Discharging leisure battery - diagnose solar panel or regulator?
November 21, 2011 5:50 AM   Subscribe

Instead of charging my leisure battery my solar panel is discharging it. How do I diagnose?

When I come back to my campervan after a month away I find the battery has discharged from >70% to <10%.

The battery is connected to a solar panel and rather swanky looking charge regulator that shows battery charge in bar format like a phone. Unfortunately the manual for the regulator is in French and German but there is no error listed as far as I can see.

There is only one cigarette lighter socket connected and it lights a single LED.
I tried replacing the battery. The new battery appears to charge just fine and is topped up with water ok too.

There is no connection to the alternator. It's a simple system, just connected to the solar panel.

It seems like the solar panel is discharging the battery, but could it be a problem with the regulator? Or do I need to take the effort to inspect the cables for water ingress?
posted by jago25_98 to Technology (5 answers total)
Are you sure the panel is wired correctly? Put a voltmeter on it and make sure the pole that is marked positive really is positive.
posted by Kid Charlemagne at 5:58 AM on November 21, 2011

Missing diode?
posted by devnull at 6:34 AM on November 21, 2011

Could be faulty regulator. Could also be a load on the battery discharging it while you assume the solar panel is charging it. To check out the possibilities you really need a voltmeter/ammeter to find out what current is flowing where and when.
posted by exphysicist345 at 1:17 PM on November 21, 2011

Response by poster: I've ordered a replacement regulator...

to keep the wiring simple I'm going to keep the regulator I already have wired in and just add this regulator as close to the battery as I can to hopefully prevent the battery from draining

will get back here and update if I find this helps
posted by jago25_98 at 11:33 AM on February 17, 2012

Response by poster: Ok. I'm not sure it's fixed!

Already replaced the battery.

Measure the voltage at the regulator. The solar panel is putting out 19v in sunlight. However, when the solar panel is connected from the regulator voltage drops to 10v. Is this correct?

The same thing happens with a different cable connecting the solar panel to the regulator.

So we replaced the regulator with a much more basic one. It only has 3 lights to indicate charge and only 2 ever seem to be lit; it's had a week to charge beyond that.
Again we measure ~10v regulator-panel and 19v when just the panel.

The regulator is wired as instructed; lights, battery and panel on the correct terminals. However, the regulator is has a green light to indicate load, but also a green light to indicate charge. This doesn't sound right but it's very simple wiring!
posted by jago25_98 at 3:25 PM on April 17, 2012

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