EZGO Power Wise 28115 G04 charger question

[JohnnieB]

Originally Posted by shrpshtr

JohnnieB,

Neither, they are actually UPS batteries out of a Data Center UPS. I'll have to get you the exact model when I get to the house this evening. Thanks.

Sounds like a righteous re-purposing project.

Also sounds like the electrician you spoke with was speaking about what the voltage of the 12V batteries ought to measure when installed in an UPS that is in its normal stand-by mode, with the batteries on float charge. So the 12.8-12.9 volt readings you are getting while the batteries are at rest, may be correct.

The at-rest voltage of a lead acid battery depends of the acid concentration of the electrolyte that was added to the cells when the battery was manufactured, so the batteries you have will have a higher at-rest voltage than what is listed on the golf cart battery charts, if they had more acid in the electrolyte to begin with. Using a higher acid concentration is a way to pack more storage capacity in a smaller box, but reduces the number of charge cycles in the battery's lifespan. Of course, that is not a significant factor for UPS batteries because they are not designed to be discharged every day and recharged every night like cart batteries are.

Ironically, the PW 28115 charger might be overcharging your batteries.
I suspect they are either AGM or Gel-Cell and your charger is designed to charge wet-cell batteries. It shuts off when the on-charge voltage climbs into the 44V-46V range (14.7V-15.3V across a 12VC in series) and the max on-charge for a 12V AGM or Gel-Cell is in the 13.8V-14.4V range. Of course, that data is for Trojan batteries and your batteries may have hotter chemistry and handle the higher on-charge voltage.

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The way you have your batteries connected (Two set of three in series that are connected in parallel) minimizes the mismatch issues.

If the at-rest voltages start drifting more than 0.2V from each other, give the low voltage batteries a boost charge with a 12V charger.

[yurtle]

Did you get a UPS charger too? That might work better than a buggy charger, since the voltage is closer to what the batteries want and it goes into float mode.

[shrpshtr]

No Yurtle, it's the same Power Wise charger that I came with my cart.