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Old 29-04-2006, 19:09   #16
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Location: Winters - Out Cruising / Summers in the NC mountains
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Alan

I have two solar panels run thru a MPPT onto a POS sub-bus bar. The alternator is also run to the same POS bus bar. The sub-bus is then connected to my house bank. The battery switch/combiner is connected to the house, start & windlass banks. I mistakenly ran an additional wire from the sub-bus straight to the battery switch/combiner. When the batts overheated, I disconnected the combiner from the house bank and the voltage dropped to the low 13s. It also blew the 30 amp fuse from between the MPPT and the bus bar.

When I realized that I had placed the wire directly between the bus bar and the switch/combiner, I removed it and every thing is working fine.

Could it have been something else? We were motoring at the time and it was a sunny day, so the solar panel was putting out some juice. The alternator usually outputs a max of 13.6, but the solar panel will feed over 20 volts to the MPPT.

????????????

Roger
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Old 29-04-2006, 21:17   #17
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Ummmm, no I don't get this at all. Rick are you seeing something I am not?
The MPPT (I am presuming this is a pulse width charge regulater for the solar panels) should not be an issue. It regulates the 20V or what ever and maintains a constant charge voltage/current into the bank. It also acts as an isolator so as the bank cannot discharge back into the panels at night. But I can't quite understand how you could blow a 30A fuse connected to it. Nor why you would have a 30A fuse anyway. 30A would require 400 odd watts of solar panel to produce. That's a lot of panels. Have you got that many? Besides, the regulator limits the current to what ever the regulator is designed for. So if it is say a 10A regulator, then it will only supply 10A of charge current at full charge/Sun. so a 15A fuse would be plenty. If you had a huge amount of panels, then you could have the 30A on the primary side of the regulator to protect the wiring to the panels.

OK, so if I get this right, you basicaly parrelled a wire from switch to banks. I don't see that as an issue that would create a problem of over charging. Unless a bank has not come up to a step voltage to allow the charger to go from say bulk to topup or float stages. This would mean the charger is poking in full current all the time and the batteries would get too hot. This is an issue that can occur with the distances and cable linking batteries in the variuose groups around the boat.
How big is the boat?? I would suggest if it is not tooo big, you take the winch bank away at run the cables to the house bank. Keep the start bank and house bank seperate with no combining switch. Or if you do have a switch, keep it in say the engine room so as you use it for an emergeny start only.
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Old 30-04-2006, 05:45   #18
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The 30A fuse came with the MPPT. Running the two parallel lines to the house bank had something to do with the problem. The moment I disconnected one, the voltage dropped to around 13.2v and it has worked fine even since. I don't understand it either, but it's working!!!

Roger
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Old 06-05-2006, 16:45   #19
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Roger-
If the tops of the cases are wavy, you definitely overheated the batteries. When AGM is overheated, some water is lost and the electrolyte will now be too concentrated, there's nothing you can do about that. Nor about any physical damage, but since the plates are isolated from each other by a fiberglass scrim that is very heat-resistant, odds are they are not shorted out even if they also warped.
You can charge them and come back in 24 hours to see what charge level they actually are holding, that will give you some idea of what capacity they have left. But if you go to a battery dealer/distributor, they should have a LOAD TEST meter. (You can also buy these but for one shot...a little pricey.) When they put the batteries on the load test, they will draw heavily from them to see what real output they can provide, and that's a better indication of health or failure. The maker will tell you what your particular cells should be tested at.

If the cases are warped...I'm not sure I'd trust them. If nothing else, buy one new starting battery and reserve that for starting, even if it is a small one. That way you can gamble "some" without having to make an expensive tow call if the AGMs remember that they should be dead.<G>
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