Starting battery size

[Water Dragon]

Is there a rule of thumb for how many "extra" CCA are required to have a reasonable reserve capacity? I've measured about 275 amps with the engine cold and ambient temp below 30F, and I want to make sure it will crank even when it's really cold.

[rsvmille]

Generally, about 1 CCA per CID or 2 for diesel to turn the engine (not including accessories. Then about 4 times that for reserve CCA.

What is manufacturer spec?


I can provide my example:
My engine is a Yanmar 3YM30. Yanmar says 64Ah (for some reason they switched from CCA ratings (ability to provide amperage e.g. start an engine at around 32F while retaining 7.2V) which doesn't make much sense for starting to me). The starter draw (when healthy) is rated maximum loaded current at 250amps. The engine is 68CID. 544CCA according to the rough guideline above, would in fact be plenty sufficient. -- I wanted to go all LiFePO4, and there aren't many starting batteries in this chemistry (that I am aware of) so ended up with a Dakota Lithium starting battery rated at 60Ah and 1000CCA.

[Water Dragon]

The engine is a Perkins 3.152, and the manual (from the 1980's) specifies 95 Ah. I agree, Ah is a strange way to specify a cranking battery. The old battery measures 10-1/8 x 6-3/4 x 8-7/8, including top posts. In looking at battery size charts, I'm not seeing anything that matches. I could fit a battery that's up to 13-1/4 inches long. I may have to just go to NAPA and see what they have, but I doubt I'll find anything with 1024 CCA that will fit in the allotted space.

[Bowdrie]

A friend of mine starts his 100hp "Jimmy" all the time with a group 24.
With the space you have a group 27 will surely fit, and it might be close but a group 31 "should" fit.
More than enough to start the Perkins.
https://www.batteriesplus.com/produc...p-31m/sli31mdp

[Nord Sal]

My engine is a 80s era 52hp four cylinder 135 cid diesel.

The msnusl specs the starting battery at 4-600 CCA.

[smac999]

the diff in price from a 24 to 27 to 31 is going to be a few dollars. get the biggest that will fit.

[Water Dragon]

Well, here's the way I figured it. I have a truck with a 444 CID diesel, and its 2 batteries total 1700 CCA, and it cranks fine in any weather. That's 3.83 CCA per CID. Which, for the Perkins 152, means a minimum 582 CCA. I found a NAPA Legend group 24 battery with 650 CCA. Tried it this morning in the cold, and it cranks fine; much better than the old one. Still takes 2-3 tries to start the engine though, since it doesn't have glow plugs like the truck does.