Battery not charging - defective charger or depleted battery?

2 Posts
Jul 6, 2010 11:43 am
Battery not charging - defective charger or depleted battery?


I have a small solar panel I use to charge a battery to power a water pump.
-30W solar panel
-Morningstar Sunguard 4.5A, 12V Pwm Charge Cntrlr

I didn't use it for about a year, and it's now completely depleted. I put it out in a sunny day, but to my surprise, it didn't charge.
I read 20V on the input of the charge controller (panel), and 0V on the output (battery).

Is this evidence that the charge controller is defective and I need to buy a new one, or is this caused because I made the mistake of letting the battery go completely dead?

I ask because I noticed that other charge controllers such as the Morningstar SunKeeper has the ability to "restart from zero voltage (boot strap mode) to recover the system in case of a fully depleted battery"

Anything I can do to get this back on track?
220 Posts
Jul 6, 2010 05:05 pm
Re: Battery not charging - defective charger or depleted battery?

hi leo,

 a reading of zero volts is never a good thing for a battery (our lead acid type). that said, the battery is probably toast...but, sometimes they surprise us and will come back enough to give limited service.

 could do your own "bootstrap" by connecting the pv module directly to the battery for an hour or two? just be very sure of polarity and keep an eye on things for a while..if we can get the voltage up above the 6 volt start up minimum she may start back up for you?

 that SG controller is a rugged little devil and hopefully it did not fry like some of the others will when connected open circuit, (no battery)

 good luck, dave

ps..if we see the battery voltage climbing up thru ~16 volts or so and still rising (during "bootstrap") that would reason to discontinue the attempt and go shopping for a new battery.
220 Posts
Jul 10, 2010 08:09 pm
Re: Battery not charging - defective charger or depleted battery?

 hi leo,

 i was re-reading this thread and wondering how you are making out...

 i can't see how i missed the obvious and easiest way to try to get back up and running..that is to put a battery charger on the battery for a while to bring that voltage back up to greater that 6 volts.

 some chargers won't start up with a dead battery either, but some of the older "dumb" chargers will (usually the heavy transformer based chargers will run into a dead battery or most any other load.

cheers, dave
2 Posts
Jul 16, 2010 01:46 pm
Re: Battery not charging - defective charger or depleted battery?

Thanks for the suggestion. I verified that the charge controller is working properly. I connected a fan to it, and it turns on.

I will try to find a AC battery charger and see if that is able to power the battery up. I'll let you know how it goes.

If I use the solar panel on the charge controller and the battery the voltage goes up slowly to about 8V and then it stops there. As soon as I remove the panel, the voltage on the battery drops to 0.5V.
I hope I can save this battery....
Jul 25, 2010 06:10 pm
Re: Battery not charging - defective charger or depleted battery?

Its 6:15 pm. Do you know where your batteries electrolyte is at?

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