Jeff, here's one that is good value: http://store.hamiltonmar...00a-730942/4,39648.html

I know that you are one of those who never asks the price of anything, but this one is less. Incidentally, the current rating has to be greater than your alternator's output, and few of us have alternators good for more than 100 amps.

Rob, you might consider a start battery for each engine and a larger deep-cycle battery as a house battery. The start batteries need to provide the cranking amps required, but they should not need much capacity since they don't supply other loads. The deep-cycle house battery needs to be sized for the longest period of time that you might sit at anchor without running the engines.

You might consider replacing incandescent lamps on board with LED's - there has been a lot of discussion elsewhere of this. It may be cheaper to reduce your electrical load than to buy additional battery capacity to supply it, depending on what your "longest time at anchor" is and so forth. You don't need much battery capacity if you don't leave the dock!

I am not a good example, but I have 50 Amp-hr AGM batteries for engine starting, and a pair of paralleled 75 Amp-hr batteries, for a total of 150 Amp-hrs. The 150 Amp-hrs is enough for 3 days on the hook with reefer, LED lights, radio, etc. all running. I have a 65-watt solar cell that helps out.

John,

Victron is well known in superyacht circles and as far as I know their stuff is pretty advanced and cheap for Euro stuff. These are my choice for my boat and I hope to get them installed next trip down (haven't bought them yet). The charging setup I have now is Byzantine, even I don't understand it.....

Starting current is more than 100 amps for sure and these combiners have a 30-second 180 amp rating. I don't know if they are smart enough to disengage if the current is too high, probably not. However, the original Marinette two-battery system had a relay that did the same thing, and most will still have the switch on their panel. You might burn the thing out, but it might be worth it depending on how big the barge bearing down on you is..... I will not use the feature, because I have two start batteries and I can switch them from engine to engine. I won't need to switch in the house batteries, I hope, but it is a nice feature to have in reserve.

I don't know what the starting current for a warm engine is, maybe Jeff would know.

This past season I replaced my original NEWMAR with a Charles for a 3 bank and switching for the AGM's I am using. I shopped the charger on the net and WM matched the lowest price I found saving a few hundred $ don't let price decide your choice without some negotiation at WM.
Now I am trying to figure out the wiring hookup to go from a 2 bank 2 alternator set up to a 3 bank with a dedicated starter battery and being able to charge all 3 while under way.
Tim

Hamilton Marine has the 100A combiners on sale for $43 this weekend and I am going to get a pair.

I have two start batteries and two house batteries. I plan to put each combiner between a start battery and a house battery. Each alternator is connected to its start battery, and when it is charged, it will switch in the house battery and charge that too. I plan to get rid of all the diodes and other stuff I have and go with the simpler circuit. I'll let you know how it works out.

You betcha. The drill is to leave the battery switch on "1" after the engine is started, and wait for the start battery to come back up to full voltage. Then, switch to "both" to put current into the house battery. The switch must be wired so that it does not leave the alternator disconnected from a battery at the same time that it has field voltage, because the resulting huge voltage spike is sure to damage something. Many battery switches turn off the field for you, watch out for Perko!

I used to have enthusiastic crew who would watch the voltmeter and then switch over at the correct time. Now that she is 16 and has reached her "whatever!" years, I would have to do it myself. So I installed a bunch of diodes to direct the alternator current to the appropriate battery automatically.

This works, but there is a voltage drop across the diodes, around 0.7 Volt, and this fools the regulator. I get away with it because my alternators put out 14.7 Volts but my AGM batteries will charge properly at 14 Volts. Still, at 70 Amps of charge, there is a loss of around 50 Watts in the diode. The practical effect is that, without the diode, the alternator will put out more current. Let's face it, diode isolators are so last decade.

With the combiners, the device waits for the voltage on the charged battery to come up, then switches in the house battery, all automatically. No more "I forgots". And the circuit is much simpler.