Equalizing batteries and thinking they are getting to hot!

Re: Equalizing batteries and thinking they are getting to hot!

Measuring voltage on a battery is a bit of guess work... If they are charging/resting/discharging, the numbers are all different. And other than resting voltage, have only a weak relationship to state of charge.

The Hydrometer (properly calibrated and used) is going to give you the most accurate numbers. Using this Crown Battery Manual (PDF):

Specific Gravity
State of Charge Level

100% 1.265 or Greater
75%  1.225 - 1.230
50%  1.185 - 1.190
25%  1.140 - 1.175
0%   1.125 or Less

And they also list battery voltages too (after a 15 second load test--to take of the "surface charge"?)...

Note that your batteries should read about 6.3 volts fully charged (room temperature, resting voltage).

And about 7.3 volts (~29.2 volts) voltage set point for absorb charging.

There are lots of theories about how best to charge your battery bank... Pick one that works for your charging setup and then monitor the bank... If the bank is "undercharged", then add time and/or voltage. If the bank is overcharged, drop time or voltage a bit...

Depending on how your charge controllers can be programmed... One method is to measure the time to Bulk Charge (from below ~29 volts to absorb point at ~29.2 volts) if that took 2 hours, then add two more hours for the absorb time (holding at ~29.2 volts). Then turn off or drop back to float (if you have a genset, you will pick turning off the generator).

Another method is to set Absorb to ~29.2 volts and set the Absorb Timer to 2-4 hours... 2 hours if the bank is lightly cycled and ~4 hours if the bank is deeply cycled.

Watch the specific gravity and water usage... If you have to add water about every 2 months to a cell--you are probably OK. If you have to add water more often that once per month, you may be charging a bit too much (excessive charging/"boiling"/equalizing is not good for a battery bank). If you are not adding water, you probably are undercharging.

A 4kW inverter/charger is pretty good sized... Your ~790 AH at 24 volt battery should be charged around ~5% to 13% rate of charge (at 20 Hour rating--these are typical numbers, always refer to mfg. instructions to confirm):

• 790 AH * 0.05 = 39.5 amps minimum
• 790 AH * 0.10 = 79 amps "nominal"
• 790 AH * 0.13 = 103 amps "healthy maximum"

Depending on the programming/capabilities of your inverter/charger, and the capacity of your genset--hopefully your numbers fall somewhere in the ~80-100 amp range for charging this batteries.

If you are having problems getting the batteries above ~1.260 specific gravity and you have a "big genset", you can try running longer with a smaller genset and battery charger to save fuel (a Honda eu2000i and ~30 amp, or a bit less, AC charger or if the inverter/charger can be programmed for lower charging current to finish the charging).

You do not know what the initial "fill" S.G. was... So you don't know if you can reach ~1.265 or not. And if absorb charging (and some deeper cycling--exercising) does not bring the S.G. back up--Then you may have started to sulfate the battery bank (unrecoverable early aging).

Battery Monitors usually have some sort of "reset to 100% full"--Like if they see 29.0 volts for >1-3 hours or something). If you do not reach those conditions, the Battery Monitors will "drift" from "true" 100%. Also, sulfation will reduce battery capacity--which the Battery Monitor cannot detect.

Anyway--My guesses from behind a keyboard.

Good Luck!
-Bill

Re: Equalizing batteries and thinking they are getting to hot!

I really do not have anything I can add... Be do'in the same thing as you reading the manuals for setting up / configuring the monitoring system.

In the end, figuring out the present state of your battery bank and how, if needed, you will need to get it back to full/proper state of change. Hopefully, getting the battery monitor sync'ed will fall out at the end.

Depending on size of of genset and such--If you have a large genset and this is your only charging source--you may end up really needing a smaller genset (and possible mating AC to DC battery charger) to finish the charging. Bulk usually ends at around 80-90% state of charge, and "absorb" (tapering towards zero charging current) takes place over the next 2-4 hours. Using a "large" genset that can drink 0.5-1+ gallon per hour vs a smaller genset that may take 1/4 to 1/9th gallon per hour for those last "4 hours" may save you a bunch of fuel costs over the long haul.

-Bill