Ideal Battery Temp

[AndyDHunt448]

Hello, I am seeking some advice please, with regard ideal battery temperature.
I have a stack of three ECS4800 batteries, and notice that the overnight temperature as winter begins, drops to 17 degrees.
I am sure this will drop further, as overnight it is still 4 degrees C outside.

So I have very recently insulated them, leaving a decent air gap around the battery, and now see the overnight temp when I force charge climbs to 27 degrees C, then drops back to 24 degrees C.

I suppose really my question is, what is the ideal Temp for these batteries please ? Is 27 degrees to high

I have read on the data sheet, the Temp range goes up to 55 degrees C - from minus 10. But this is such a wide range. I expect there must be an optimal smaller range to aim for, to prolong battery life and efficiency.

Thank you

Cheers Andy

[Dave Foster]

Hi Andy, I think that one has just been answered quite comprehensively on this post so i'll refer you to that viewtopic.php?t=511

The best temperature to maintain is between 20-30C - the BMS reports it's internal temperature which spikes when you charge the battery so you have to ignore the high peaks and look for the average and they run perfectly well up to their 50C max temperature (but don't go beyond see second note below).

The most important thing to bare in mind is that low temperatures don't damage the batteries, it just stops the battery chemistry working (obviously that's not great from an operational point of view, but at least they aren't damaged) and they will recover again once it is warm.

However sustained high temperatures are bad for batteries (>50C) and that will damage them, so the first rule of insulation is that you should remove it during the warmer months (May-September) or provide very good air flow and should the batteries exceed 50C stop charging them until their temperatures cool down.

[calum]

As an anecdote, we have our batteries in our garage, which is unheated, north facing and in the shade of the house. As a result it's always fairly cool and I've been able to leave my batteries in their insulated box (9mm OSB, lined with 50mm of EPS sheet) pretty much all year, I just prop the lid open in the warmer weather. I have Home Assistant connected to the BMS and giving me data on the highest and lowest temperatures the battery cells are at, so I can see in real time how the temps are changing as the system charges, discharges, etc, so I can be confident of how well they are being treated. For instance, I can see that over the summer the batteries have touched 30C at the high end when being charged by the panels, but otherwise they sit in the mid 20s.

If my batteries were in, for instance, a loft space they'd be a LOT warmer in the summer and I definitely wouldn't want to be leaving them insulated in that circumstance, if I was relying on passive cooling.
That said, if you were concerned about overheating you might decide to duct in cooler air from outside, in which case it might well be best to insulate the batteries from the high temperatures in the space they were in.

I have a feeling that the cold will still end up de-rating the batteries this winter as the lower packs will get a lot cooler than the upper ones, so I will probably look into some trace heating for the lower part of the enclosure, and possibly a fan to stir the air in there and equalise the temps a bit more.

[AndyDHunt448]

Thank you very much to both of you for you advice. Cheers Andy