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SouthBrooklyn 10-28-2010 12:43 PM

Emergency battery charge ?
2 Attachment(s)

I read just about all postings related to batteries and chargers and is getting a little complicated. Here is my situation. My boat has a two battery bank with an off/1/2/both switch and a third battery used solely for an inverter. At this point in time even if the switch is set to off I am able to use the lights. The previous owner told me that the switch works only with the outboard. Is that right?

Speaking about the outboard, does in use electricity for running or just for starting?

Previously, the boat was moored and the owner was charging the batteries at home. I have the boat docked, but she doesn't have any shore power system installed.

Last week I ordered a Guest 10A 2Bank Charger (3 stage) and when I was supposed to receive it, I found out it is back-ordered and I have to wait another two weeks. I am afraid the batteries charge will go too low, although I didn't use lights at all and the engine about 2-3 hours. I read that a voltmeter is not very reliable, so I don't know how to check the batteries right now.

I have a marinco adapter and a Sears 10/2A charger at home. Should I use it until I get the other charger? How do I ensure I don't overcharge the batteries. Should I disconnect the batteries and charge them individually?
10A or 2A?

What is the best course of action for the long run?

Thank you.

hellosailor 10-28-2010 01:05 PM

The best course of action in the long run is to get a book like "the 12 volt doctor" or something similar explaining marine charging systems, then trace out and document your entire system since there's telling how the PO actually set it up.

Use a pencil, don't be afraid to erase.<G> Once it is done you can color the lines red and black too, if that helps. Seriously.

In the meantime...Yes, using your Sears charger, set on the "slow" charge option should be just fine. At a 2A charge rate connected to two batteries (no need to split them) it almost certainly can't overcharge them in any short time. Check the electrolyte level first, top up with distilled water if needed, and use a cheap $20 multimeter to check the charge voltage. When the batteries reach a peak and then stop (somewhere between 12.8 and 13.6 volts) that's "full enough" for right now. Let them sit overnight, check the voltage again, if it has fallen below 12.4-12.6, give them another 24 hours of charge and call that good enough for now.

Most small outboards don't need a battery at all, once you add the electric starter they need power to start, and often have a small magneto to provide a little power while they are running, for the running lights and to recharge the starter drain.

mitiempo 10-28-2010 04:01 PM

I agree with what Hellosailor posted.

You should be able to use the 1/2/both/off switch to turn off all power (except bilge pump which should be wired direct and fused).

It looks like the 2 batteries in your picture are the same. I would parallel them and put them on #1 on the switch and use them as "house" and take the third battery and wire it to #2 as a start battery. That way you would be drawing from a larger bank for both house loads and the inverter. It also simplifies the system which is always a good thing.

This assumes that the other battery is not a larger deep cycle - the one used for the inverter.

Stillraining 10-28-2010 04:14 PM

Yep ..he has it wired wrong....Follow the above posts advice...they will sort you out.

SouthBrooklyn 10-28-2010 10:34 PM

Thank you for your suggestions.

hellosailor, I've already got "the 12 volt doctor", by tomorrow morning I'll have a PhD in Sailboats Electric Systems and I will start working on the wiring diagram.

mitiempo, I will look into that battery grouping, but first I need to check what type they are. funny thing you mention the bilge pump, the boat doesn't have an automatic one, just a manual whale pump in the cockpit.
Is this bad? Very bad? For the rest of this fall I will do a few day sails. Next year I plan on going all the way around Long Island, and then up and down the coast, from New York City. Should I install an electric bilge pump? Two years ago I passed through Victoria Harbour on my way to the Desolation Sound. Great places. I hope to come again sometime...

Stillraining, I will.

Thanks again.

mitiempo 10-28-2010 10:42 PM

My boat had only a manual pump in the cockpit before my purchase. I am installing an electric auto bilge pump but I don't expect it to get much use. I think it is a good idea though.

jjablonowski 10-29-2010 09:33 AM

Mitiempo, above: "use the 1/both/2/off switch to turn off all power (except bilge pump which should be wired direct and fused)."

To which I'd add, a direct wire (also fused) to the am/fm radio if you'd like to keep preset stations in memory.

mitiempo 10-29-2010 01:05 PM

Yes, the radio memory wire as well.

Stu Jackson 10-29-2010 07:13 PM

And then get your alternator output off the C post of the 1-2-B switch and wire it directly to your house bank. Diss the separate inverter battery and make it all one big house bank and run the inverter off the house bank. You appear to already have an ACR, so you can easily automatically link your reserve and house banks. Draw a wiring diagram.

See Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams and 310 Battery Info - Page 2 -

SouthBrooklyn 10-31-2010 12:42 PM

2 Attachment(s)
Here are the existing and the updated diagrams. And a few notes.

So far I didn't have use of the inverter, I am keeping it "just in case".

I still have to check how is the grounding presently done and to get more info on grounding.

I might use AC on board in the future, but right now I don't need it.

So, is my updated diagram working?


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