12v 24v question

[PowerTech]

a work boat with a new engine.the new engine is 24v the old one was 12v.a 24 volt bank will be instaled to control engine function.but the 12v bank will stay to run the house and start the generator.What i would like to know, is there a device like a isolator that will take juice from the 24v alternator and split in up to charge 12 and 24 volt seperate systems?Thanks

[DGreenwood]

First I would consider how difficult it would be to convert your house system over to 24 V...it may be easier that you think. Most lighting involves changing bulbs and many of the more modern electronics can take 8-32V. Motors (such as pumps and Reefers) are another story. Think about that first.
Barring that:
You can build or buy a converter. It basically chokes 24V down to whatever voltage.
Better yet just mount a second alternator that is 12 V and has its own regulator.
The problem with using the 24 V alt to charge 12v is the fact that charging rate is controlled by controlling the field voltage in the alternator so you cannot charge both a 12V bank and a 24 V bank at the same time.
Anybody else have any ideas?

[ABoatGuy]

Another solution would be to keep the 24V alternator and battery bank and center tap it using a battery equalizer to provide 12V for loads that you can't or don't want to convert to 24V. The equalizer balances the load on the two sides of the center tap. A simple center tap without an equalizer isn't recommended.

They are commonly used on 24V power boats to power 12V accessories.

See: http://www.vanner.com/htm/pro_01.htm...51112&a=a&pt=3

[PowerTech]

equlizer it is. Thanks

[Frosty]

I had a boat like that once 24v start--12v house. I had 2 alternators on the engine and another 12v on the gen. They would all work together at the same time!! The 24v side was completely dedicated to eng start, anchor winch and wash. Easy to fit the 12v alternator, you would think that all the negatives would get upset but they dont, and yes the engine was common negative to 24v-and 12v

[PowerTech]

The new engine turned out to be 12v we were told it was 24v by the distributer.The distributer only carys 24v versions of the motor but got us this one in a hurry from a huricane damaged marina that came from some ware else I geus.The motor was on back order,and I hope the nice people that let us do the swap don't get stuck with a 24v pain in the arse.Thank for all the replys I did learn something anyway.

[Andina]

Picking off 12 volts from the center of the 24 volt bank to charge and maintain your 12 volt system is unwise, although not uncommon. When two batteries are in series to provide 24 volts it is very important to keep the voltages on the two balanced so they charge and discharge equally. If 24 volt charging is being shared on the 12 volt end by additional batteries, then the current to charge them both has to flow through the top battery. This will cause the top battery to be fully charged long before the bottom batteries and it will gas heavily and be damaged.