Battery Size Questions

[American]

We have a 2010 Chevy Express Gas V8, 6.0l and I'm going to buy a new battery.

The old one has no markings. AutoZone says minimum size is 78 group size, 600 cold cranking amps

Here's my question. Do I need to get a bigger size battery to account for the extra bus lights and the big AC in the back? Can you ever buy "too big" of a battery? The compartment for the battery is big enough to fit any size. I just can not find good info on battery size for short bus. Thank you in advance

[Albatross]

No, you can never get "too big" of a battery, generally-speaking.



Look for more CCA (Cold-Cranking Amps); it should be easy to find in a Group 78 battery. I think mine are in the 750-850 CCA range, and they are group 78 yellow-tops.


Considering that you've got an extra big AC in the back, I would actually consider getting two, and putting them together in a parallel configuration, with some monster 4/0 battery cables, so that they can share the load, and each battery will have less stress on it. I would also consider bumping up your alternator's output as well, if that hasn't already been done.

[Jolly Roger bus 223]

what bus body do you have?
some manufacturers hid a second battery to handle the extra load under the front entry steps.
when i get time and remember i will look at what my single battery is.
but seperated anything bus starting running from anything house side.
my bus did have the rear A/C but it was deleted when i got the bus and i as needed have replaced battery and alternator with what i pulled out of it. dont know what the previous owner did.

[American]

Here is the new battery I put in plus a photo of the old one. The new marine battery is from an RV I bought but now I'm second guessing my choice

[American]

The tip one is the old one, the bottom is the marine. Sorry they are upside down ��

[American]

Thank you Albatross. Do you think the marine battery I am using is ok

[nikitis]

Originally Posted by American

Thank you Albatross. Do you think the marine battery I am using is ok

600 CCA is the lowest you can find likely. I'd shoot for 800 CCA minimum. Not to say 600 CCA wouldn't work, but you may be caught out some day with being unable to crank the engine as those batteries get old. If you had 3 of them at 600 it would be better as it would share the amperages across all 3, but still.

[Albatross]

Originally Posted by American

Thank you Albatross. Do you think the marine battery I am using is ok

So the chemistry and structure of marine batteries are a little bit different from "starting" --or normal--automotive batteries. "Marine" batteries are built to handle a larger "depth-of-discharge" while lasting longer, whereas normal automotive/starting batteries are designed to put out maximum cranking amps, but will be permanently damaged if they are discharged below 50%.



You want real starting batteries for your starter/bus circuit; you can use "marine" batteries for your house (120VAC) side of the bus electrical systems.


It also needs to be said that you really, really need to use the exact same batteries if you're going to run batteries in parallel. And that also means of the same age.... If you've got one walmart-brand durastart battery, and it's more than 6 months old, you really don't want to just go out and buy another of the exact same kind because of the difference in wear and tear on the battery.


The reasons for this is because the inside of the cells change as they get used, and because they change over time, adding new cells to an existing system will change the whole makeup of the system, and it will usually cause both batteries to never be in the same place at the same time, which means that as they get charged or discharged, both batteries will not have the proper voltage for their state, leading to damage to both batteries. If this were not the case, then we would likely buy individual battery cells, kind of like you can sometimes do with Li-ion batteries. This is why when you buy an auto battery, there are actually six cells inside it, because they all need to be in the same place as they are charging and discharging in order to stay balanced and healthy.


Sorry, but you're probably going to have to spend the money and buy two brand-new batteries in order to fix your issue.

[AlphaHare]

Here's a chart for "Group" size. IMO most of these smaller ones are practically identical in terms of capacity, and the Group is about form factor - LxWxH

Your Duralast is a group 24, the Eveready is group 78.

https://shop.advanceautoparts.com/r/...ery-size-chart

CCA is what you should look for first. If Navistar says 600 CCA, and you have two of them in parallel, I think that's probably plenty for a gas engine.

"Reserve" Capacity is Minutes at a 25A load before the voltage drops to a certain level. Used often in light duty-dual use, where the starting battery may also be the house battery. Not your application, but a way to compare Amp Hours between batteries.

Two batteries are not going to run the stock bus AC. For that, the engine is probably driving the AC compressor off the V-Belt and the only 'extra' power you need is for the additional blower fans on the evaporator and condenser.

As others have said, best to have a high output alternator. They are often standard in school bus / ambulance prep cut-away chassis.

[American]

Originally Posted by AlphaHare

As others have said, best to have a high output alternator. They are often standard in school bus / ambulance prep cut-away chassis.

I actually had not considered this. Interesting idea. I have been running the AC with the 1 battery that was an 800. This was in the bus when I purchased it and never thought about it. I bet the battery was getting killed.

[American]

Originally Posted by Albatross

Sorry, but you're probably going to have to spend the money and buy two brand-new batteries in order to fix your issue.

It was really just a "get by" until I understood what I needed to purchase. Your info is really helpful. Thank you

[AlphaHare]

Originally Posted by American

I actually had not considered this. Interesting idea. I have been running the AC with the 1 battery that was an 800. This was in the bus when I purchased it and never thought about it. I bet the battery was getting killed.

You have another thread going on as well. I'll bet your alternator (or wiring) is unhappy if you get a charging error without the AC running.

[Albatross]

Originally Posted by AlphaHare

As others have said, best to have a high output alternator. They are often standard in school bus / ambulance prep cut-away chassis.

Originally Posted by AlphaHare

You have another thread going on as well. I'll bet your alternator (or wiring) is unhappy if you get a charging error without the AC running.

This, 100%. I've got a 200-Amp alternator specially-bought for the application. I got mine from Summit, and the only one they had was in some kind of super-chrome finish, but it was relatively cheap (I think around $250.00) compared to the cost of messing up, messing with, or burning out your electrical side of things.


And compared to the cost of a lot of other things, it's a relatively small price to pay to do the things right.

[American]

Originally Posted by AlphaHare

You have another thread going on as well. I'll bet your alternator (or wiring) is unhappy if you get a charging error without the AC running.

Perhaps. Let me tell you timing of events and see what you think.

First. No issues with Battery Charging System in hot Texas summer
2nd. Warning on Battery charging system running Ac periodically.
3rd. Changed out battery to RV marine battery after cleaning ground wires I was aware of and had to clean in the past.
4th. Periodically get warning message.
5th. How do I get a Quality Test on my alternator? O'Reilly's tested and said OK but I am second guessing that test.

[AlphaHare]

Who's your body manufacturer?

First - let's take the batteries out of the equation. That's a red herring, and unrelated to the charging/electrical problem. If the batteries can start the engine reliably, but turning on the AC throws a charging error light (generally low voltage) or the bus engine dies, the bus is telling you there is an electrical issue pulling down the voltage.

Not knowing your timeline, but following the sequence of events, I'm guessing you have either a failing ground, or a 12V connection that's loose. This is a creeping issue, as it seems to have become worse over time.

A dead short should blow a fuse, but a loose connection could add just enough resistance to create a voltage drop and subsequent current increase. The load isn't changing (the evaporator and condenser fan motors) so voltage drop can significantly increase the amperage required. These are long runs and my bus was rated 24 amps max on the evaporator and 54 amps max on the condenser, and had 50 and 70 amp relays controlling them.

A failing ground might have a similar mode of failure.

This is how I would approach it. First validate the grounds. It's easier.

The alternator should have a big, bare, braided copper strap to the chassis or block. Relatively protected, but prone to vibration and will deteriorate in 14 years.

If your alternator is attached to the block, then the block should also have a braided strap, somewhere, to the chassis frame.

Ditto the batteries (but this is probably a cable). Make sure they're all solid. Pull on the cables, pull on the lugs, wiggle them around, nothing should feel loose.

The condenser assembly under the bus probably has an independent ground to chassis for the motors. Mine did. Again, find it and inspect it. It's handling all the current for the big fans there.

The evaporator assembly at the back of the bus will also probably have an independent ground to chassis. Same as above. High current, longer runs more prone to voltage drop.

If all that looks good, then maybe some testing to isolate.

My bus had 3 circuit breakers under the hood, one to WC lift, one to the control PCBs over the driver, and one to the AC power relays. If yours has this last one, turn it off and see if the bus stops throwing the charging error. Guessing it won't, just like not running the AC at all.

Next, pull the power relay(s) for the just evaporator fans and see if it behaves the same way.

If good, replace and pull the condenser fan relay(s).

My bus had both low speed and high speed relays, with an option for a third. It might not be just one relay.

Hopefully, one of the last two options will show a difference and that's where you should start tracing the fan motor connections.

It's even possible that one of the fan motors is slowly seizing up and that would be a big current draw till it eventually dies.

That's all I got!

[American]

Originally Posted by AlphaHare

That's all I got!

Wow. I just read this to my family and we were all taking notes. Unbeknownst to you, your message filled in a bunch of gaps that was hard to write all things here.

I'm going to go about this just as you have said. I will notate this thread when I see what happens for future readers if this thread.

Sincere thank you for your help. Our bus is a Collins with a wheel chair ramp. A 2010Chevy 3500, V8, 6.0 to be exact.

Thanks again. Doug

[American]

AC fans ground.

Note:
I am going to update how bad my grounds "all over my bus" look. After I clean each one I will repost how it affects my battery. In the past, this made a huge difference in how my bus works. I just didn't realize how many grounds are on this bus.

[American]

Originally Posted by American

AC fans ground.

Note:
I am going to update how bad my grounds "all over my bus" look. After I clean each one I will repost how it affects my battery. In the past, this made a huge difference in how my bus works. I just didn't realize how many grounds are on this bus.

I couldn't get the screw out due to the rust. Ended up "drilling" it out which ended up destroying the end of the wire. Perhaps I should have just cut the wire and reset it in new position.