[C38] Fwd: Battery Power

Charles Finn charles at finn.ws
Wed Feb 17 18:38:45 EST 2010


Mike,
If you are reading 10.7... time to get a new battery! Theoretically, 
each cell can provide 2.1 volts, which adds up to a max reading of (6 
cells x 2.1)= 12.6 volts. You might be a bit concerned if you have been 
using the "ALL" setting on your battery switch as battery voltage 
differentials will harm you good battery. This is why many folks 
advocate buying your batteries together.

The best way to figure out which battery is the engine starter is to 
look for the heavy wire going to your starter. Begin at the battery or 
the starter and trace back. My guess is the smaller battery is your 
starting battery as 10.7 volts probably wouldn't turn your engine over 
as that is not the load voltage!

I personally like to completely isolate my starter battery from the 
house bank. I have installed a third battery for starting the boat in 
what was the shower sump, which is right on top of the keel. A good size 
battery fits snugly in the box and is easily strapped in. This way, I 
can use both house batteries without worrying that I have drained too 
much power to start the engine. I even carry a set of jumper cables in 
case the starter battery dies and I have to jump from the house bank.

I highly recommend a book: Boatowner's Mechanical and Electrical Manual, 
by Nigel Calder. I think he is the best at explaining complicated issues 
in common "sense" terms. Sometimes, I have to read it a couple of times, 
but eventually it makes sense even to me! It is always on the boat and I 
refer to it often.

Chuck Finn
Mighty Quinn #114


Robert Miller wrote:
>
> If one of your batteries shows 10.70 volts with a voltmeter, it is 
> gone. Put a load on that battery and it will drop lower. Don’t know 
> how you are set up but it looks like you can use either battery or 
> both to start the engine. I have four AGMs in my 38 with two 1/2/Both 
> switches. Once I am underway under sail, I set one switch to Both and 
> the other to 1 leaving one battery isolated to start the engine. That 
> leaves 3 house batteries and one in reserve to restart the engine.
>
> Bob
>
> “Bolero” #113 at Southwestern YC in San Diego
>
> ------------------------------------------------------------------------
>
> *From:* listserve-bounces at catalina38.org 
> [mailto:listserve-bounces at catalina38.org] *On Behalf Of *therorl at aol.com
> *Sent:* Wednesday, February 17, 2010 2:40 PM
> *To:* listserve at catalina38.org
> *Subject:* [C38] Fwd: Battery Power
>
> -----Original Message-----
> From: Charles <chas at finn.ws>
> To: therorl at aol.com
> Sent: Wed, Feb 17, 2010 2:04 pm
> Subject: Re: Battery Power
>
> therorl at aol.com <mailto:therorl at aol.com> wrote:
> > I've had trouble lately with my battery not having a full charge when 
> > I go to start the engine. I've turned off all the shore power, 
> checked > both battery's with a volt meter and the larger off the two 
> battery's > reads 10.70 volts. Is this enough juice or do I need a new 
> battery. I > was told at one time that a deep cell battery should read 
> at 12.5 volts.
> >
> > Also, I can't distinguish the house battery from the engine battery. 
> > To me it would stand to to reason that the larger of the two 
> battery's > would be the house battery and the smaller for the engine. 
> But, if I > disconnect the shore power and switch to the number 1 
> battery my cabin > lights will come on. The same thing happens if I 
> switch to the number > 2 battery. Can someone help me out!!!!!
> >
> > Mike
> > Catalina 38 #271
> >
> Mike,
> I think somehow you are sending to the wrong email address as it came 
> to my personal account. The correct one is: listserve at catalina38.org 
> <mailto:listserve at catalina38.org>
>
> ------------------------------------------------------------------------
>
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