battery maintainers

lvmci · July 20, 2013, 07:34:27 PM

Hi All, my 66MCI5A has the knife switch in the front bay to disconnect the 2 starter batteries. With the knife switch thrown to disconnect, but cables connected, would an ac battery charger/maintainer connected to one charge both or would each battery need its own charger, even tho connected thru the battery to engine cables, charge only the battery it is connected to. My thoughts are that the cables that make the 24volts would make one battery to the charger, confusing the electronics that measure the one volt drop, that starts the charging process. I would like to have the starter batteries, charged and maintained while on shore power, which is not currently the way it is. Am I correct in my thoughts? Lvmci...

Lin · July 20, 2013, 08:22:20 PM

You can charge one battery with one 12v charger or both with a 24v charger. Motorized wheelchairs are often set up as 24v, so I good wheelchair charger would work as a permanent system. They are expensive new, but can be had reasonably used.

gumpy · July 20, 2013, 08:24:53 PM

I'm really confused by what you wrote, but let me see if I can decipher it...

Your MC5 is 24v, correct? So, there are two 12v batteries which are connected in series to give you 24v.

You have a disconnect switch on the positive lead from (probably) the right hand battery, and the negative lead from the other (left) battery is connected to the bus frame.

You want to put a charger (I'm assuming 12v charger) on one of the batteries to charge both of them while the bus is parked and on shore power? Is that correct?

Well, if this is correct, then the answer is, maybe...

If you connected the 12v charger to the left battery, with the negative from the charger going to the left battery negative post and the positive from the charger going to
the left battery positive post, then you would essentially be charging that one battery with 12v. Now, because battery charge will "flow" from a higher potential to a lower
potential, you would, in theory, actually be charging both batteries as the two batteries try to equalize the charge between themselves. It's not a very efficient way to
float batteries, and will always result in one battery (left) being charged more than the other.

You would be far better off buying a 24v charger and connecting it to the whole pack. And yes, it would work just fine with the disconnect switch open if the charger
is connected to the battery posts.

Now, if my assumptions are incorrect about your description, then clarify your question and we'll try again...

lvmci · July 20, 2013, 11:06:25 PM

Thanks Lin, do wheel chairs have 2 12volt batteries or one 24 volt, do the 24 volt chargers act like battery maintainers, checking for 1 volt loss then charging for a while
? Craig, I tried to make my question concise, obviously failed at that, I was asking about one battery charger or two, would they work together or against eachother if the batteries were tied together, I was unfamiliar with 24 volt charger, which seems to solve the issue, thanks, lvmci...

bevans6 · July 21, 2013, 03:29:43 AM

I just use a 24 volt wheelchair charger, supposed to be fully automatic but I don't leave it connected all the time - it seems to get confused by the 250 AH of the two 8D's.

Brian

gumpy · July 21, 2013, 06:25:38 AM

Quote from: lvmci on July 20, 2013, 11:06:25 PM
Craig, I tried to make my question concise, obviously failed at that, I was asking about one battery charger or two, would they work together or against eachother if the batteries were tied together, I was unfamiliar with 24 volt charger, which seems to solve the issue, thanks, lvmci...

Ok. I didn't get the two charger part.

If you connected one 12v charger to each battery, then you effectively be charging each battery individually. This would work, as long as the chargers were connected directly
to the respective battery's individual terminals. It also would work regardless if the disconnect were open or closed.

However, the better option would be to get a 24v charger. I like the idea of using a wheel chair charger if you can find one at a reasonable price.

Another option, if you have a 24v house battery system, is to add a cross over cable from your house system to your starting system and charge them off your house inverter.
You didn't indicate anything regarding your house system, so just throwing this out in case that's an option for you. That's what I do. Whenever I'm plugged in, my Trace
inverter is floating both the house and coach batteries.

Lin · July 21, 2013, 07:25:12 AM

Wheel chairs generally have 2 12v batteries. We use a wheelchair charger which is multi stage. It starts at 8 amps and goes down to 2 amps. I believe that it does go into a maintenance mode, but I am not sure. I do not leave it on all the time though.

Ed Hackenbruch · July 21, 2013, 07:37:51 AM

Are you having a problem with your starting batteries not holding a charge? Reason i ask is if i recall right, you use your bus quite often? My 5 can sit for 4-6 months without being started and will fire right up. I used to throw the knife switch when sitting for any length of time but after forgetting to do it a time or two and finding that the bus would fire up, i don't bother anymore.

Dave5Cs · July 21, 2013, 09:27:49 AM

Same as Ed, I never throw the switch to off. We leave it plugged in with converter on off at inside control panel. Any time I want to start it I turn the inside battery switch on and start it up. My inverter charges them up and then shuts off. If they get down for any reason the converter will bring them back up.

Dave5Cs

chessie4905 · July 21, 2013, 09:46:35 AM

We have a trace, and a battery isolator and also a 24 to 12 volt , which is connected to start batteries. The inverter charges/maintains the house batteries and also the starting batteries. The shutoff switch just shuts off the draw from the start batteries.
Btw, some chargers will slowly drain a battery when connected, but not plugged in.

Ed Hackenbruch · July 21, 2013, 10:19:06 AM

I probably should have mentioned that the only time my starting batteries receive a charge is when the bus is running.

lvmci · July 21, 2013, 06:47:27 PM

Hi All, thanks for the thoughts, I have 3 sets of batteries, starter bank, house bank and a single car type battery for generator start and camera system, it however has a 12 volt feed I think from the starter batteries installed by the previous owner, I plan on tracking it down and put it on a cutoff swiitch, my question has to do more with maintaing a maximum charge while sitting in a park. I have had problems in some of the old parks with brown-outs and low voltage in summer afternoons, I bought a low hi voltage cutoff protector because of that, I dont want to burn up an airconditioner or fridge compressor. If I dont throw the switch off from the start batteries, when the electricity is shut down for low voltage I have a phantom draw that brings down the start batteries, when the automatic systems kick in for the fridge, and other electric systems to keep them going. Ed I have been working a lot in LA lately and it does get used more than most, I had a bad set of new batteries, group 31s, from napa and replaced them lat week, Thanks, lvmci...