Size battery

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lipets

Senior Member
Joined
Jun 27, 2019
Messages
469
Location
USA
Vessel Make
Benneteau Swift 42
What size start battery recommend for 11K Onan, there was a big one originally I think a 8d would have fit in the box


Can't see a reason for anything that big & heavy


It was replaced with a group 27 that is too now 4 years old, and barely started.


So just another 27 or maybe 31??
 
If a group 27 won’t start it then it probably needs some maintenance. Lots of people use a group 24. But I think if a 27 will fit in the box that is what I would use.
 
My Lehmans only have group 27s. I would certainly think a group 27 would be fine for the Onan.

Ken
 
A good condition M24 starting battery should do it. M27 more than enough. I would wonder what is up with the existing battery but not too much effort.
 
How is the noisemaker batt charged when not in use?
 
Not sure how it's charged, looking thru manual doesn't say, I assume thru the battery charger with shore power.


I checked again yesterday it's G24 that is unknown age, so it's been able to start it for prior owner for several years.
 
Not sure how it's charged, looking thru manual doesn't say, I assume thru the battery charger with shore power.


I checked again yesterday it's G24 that is unknown age, so it's been able to start it for prior owner for several years.
May not be charged via ShorePower at all...could just be via small alt on genset itself. Four years is a pretty short service life.
 
I believe I have heard discussion that some generators have no alternator. With such a short life one of the first items to check would be how does the battery get charged.

Ken
 
I believe I have heard discussion that some generators have no alternator. With such a short life one of the first items to check would be how does the battery get charged.

Ken



No alternator on my genset. The genset battery is charged, in my case, from a DC-DC charger from the house battery.

The only way to find out would be to trace the wires.
 
A good grp 27 should start an 11kW just fine. If it does not, batt size is not the issue. Charging, cables, wrong type 27, something. That engine is like 2liter. I can start an 8liter on a healthy 27.
 
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