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Old 06-14-2021, 11:31 AM   #1
Mini-Skoolie
 
Join Date: Sep 2018
Location: Austin, Texas
Posts: 35
Year: 2002
Chassis: IC RE300
Engine: DT466E (250HP/880TQ) / MD3060
Rated Cap: 84
12/24 Battery Configuration

Hey All,
I am trying to get 80A @ 24V to power some electric pusher fans for my IC RE300 bus. Rather than getting a converter, can someone tell me why I could not connect 2 of my 3 auto batteries in series and use them and upgrade the alternator?

Currently I have a 160A alternator, based on the removal of the wabaso pumps and a few other things, I think that the 160A may be enough, but there is plenty of options out there to get 240A-300A in a replacement alternator.

Can someone weigh in and poke holes in this idea? Obviously fuses would be in place.


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Old 06-15-2021, 10:03 AM   #2
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So... you want to charge up three batteries in parallel at 12V, then disconnect them, wire two of them in series for 24V, and run a 80A load from those two batteries?

Then, after running the load for, say, 30 minutes, your two batteries will be depleted. Next, you disconnect them, wire them back up in parallel, and drive around for 5 hours to get those two batteries recharged?

It is going to kill your batteries after just a few cycles – because they are starter batteries. But even if we forget that problem, and you would replace two out of three batteries with deep-cycle batteries, how are you going to actually start your bus? Using just one? Or were you planning to connect the batteries back in parallel first, and then try to start your bus? Well, the poor remaining battery will not only have to crank your engine, but it also will be charging your two depleted deep-cycle batteries you just hooked up.
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Old 06-15-2021, 10:15 AM   #3
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Year: 1991
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Why do we need the pusher fans?
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Old 06-15-2021, 12:16 PM   #4
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Try drawing your layout again from the top and you will see that by doing a simultaneous parallel and series configuration you will end up shorting directly across the terminals of the batteries, creating sparks and a thermonuclear meltdown. Well at least sparks and probably a fire.

It could be possible to do this with some protection diodes, but I would have to ponder that in my brain for a bit.

In 24 volt buses, like some of our highway coaches or transit buses, it's common to have a 24 volt system with some 12 volt tapped off one battery. But that's a different thing altogether and even that is not ideal. The battery that is providing the 12 volt power is always going to be drained and cycled more than the other battery in that string, which is charged with a 24 volt alternator.
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Old 06-15-2021, 08:34 PM   #5
Mini-Skoolie
 
Join Date: Sep 2018
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Chassis: IC RE300
Engine: DT466E (250HP/880TQ) / MD3060
Rated Cap: 84
Yup. Thanks. The short is what I was missing.

Diode’s or a decent idea but they likely have to be massive. Trying to get creative about making a 24 V system and not having to put together an entirely separate systems.
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Old 06-15-2021, 08:35 PM   #6
Mini-Skoolie
 
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Chassis: IC RE300
Engine: DT466E (250HP/880TQ) / MD3060
Rated Cap: 84
Hmm need to think
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Old 06-15-2021, 08:37 PM   #7
Mini-Skoolie
 
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Engine: DT466E (250HP/880TQ) / MD3060
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Quote:
Originally Posted by Bert06840 View Post
So... you want to charge up three batteries in parallel at 12V, then disconnect them, wire two of them in series for 24V, and run a 80A load from those two batteries?

Then, after running the load for, say, 30 minutes, your two batteries will be depleted. Next, you disconnect them, wire them back up in parallel, and drive around for 5 hours to get those two batteries recharged?

It is going to kill your batteries after just a few cycles – because they are starter batteries. But even if we forget that problem, and you would replace two out of three batteries with deep-cycle batteries, how are you going to actually start your bus? Using just one? Or were you planning to connect the batteries back in parallel first, and then try to start your bus? Well, the poor remaining battery will not only have to crank your engine, but it also will be charging your two depleted deep-cycle batteries you just hooked up.
Sorry, but I’m not sure on what planet you think that this would be the proposed process…

Who in the word would do that.

Larger alternator for charging. And something to allow for 12 and 24v connections.
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Old 06-15-2021, 08:38 PM   #8
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Quote:
Originally Posted by s2mikon View Post
Why do we need the pusher fans?
Rear engine
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Old 06-15-2021, 09:31 PM   #9
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Quote:
Originally Posted by halfdime View Post
…what planet you think that this would be the proposed process…

Who in the word would do that.
There is need to be a jerk, particularly if you don’t know what you’re talking about.

People are here to learn and help one another.
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Old 06-15-2021, 09:34 PM   #10
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Quote:
Originally Posted by rossvtaylor View Post

In 24 volt buses, like some of our highway coaches or transit buses, it's common to have a 24 volt system with some 12 volt tapped off one battery. But that's a different thing altogether and even that is not ideal. The battery that is providing the 12 volt power is always going to be drained and cycled more than the other battery in that string, which is charged with a 24 volt alternator.
It’s actually a very good system, BUT it requires a battery equalizer. My bus has this Vanner module:

https://www.invertersupply.com/index...hoCgCkQAvD_BwE

I measure my batteries religiously and it’s always spot on, down to the 10mV level.
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Old 06-15-2021, 10:01 PM   #11
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Quote:
Originally Posted by Bert06840 View Post
It’s actually a very good system, BUT it requires a battery equalizer.
Here’s a diagram:

IMG_0283.jpg
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Old 06-15-2021, 10:23 PM   #12
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Nice, Bert, thanks for that info. What kind of bus do you have? Our more vintage 24v buses lack that. Our Phantoms have that Vanner system, but the old ones are pretty basic.
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Old 06-15-2021, 11:27 PM   #13
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Quote:
Originally Posted by rossvtaylor View Post
Nice, Bert, thanks for that info. What kind of bus do you have? Our more vintage 24v buses lack that. Our Phantoms have that Vanner system, but the old ones are pretty basic.

I got this ratty but lovely 2009 29-footer Gillig…!

IMG_9999.jpg
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Old 06-15-2021, 11:33 PM   #14
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Quote:
Originally Posted by Bert06840 View Post
I got this ratty but lovely 2009 29-footer Gillig…!

Attachment 58506
Ah, she is lovely! Our Vanner modules are located right behind the driver's seat on the side wall, hidden behind one of the passenger seat backs. Is that where yours is?
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Old 06-15-2021, 11:57 PM   #15
Mini-Skoolie
 
Join Date: Sep 2018
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Posts: 35
Year: 2002
Chassis: IC RE300
Engine: DT466E (250HP/880TQ) / MD3060
Rated Cap: 84
Quote:
Originally Posted by Bert06840 View Post
There is need to be a jerk, particularly if you don’t know what you’re talking about.

People are here to learn and help one another.
Apologies, not trying to be a jerk.

I’m guessing I read into a tone that was not there in your post that had some pretty wild assumptions of connecting draining and disconnecting batteries every thirty minutes.

I for sure don’t know everything. Happy to share my knowledge and learn from others.
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Old 06-16-2021, 07:01 AM   #16
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Besides Vanner Equalizer, see Yandina "trollbridge" autoswitching 12V / 24v
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Old 06-19-2021, 07:50 PM   #17
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I use these equalizers

https://www.amazon.com/Victron-BBA00...y-Balancer/dp/

It only does 1 amp but might work if the 12 volt load is only on intermittently so the equalizer can catch up with the balancing.
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Old 06-19-2021, 11:51 PM   #18
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OP said 80A
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