is 28v too much for my bateries?

i hav four 6v @225ah trojan bateries(conected in series 24v),400w solar panel, and a epever 30a charge controller. my charge controller is reading over 28v. is this ok? or is something wrong with charging(overcharging?

3 Answers

  • 4 months ago
    Favourite answer

    Hey Rebel, sounds like you have that refrigerator system running now.  28 volts is pretty normal for a 24 volt system while it is charging.  We have our set a bit lower, at 26.8 volts.  I do that intentionally since we are grid connected, this way the charge controller is always running full on while the inverter keeps the voltage a volt or so lower, feeding power out into the grid while the charge controller thinks the batteries are not completely full, and keeps feeding all available solar current in.

    Rick is suggesting 30 volts is better.  There is nothing wrong with that, but most people I know with solar arrays use 30 volts for occasional equilization charging, maybe for an hour each month.  This forces the last bit of sulferic acid out of each cell in a multi battery system, sort of resetting the clock.  At 30 volts the cells will gas quite a bit, and need water added frequently, even more in warm temperatures.  And they do produce a fair amount of Hydrogen when gassing like this.  If you have these batteries inside your camper, they need to be vented to outdoors if you are going to run them at 30 volts.  28 volts will make them gas quite a bit less than 30 volts.  You can look this up at Trojans website, or better yet, if you have time, check if your local library has a copy of, "The Complete Battery Book," by Richard Perez.  You only need to read the 2 or 3 chapters on lead acid battery charging.  Richard was the founding editor of Home Power Magazine, and he is pretty much considered a guru on charging batteries.  As long as your charge controller is limiting the voltage to 28 volts when the batteries are fully charged, it's all working fine.  Take care Rebel, Rudydoo

  • rick
    Lv 7
    4 months ago

    Probably 30+V would be better for charging voltage. Certainly NOT overcharging. A fully charged 12 cell lead acid system will have  26.4 no load volts. 1.6 volts above won't do much more than maintain. With no solar input at night, internal resistance, leakage from contamination on the surface of the batteries, and the always present inverse voltage present in circuitry, 28 volts might not even keep them fully charged, with no power drawn from the system.

  • 4 months ago

    It should be fine while on the charge. It will drop back down to 24V while not charging. Your car does the same thing. While the engine is running your alternator is putting out around 14.5 volts while the battery is only 12V.

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