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nodders 06-04-2014 02:07 PM

replacing starting battery
 
I have a 28 ft boat with two batteries. We do some extended cruising but limit the power we use at anchor considerably. I often will hoist a led light to the masthead at night rather than use the anchor light.

The deep cell house battery seems fine, but the starter battery is not taking a charge very well, although it has enough juice for now to get the motor going (Yanmar 2GM).

Should I go for a starter battery or could I use another deep cell?

Alex W 06-04-2014 03:40 PM

Re: replacing starting battery
 
First thing: switch the anchor light out to a LED. A 1-2W LED (typical anchor light) will run for days and days on a group 24 battery.

I just switched from a high CCA starter battery to using my pair of house batteries to start the engine. It works fine on my Yanmar 2GM20F. I have a small backup 3rd battery as my emergency battery should the house batteries get run all the way down. That one is never used for anything else. It's small size (U1 form factor) made it easy to fit into my 28' boat.

deniseO30 06-04-2014 03:43 PM

Re: replacing starting battery
 
Before you buy.. just a suggestion, take each battery and have them load tested. they need to be charged for a good reading. Seems to me one house battery can handle the needs overnight.

eherlihy 06-04-2014 03:54 PM

Re: replacing starting battery
 
I faced the same decision last year. Like you, I use an LED anchor light which I raise in the rigging, rather than the all around white light at the top of the mast. The LED light shines softly on the boat to make it more visible, and meets the CFR for an anchor light.

My boat had two group 27 batteries; one 10 years old, and the other 7 years old. I replaced them with two group 29 batteries (105 AH), and use one for the house, and the other for the start. I can use either as a start, or house. A marine deep cycle battery works fine for starting a diesel.

Someday, I will combine these two batteries, move them to another location, and add a small, cheap, start battery.

christian.hess 06-06-2014 10:37 AM

Re: replacing starting battery
 
or you can just buy a cheap high cca truck battery for now

Im not a fan of pairing an old battery with a new one unless its like 6 months old or something rather have a new bank or maintain an older one

hellosailor 06-06-2014 03:23 PM

Re: replacing starting battery
 
Starting a small diesel isn't a big deal, any full size deep cycle battery will be able to handle it. So I'd say have them both load tested. Replace one or both as needed, with deep cycle battery(s). And try not to cringe at the price of replacing lights (all of them) with LEDs, because LEDs pay for themselves with all the power they save.

JimsCAL 06-11-2014 12:31 PM

Re: replacing starting battery
 
On a smaller boat like yours, I would just go with another deep cycle. It will start the diesel just fine and will survive occasional discharges much better.

Stu Jackson 06-11-2014 08:24 PM

Re: replacing starting battery
 
Quote:

Originally Posted by eherlihy (Post 1900354)
I faced the same decision last year. Like you, I use an LED anchor light which I raise in the rigging, rather than the all around white light at the top of the mast. The LED light shines softly on the boat to make it more visible, and meets the CFR for an anchor light.

My boat had two group 27 batteries; one 10 years old, and the other 7 years old. I replaced them with two group 29 batteries (105 AH), and use one for the house, and the other for the start. I can use either as a start, or house. A marine deep cycle battery works fine for starting a diesel.

Someday, I will combine these two batteries, move them to another location, and add a small, cheap, start battery.

eh's description is a classic example of the evolution of boating electrical support systems.

2 separate banks (a bank being a single to any multiple of batteries) was the older style. The currently preferred arrangement is as large a house bank as possible with a separate either start or reserve smaller bank. Reasons are explained in Charlie's book.

MedSailor 07-08-2014 07:28 PM

Re: replacing starting battery
 
Quote:

Originally Posted by JimsCAL (Post 1920306)
On a smaller boat like yours, I would just go with another deep cycle. It will start the diesel just fine and will survive occasional discharges much better.

This has always been my thinking, but I doubt myself sometimes. So, to be clear using a deep cycle battery for starting is NOT going to damage it, or shorten it's life?

I just replaced my G-29 starting battery with a deep cycle that is rated for higher CCAs and MCAs. Go figure.... ;)

MedSailor

hellosailor 07-08-2014 07:56 PM

Re: replacing starting battery
 
"So, to be clear using a deep cycle battery for starting is NOT going to damage it, or shorten it's life? "

How long is your piece of string?

IF the impulse load for the starter is less than the maximum impulse load the battery can supply there will be no damage. If the battery is too small, and you grind the starter too long, you'll melt the plates.

With a conventional 1.5kW or 2.5kW starter and a Group27 or Group 31 or larger battery...check with the manufacturer, there is probably no problem. You want certain? Check with the manufacturer.


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