loud i'm planning on putting it to room outside house.
Because of environment temperature is kind of mad and may variate from -30 defree celsius (-22f) to +35c (104f) i expect lower temperature in this room to be about -5c (23f), maybe -10c in worst cases.
I'm gonna build insulated box for battery, and ordered BMS with heating function, and heating pad (one for bottom, a bit smaller that battery, battery is 35*28 sm, heating pad is 30*25sm).
1) Do you think that will be enough?
2) Most important, i cannot find any documentation about heating function. BMS has red and black wire on heating connector, and several green wires connected to one connector. How to connect it? Like green to heating pad negative and heading pad positive to battery positive?
What is red and black wire stands for?
And i've seen some video where some guy connecting it through relay, what the purpose of this?
3) Is ot okay if inverter won't have any insulated box or like that, and will it work ok on cold enviroment (the manufacturer declares that range is -10 to +50 c (14 to 122f)

Thanks very much for help.
 

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1) Do you think that will be enough?
I do not. I would double it
And i've seen some video where some guy connecting it through relay, what the purpose of this?
The Jk BMS ony heats when its charging from solar. A relay would enable external control to use the battery to start warming earlier, before solar, and capture more solar if the battery didnt heat up enough in time.

Example: Battery is 0F it starts heating at 7 am with all of its 65 watts. If the battery was already warm you would be getting 200 watts. 140 watts wasted because the battery will not charge at all if it is cold and cant use more power than the heaters, resulting in nothing but loss.

Your climate and mine is similar.
 
I do not. I would double it

The Jk BMS ony heats when its charging from solar. A relay would enable external control to use the battery to start warming earlier, before solar, and capture more solar if the battery didnt heat up enough in time.

Example: Battery is 0F it starts heating at 7 am with all of its 65 watts. If the battery was already warm you would be getting 200 watts. 140 watts wasted because the battery will not charge at all if it is cold and cant use more power than the heaters, resulting in nothing but loss.

Your climate and mine is similar.
So, the problem is in this system i'll not only use it for solar panels charging.
Here in Ukraine i'm out of power about 10 to to 16 regularly, sometimes 20 hours per day.
Lets imagine scenario, i was out of power all day long, and at the night i have supply for 3-4 hours. In this case i also want it to charge (from grid) as much as possible. So in general, at the moment when power supply is so unstable i want it to always be able to take charge.

Is there any setting in JK bms that allows to enable some mode when battery is always over 0 degree celsius?
 
Is there any setting in JK bms that allows to enable some mode when battery is always over 0 degree celsius?
Not that I'm aware of.
That is where the relays woud be used.


This is a challenging situation.
There is no way for me to know how much power you would need to keep the batteries warm enough all the time
 
As I mentioned, your climate and mine are very similar.

I would dig a very large hole 8×6x6 feet, four feet deep. Put a very insulated shack in the hole. Insulate again, as much as you can afford. I would have 12 DC incandescent light bulbs on switches that I could remote control and also automate depending on temp. This would be in addition to the battery warmers on a relay and connected to wifi for automaton.

You will need the temp to be at least 10F or so before I would turn on the inverter.

The problem here is that you could be spending 5000 watts per day keeping everything above freezing.

You would need a very large battery bank to make this worth it.

If I had a better idea than this, my system would be outside.

Oh, the reason to get 4 feet deep is to be past the frost. That way the earth will help you stay warmer. I think anyway.

I know you wouldn't have wifi with the power down. Just saying what my plan was to get my stuff outside.
 
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I don't have this issue in Florida but when I lived up north in an apartment I loved my warm waterbed.

How about a waterbed heading pad with thermostat? I can imagine that 48VDC would still produce some heat. Get a mechanical pressure thermostat.
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