Domestic bank discharged - why?

[Gordonmc]

I recently installed solar panels on the boat, two 50 W which came as a hinged pair.
I wired them to a regulator (new) and the regulator to the bank of two 110 AH lead-acid batteries.
For the last six weeks or so all seemed fine with the batteries sitting at 13.5 v +. This weekend I went to the boat and they were dead. Zilch Vs. The boat systems were off at the 1-2-both-off switch, although the always on system for the bilge pumps was active. The pumps had not run.
I disconnected the batteries and clipped on a charger which showed the error light. After a day doing nothing I tried again and got the batteries seperately to accept a charge.
One is showing 12.5 V. The other is awaiting a full charge.
My initial thought was that batteries have discharged though the panels, which means both the regulator and the panel diodes have failed.
Any other ideas?
What would be the best test for system discharge?

 

[angelsson]

I recently installed solar panels on the boat, two 50 amp which came as a hinged pair.
I wired them to a regulator (new) and the regulator to the bank of two 110 AH lead-acid batteries.
For the last six weeks or so all seemed fine with the batteries sitting at 13.5 v +. This weekend I went to the boat and they were dead. Zilch Vs. The boat systems were off at the 1-2-both-off switch, although the always on system for the bilge pumps was active. The pumps had not run.
I disconnected the batteries and clipped on a charger which showed the error light. After a day doing nothing I tried again and got the batteries seperately to accept a charge.
One is showing 12.5 V. The other is awaiting a full charge.
My initial thought was that batteries have discharged though the panels, which means both the regulator and the panel diodes have failed.
Any other ideas?
What would be the best test for system discharge?

There are more qualified here to answer than me, but are you sure they are 50 amp?

As to the discharged batteries, don't be fooled by the coincidence of the new panels, could be something entirely different, a short in a circuit for example. But of course it could be discharging back to panels, I have a regulator on mine which prevents that happening.

 

[maby]

Whatever the original cause, the chances are that both batteries are now dead - lead-acid batteries do not take kindly to being run down to zero volts. At the very least, they will require several cycles of carefully managed charging and discharging to coax them back to life and they will have lost capacity, I'm afraid.

I very much doubt that you really mean 50A panels - those would cost as much as the boat and probably be larger than it is. 50W sounds more likely. The diodes could have failed, though it would be unusual.

For testing, you need to get some charge back into at least one of the batteries, then disconnect the cable from one of the posts and put a current meter into the circuit. If you don't already have one, you can buy something suitable from Maplins quite cheaply. Get something that will read up to several amps DC and check the reading with one light switched on - just to make sure that you have a circuit, then switch everything off and make sure the drain has fallen to zero, or very nearly so. Get a figure with your solar panel in-circuit and brightly illuminated, then shield it with something dark and look for reverse leakage current. That should be down in the milliamps and require that you change the range on your ammeter. Do not run anything high load with the meter in circuit - you will blow it. Cheap meters from Maplins will only read up to a few amps - nothing like the current drain of the starter motor!