Smallest battery for 2GM20

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nathanlee

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I'm replacing my batteries with AGM, and because I want to get a bigger domestic battery in there, I could do with downsizing the 85ah flooded starter battery. The Yanmar manual says it should be a 75ah battery, but what's the smallest I could realistically get away with if it was a good quality AGM?

I was thinking perhaps a 60ah?
 
Starter batteries are measure in CCA - Cold Cranking Amps not in AH.

A quick trawl through a halfords or equivalent car battery supplier will find something small, suitable and cheap. Boat engine start batteries tend to be much bigger than needed for a normal start, so that there is ample reserve for multiple starts.

My engine start battery is 1000 CCA and you need a crane to lift it, but that is to start both engines 3GM30 (shortly to be 3YM30 :cool:)
 
nathanlee said:
I'm replacing my batteries with AGM, and because I want to get a bigger domestic battery in there, I could do with downsizing the 85ah flooded starter battery. The Yanmar manual says it should be a 75ah battery, but what's the smallest I could realistically get away with if it was a good quality AGM?

I was thinking perhaps a 60ah?
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the one just removed from shmbo`s 1.9D seat was 540 CCA i replaced it with a 670 CCA

http://www.batterymegastore.co.uk/product/57220/
 
If space is limited, then we propose an optima red top engine start 50ahr.
Cost £144.07 + vat.
Dims: 254 x 174 x 195
regards
Adverc BM Ltd
 
As Talbot says, capacity in amp hours is a largely irrelevant measure for starter batteries.

Best way to save space is probably a Red Flash purpose-made starter battery - it's AGM and has limited capacity, but it provides plenty of amps for starting and is very small.

My 2GM20 always starts on the button, but if some kind of engine problem meant you ran down the starter battery due to its small capacity, you could always bring in the domestic bank as backup.

Pete
 
As already suggested, look at CCA.

For comparison, Beta Marine recommends 450 – 540 CCA for starter batteries to their 20 and 25 hp engines.

Based on this I chose a Red Flash 1100 (500 CCA/37 Ah) for my 20 hp Beta.
This was seven years ago – no problems so far.
 
I have a Red Flash 1100 starting my Volvo 2003 28HP.The supplier said that the Red Flash 1000 would do the job but as the 1100 was only a few pounds more at the time I went for the bigger size.Have used it for 6 seasons now without problems.
 
nathanlee said:
I'm replacing my batteries with AGM, and because I want to get a bigger domestic battery in there, I could do with downsizing the 85ah flooded starter battery. The Yanmar manual says it should be a 75ah battery, but what's the smallest I could realistically get away with if it was a good quality AGM?

I was thinking perhaps a 60ah?
Click to expand...

If you are going down this route, then take a deep breath and get a Red Flash or an Odyssey. As already suggested it is CCA rather than AH capacity that is important. The advantage of a Red Flash is that it is roughly half the size of an equivalent wet battery and can be mounted in any orientation. A Red Flash 750 or the slightly bigger capacity 1100 are suitable sizes or an Odyssey PC 925. Twice the price of a 75AH car type battery but frees up space to increase the service bank.
 
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Yes. Twice the price of a car battery as I said. However, if you want the benefits it is priceless!

Nathan asked for the smallest AGM starter battery, and that is it. Whether he wants to pay the £150 is then his decision.
 
That is way OTT and not necessary for a little Yanmar. That is for starting a big truck engine.

Your original £50 type battery is adequate to start the engine (which is only half the size of even the smallest car engine) but is big compared with an AGM and probably won't last as long. That is what you pay the extra for.
 
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Zagato said:
Just spoken to Tanya.co.uk and lady suggested getting this as it will start your engine and act as a leisure back up has 1000CCA

http://www.tayna.co.uk/EXV90-Enduroline-Calcium-Leisure-Battery-P8281.html

Not cheap though :eek: I was going for something about £48 last time I researched this, probably just a marine leaisure 70AMP.
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That's silly it's 90Ah.
If it's just for starting the Yanmar this would easily do it http://www.tayna.co.uk/063-Enduroline-Car-Battery-380CCA-P8401.html

Red Flash batteries have fantastic output but are priced accordingly.
I'd recommend buying from http://www.dmsshop.co.uk/ as DMS are the master distributor and provide tech backup. Tayna buy through DMS.

Yes Tayna have been quoting exaggerated CCA figured for Red Flash - correct figures from DMS.
 
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Zagato said:
I was going for something about £48 last time I researched this
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For what it's worth, I've had three years of more or less trouble-free use from a pair of bog-standard Halfords leisure batteries on Kindred Spirit. You don't always need the best possible kit.

Pete
 
Zagato said:
Nathan what does the manual say about the CCA for a Yanmar 2GM20? I don't have one :(
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Rather stupidly, it doesn't say anything.

PDFs of both workshop and user manuals for the 2GM20 are available online. I don't have the link to hand, but they're not hard to find.

Pete
 
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