Charging Start Batteries for 24 V System

qayqayt · April 25, 2014, 09:23:42 AM

I have much appreciated all the help and advice as we limp home after our problem filled trip. One more for you. We have a pair of 8D batteries set up for a 24 volt system. If I wanted to put a charger on, would I connect it to the positive on one battery and the negative on the other?

Bryan

Utahclaimjumper · April 25, 2014, 10:07:34 AM

If you have 12V batteries wired in series parallel, and trying to use a 12V charger, just charge one battery at a time.>>>Dan

Red Rider · April 25, 2014, 10:22:55 AM

Glad to see you made it home. I'm happy to know all your trips haven't been like this last one. Maybe we should head back to Cody and start over?

I agree with what Dan said but after two weeks on the road, Why do your start batteries need charging?

Lin · April 25, 2014, 10:25:42 AM

Just to clarify-- Your two 8d's are 12 volt, so they are connected in series to get 24 volt. Essentially, this is combining two 12 volt batteries to make the equivalent of one 24 volt battery. So yes, if you have a 24 volt charger, you can charge both at the same time connecting the charger to the outside positive and negative. Make sure not to connect the charger to the inside ones. That positive and negative are connect to each other and will short your charger if you try to connect to them. If you take voltage readings from one battery's positive to the other battery's negative, you want the ones that shows 24+ voltage.

If you only have a 12 volt charger, charge each battery separately.

boogiethecat · April 26, 2014, 07:46:01 AM

My local surplus store almost always has 8 amp 24 volt interacter chargers available for $50.. if you want me to get you one and ship it to you i'll be happy to.
These are really robust, can be built right into your bus and do 3 stage. Quite a good charger. They came from some military application and are either new or barely used...
see: http://interacter.com/products/professional-series-specs/ part number is PS2408

lvmci · April 26, 2014, 08:04:52 AM

Hi All, one of the aspects of charging two seperate batteries as one, is each battery is not always in the same shape as the other, I have two 12V chargers, hooked up separately, when on post power, I hook up the maintainers, the leds almost always show more time to charge one over the other and I bought these 2 batteries at the same time, they're the same age, from the same napa store. Lvmci...

Lin · April 26, 2014, 08:39:11 AM

I would like to hear something on this from someone who really knows what they are talking about but even though that is not me, I would speculate that what you have going on is really the norm. It would be very surprising to me if the batteries charge in exactly the same way. I would guess that in theory charging them each separately is superior but really makes no discernible different for us. I have installed that same charger in the above link that came from Boogie's source and am totally fine with it. However, I do not leave it on all the time- just flip it on for a while every couple of weeks or so.

Utahclaimjumper · April 26, 2014, 08:40:01 AM

They also will not have the same lapse rate, (1-2 percent of loss per DAY) do to the variables in construction. It stands to reason that the charging rate will also be different.>>>Dan

qayqayt · April 26, 2014, 09:33:59 AM

We bought a charger at a local auto parts store for $60. It seems to be doing the trick. The GM manual says that a 9 amp charge over 24 hours is the best way to charge them up. I took your advice and disconnected the batteries and am charging them one at a time. The first one charged up in 5 hours so we're waiting on the other one this morning.

Sorry Mike, but we haven't made it home yet. We're in Oregon City. I suspect an alternator problem, but would like to try and limp home. We're only about 6 or 7 hours away. This trip has been one ongoing bad dream. At some point I'll write it up in a blog and share it with everyone.

Bryan

Red Rider · April 26, 2014, 10:09:56 AM

Well Bryan,

If you can discount all the mechanical issues, you two have seen a lot of country's. Can't wait for your manuscript. Nina and I enjoyed the one you wrote last year.

Good luck "limping".

Zeroclearance · April 26, 2014, 10:24:39 AM

Bryan, so you are heading back to BC. What did you end up doing to get your engine up and running. Was it just one head? Broken rings?? You started the previous thread, what ended up happening??

Purplewillie · April 26, 2014, 07:17:15 PM

Bryan , I also was curious how you made out with your engine troubles?
Mark

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eddiepotts · April 26, 2014, 11:11:39 PM

I think you can measure a sandwich with dial calipers to cut in half to share but is that really necessary? I have always just remove 1 leg of the center cable and used jumper cables to charge 2 batteries in one charging time limit. When I worked at Monkeywards back in the day we had a wall with charging cables and 1 charger running it all. I always leave the center cable off until it is time to start the bus if it is going to sit for any length of time. When my alternator did not work I could go for days on the charged batteries depending on how often we stopped and had to start them again or use the running lights. I would even use two jumper cables and use my generator 12v alternator to charge them for a while if we stopped for dinner or something. I just don't see the point of precision charging on a battery. If I am going to charge one in 5 hours they will both be done to the best they are going to get in that same 5 hours.