C12 starting batteries

[Beaver_Thunder]

Was wondering if anyone on here has a C12 and what do they have for chassis batteries to start that motor. I have two Interstate batteries (model 31-MHD with 950 CCA and 1190 CA), with the batteries fully charged, I’m unable to start the engine cold without using the emergency switch. Best I can tell the starter is direct drive and the batteries are good (I have taken the batteries to the Interstate store and they have checked the batteries and say they are in perfect working order). I’m wondering if I have undersized batteries, curious what other C12 owners have set up for battery capacity.

[RFCN2]

My C-12 has two 8D starter batteries. I have no idea what the CCA is. I just replaced the original ones with similar when they went out ten 1/2 years ago and then again 2 years ago. When I bought the coach it was 7 years old and the batteries were original. BTW on the second pair they worked fine until they did not. No warning for failure. Likely yours need replacement.

[gsander1]

Beaver Thunder wrote:

gsander1 wrote:
My C12 has two Heavy duty 8D starting batteries.

George,

What is the CCA for the 8D's?

Cranking Amps = 1,720
Cold Cranking Amps = 1,400

[myface]

May have bad starter.

[Beaver_Thunder]

gsander1 wrote:
My C12 has two Heavy duty 8D starting batteries.

George,

What is the CCA for the 8D's?

[gsander1]

My C12 has two Heavy duty 8D starting batteries.

[Beaver_Thunder]

I wanted to follow thru and let everyone know I found the source of my issue, bad ground. The problem was in the battery shut off switch, the nut that holds the stud to the switch had worked it's way loose. I only noticed this because there was a little play in the battery cable, barley noticeable. After tightening the stud the engine crank was sufficient but really slow, so I went ahead replaced the batteries with a bigger set of 31's with 1025 CCA's, huge difference. I would have preferred to go with 3 batteries but there isn't enough room to add a third battery. I also found this on the web (for what it's worth) for recommend CCA for big bore engines:
Recommended mimimum CCA @temps above 32deg is 1460
Recommended minimum CCA @temps above 0deg is 1600
Recommended minimum CCA @temps below 0deg is 1800

Anyways thanks everyone.

[wolfe10]

That Caterpillar Corp could not give you the information is EMBARRASSING!!!

I can tell you that applications with the Cummins M11 which is close to the size of your engine use 3 group 31 batteries.

But, bottom line, if connections are clean and tight and you need to use the boost switch and with the boost switch the engine turns over and starts as it should, you do not have enough amps in the chassis battery bank.

[Beaver_Thunder]

Thanks so the CAT help line, so I called it, they were not able to give a CCA for my engine, so I called the local CAT dealership and asked them, they said they didn't have that data and that if it was listed anywhere it should be in the Chassis manual. He did mention that it could be the starter and asked if I had done a draw test on it. So I guess first thing I need to do is check the batteries and go from there.

[oldave]

Occasionally owners of coaches with large engines post about starting problems
most of them seem to correct those problems with a gear reduction starter .
Here is a site with some info .

https://www.elreg.com/blog/why-are-gear-reduction-starters-replacing-direct-drive-starters/

[wolfe10]

Caterpillar RV Helpline: 877 777-3126. Have your engine serial number handy.

[Beaver_Thunder]

A little back ground on the coach. We have owned it less than a year. It has never started cold without the Boost switch. When we bought the coach, it had recently had the inverter replaced, the prior owner said that after that, the chassis batteries would no longer stay charged. So after I got it home and doing some investigation I found that the combiner (magnum ME-SBC) wasn't wired correctly, so after correcting that issue, the chassis batteries are now being charged and maintained. My next step was to take the batteries down to get tested, I figured they were probably bad due to lack of charging (about a year), well they told me that they were fine. I've looked thru the Magnum chassis manual, CAT manual and owner manual and have not found any reference to the CCA required for this engine. Is there any other place I should look? I'm not confident that the batteries are fine either, could be one bad cell but I'm not convinced they are bad either. The batteries are only 2 years old. Anyways, long story. Thanks for the input.

[Executive45]

This post begs the question. Has your engine ALWAYS done this or is this a new phenomenon? If it's always done it then you need to check if they are the correct batteries. Your user manual should give you that info. If it's new then you need to check other things. My coach uses the same batteries with no issues. Like you though, I did have my batteries checked this year as they were six years old and my coach seemed to struggle to start. "They" told me the batteries were perfect, that is, until they were not. Checking them a week later "they" said two cells were failing. Two new batteries and I'm in business again. YMMV....Dennis

[wolfe10]

Caterpillar 12 liter diesel.

And, your Caterpillar owners manual or a call to Caterpillar will tell you the minimum CCAs.

[pianotuna]

What is a c-12?