Charging Dead Batteries

Milton Bertin · 13-04-2009, 10:10

My boat has a Yanmar 3QM30, the original alternator fails so I put a new, more powerful, one, but the shop that sell it make a point in emphasis that an alternator will not charge death batteries (that was my situation, my 450 AH bank was discharged by the autopilot, to the extend that the density measure don’t go up to red!!!!).

It was true, it never charges that bank, I’m wondering if I put 3 diodes in series with the ground connection of the regulator and a switch to shortcutting them ( with 3 diodes bypassed it will be as original, with one diode between regulator and ground the voltage will rise 0.7 V, with 2 1.5 etc.).

I expect that with this scheme to increase voltage I can charge death batteries, just looking not to obtain excessive current from the alternator.

Any comments, will be too risky???

13-04-2009, 10:10	#1
Milton Bertin Registered User Join Date: Apr 2009 Posts: 13	Charging Dead Batteries My boat has a Yanmar 3QM30, the original alternator fails so I put a new, more powerful, one, but the shop that sell it make a point in emphasis that an alternator will not charge death batteries (that was my situation, my 450 AH bank was discharged by the autopilot, to the extend that the density measure don’t go up to red!!!!). It was true, it never charges that bank, I’m wondering if I put 3 diodes in series with the ground connection of the regulator and a switch to shortcutting them ( with 3 diodes bypassed it will be as original, with one diode between regulator and ground the voltage will rise 0.7 V, with 2 1.5 etc.). I expect that with this scheme to increase voltage I can charge death batteries, just looking not to obtain excessive current from the alternator. Any comments, will be too risky???

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