Thread: Solar panels not keeping batteries charged up. Need assistance to diagnose.

Quote: In the midday sun, with all 6 panels going into the 12V charger, I was getting 4.6A at 12.9 volts going in, which seems really low for 6 x 100W panels.




I have been mucking around with solar for about 12 months now - mostly household, but recently set up 2x 100w foldable panels & a 15 amp mppt controller for my camping trips. One thing I have noticed is that the output varies with the charge already in the battery. IE if conditions are optimum & they are feeding in to a battery that is 85% charged they will feed in 3 or 4 amps & if I then put the clips on a 50% (12.1v) battery it will go to 8 amps, so I would run the test again with "flatter" batteries, as 12.9V is 100% charged.
Cheers, David
PS I think it was you I purchased a 15 amp PMP controller off its going great..

Originally Posted by DeeJay

Quote: In the midday sun, with all 6 panels going into the 12V charger, I was getting 4.6A at 12.9 volts going in, which seems really low for 6 x 100W panels.




I have been mucking around with solar for about 12 months now - mostly household, but recently set up 2x 100w foldable panels & a 15 amp mppt controller for my camping trips. One thing I have noticed is that the output varies with the charge already in the battery. IE if conditions are optimum & they are feeding in to a battery that is 85% charged they will feed in 3 or 4 amps & if I then put the clips on a 50% (12.1v) battery it will go to 8 amps, so I would run the test again with "flatter" batteries, as 12.9V is 100% charged.
Cheers, David
PS I think it was you I purchased a 15 amp PMP controller off its going great..

this only applies to regulated panels.

an unregulated panel will dump all the amps it can produce into a battery until it raises the battery voltage to its peak power voltage( which in spudboys case, is 17.7V ) this is clearly a not good voltage for his batteries.

the regulation of solar panels works (for the purpose of general charging and rough concept) exactly the same as an old school alternator. it will try to produce all the amps it can/needs to from the power available to it to maintain a fixed voltage.

whats very cool is to watch the volts and amps going into a solar regulator and compare it to whats going out.

OK - sorry for the delay getting on to this. Spent the weekend away camping on the Murray. Just a 2 man tent and a station wagon - like the good old days! Purnong-Campground-Murray-River-SA

Progress on my solar issue:

• I've recharged the 3 batteries, all at once with one charger
• I'm now load testing them with the 50W halogen globes, as 3 separate batteries

Here's something interesting though. These Optima batteries have 2 posts: one traditional round (automotive) post and another M8 threaded post with a wingnut. So each battery has effectively 2 positive terminals and 2 negative terminals.

The interesting thing is, if I measure the voltage on the pair of round (automotive) terminals I get a higher reading that if I measure on the M8 threaded terminals

On 2 batteries, it is a small difference, like 0.05V, but on one battery is it around a 0.11V. For example, the round terminals are reading 12.00V but the threaded posts are reading 11.89V, on the same battery.

That can't be right!

Sounds like you need to get serious about cleaning, polishing and tightening your battery terminals. Clean metal to clean metal, no oxides, no paint, no sloppiness and maybe the current will willingly flow.

Hmmm - but I am probing them with multi-meter prongs, which have a very sharp point on the end. Am pressing with equal hardness on each post!

One is stainless (threaded one) and the other is lead...

Here's some more results of the 3 batteries, this time under a 4.3A load instead of a 0.8A load. Only recorded 8 hours of stats instead of 20 hours this time.

Hi David and your batteries are still showing they are down on full capacity.

But a ROUGH calculation is that it is only about a little under 10%, which is not bad.

OK - thanks for that info. So not time to chuck them out just yet?

Looks like the next thing to test is the solar panels.