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Ken Klunder (Novice) (209.112.145.41)

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Posted on Wednesday, May 15, 2002 - 4:54 pm:   

I thank the people who helped me attempt to understand this 12 vs volt systems. You guys made it sound easy, except for me totally understanding it.
We will be using two banks of batteries: bus starting and operation batteries and coach(house batteries). We are not sure if the batteries which supply energy to the living area are correctly called coach batteries. The question, is it possible to operate the bus on 24 volts -- charging starting and bus operation batteries, driving and clearance lights, coach (house) batteries, etc -- and then some where behind the coach batteries change it to 12 volts for use in the coach (house) area of the conversion?
Again, we are really new to the process of converting, so please humor us if this is a stupid question. Thanks in advance for the advice.
Scott Whitney (24.205.232.249)

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Posted on Wednesday, May 15, 2002 - 5:23 pm:   

Hi Ken,

Just a little terminology to help clarify. . .

Bus batteries/coach batteries/chassis batteries = batteries used to start engine and run bus sytems like headlights etc. Usually are starting type.

House batteries = batteries used to run living systems. Usually deep cycle type.

To convert 24vdc to 12vdc you can use a voltage converter. However, the general consenus seems to be a battery equalizer is the preferred method to get 12V from a 24V bank.

You can, however, have a 12vdc house bank and retain your 24vdc coach bank (using a second 12v alternator to charge). But if it were me, with a 24v bus, I'd make the house bank 24v also. Having said that, my bus is all 12v so my hands-on experience is only in 12v systems.

Scott
Stephen Fessenden (Sffess) (63.27.88.10)

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Posted on Wednesday, May 15, 2002 - 6:27 pm:   

Good answer Scott.
Two other possible terms used.

Conversion batteries = House batteries. (From Executive Coach manual)

Engine batteries = Bus, coach, chassis batteries.

I have decided not to call the bus batteries coach batteries in posts because it could be confused with house batteries. I prefer house and engine batteries because no one could possible misunderstand which I mean. I still have to think which one is meant by coach batteries when I read it.
Jim Stacy (12.87.108.56)

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Posted on Wednesday, May 15, 2002 - 9:08 pm:   

Ken,

It's very easy to have a 24 volt engine battery system to run those things that you already have 24 volt - starter, original equipment blowers, relays and such lightbulbs that you have not changed over yet. About $100 will buy a decent 130 amp 12V alternator with integral regulator. You just mount the alternator on the grounded engine and connect the single wire to the 12 V house battery bank. You then have the best of both worlds since appliances (refrigerator, radio, cd system, GPS, laptop, etc) are all designed for 12 volt, and the cost is very reasonable.

Since you have expressed an interest in boondocking, you will probably have a propane system that will take the heavy loads off what an all electric coach would have, such as electric refer, bus heat, and water heater. You don't need 250 amps @ 24 volts to keep your house batteries charged. The little 12v alternator will do just fine. If you don't need 4000 watts of invertor output, the 24 volt, battery equalizer program is a pain. Best to keep it simple. IMHO.

Jim Stacy
Tom Caffrey (Pvcces) (64.114.233.189)

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Posted on Thursday, May 16, 2002 - 10:16 pm:   

Hi Ken,

Jim Stacy's idea about adding a 12 volt alternator has an additional benefit that you wouldn't get with everything on the same voltage.

Besides discharging batteries too deeply, recharging them too quickly is one of the worst things you can do to them.

When everything is recharged by the same alternator and the alternator is over 200 amps, this is very easy to do if you do not have a lot of batteries installed.

With a separate alternator, it will be much easier to match its output to your house battery capacity. If 100 amps is safe for the batteries, and you install 100 amp alternator, they will not be recharged too fast.

It seems like that would make a nice combination system.

Tom Caffrey PD4106-2576

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