Battery Experts

If you trust the maker then follow their recommendations.

ddrueckh wrote:
I purchased two new 6 volt golf cart batteries from Costco. They are Interstate brand GC2-RD. 208 AH. Per the specs, it says that the absorption phase should be 7.65 volts. That would be 15.3 volts for both batteries tied in series. That seems really high. Should I set my solar charge controller to 15.3 for the acceptance charge or leave it at the 14.8 that I have it set at now? Thanks.

That would depend on the type of charge controller you have and how it stages the charge. I'm sure you know the battery specs call for 7.2 Bulk, 7.65 Absorb and 6.7 Float. I'm not sure what your charge controller means when is says "acceptance" and charging voltages are impacted by ambient temperature too.

Your charge controller model might be helpful.

There was a post in the Tech Issues section about these Interstate 6V batteries and the high charging voltage. It is a bit higher than Trojan or other mfg.'s call for with absorption voltage. It will not hurt the batteries to have 15.3V on them for the typical absorption stage time.

The Science: Temperature is directly related to charge levels so it may be in your interest to, at the least, monitor battery temperatures at your local ambient. You could also contact Interstate and find the actual maker of the battery. Interstate doesn't make any batteries, they rebrand them. If you find the maker of the battery, they may have a different charge level specified.

Post the name and model of your controller for specific info about settings.

Interstate batteries are made by Johnson Controls. For what it is worth.

Shadow Catcher wrote:
Interstate batteries are made by Johnson Controls. For what it is worth.

Not to many battery posts out there that some one doesn't point that out,,, I am sure its a large factory with varying levels of quality depending on what is ordered. I just purchased an Optima AGM Yellow top, made by Johnson Controls,hopefully from their High Quality side, and I have had numerous Interstate lead acid batteries Made by Johnson controls.
I am sure Costco speced those batteries and required quality components as I have two also.
I hope we can agree that its a large company and you can get good quality,medium quality and junk!!
Know what you are looking for and do your research..

I don't do Interstate because of the high absorb voltage.

14.6 to 14.8 is fine for daily charge while in use.

smkettner wrote:
14.6 to 14.8 is fine for daily charge while in use.

This is the setting that I use for the pair of 6V Energizer's that I have. The charge controller varies the voltage with temperature compensation.