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Old 25-05-2018, 01:17   #1
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Join Date: Mar 2012
Posts: 12
A Solar Reg Mystery

Ok, I really need some serious guru help on this one.

I have 2x100W solar panels in series giving 24V. I have two banks of 2x12volt flooded lead acid batteries in series to give 24V. The two banks are independent with a battery switch in between (Off, #1 or #2 or Both). The elephant in the room is one bank of batteries gets up to 32.5V on its regulator while the other floats nicely at 27.5V. I can switch the same panels to either bank. Bank #1 same panels, same model reg, 27.5V float. Bank #2, same panels, same model reg, 32.5V....Any Ideas? I thought ok bad Bank #2 regulator, changed it out, same result. I thought bad wiring. Wired the regulator directly to the batteries, no big battery cables or anything else in between, same result. Decided the only odd one out was the cable connecting the two Bank #2 batteries in series, changed it out, same result.

What the going on?

I assumed there was a millivolt drop across an Ok but at low current relatively poor connection, causing the regulator to not see actual battery voltage, but my efforts to eliminate that idea have not borne any fruit. What next? Cable length? Doubtful as the bank that works just fine (Bank #1) is on the other side of the hull, so has much longer cables. Battery condition? Bank #1 is older batteries. Bank #2 brand new, because this over voltage kills them and I would really like to stop that happening.

This has been on-going for quite some time. I'm on the 2nd solar reg for this bank and the 3rd set of batteries. Yet I am no closer to solving the problem.

I want Bank #2 up, charged and at float as it runs the auto bilge pump and I really, really, really want that to work if needed.

A clue, might be, my anodes are eaten away pretty quickly. I found one wiring error by the Previous Owner. A switched negative at the helm panel with positive always on to the auto bilge pump. Don't ask me how I found that....nearly sunk the boat. But as far as I can tell all wiring errors are eliminated (I'm an electronics tech/engineer, so pretty sure). Mains does have an isolator in the earth line, but I don't use mains power. So that's not causing the depletion or the regulator issue.

I'll be keen to see if anyone has any ideas.

Thanks in advance for any suggestions.
mrh123 is offline   Reply With Quote
Old 25-05-2018, 01:52   #2
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Join Date: Oct 2012
Location: Gulf Harbour, New Zealand
Boat: Farr Phase 4, 12.8m
Posts: 1,155
Re: A Solar Reg Mystery

What regulators are they?
Could it be the voltage sense wire on reg 2 has excessive resistance? Or is voltage sense taken from the main connection cable?
Get a silver silver chloride reference electrode and check the voltage reading to the batt neg, with and without solar regs connected.... is there a difference in the voltage, and what is the base (both regs off and mains off) reading?
Matt Paulin
Neptune's Gear is offline   Reply With Quote


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