24 volt engines 12 volt boat

omega2

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Ok chaps, how do I go about this, at present we have 12 volt system for the whole boat i.e. starters alternators and all the gubbins. However we are thinking of going 24 volt on the starter/alternator front, to assist starting in the winter. We have already got 2 batteries to each engine and assume we would connect them in series to produce 24 volts, but how would we reduce this to look after the lighting and the rest of the instruments/fittings. Please explain in as simple terms as possible.
 

jfm

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Not sure why it would help winter starting?

Many electronics operate 9-40v, so ok. Need to read the labels on them. For the rest you need 24-12 step down converters. Widely available, though not cheap.

For lights you can just swap the bulbs for the same size in 24v. You could rewire them into pairs, in series, but that's a lot of faffing, much easier to switch the bulbs imho

This is a big exercise though. Two new alternators. Two new starter motors. New windlass. And new battery charger (if you have a genset/shorepowered charger). Eek
 

halcyon

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Change the starter for a 24 volt one, then put a relay in that changes the batteries from parallel to series for engine starting, leave the 12 volt connected to one battery/bank. Once the engine is started the relay drops back to parallel, and the 12 alternator charges the batteries as normal.
Relay are used / or were used on rally cars for engine starting, so try that area.

Brian
 

smileygirl

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you would have to fit a 24V alternator and starter (truck parts?). put two 12V batteries in series. Then the alternator will charge up both batteries.
You take your 12V supply for electronics etc from the connection that joins the two batteries in series and earth/ground/0V engine body.
If you need more capacity put two batteries in parallel for the electronics etc and a single battery in series with them to give you 24V.

However it might be better to find out why the engines are difficult to start when cold - might be easier to fit an engine heater and timer. I used to have ford mermaids and you could get a mini immersion heater that fitted in one of the core plugs on the engine block, and connect to mains and warm them up nicely.
 

ccscott49

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Exactly right, thats the way to go, remember an imp rally car having exactly the same system for starting. No messing around with bulbs or anything.
 

compie1

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if you have problems starting in the winter you can do 2 things:

Use block heater to keep yr oil/water warm before you start or years ago they used to have 9v rotors for the starter motor worked fine wander if the still make them
 
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