Charging NiMH (eneloop pros) and sealed lead acid in sub-zero (<32degF) conditions


Newly Enlightened
Oct 12, 2021
London UK
Hello all,

I wanted to ask some advice about charging batteries outdoors in the cold. I know it's a niche topic, and many will just say 'don't'. Anyhow...

Lithiums aside, as I know most common chemistries become dangerous if charged when the electrolyte is frozen.

I'm trying to work out the superior chemistry between lead acid (a good, modern Leoch branded SLA) and a battery of similar voltage made from eneloop pros, which have cold performance claims (though always about discharge in the marketing, never charge).

I understand both chemistries will perform worse in the cold when charging than in the warm (presumably in terms of total capacity and/or speed), but my three questions are:

1. Is one chemistry likely to perform much more closely to 'normal' than the other?
2. What have they done to eneloop pros to add in this sub-zero performance that's absent in normal eneloops?
3. Performance aside, can anyone specifically point to something likely to happen to one or both chemistries in the deep cold that might quickly destroy or ruin the battery? Like how most wet lithium rechargeables run the risk of failure or fire?

Thanks in advance.