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Old 03-10-2019, 07:29 AM   #1
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Are My Batteries Toast?

When I got my bus ('05 FS65, Cat C7), I knew one battery tested bad. After sitting for a while it wouldn't turn over. I pulled the bad battery and replaced it. Started right up. Voltmeter on the dash read 14.1 while running. It all seemed good. The bus sat for a while more, and yesterday wouldn't even try to turn over. I put the multimeter on the batteries and it read around 8 volts.

Questions:
I have three Group 31 batteries. Is that optimum?
Should I pull each battery and test individually?
Are my batteries toast and need replacement?

I am going to try to determine if there is a parasitic draw (I'm totally new to this). Any advice or comments are welcome.

Joe
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Old 03-10-2019, 07:41 AM   #2
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Quote:
Originally Posted by TeacherJoe View Post
When I got my bus ('05 FS65, Cat C7), I knew one battery tested bad. After sitting for a while it wouldn't turn over. I pulled the bad battery and replaced it. Started right up. Voltmeter on the dash read 14.1 while running. It all seemed good. The bus sat for a while more, and yesterday wouldn't even try to turn over. I put the multimeter on the batteries and it read around 8 volts.

Questions:
I have three Group 31 batteries. Is that optimum?
Should I pull each battery and test individually?
Are my batteries toast and need replacement?

I am going to try to determine if there is a parasitic draw (I'm totally new to this). Any advice or comments are welcome.

Joe
If you have one bad battery the rest will go bad in short order.
I run 2 g31's. Some run 3 in colder climates. I've never had any issues starting any bus with even one.
I'd buy a couple brand new batteries and start fresh.
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Old 03-10-2019, 07:50 AM   #3
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Originally Posted by EastCoastCB View Post
If you have one bad battery the rest will go bad in short order.
I run 2 g31's. Some run 3 in colder climates. I've never had any issues starting any bus with even one.
I'd buy a couple brand new batteries and start fresh.
Thanks. Thatís what I was thinking. However, I donít want to throw batteries at a faulty system. I feel like I need to rule out a parasitic draw. Am I overthinking it?

Joe
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Old 03-10-2019, 07:56 AM   #4
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Thanks. Thatís what I was thinking. However, I donít want to throw batteries at a faulty system. I feel like I need to rule out a parasitic draw. Am I overthinking it?

Joe
You'll need batteries either way.
Buy em cheap. If you have a Rural King they sell G31's for $79. Those are what I run. They're decent enough.
Your bus has a lot of electrical stuff. Start checking out everything with a multimeter.
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Old 03-10-2019, 08:12 AM   #5
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Seems like our busses often have at least a little parasitic drain even if nothing is ďwrong.Ē

I have breakers in the engine bay that I flip any time I donít need to start for a while. You may also, and if not if may be worth adding a marine style disconnect.
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Old 03-10-2019, 08:31 AM   #6
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bad batteries cause phantom problems.

if your parasitic draw is not obvious, replace the batteries, and it will probably go away.
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Old 03-10-2019, 09:06 AM   #7
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Disconnect your batteries from the bus and each other, charge them properly and then test them or get them tested.
You do have a parasitic draw, they just don't go flat typically from sitting.
Clean up battery posts and cable ends, both ends and ground connections.

A simple paste of baking soda and water brushed on posts etc aids in cleaning then brush off residue with a wire brush.
If you can check the specific gravity on each battery cell.


When all is well just connect one and begin checking for that parasitic draw.
There is a simple way of doing that, mentioned in other battery threads here.
Do all of these steps before throwing money at new batteries.



John
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Old 03-10-2019, 09:38 AM   #8
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Quote:
Originally Posted by BlackJohn View Post
Disconnect your batteries from the bus and each other, charge them properly and then test them or get them tested.
You do have a parasitic draw, they just don't go flat typically from sitting.
Clean up battery posts and cable ends, both ends and ground connections.

A simple paste of baking soda and water brushed on posts etc aids in cleaning then brush off residue with a wire brush.
If you can check the specific gravity on each battery cell.


When all is well just connect one and begin checking for that parasitic draw.
There is a simple way of doing that, mentioned in other battery threads here.
Do all of these steps before throwing money at new batteries.



John
This sounds like a plan. Thanks for the help everyone.

Joe
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Old 03-10-2019, 09:44 AM   #9
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Your C7 is controlled by a computer just like all newer vehicles so you will definitely have a parasitic draw all the time, but you could disconnect it and look for a draw from something else also.
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Old 03-10-2019, 09:59 AM   #10
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Your C7 is controlled by a computer just like all newer vehicles so you will definitely have a parasitic draw all the time, but you could disconnect it and look for a draw from something else also.



How much draw is there Rick from these computers anyway?
Enough to kill two Group 31's?
Most vehicles get driven and so charge batteries up again but buses do sit more, private ones anyway. I could see it over a few weeks or months happening without charging at all. Something else going on here I presume.


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