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12v to 24v


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I have been asked by a client to fit a 24v windlass to their existing 12v system and am trying to do away with a 24v alternator, separate battery bank etc. I am thinking of adding 1 more battery and having a solenoid switch for the windlass connected between the start battery and the new battery in series to supply 24V only to the windlass when in use plus normally closed relays on - & + to charge at 12V paralleled from the start battery. These relays would open when solenoid is activated. Am I missing something or would this actually work?

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Where they have the switch is where I intended fitting the solenoid, activated by the windlass control. I had thought of using a load like the headlamps but it is a sail boat so this system would place current draw on the batteries when sailing. I guess I should think about a fail safe system for the charging disconnect (ie 2 NC relays in series instead of just 1) but I'm not too concerned about timing as I'm sure the relays would open quicker than solenoid closes. Mmmm, maybe a time delay relay for the solenoid actuation?

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Use a multi pole Solenoid Pete. So that as one set of contacts change, the other set become opposite. There should be a small time difference in fractions of a second where both sets of contacts are open between change over so as you don't have any short.

The only biggy is a solenoid like that, being suitable to handle the huge current demand. Or you could have a small double throw switch at the dash that selects the solinoid at battery. So switch to left say, would be normal 12V, switch to right would be 24V for winch. Three position would be even safer, so as the center position is off to everything and allows that time for one to change to the other so there is no chance of a flash over.

 

Aside from all that, is there a really major reason why he has a 24V winch?? Would it not be cheaper and easier to swap to a 12V motor on it? Or sell the 24V and buy a 12V? Big Solenoids capable of doing what you are trying to do are not cheap, If you want quality that is and then add in your time if you are and then all the things you don't think about like battery eye terminals and battery cable and blah blah.

 

The other thing to be very wary of, is adding a new batery to an older existing battery bank. If the existing one is older than a year, forget it. You will never get all of them to charge evenly and one battery will end up never fully charging and another could boil.

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Wouldn't a 2 pole solenoid enable 12V to the engine when windlass is in use?

The reason for the 24V is that the boat is a 75 foot cat and they haven't found a 12V unit that will do the job. Also reduces cable size for the long run to the winch.

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OK she's a biggun. Then why not a 24V bank for winch only and then a simple 12 to 24V charger. You don't need to have a seperate alternator, just a charger. Place bank as far forward as practicle for a Cat and then run the cables from there.

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Thought of the 12 - 24V charger but all I can find are 12 - 12V units or 12 -24V converters. The converters produce a current drain and do not have any current regulation. Trying to keep things simple, light and cost effective.

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Yes low charge current would be the only negative. Maybe there are higher output devices available. Certainly good practice is to have the engine running while winching to keep the voltage up, but in your case, with solenoids switched, that won't be happening anyway.

Certainly pluses and minuses with either idea and I guess it just comes down to which is going to be easiest for you to implement.

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