# Need Help With Battery Selection; AGM vs SLA



## WhiteDog70810 (May 6, 2008)

All,

I need a starter battery for a 20 hp honda Go-Devil.  The owners manual specifically says to use a 12V 45AH battery.  I can easily find batteries that meet this spec, but they are usually >$130 and are SLA.  I seem to recall hearing that the plates of some batteries, I believe SLAs, were sensitive to vibration/concussion and would have a shorter life when mounted in the bow of the boat despite doing fine when mounted in the transom.   In my case, everything possible must be in the bow to counter balance that heavy dang Go-Devil.

I can find cheaper 12V AGM crank batteries that I believe to be more vibration tolerant, but they are usually labeled as being xxx CCA.  I can find deep cycle AGMs that are 12V 55AH and higher, but I really don't want that heavy or expensive of a battery just to crank a motor. 

My understanding of AH vs CCA is limited to AH relates to rate of steady flow of power while CCA relates to how big a burst of power the battery can provide at start.  From what I gather, they are separate measurements for which there is no conversion.  For my purposes, a crank battery seems more appropriate for my use since I only need to start the motor and little else, but the owner's guide doesn't give any guidance regarding CCA requirements.  I am very leary of not following the owners manual.

So my questions are:

1.) AGM vs SLA?  Which handle vibration better?  Is vibration really a factor if properly strapped down so they don't bounce?

2.) What CCA = 45AH? ...given that they measure entirely different things and are not meant to be compared. :-?

3.) Finally, what gauge and type of wire should I use for a 14' run from motor to battery?  I will not be using a trolling motor off this system, but I want to build it correctly so that I don't need to mess with it ever again as much.

Thanks in advance,

Nate


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## DuckNut (Apr 3, 2009)

I have used a lawnmower battery for years with a 27hp Vanguard.

For wire - I have no clue. The thicker the better but just not so stiff that it binds when you steer.


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## Brett (Jul 16, 2008)

Grab y'er inductive ammeter, measure the peak draw needed to crank it over.
Once you know peak starter amps you can calculate your wire size based on the amps
and total round trip of the circuit measured in feet.

http://www.powerstream.com/Wire_Size.htm


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## WhiteDog70810 (May 6, 2008)

> Grab y'er inductive ammeter, measure the peak draw needed to crank it over.
> Once you know peak starter amps you can calculate your wire size based on the amps
> and total round trip of the circuit measured in feet.
> 
> http://www.powerstream.com/Wire_Size.htm


My inductive what? Dude, I barely passed physics II...

Nate


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## WhiteDog70810 (May 6, 2008)

I went ahead and bought a Diehard lawnmower battery this evening. While I have Optima tastes, I have a Diehard budget. It is a lot lighter also. I found a source that said I needed over 300 CCA (mine has 320 CCA). My source was not Honda proper, but the guy makes a living selling equipment powered by small engines.

I am over thinking this, but I hate thoughtless electrical rigging more.

Nate


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## Marshfly (Nov 4, 2012)

You did the right thing. It's a lawnmower engine. Get a lawnmower battery and be done with it.


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