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Old 07-02-2018, 11:40 AM   #1
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Generator battery

I have an 8kw Northern Lights gen set and think it's time to get a new start battery. I currently have a group 24 battery. Out of curiousity, what size battery are others using for a similar size gen set?

I have no problem going back to a similar battery but wondering if through the years, past owners have downgraded/upgraded by not putting properly sized battery in.

Thanks
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Old 07-02-2018, 12:29 PM   #2
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we have a 7.5 kw and use a group 24. That's whats been in the boat since purchase 3+ years ago. When replacement time comes, we'll probably replace with like. Unless this thread reveals something to consider.....
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Old 07-02-2018, 01:14 PM   #3
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Quote:
Originally Posted by cosmo View Post
I have an 8kw Northern Lights gen set and think it's time to get a new start battery. I currently have a group 24 battery. Out of curiousity, what size battery are others using for a similar size gen set?

I have no problem going back to a similar battery but wondering if through the years, past owners have downgraded/upgraded by not putting properly sized battery in.

Thanks
I have the same generator and use a group 24 start battery. It is all that should ever be needed.

Ken
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Old 07-02-2018, 01:23 PM   #4
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We had the same generator in our last boat and it came with a Group 24 battery from Walmart. We replaced it under warranty when it failed. Worked great.
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Old 07-02-2018, 02:09 PM   #5
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8k westerbeke using a group 24
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Old 07-02-2018, 02:26 PM   #6
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I will likely stay with the 24 also. I know my current battery is long in the tooth and wed be lost without our genny.

Thanks
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Old 07-02-2018, 05:07 PM   #7
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https://www.batterystuff.com/kb/tool...oup-sizes.html
What ever can fit!
My Onan needs at least 200 CCA to crank over and start.
I use a standard automotive type starting battery with post tops.
I created a battery tray to take a number of different sizes of batteries, so not limited to anyone size, this is like almost any size will work as long as it fits in the box and can easily start the gen.Yes, I think it is a 24 in their now as it is a common size.
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Old 07-02-2018, 07:40 PM   #8
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My old WB 8 BTD and my new Phasor 8 kw use M24 battery.
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Old 07-02-2018, 08:25 PM   #9
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With a 1977 7.5 kw Kohler I use group 27 starter batt
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Old 07-02-2018, 08:50 PM   #10
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Onan prescribe a 150AH(?= a 6D) for my Kubota engined MDKD 6.5. Seems overkill for a small engine, but it`s what they say,and of course it has to preheat as well as start. I keep it nicely charged with its own small solar panel and regulator.
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Old 07-03-2018, 05:22 AM   #11
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IF a gp 31 would fit with no hassle I would go bigger.

While a gp24 is fine for day to day use , eventually something will be a problem ,

and the size of the battery will be the key to multiple start attempts.
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Old 07-03-2018, 07:00 AM   #12
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For starter power redundant/safety sake...

Black battery box between propulsion engine and gen set engine carries a completely isolated LA G 27 starter batt with trickle charger that performs each time the 120 v breaker is activated by either shore power or by gen set power. It's charge level is kept at top end with never any draw down.

That isolated "emergency" batt is my go-to insurance for replacing batts on the gen set or in our tow behind runabout, when/if necessary. During last decade it was utilized once for each item. Soon as it's needed I replace that isolated batt with a brand-new LA G 27.

It also could be used as starter batt for the main engines if needed. I have the mains hooked into our house bank that has 4 LA G 37 linked in parallel that charge off a Professional Mariner on its own breaker and/or by the alternator from starboard engine.
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Old 07-03-2018, 07:21 AM   #13
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I use a group 31. I think it's 6 or 7 years old now. It is only charged by the gen set alternator.
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Old 07-03-2018, 07:39 AM   #14
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Item I forgot to mention in post #12. Gen set batt is also solar charged.
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Old 07-03-2018, 10:05 AM   #15
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Right after I purchased Kinship, the Genset battery died. I think the very last time it had enough juice to the start the Genset was during the survey. It was the original Chinese SLA battery of indeterminate size (smaller than a 4D but bigger than a 31). I replaced it with a group 27 AGM I bought on sale at WEst Marine.

My Genset is only a 5KW Northern Lights.

The genset battery is charged via a Balmar Duo-charger off the house bank. That seemed to work really well for the original SLA battery as it lasted 7 years.
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Old 07-04-2018, 07:41 AM   #16
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I did it a little different. Gennie and main engine share a batt. But it can be paralleled to house batt.

All the little Japanese gennie engines will start fine on a grp 24, with the exception of some older Westerbeke 8kW with Mitsubishi engines and reduction gear starters. I find those naturally crank over rather slow and can be tough to start unless batt and cables are in good shape.

Some old Onan MDJ series also need some serious batt power to start, but not that many left out there.
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Old 07-09-2018, 02:56 PM   #17
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Onan 8Kw had a group 27 we just replaced. Above comment about the pre-heater made me think that might be why. In summer rarely need to pre-heat. Last winter, oh yeah.
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Old 07-10-2018, 06:50 AM   #18
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Quote:
Originally Posted by cosmo View Post
I have an 8kw Northern Lights gen set and think it's time to get a new start battery. I currently have a group 24 battery. Out of curiousity, what size battery are others using for a similar size gen set?

I have no problem going back to a similar battery but wondering if through the years, past owners have downgraded/upgraded by not putting properly sized battery in.

Our start battery for our 8 kW genset is a Group 34 Odyssey AGM (PC-1500).

-Chris
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Old 07-10-2018, 07:21 AM   #19
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Our start battery for our 8 kW genset is a Group 34 Odyssey AGM (PC-1500).

-Chris
With batt that big - you need only an inverter! - LOL
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Old 07-10-2018, 12:53 PM   #20
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With batt that big - you need only an inverter! - LOL

Nah... the Group 34 is similar to a 24...

-Chris
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