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Anybody know anything about charging systems... and if you could enlighten me as to this idea I have on charging my batteries off my main motor (125hp merc). Do you see any flaws in this design?

It uses a four pole dual throw switch



(Mini, I leave Thursday for Ark. will let you know the results...)
 

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PM Hammer, he is very good at electrical.
 

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Elecrtically, it should work other than you have two different voltage generators. What about the batteries? Are they 12 or 24 volts? If they are twelve, you will need to change things a bit to run them in series instead of parallel while charging off the trolling generator. If they are twenty four, It might get a bit more messy to bother with.
 

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I assume your trolling batteries are 12v and by joining them together obtaining 24v for your little motor. That part seems fine. Not enough info on the switch though. My question is are you using an isolator to keep them charged equal? or so one doesn't drain the others?
 

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QUOTE(HazyMemory @ Feb 25 2003, 09:01 AM)What about the batteries? Are they 12 or 24 volts? If they are twelve, you will need to change things a bit to run them in series instead of parallel while charging off the trolling generator. If they are twenty four, It might get a bit more messy to bother with.
Look closer at the column of terminals on the right. In position 1 (troll) he is routing the (-) of trolling batt 2 to the (+) of trolling batt 1. So he is running in series. If they where 24 volt trolling battries he could not charge them from the 12V altenator without a transformer to step up the voltage.
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A see nothing wrong with your routing but I am not an expert and it's late, so I urge you to get a second oppinion.

There are some concerns that you need to consider if you wire it like this.

Find out how many amps the altenaror in your motor is rated for.

Make sure that your switch and wiring are heavy enough to handle the current.

Put fuses inline on the (+) wires as close to each battery as you can, so that if any where along your circut should ground out you will be protected.

Most outbords don't charge 1 battery well at idle or slow speeds let alone 3.

If you are going to run the trolling motor untill the batteries are near dead and you only have a short cruise back to the ramp you won't get much of a charge.

If you leave the switch in the charge position after you shut off the outbord and the trolling battries are still neerly dead thay will draw current from the crancking battery untill the voltage in all 3 battries are near equal. This may leave you without enough juice to crank.

You can fix this two ways. NEVER forget to put the switch in the troll position when you are done for the day or add a 12v relay (normally open) between your charging system and where you feed 12v(+) to the switch at the center two posts. Wire it so that the relay only sends power to the switch when the ignition is in the run possition. You would trigger this relay from the ingnition post on your ignition switch

My last concern is a biggie (fire risk). If you crank the outbord with the switch in the charge possition you will be cranking with all 3 battries. Unless you plan to run battery cable for your entire circut and a very heavy duty switch, which I doubt. This will be too much load and melt the smaller wires going to your switch and trolling battries. Or at very least blow the fuses that I sugested you install. This would most likely happen if your main cranking battery was low or durring long periods of cranking if the motor dosen't start right a way.

Again you can fix this two ways. NEVER forget to put the switch in the troll position when you are cranking or add another 12v relay (normally closed) that cuts power to your new circuit when the key is in the crank position. You would trigger this relay from the start/crank terminal on the ignition switch.

In case you don't know what relays do here is a brief run down.

A relay is a switch that is "flipped" electronicly. There are two basic types.

Normally open, (normally off) that stops the flow of current unless power is applied to the "trigger/switch" terminal of the relay.

Normally close, (normally on) that allows the flow of current untill power is applied to the "trigger/switch" terminal of the relay.

In either case the triggering circuit needs to be grounded. Most metal cased realys ground when you bolt them to a grounded chassis or frame. If you mount them to wood or some other ungrounded spot on the boat you will have to run a ground wire. A plastic bodied ralay will have a ground lead.

If you get lucky enouogh to find a 12v source that is hot when the key is in the run position but not when in the crank position, use it to trigger the first relay and you won't need the second. It is fairly common to find a 12v source like this on a car (all of your accessories turn off wile you crank) but I don't know if they wire outbord boats like that.

Good luck. I hope that this rambling helps.

 
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