low height starter battery

[mr_f]

I am hoping to add a dedicated starter battery to my Pearson 33-2 so I can use my two group 31s combined as the house bank. The problem is the likely space is not tall enough for the batteries I have seen. I have about 9.5" of height available, which is just barely tall enough with no space above the terminals, but once I add a battery bucket, I seem to be out of luck.

What are my options? I have seen some low-profile AGM batteries, but I don't know enough to figure out how that complicates things in terms of charging.

I also could use some help figuring out how large a battery I need to start the Yanmar 2GM20F.

Any advice would be appreciated.

EDIT: I now see that a group 34 will fit. Still would appreciate any advise. Is that enough battery? If I wire the house bank and starter battery following MaineSail's suggestion on how to better use the 1-2-Both switch (alternator and charger to the house bank and use a combiner) will I be in good shape?

 

[fireman416]

Go to local auto store and check out side post mounted car batteries. There is bound to be some that will fit in that space. For a small engine a 650 of higher cranking amp batt will get you going.

 

[capt_clyde]

There probably are several batteries that will fit and a group 34 may be a good choice. Last year I replaced my starter battery and went to a group 65. The primary reason I used the 65 is that it delivers a lot of cold cranking amps (880) in a reasonably sized package (12 1/16" Long x 7 1/2" wide x 7 9/16" high. Things to keep in mind are...diesels require a lot more cold cranking amps (CCA) than do gas engines and as the battery ages the CCA will decline. CCA is one of those things where more IS better. Simply put it is a measure of the batteries ability to deliver electricity but the amount of current (amps) delivered is governed by Ohms law.
Here is a page that lists the physical dimensions of most car batteries. http://www.rtpnet.org/~teaa/bcigroup.http
I would also check with the manufacturer of your engine for the minimum CCA recomendation.

 

[JK_Boston_Catalina310]

I think the group 34 is overkill for a reserve battery for simply starting your engine in a case where you have depleted your main bank. Maine Sail has mentioned many times that our small diesels use very little of the reported amps for starting. He has a couple of videos of starting his boat with monitors hooked up that show this.

I am in the middle of the project that Maine Sail describes. (http://svsmitty.wordpress.com/2013/03/04/electrical-charging-system-upgrade-mostly-complete/) I have put in the ACR and rewired most of the system. I just need to borrow a friend's large crimpers to finish the job. I have a 23HP Westerbeke and I am going with a group 24 for a reserve battery. That will have plenty of juice to start the motor if needed.

 

[mr_f]

Thanks for the input. Especially the link to your blog JK_Boston_Catalina310. That will be very helpful. But as near as I can tell, the 34 is smaller than the 24.

As it stands, I may be more confused than when I started. Seems we have two votes for not needing much in the way of a battery, and one for wanting something bigger.

 

[fireman416]

Thanks for the input. Especially the link to your blog JK_Boston_Catalina310. That will be very helpful. But as near as I can tell, the 34 is smaller than the 24.

As it stands, I may be more confused than when I started. Seems we have two votes for not needing much in the way of a battery, and one for wanting something bigger.

Keep it simple stupid always works for me. Try not over complicate what is simply a battery for cranking a small engine. Find one that fits the space that won't cost a fortune, and unless you plan on running this thing in the winter high end cold cranking amp batteries are an overkill...

 

[JK_Boston_Catalina310]

Battery Size

I don't think you need that big of a battery. Here is a Yanmar manual and it only calls for 12V - 70AH minimum for the battery. http://l-36.com/manuals/yanmar_pdfs/owners_manual/128270-4E.pdf - page 31 of the PDF.

 

[Stu Jackson]

fireman's right. A battery that will fit will work. One of those "bigger is better" doesn't apply.

While you're at it, check and redo the battery ground connection to your engine. It's usually THE place for problems to occur.

 

[Maine Sail]

Any short "side post" car battery will work and there are many to choose from..

 

[SycloneDriver]

We use Otpima SC34M to start our diesel generators at work. Most of the generators are a minium of 30kw - 35kw 4 & 6 cylinder diesel motors, 3.4 - 3.9 liter. I would think any group 34 batterie would be fine.

Remember that you can mount an AGM battery on its side if need be. You could wire two 6volt batteries togather and mount them creatively. I have seen 6volt AGM batteries that look like a 6pack split down the middle.

 

[mr_f]

Thanks for all the help.