question

Ivar Eisma avatar image
Ivar Eisma asked

Cold weather lifepo4, or back to AGM.

I have small system with a Redodo self heating LifePO4. It's supposed to use build in heatpads to get the cells above 5 celcius to charge, and should be able to discharge up to -20. It doesn't.

I keep running into problems, the battery shuts off when cold and doesnt start back up untill I warm it and recharge manually. The manufacturer is pretending they don't understand what's going wrong, but I'm doing nothing wrong it's just not a properly designed BMS.

I know people use heated boxes and other DIY stuff, but I'm not willing to go that route. It's an unheated cabin, and I'm away for over a month very often. Temperatures are sometimes -20 celcius inside, not much colder.

I think I'm going back to AGM. I'm not worried about shorter lifespan, or reduced capacity in cold temps compared to Lifepo4. I can just buy a larger pack. I just need a system that charges and stays charged when I'm not there so I can use it when I arrive. Is going back to AGM a dumb idea? It works fine in my car in those temps, I see no reason why it would not work in the cabin.

AGM Battery
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

6 Answers
janieronen avatar image
janieronen answered ·

Our area cabins are also in same temperatures during winter and AGMs are in big trouble without proper isolated box. What we do is bury battery case in a pit / cellar to avoid extreme temperatures. That helps also in summer season with too high temps which specially are bad for lead batteries.

With heated LFPs have often issue how heating circuit is controlled as it kicks in only when charging begins and cuts battery out. That can mix up inverter-charger. I prefer always using standard LFP-batteries with low temp protection and adding heating/cooling.

Have you plotted out battery temp, volt & amp curves when issues arise?

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Ivar Eisma avatar image
Ivar Eisma answered ·

Yes, I have logs of everything that I also send to the battery manufacturer. The BMS simply shuts off at some point. I can see the heating pads drawing amps at the start of the day, but it's not effective. Once the battery is warmer it's used so much energy that a winter say doesn't top it back up much. I'm in Norway, so there isn't much sun to begin with in winter.

The reason I am considering AGM:

-Does not freeze at -20 if full.

-Will not just stop working, no BMS.

-I can live with a massive capacity reduction, I plan to add 4x Ah what I have in lifepo now.

-Once the cabin heats up, I will be back to a reasonable capacity. I can heat the cabin remotely for a few hours before I arrive.

-I do not expect them to last 10 years, I'm buying a brand that can be recycled.


Only thing I don't fully understand, will a Victron mppt charge at these low temperatures. Or will it also shut everything off. I could set a maximum of lets say 10 amps, I only need to keep batteries topped off. I have very low draw, when I'm not there there is no draw other than the Victron stuff powered up.


Digging a hole is not really an option in this location due to it being on rock. But it's an interesting solution.







2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Ivar Eisma avatar image
Ivar Eisma answered ·

screenshot-20231020-195931-vrm.jpg

This is one of the logs where it shuts off...


screenshot-20231020-195931-vrm.jpg (465.1 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

jetske avatar image
jetske answered ·

Dear Ivar
I am also in (northern) Norway right now, and still figuring out how my system works in the cold. So i thought maybe we could help one another out? however i have no understanding of all this and might probably need some more help from you then you will get from me (sorry!)

you say
"Only thing I don't fully understand, will a Victron mppt charge at these low temperatures. Or will it also shut everything off. I could set a maximum of lets say 10 amps, I only need to keep batteries topped off. I have very low draw, when I'm not there there is no draw other than the Victron stuff powered up."


I have a LifePO4 battery connected to my solar panels and a blue smart IP65 charger. There is also this victron mppt box (100/30) hanging next to it, so i guess i might help you answer your question, if only i had a bit more knowledge about all this. I have read manuals and such bit i don't get any wiser..

I am here an entire winter season but will not use my van, so he is parked outside, not really sheltered. I used to connect him to the electrical network once a week to see what happens but then i read yesterday that you should not try to charge a lifePO4 battery when temperatures are below 0. On my LifePO4battery app i get an error code that it's too cold to charge, but she stays at 100%
The car battery though is struggling since the car almost didn't start yesterday (while the LifePO4 battery should feed this one as well, so i am confused..)

I think i will try to buy one of these cabin heaters and try to keep them blowing hot air.. and keep the car plugged in to the electric network. Or would that be a bad idea?
And can my lay out help you with your question? i have installed the victron app but fail to make a connection so for now i cannot send any print screens but once that i am logged in a print screen might be handy for you?

I have no clue, it's all pretty new to me, but let me know if i can help. And thanks a lot for your advice as well!!
ha det bra

vennlig hilsen

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Ivar Eisma avatar image
Ivar Eisma answered ·

My setup is working well now with AGM batteries added, i get almost a week out of it if there is no sun at all.

I dont mind helping you out with your system Jetske, unforunately im not yet fluent in norwegian (im dutch). Can you post pictures of your setup so i can see how its set up and wired, and sizes of your batteries (in AH) and our solar panels you know ?


2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

jetske avatar image jetske commented ·
you are dutch?! me too :)

dan praten we misschien beter verder in het Nederlands (Nuja ik ben Belgische, maar vaak zien ze me daar niet ;)). Ik zag jouw antwoord op mijn vraag in de community en heb daar even al gestuurd.
Is het makkelijker om via mail/whatsapp verder te communiceren? of is het niet zo veilig/toegestaan om die dingen hier te posten?
groetjes!

0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ jetske commented ·
Be careful. There's no private messaging here and publishing contact details invites spam and worse.
1 Like 1 ·
k-k avatar image
k-k answered ·

Just a idea: what about a small savonius rotor with 60W generator for a reptilia-heatmat in a styrodur box with the batterie inside.

12V car-seat heatmats are doing sometimes real wonders too

Diesel heaters work from 9V-18V (to start them - use winter diesel!) so you can start engines after warming up the motorbatterie.

(For your hands use "knick-knack" heatpads)


3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Ivar Eisma avatar image Ivar Eisma commented ·
Thats all a nice idea, but the reality in the North is a little bit different. I have a 7kilowatt heater in the cabin, and it takes two days to fully heat a small cabin with it. I doubt a 60w genarator will even do anything when its -25C. The reason I went back to AGM, it has always worked well for me in my campervan before and it is just more reliable in these temperatures.


The difference: LifePO shuts off without warning. A 100Ah LifePo got me one and a half day including the power it took to heat the battery. A 400Ah AGM bank lasts me 6 days without any need to heat the batteries. I managed to get 6V premium AGM cells for Hoppecke for the same price as the LifePo cost me, so that a win in my situation.

3 Likes 3 ·
k-k avatar image k-k Ivar Eisma commented ·
60W for a 30W heatmat in a styrodur-box only for the batterie (as thermo isolatet compartment) was my intension. And even if you have a dieselheater: why not use an extra tubing from the hot outlet to the thermo-batteriebox. I am sure the Hoppecke's would like that too. Do you mean the HPPL serie and do you have experience with OGiV's in the cold ?


I am just testing a parallel set of lead (VRLA} and Li-ion on low voltage (13.2V||13.7V) but havent had the time to put them in a freezer on minus C°. So i don't know the behavior of the Li-ion yet.

I agree with you, especially on hard switching BMS. How do you managed it to get LFP-similar prices - LFP prices seem to go down nowodays.

0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ commented ·
Way off topic, but for hands there are also catalytic heaters that run off lighter fuel. Zippo make them, also many off brand varieties.
0 Likes 0 ·

Related Resources

Additional resources still need to be added for this topic