Start battery size

[Liambennett]

Hi all,
I’m trying to determine what size batteries to start a Cummins VT555m.
I have fitted a 24v starter to it.
I have a separate 12v bank for the rest of the boat.
I was thinking of 2 x 1000A CCA 110Ah in series
Would this be enough ?


Thanks for the help !

[SteveK]

That would give you 24V and 1000CCA. sounds like enough, but I do not know the draw of that engine

[Bacchus]

Mfg usually specify CCA for each eng. Do you have access to the manual?

[Nickwadsley]

I have a pair of the dreaded triple nickels and I use a pair of blue top optimas with 800 cold cranking amps to start (12 volt starters)them
3 years ...
Start right up
Knock on wood
Engines purr along nicely

[DennisB1]

I have cat 3208 which are similar in size. The starting current at 12 volts is in the area of 1000 amps. At 24 volts you could expect about 500 amps. Your two batteries in series would do a good job. I use a single Northstar AGM 215amp for the Cat engines.

[Liambennett]

Thanks for all the reply’s,
Would you recommend using AGM’s ?

[BruceK]

Originally Posted by Liambennett

Thanks for all the reply’s,
Would you recommend using AGM’s ?

The Blue Top Optima batts recommended above are AGM. I recently replaced one "like for like" for the bowthruster.

[Datenight]

A single group 31 started my 30 year old Perkins 6-354 instantly. Of course is 201 cubic inches less. Two should be fine.

Rob

[pjtemplin]

Originally Posted by Liambennett

Thanks for all the replyies.
Would you recommend using AGMs ?

I would recommend using the same chemistry your boat has today UNLESS you confirm that ALL charging systems for that battery bank are adaptable to an AGM charge profile AND you confirm that you have no "weak links" or surprises that could impact the other battery bank(s) if you switch that one to AGM.

[Bacchus]

Originally Posted by Liambennett

Thanks for all the reply’s,
Would you recommend using AGM’s ?

I switched from FLA 8Ds to AGM 8Ds with only change being the setting on shore charger. That was 10 seasons ago and I am very pleased.
Only change I'm planning when the time comes is to replace each 8D with a pair of AGM GP31s.. The Sams Club AGM GP31s ( by East Penn) have both post & stud so I can use the same cables w post clamps and use the studs for the new paralleling jumpers... arranged in a balanced configuration.
I've heard AGMs not ideal for hi amp loads but the existing starting & thruster bank is actually still stronger than the house bank. That makes sense to me as the DOD is likely much lower than house to higher cycle life makes sense.