LIfepo4 charging in winter.

[somawheels]

I am considering buying Lithium batteries for my offgrid home where I live permanently.
Here in the UK, winter temperatures can go bellow 0 degrees, in which case charging the battery would ruin the battery.

The system (inverter-charger and solar charger) is located in an un-heated shed.

Does anyone know of a possible solution to this problem?

[Ampster]

How often and how long is it at those temps. Is that temperature C or F. Do you use a generator for power?

[somawheels]

It is rare for the temp to be bellow 0. Some years it does not get this cold, some years it could be between 0 and -12 degrees for a couple of weeks.

I considered using a thermostat heater, however, im not sure this is a good idea because well.. what if the heating system fails? what if there is not sufficient power to run the heating system? I do have a generator, so I could disconnect the battery, then heat up the batterey via generator power, then re-connect batterries. However this is a very risky, impractical solution.

Edit: on second thoughts, perhaps I could setup two heating systems - one which runs of an external batterry, and one which runs of the inverter/main power. Does that sound OK?

[Ampster]

Two systems are better than one. Can you use the heat from the generator for one system? Can I assume the temperature is Celsius?

[somawheels]

Indeed the temperatures are in Celcius. The generator is in another separate shed unfortunately.
I am thinking I could wrap the battery in heating mats and something insulative. I am thinking of using low power heating elements with a thermostat. How-ever, I am unsure how much heat and electricity I would need to keep the battery above 0 degrees in -15 degree weather.

[PNjunction]

If you want to wing it, you do what some motorcycle LFP guys do - put a small load on the batts to warm them up internally, and then charge. Most often, they'll turn on the headlamp for 30 seconds, and then fire up. That way their alternator doesn't just burn up the LFP's that aren't rated for sub-zero temps.

Still, that's a risky business between an motorcycle LFP and a whole-house system!

Considering the initial cost of the system, the extra heater etc etc - it may not be worth it.

The only successful diy solar systems in the UK or elsewhere with cold temps, and limited sun hours was the use of PURE-LEAD agm's. With a very large solar array. Low internal resistance from the pure-leads can take the large array up to 0.5 to 1C if you can afford it. And the agm's don't freeze.

Try LFP if you want. But will it be your *first* venture? Then the risk of wallet expansion on a system you change later anyway may be an eye opener if you make a mistake in your power budget and repurchasing more LFP all over again.

If the need is large, instead of tacking a bunch of Optima / Odyssey / other pure-leads together, there are some big boys like Lifeline pure-leads I believe.

Keeping them from walking down in capacity if the issue - from not getting a truly decent full charge. Once every two weeks or so, you can use a gas-generator for bulk, and let the sun, such as it is, do the rest. More often if you can afford the petrol cost.

Old-school, but it STILL works!

[NEOH]

I am considering buying Lithium batteries for my offgrid home where I live permanently.
Here in the UK, winter temperatures can go bellow 0 degrees, in which case charging the battery would ruin the battery.

The system (inverter-charger and solar charger) is located in an un-heated shed.

Does anyone know of a possible solution to this problem?

Can you put the battery inside a box made of three layers of 2" Solid Foam Insulation?
Add an electronic thermostat and very low wattage heater, to keep battery above freezing.
This has been done successfully with lead acid batteries.

Add a power vent if you need to cool it down, in the summer.

[Mike90250]

it's even worse ! Below 40F. ( 4.5C) power output starts to fall off, and you need to be careful recharging. You usually don't get the full package of data sheets till you purchase the battery and start filling out the warranty registration forms.

But foam sheeting and a modest blanket heater should keep them warm enough IF you lay out the heaters well.

[somawheels]

I see. I am Considering Lithium batterries, because I think they may be more suited to small offgrid systems in UK weather.

I have had lead acid Batteries once before, however they only lasted 3 years.
I think this is mainly due to too many deep discharges and too little charging. However, I have read Lithium Batterries are not supposed to suffer much from undercharging and over draining, and are more efficient, so they seemed like a good idea, as they should last much longer than lead acid in a system like mine.


I do have a generator, however I dont think my generator charger worked properly. I am planning to upgrade this.
My lead acid bank was was a 400AH 24V batterry bank. I have 1.5kw of solar panels, which is no where near enough to keep the lead acid batteries in good health.

[somawheels]

it's even worse ! Below 40F. ( 4.5C) power output starts to fall off, and you need to be careful recharging. You usually don't get the full package of data sheets till you purchase the battery and start filling out the warranty registration forms.

But foam sheeting and a modest blanket heater should keep them warm enough IF you lay out the heaters well.

Im not sure what you mean mike.

Have any of you guys had Lithium offgrid systems before? What was your experience with them like?

[NEOH]

Im not sure what you mean mike.

Have any of you guys had Lithium offgrid systems before? What was your experience with them like?

Relion has a "Low Temperature" LiFePO4 battery that works down to -20C and -2F.
It has an internal heater.
Add 6" ( 3 x 2" layers ) of solid foam and you will have no problem keeping the battery warm enough to recharge.
Charging warms the battery.

[Ampster]

.....

Have any of you guys had Lithium offgrid systems before? What was your experience with them like?

I have had some Lithium experience with a EV conversion I did 7 years ago and owned or leased 5 different production EVs in the past 7 years. I don't have any offgrid experience but have also had good luck with two hybrid grid tie systems using Lithium batteries. I agree with your assessment that they last longer if you conservatively charge and discharge them. They also do not need to be fully charged all time like lead acid. Most of the knowledge and experience on this forum is with lead acid. Although I would guess that many have a cell phone and laptop that has worked well for them.
I have not however had any cold weather experience. If you can find a solution to the few times a year your weather is at or below zero Celsius they could be cost effective for you. Everything in life has risks, it is how you manage those risks that matters.

[somawheels]

Relion has a "Low Temperature" LiFePO4 battery that works down to -20C and -2F.
It has an internal heater.
Add 6" ( 3 x 2" layers ) of solid foam and you will have no problem keeping the battery warm enough to recharge.
Charging warms the battery.

Relion batterries are nice, but unfortunately, are way far more expensive than other LiFePO4 batterries.
If only there were lithium batterries that automatically refused to charge at low temperatures. This way there would not be any risk of accidentally ruining the battery.

[Mike90250]

Im not sure what you mean mike.

Have any of you guys had Lithium offgrid systems before? What was your experience with them like?

i have cleaned up 2 burned out Li systems and both were replaced with lead acid.. I mean flames and burned sheds, nearly a forest fire.
Li batteries are not something to play with unless you understand all the ways they can fail catastrophically, and take proper steps to avoid that.


https://batteryuniversity.com/learn/article/safety_concerns_with_li_ion

https://batteryuniversity.com/learn/article/safety_concerns_with_li_ion

Incorrect uses of all batteries are excessive vibration, elevated heat and charging Li-ion below freezing. (See BU-410 : Charging at High and Low Temperature.) Li-ion and lead acid batteries cannot be fully discharged and must be stored with a remaining charge.

https://batteryuniversity.com/index....w_temperatures

[FONT=Arial]Li ion can be fast charged from 5C to 45C (41 to 113F). Below 5C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode .

[somawheels]

i have cleaned up 2 burned out Li systems and both were replaced with lead acid.. I mean flames and burned sheds, nearly a forest fire.
Li batteries are not something to play with unless you understand all the ways they can fail catastrophically, and take proper steps to avoid that.

Oh dear, thats terrible. Were these lithium systems using Lithium Iron Phosphate batteries? I had read they were relatively safe compared to lead acid.