How cold is to cold to use water based batteries? Everyone says you have to use gel batteries in cold climate and this is my first winter and I do have water-acid. We get down to 20 maybe a little lower is that to cold and will improving insulation etc. make any difference?

I would appreciate any info everyone can share.

The absolute stopping point is when electrolyte freezes. The reaction slows down before this but still useable.

The freezing point depends on state of charge. The more discharged the less sulfuric acid in solution and more water therefore a higher freezing point.

At 40% state of charge the specific gravity is 1.148 (18% acid) and electrolyte will freeze at -16 deg F. At 100% state of charge the specific gravity is 1.278 (33% acid) and electrolyte freezing point is -92 degs F.

This also assumes no stratification which is when acid concentration is higher at bottom of battery and lower at top due to long term float charge with no significant discharging or charging to keep mixture uniform.

Living in S. Fla. I have not had necessity to worry too much about this.

Forget gel cells for any renewable energy application. The best battery for cold weather renewable is AGM. However it is still a lead acid battery.

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Dereck, PE, MSEE
Moderator

Thanks guys, great info. Doesn't sound like my temps are going to be severe enough. I have a well insulated enclosure and it is off the ground, sounds like I will be OK, but would appreciate any additional input members have.