Batteries in cold weather

[Mallison359]

Hi guys, I have a solar system in my shed, the weather has been really cold of late and getting colder. I've noticed the batteries draining quicker so I can only surmise it's having an impact.

So my question, how do I keep the batteries warm enough without overheating them.

[Sunking]

Turn the heat up. Just keep it under 35 C

[Mallison359]

Turn the heat up. Just keep it under 35 C

I don't have a dedicated heat source in the shed. I have the load on the charge controller off while not in use so the batteries get as much charge as possible.

Do you think I could put the batteries in a wooden box, insulated with foil and polystyrene?

[inetdog]

I don't have a dedicated heat source in the shed. I have the load on the charge controller off while not in use so the batteries get as much charge as possible.

Do you think I could put the batteries in a wooden box, insulated with foil and polystyrene?

If working with foil inside the box, make sure that there is no chance that torn foil could short out the battery terminals.
And watch out for corrosion from acid vapor is you you have FLA batteries.
There is also the risk is that in summer the batteries will overheat.

[Sunking]

Here is the deal. Batteries regardless of type are double edge swords. As temps go up, capacity goes up and aging accelerates. Exact opposite when temps drop capacity goes down and aging slows.

FLA batteries are fairly resilient in terms of cold weather performance. If kept fully charged cold weather is not a big problem other than capacity loss which is temporary. At 100% SOC specific gravity will not freeze until temps drop to lower than -40F (-40C). Down side is capacity drops with temps. Battery capacity ratings are misleading and made at room temps of 77F or 25C. That 100 AH battery is only a 60 AH battery 0F of which only 30 AH is usable. Now some will say from experience winter kills batteries which is a half truth. Cold temps will finish off a weak battery. The battery was already dead, they just did not know it till that first cold morning.

So you have a solar battery system in a shed outside without any environmental control. Not much you can do. Putting it in a box will only add some thermal lag, but not much else. The only heat generated is that from charging and discharging. If you turn everything off to prevent discharging also stops charging and any heat generation. If your battery was weak to begin with, then nothing can be done. If you have a good battery, you are limited to how ever much you rsolar system can generate and 90% of all off-grid systems are grossly undersized.

So in the end not much of anything you can do other than bring the battery indoors and use a commercial AC charger from your mains.

[lkruper]

Hi guys, I have a solar system in my shed, the weather has been really cold of late and getting colder. I've noticed the batteries draining quicker so I can only surmise it's having an impact.

So my question, how do I keep the batteries warm enough without overheating them.

You could increase your battery capacity to account for the cold months. As has been mentioned, cold does not hurt batteries, it just causes them to have a lower capacity that is temporary.