Starting Batteries

[binkmann10]

I am getting ready to replace both house batteries and starting batteries on board my 1991 Catalina 42. I have a Yanmar diesel engine which is started by 12 volts, and when I took the starting batteries out I saw the previous owner had used 2- 6 volt batteries in series for starting. I was planning to use 2-12 volt batteries in parallel or a total of 2000 reserve minutes, and 1600 cold cranking amps. Is there a reason i am not aware of to stay with the two 6 volts? I will be using 6 volt batteries for the house batteries, but did not see an advantage of using them as starting batteries. Educate me.

JB

[S/V Illusion]

So-called golf cart batteries are designed for deep cycling but that doesn't preclude them from being used in starting service. Either will work and it's largely a matter of personal preference with arguments pro and con for either option.

[binkmann10]

I just want to make sure if I use the 2 12 volts I will have ample starting power. If I understand the differences, starting batteries need higher amps to turn the motor, and is the advantage of 12 volt auto type batteries over 2- 6 volt batteries. which are better for reserve. It it possible to damage an engine with too many cold cranking amps? The 6 volts are not even rated for cca. I am planning a trip close to Alaska, and want the maximum power possible.

[S/V Illusion]

The only time CCA is significant would be in a climate such as Alaska so you'd be better served with starting batteries - one should be fine; two may be overkill but nothing wrong or harmful can occur. Batteries don't push out amps, they store them and only release what the demand requires..

[Stumble]

Joe,

Two starting batteries is pretty rediculously over specced for your boat. The typical recomendation is that you should have twice the starting load in CCA's. I don't know what engine you have, but the Yanmar 4JH4-HTE which is a 100hp engine has a max draw of 1.5kw while starting. At 12v that means you need roughly 125 CCA's to start the engine. Doubling that gives you 225, so let's say 250 to make the math easy... You are installing more than 8 times that in battery power.

To use than much juice you would have to hold the starter down for... 4 solid minutes before the batteries fell below spec. If you tried that your starter would be gone long before anyway.

I would guess your engine isn't 100hp so the power demands would be even lower, and the starter time would go up proportionally. Somewhere in the paperwork for the engine there should be a CCA rating that the engine uses, just double that and get a battery to match it.

Just think about it like this. What side starting battery do you have in your car? My guess is you car has at least twice the HP that your boat does, likely much much more. Why would you need all that extra capacity to get your boat started?

[Heritage]

Check the owners manual to determine the battery capacity required for starting. It may refer to CCA, which is the battery capacity at 0F, and MCA which is at 32F. It is unlikely that you will ever start the engine at zero, so pay attention to only the MCA.

It doesn't matter whether you use 2-6V in series, or one 12V. Using a battery in excess of your engines requirement will hurt only your pocketbook.

Start batteries are very different than house batteries. They are required to supply high amperage, but only for a few seconds. It is not necessary to use a "marine" start battery. A battery sold as a vehicle or machinery start battery will do fine, but the label will probably only refer to the CCA capacity, since it is assumed that it will be used to start an engine in the winter. Refer to the West Marine catalogue to determine the relationship of CCA to MCA.

I have seen many boats where the start battery was far in excess of what the engine requires. I recently replaced the starting battery on my boat main engine, a 6 cyl Cummins, with one good quality group 31 flooded, because it met the engine requirements. My generators engine requirements can be met with a lawn mower battery.

[redsky49]

There may be an advantage in having a single battery type and size on board, should you have a failed cell. You also might get a better price if you buy multiples of the same battery. Sometimes it pays to negotiate for multiple items.

[btrayfors]

You don't need two starting batteries for a single diesel on a Catalina 42. Period.

Nor do you need two golf-cart batteries. As was pointed out, these are deep-cycle batteries which are much more appropriate for the house bank.

A single starting battery is all you need. I use a Group 31 Deka; it's really overkill for my 4-108, but has more than enough cranking amps for starting.

Put any additional lead into the house bank. You can't have too large a house bank :-)

Bill

[Efraim]

Nothing wrong with two starting batteries but, as has been mentioned it's huge overkill, you'll probably never see any benefit to your planned set up. If you have the room, and it sound like you do, instead of putting in two starting batteries, why not just add another house battery - that would be putting those extra amps to some use.

[noelex 77]

Does anything else run from the start bank

Anchor winch?
Bow thruster?

This is the main reason for having, and designing the room, to fit such a large start bank.
Depending on what you have connected the larger batteries may be necessary and appropriate. If it is just starting a single 12v will be adequate.

[rocma]

Originally Posted by JoeBink

I am getting ready to replace both house batteries and starting batteries on board my 1991 Catalina 42. I have a Yanmar diesel engine which is started by 12 volts, and when I took the starting batteries out I saw the previous owner had used 2- 6 volt batteries in series for starting. I was planning to use 2-12 volt batteries in parallel or a total of 2000 reserve minutes, and 1600 cold cranking amps. Is there a reason i am not aware of to stay with the two 6 volts? I will be using 6 volt batteries for the house batteries, but did not see an advantage of using them as starting batteries. Educate me.

JB

Why so many cranking amps?

I assume your Yanmar is something like 56 or maybe 75 HP? Just get an Optima Red Top 45Ah, which are commonly used in tractors. Or, if you want a little more "umpf" get the new Optima 75Ah blue top at 975 CCA. More than enough power to start your Yanmar and they are made to handle deep discharge, no maintenance, you can mount them sideways it you want. They are also more compact and lighter than regular batteries and charge faster. Basically it is a spiral AGM. I only want Optimas on my boat now!

[GordMay]

Yanmar Marine Battery Requirements
➥ Sailboat Supplies, Engine Parts and Boat Parts

A Yanmar 3GM30, for instance, requires a minimum 70 A/Hr, 385 CCA, or 455 MCA starting battery, so almost any starting battery should suffice; tho' (if you can afford the cost, space, & weight) more can't hurt.

Typical Battery Specs ➥ Interstate Batteries

[binkmann10]

Thanks for all the opinions and for the links GordMay. The only reason I bought two 12 volt batteries in the first place is because I had glanced in the battery bank and saw two batteries not realizing they were 6 volt and not 12 volts. My engine is a 50 HP 4JH2E, so needs a single battery worth of starting amps. I still may install both anyway since I have them, prefer overkill to under, and the battery cost of $60 won't break the bank (this month anyway). I had just never seen golf cart batteries used as starting batteries so was concerned I was missing a reason. Thank you again for sharing your opinions and experience with me.

[westsail42]

What they said.

No harm in overdoing it with two paralleled starting batteries if there is space for it.

I have been in a situation where my yanmar 3GMF was "flooding" the cylinders (so to speak) on very cold winter starts. The only way to get the engine going was to wait 12 hours, or, overcrank the starter. I was happy my starter battery was oversized to supply the amps.

Turns out bad injectors caused the "flooding".

[barnakiel]

Last summer I worked on a boat where really big engines were started from toilet rolls. Single one per each engine. This boat sails in cold climates, no issues starting ever.

No harm in extra cranking power except that one can spend the bucks elsewhere in a more productive way!

b.