Flooded acid battery voltage and temperature.

Hello everyone,
I've looked for the answer to this question for awhile now and have found conflicting results. I know usable capability changes with battery temperature when using LA batteries.
But does temperature change voltage?
I have 8 6v golf cart batteries in a series for a system voltage of 48v. If I fully charged the batteries @ 77F and then put them in the freezer for a week. (-20F) Will the batteries still measure the same voltage ?
My weekend cabin has high temperature of 95F and typical low of -50F. The batteries are temporarily stored in a semi insulated box with 15 feet of heat tape for a heat source. Once the batteries are mostly charged, the heat tape turns on. With the cloudy winters and cold here, the batteries seem to get around 0F.
Anyone have a idea?
Thanks
Ed
1000W panels Kid CC 184 ah battery bank @ 48v
Weekend cabin, 250w inverter.
Looking to upgrade inverter!
Looking to upgrade inverter!
Comments
We are all comfortable with the automatic temperature compensation for charging (as battery gets colder, the charging voltage is automatically increased by most "higher function" chargers--It appears typically the "correction range is from 0F to 122F or so).
Since I live in an area where the average temperatures are from 50F to 75F, I have never had the chance to see what cold and heat do to resting voltages.
However, this guy is in Maine and used an older FLA battery to check resting voltage from winter through summer (random data collection).
It appears that his default assumption was that the battery resting voltage does not change over a wide range temperatures vs state of charge... He did find that the "resting voltage" may take 6-12 hours "to settle" on a "warm battery" but take upwards of 10+ days on a cold soaked FLA battery (resting voltage is showing residual surface charge voltage days after charging, even partial charging). The observation from his testing was that surface charge to resting voltage was the result of dissipating the surface charge and not the result of "self discharge" current (which is very low at below freezing temperatures anyway).
Tests were done on an ~5 year old "WalMart" battery used in a boat--Which was about 80% of new capacity at full charge.
Anyway--A couple of links:
https://www.pbase.com/mainecruising/battery_state_of_charge
https://www.pbase.com/mainecruising/self_discharge
On another method to ask/answer your question, there is a rough formula for resting voltage vs state of charge from an old thread:
https://forum.solar-electric.com/discussion/comment/92455#Comment_92455
Also on that page is the formula between cell resting voltage and specific gravity:
So, if you are getting 46 volts after resting, if the formula is correct (and your battery is around 77F) your specific gravity should be:
- 46v/24cells - 0.845 = 1.072 (dead?)
- 47v/24cells - 0.845 = 1.113 (~20% state of charge)
Yuasa states that the temperature correction for SG is:- specific gravity changes by +.001 for every -3 degrees Fahrenheit.
J.R. Buchanan did a nice set of charts on battery SG and temperature based on a 100% charge = 1.265 SG.-Bill "not a battery engineer" B.
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