Cranking voltage

[sledhead]

my cat is a bitch to start . the first revolution always sounds like it will never start ( sloooow ) then it moves faster and its running . it has never not started yet but it does this every time when the engine is cold . when its warm it starts fine . this is with 4  x 31 cat batteries that are 26 months old . I do have a 400 amp boost switch so I can use the house batteries            
 ( 660 amps ) to help . hope I never need to use it  but it is there if I need it

https://photos.app.goo.gl/eoEyiWEDbBYSPzEz2

https://photos.app.goo.gl/tK7h6kxNrrK4USmA2

https://photos.app.goo.gl/KfVyaqP8xbiYIAzz2

dave

[thomasinnv]

I was able to order online and get a 10% discount thru napa so it brings the price down to 203 ea. I will pick them up at the local napa tomorrow. Good thing I have cores, they are 72 ea core charge now. Wow.

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[luvrbus]

Yep you want a core when buying batteries in OK for sure

[chessie4905]

Sledhead, your description tells me you have some sort of an issue. Batteries, poor connection, starter going bad or combination of two or more. I think you should or have someone do some diagnostics with a meter, heat gun and battery hydrometer if it is not sealed type. I'd check for one or more low cells first.

[Branderson]

I think someone just mentioned it in another recent thread but if the starter batteries are low and it causes the engine to slowly crank, can't that burn out a starter even if it's brand new?

[bevans6]

The starter draws "power" from the batteries to do it's work.  The work is fairly constant, except for the in-rush of getting started, and since power is volts times amps, if the volts go down the amps go up as the motor tries to draw the power it needs.  Wire is sized to be able to carry amps, since amps are what generates heat in the wire.  As volts go down and amps go up, it's easy to exceed the ampacity of the wire, brushes and connectors inside the starter.  Hence the possibility of damaging a starter if you try to run it with a low battery charge.   The good news is that as a battery ages and gets old, it loses it ability to deliver current, so an old worn out battery that doesn't maintain a great charge and is going to fail a load test loses some of it's ability to deliver enough current to damage the starter.

Brian

[luvrbus]

Low voltage is a fast death for the older Delco starters like the 42 the 39Mt is a lot more forgiving being a reduction type and not a direct drive from the past   

[thomasinnv]

Checked them again this morning. One battery tests good at 1525cca and resting voltage of 12.85. The other made me laugh. 215cca with resting voltage of 10.5. I'm going with "dead cell". They are now in the back of the truck and will be replaced shortly. I hate to see the one good battery thrown in the core pile, but no way I'm not replacing both of them.

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[eagle19952]

I think someone just mentioned it in another recent thread but if the starter batteries are low and it causes the engine to slowly crank, can't that burn out a starter even if it's brand new?

YUP, worst thing you can do to a starter.

[thomasinnv]

New batteries in place and the old girl is happy once again. Now on to the next problem. Headlights stay on all the time unless I shut off the main disconnect. Bus has daytime running lights so thats going to male it a little more fun to diagnose. I'm suspecting a faulty switch or relay sticking. Me thinks the bad battery/low voltage situation is the likely cuase of this problem.

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[edvanland]

Tractor supply 8 D for $155 found that out to late paid over $200 at NAPA

[luvrbus]

Tractor supply 8 D for $155 found that out to late paid over $200 at NAPA

Must have been on sale ED the 4-D's here at TSC are $160.00

[thomasinnv]

Tractor supply 8 D for $155 found that out to late paid over $200 at NAPA

I wonder what the warranty is and if they are the 1100 or 1400cca?

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[eagle19952]

I wonder what the warranty is and if they are the 1100 or 1400cca?

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I have bought DEKA AGM 1400 CCA  that came off the shelf testing 1600cca. I think those #'s are advertising...
or minimums from the legal department.
used topay 160$ for NAPA 8d's retail, jobber was less....
I think the good old days are gone

[thomasinnv]

I was very surprised that a 4 year old 8d tested out at over 1500cca.

Yes the good ole days are gone. No more 150 dollar 8d batteries, no more $1 a gallon diesel, no more $3.99 a gallon oil.

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