Yanmar 3GM30 Starting Battery Size ?

[daddle]

For both good and silly reasons yachties like huge starting batteries. Interesting that my diesel tractor back home has a diesel not unlike my boat. Same HP. The battery is *tiny*. Like that in a tiny automobile. Lunch box size. A little bigger than a motorcycle battery. Starts every time. Even in cold weather. Don't know the CCA.

[westwinds]

Check reply number 7: Cold Cranking Amps to Amp Hour formula? where it states that 400-450 CCA equals 56 AH. For the 3GM30, doing a little math gives 457 -514 CCA for 64 AH. An Interstate battery available at most auto parts stores has a 600 CCA rating for a group 27 deep cycle and in group 24 a 500 CCA for their heavy duty group 24. The extra heavy duty group 24 is 800 CCA. Interstate Batteries

[Saltyrope]

Originally Posted by daddle

For both good and silly reasons yachties like huge starting batteries. Interesting that my diesel tractor back home has a diesel not unlike my boat. Same HP. The battery is *tiny*. Like that in a tiny automobile. Lunch box size. A little bigger than a motorcycle battery. Starts every time. Even in cold weather. Don't know the CCA.

Hi Daddle, Several reasons that your tractor battery may be smaller. One is that many boat engines are marinised industrial / tractor engines and tractor engines are what one may call de-rated engines as are basic work boat engines. Have a look at the Kubota basic engine for instance and see how many boat engines use the Kubota as a starting point then improve its horsepower output by various means including inducing higher compression ratings then call it a medium duty or even light duty engine. A good test is to try and start your tractor via its crank handle if one is supplied and then try and do the same with the same basic block after it has been uprated to a higher performance level. You may find that the latter needs more person power to turn the engine over.
And of course, if your tractor battery goes flat, there is no problem with leaving it firmly 'anchored' to the ground while you go get another charged up one. Happy ploughing! Cheers, John.

[GordMay]

There is no direct correlation between CCA and amp-hours nor BCI Group Size.

Some battery definitions:

AMPERE-HOUR (Amp-hr or AH): A unit of measurement for battery capacity obtained by multiplying the current flow in amperes by the time of the discharge in hours.

BCI GROUP NUMBER: The BCI Group Number defines a battery by describing the following characteristics:
A.) Its maximum dimensions (L x W x H)
B.) Voltage (6 volt or 12 volt)
C.) Post configuration
D.) The type of terminal used (top, side, flag, etc.)
It should be noted that the BCI (Battery Council International) Group Number does not designate a battery's capacity, it merely defines the above listed physical characteristics.

COLD CRANKING AMPS (CCA): The cold-crank rating is the primary rating presently used for automotive batteries. CCA's are the number of amperes a battery can deliver for 30 seconds at 0° F and still maintain a minimum voltage of 1.2 volts per cell (7.2 volts for a 12 volt battery).

RESERVE CAPACITY RATING: The time in minutes that the battery will deliver 25 amps at 80° F until it falls below 1.75 volts per cell (10.5 volts for a 12 volt battery).

[Maine Sail]

Originally Posted by GordMay

There is no direct correlation between CCA and amp-hours nor BCI Group Size.

Some battery definitions:

AMPERE-HOUR (Amp-hr or AH): A unit of measurement for battery capacity obtained by multiplying the current flow in amperes by the time of the discharge in hours.

BCI GROUP NUMBER: The BCI Group Number defines a battery by describing the following characteristics:
A.) Its maximum dimensions (L x W x H)
B.) Voltage (6 volt or 12 volt)
C.) Post configuration
D.) The type of terminal used (top, side, flag, etc.)
It should be noted that the BCI (Battery Council International) Group Number does not designate a battery's capacity, it merely defines the above listed physical characteristics.

COLD CRANKING AMPS (CCA): The cold-crank rating is the primary rating presently used for automotive batteries. CCA's are the number of amperes a battery can deliver for 30 seconds at 0° F and still maintain a minimum voltage of 1.2 volts per cell (7.2 volts for a 12 volt battery).

RESERVE CAPACITY RATING: The time in minutes that the battery will deliver 25 amps at 80° F until it falls below 1.75 volts per cell (10.5 volts for a 12 volt battery).

Thank you Gord!

Lots of boaters prefer to use a deep cycle type battery for starting because that battery may someday be needed to run house loads if the house bank were to fail or there was another issue that required the second bank to become a "reserve" bank.. They also tend to last longer than a thin plate battery.

Deep cycle batteries will have no issues starting a Yanmar 3 cyl engine. Lots of the popular 12V "deep cycle" batteries are pumping out over 500CCA (CCA is at 0F) and at 70F closer to 700+CA.

The very popular Deka/East Penn group 24 deep cycle (also re-labeled and sold by Sam's Club, West Marine, O'Reilly Auto, NAPA and others) will easily produce 500CCA at 0F. The "MCA" or marine cranking amps rating is at 32F and will be about 625 MCA. When you get up to 70F these tiny group 24 deep cycle batts are pumping out over 700CA.

These little engines require very little in the way of starting current and even a small group 24 deep cycle will spin them with ease... The Trojan SCS-150 deep cycle is basically the same size as a group 24 and has 530CCA and 650MCA and is closer to 800CA at 70F...

There is no direct equation between Ah capacity and CCA, MCA or CA but as Yanmar knows any battery that meets their required Ah capcity will easily start their engines. Westerbeke, Universal and others all spec a CCA but Yanmar specs a min Ah capacity in the older manuals.


Trojan Battery: Can I use my deep cycle battery to start my engine?



Answer: Deep cycle batteries can be used for engine starting but starting batteries should not be used for deep cycle applications. A deep cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep cycle battery is still more than adequate for the purpose of starting an engine.

[mrohr]

Thanks Gord,that cleared some cobwebs from my brain.
Now for the non technical answer.I have the 3gm30 (rather old) and often fire her up using my even older house battery (just a sears off the shelf flooded 12V ,not particularly large) and that old yanny always comes to life,but I,m not sailing in remote areas and and so am somewhat caviler in my day saying with a handy boat.When I'm cruising I tend to pay more attention to proper protocols.

[DotDun]

Originally Posted by Saltyrope

.....those that cruise in more challenging areas will already know the value of having a bit of redundancy built into their systems. The single biggest cause of breakdowns at sea is a flat battery.

The single biggest cause of breakdowns is lack of maintenance, a flat battery is just a symptom.

I don't consider a group 27 battery offering any redundancy over a group 24 battery. Two batteries is redundancy.

A battery is a ticking time bomb, it'll last X cycles or X years, whichever comes first. A proper maintenance plan will replace them prior to that threshold.

[westwinds]

Originally Posted by Maine Sail

Thank you Gord!

Lots of boaters prefer to use a deep cycle type battery for starting because that battery may someday be needed to run house loads if the house bank were to fail or there was another issue that required the second bank to become a "reserve" bank.. They also tend to last longer than a thin plate battery.

Deep cycle batteries will have no issues starting a Yanmar 3 cyl engine. Lots of the popular 12V "deep cycle" batteries are pumping out over 500CCA (CCA is at 0F) and at 70F closer to 700+CA.

The very popular Deka/East Penn group 24 deep cycle (also re-labeled and sold by Sam's Club, West Marine, O'Reilly Auto, NAPA and others) will easily produce 500CCA at 0F. The "MCA" or marine cranking amps rating is at 32F and will be about 625 MCA. When you get up to 70F these tiny group 24 deep cycle batts are pumping out over 700CA.

These little engines require very little in the way of starting current and even a small group 24 deep cycle will spin them with ease... The Trojan SCS-150 deep cycle is basically the same size as a group 24 and has 530CCA and 650MCA and is closer to 800CA at 70F...

There is no direct equation between Ah capacity and CCA, MCA or CA but as Yanmar knows any battery that meets their required Ah capcity will easily start their engines. Westerbeke, Universal and others all spec a CCA but Yanmar specs a min Ah capacity in the older manuals.


Trojan Battery: Can I use my deep cycle battery to start my engine?



Answer: Deep cycle batteries can be used for engine starting but starting batteries should not be used for deep cycle applications. A deep cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep cycle battery is still more than adequate for the purpose of starting an engine.

Well then all an older Yanmar owner has to do is select a deep cycle battery that has more than 64 amp-hours and good to go? I wonder if Yanmar took into account that a boater might use a deep cycle for starting.

[Azul]

I have a Yanmar 3GM30 and it starts instantly with a single Group 29 deep cycle battery, I have two of them on separate banks (with plans for two more) but now leave the Guest battery switch on "All" after noting with a multimeter there is an inconsequential drop in the bank's voltage after a start, and my solar panels keep the batteries topped off anyway. For this small motor I don't see an advantage in having a separate starter battery and think the money would be perhaps better spent on a small solar panel to maintain the batteries or money/space for another house battery, and yes my original Yanmar manual states that 70AH is sufficient- I thought it was a typo when I first read it. Having loaded every tool and home appliance aboard I thought I might remotely use I still have tons of storage room except in the designated battery area- I suspect this space is even more at a premium on smaller boats.

Further, I don't believe batteries will just suddenly die therefore should be replaced at X interval routinely. It would be more cost effective to monitor their state of health with a multimeter or battery monitor and replace them as their ability to hold a charge gradually fails. Batteries and ground tackle are two areas where redundancy is not just a good idea but mandatory.

[westwinds]

I did find a conversion formula here: View topic - converting Amp Hour to CCA rating for battery | Australian 4WD Action Take CCA and divide by 7.25 to get amp-hours. This is for a starting battery, not deep cycle.

[ReMetau]

We have a Yanmar 3qm30. We use a dedicated starter battery group 24 with 1000 MCA.

[David M]

Call the manufacturer or a dealer and ask how much current the starter motor draws. Then get a battery whose CCA is greater than the starter motor draws. Amp-hours only matter to batteries whose loads draw for a longer period of time....much longer than the few seconds that a starter motor draws current.

[Saltyrope]

Great post Gord May. Thank you. Precise, to the point, gives all the correct perameters. And what a great forum with all the diffferent approaches to the same subject. My own experience with many deliveries is that isolating the start battery is the biggest concern, so that after a few days of sailing and the house and electronics batteries are down, the engine always has a full battery to start the engine. Regards, John.

[roverhi]

FWIW, When I bought my boat it had a Group 24 battery for the 3gm30f starting battery. Worked fine for 4 years but decided to switch it out before I left for Hawaii. Bought a group 27 which is heavier and was hard to muscle in place. Hope I can get it out of the very restricted area that the battery is in when the time comes to replace it. If I had to do it again, would go with a group 24. It's only used as a starting battery so need for any additional storage.

[Ex-Calif]

Originally Posted by GordMay

There is no direct correlation between CCA and amp-hours nor BCI Group Size.

Some battery definitions:

AMPERE-HOUR (Amp-hr or AH): A unit of measurement for battery capacity obtained by multiplying the current flow in amperes by the time of the discharge in hours.

BCI GROUP NUMBER: The BCI Group Number defines a battery by describing the following characteristics:
A.) Its maximum dimensions (L x W x H)
B.) Voltage (6 volt or 12 volt)
C.) Post configuration
D.) The type of terminal used (top, side, flag, etc.)
It should be noted that the BCI (Battery Council International) Group Number does not designate a battery's capacity, it merely defines the above listed physical characteristics.

COLD CRANKING AMPS (CCA): The cold-crank rating is the primary rating presently used for automotive batteries. CCA's are the number of amperes a battery can deliver for 30 seconds at 0° F and still maintain a minimum voltage of 1.2 volts per cell (7.2 volts for a 12 volt battery).

RESERVE CAPACITY RATING: The time in minutes that the battery will deliver 25 amps at 80° F until it falls below 1.75 volts per cell (10.5 volts for a 12 volt battery).

Thanks Gord,

My Delco Marine says it is a G24 with 70ah and 600 CCA. So I guess I don't have to guess.

Back to the OP question - G24 will do it. G27 is conservative.