dual battery question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

retodd7711 · 07-05-2008, 11:02 PM

I want to run dual batteries on my boat, but I need some advice.
How exactly do I connect them?
Right now they are connected to an isolator switch, but it's only charging one battery. I want to eliminate this(I think it's faulty)
Hot to hot, ground to ground?
If I connect 2nd battery to starter and ground, how will it get charged?
A little advice would get you 2 stars in my book.

Longhorn Man · 07-05-2008, 11:59 PM

Just hook the batterys positive to positive with the same guage cable that the main battery has on it already... and you'll be golden.

**N2TRUX** · 07-06-2008, 12:18 AM

If I were you I would replace the isolator. In a car/truck application it's not really needed. In a marine application it's nice to have one battery that is isolated for cranking purposes only.

It's kinda hard to get a jump start out on the lake...

LONGHAIR · 07-06-2008, 07:39 AM

I'm with Ken on this one. If both are connected in parallel, they increase your amperage...which you may or may not need, but they are truly "tied together". They will both charge that way, but they also die together too.
The "isolator" does exactly as the name implies. It uses the same charging source, but the batteries themselves are seperated. You don't get the increased amperage, like would be used to start a Diesel engine or run a winch....but it leaves the "starting" battery alone for starting. Then you have a back-up, if needed, or just a reliable source of power w/o worrying about starting later.

If it was originally wired to run an isolator, I would replace it.

retodd7711 · 07-06-2008, 08:23 AM

It just keeps getting better

After replacing the isolator(thanks guys, good advice) I still had a no start condition.
Tested both batteries, one is bad.
1000 CCA Deep cycle marine battery.
Can you say cash drain?

Mickey_D · 07-06-2008, 10:37 AM

Check if there's an electric golf cart servicing place around you. They quite often use marine deep cycle batteries for the traction motor and replace them every two years whether they need it or not. You could possibly pick up a darned good battery for pennies on the dollar that way.

retodd7711 · 07-06-2008, 11:24 AM

One last question.
How do I check if both batteries are charging?
I can borrow a multi-meter, but I'm not 100% what I'm looking for.

**truckdude239** · 07-06-2008, 03:12 PM

check the voltage ont the battery not running then you should see and increase to like 14 volts running

screwballl · 07-06-2008, 03:24 PM

BOAT: device designed to take your money

retodd7711 · 07-06-2008, 07:55 PM

Quote:

Originally Posted by screwballl

BOAT: device designed to take your money

2 happiest days in a boat owners life:The day he bought it
and the day he sold it.

**WorkinLonghorn** · 07-06-2008, 11:47 PM

There's some info here that's pretty interesting;
http://www.tmcowners.com/teamtalk/sh...t=dual+battery

07-05-2008, 11:02 PM	#1
retodd7711 chrome makes it go FASTER! Join Date: Feb 2007 Location: Cleveland Tennessee Posts: 2,884	dual battery question I want to run dual batteries on my boat, but I need some advice. How exactly do I connect them? Right now they are connected to an isolator switch, but it's only charging one battery. I want to eliminate this(I think it's faulty) Hot to hot, ground to ground? If I connect 2nd battery to starter and ground, how will it get charged? A little advice would get you 2 stars in my book. __________________ She can't cook and she won't clean. But she looks good in a skirt and she brings me beer. She can stay for now. EDIT:: But she left me anyway, So forget her. 1962 GMC Stepside V6 4 speed My rolling resto thread http://67-72chevytrucks.com/vboard/s...d.php?t=324226 My old farm truck http://67-72chevytrucks.com/vboard/s...=1#post3465005 Last edited by retodd7711; 07-05-2008 at 11:05 PM.

07-05-2008, 11:59 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: dual battery question Just hook the batterys positive to positive with the same guage cable that the main battery has on it already... and you'll be golden.

07-06-2008, 12:18 AM	#3
N2TRUX Happy to be here Join Date: Mar 2000 Location: Cypress, TX Posts: 39,021	Re: dual battery question If I were you I would replace the isolator. In a car/truck application it's not really needed. In a marine application it's nice to have one battery that is isolated for cranking purposes only. It's kinda hard to get a jump start out on the lake... __________________ Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra"

07-06-2008, 07:39 AM	#4
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: dual battery question I'm with Ken on this one. If both are connected in parallel, they increase your amperage...which you may or may not need, but they are truly "tied together". They will both charge that way, but they also die together too. The "isolator" does exactly as the name implies. It uses the same charging source, but the batteries themselves are seperated. You don't get the increased amperage, like would be used to start a Diesel engine or run a winch....but it leaves the "starting" battery alone for starting. Then you have a back-up, if needed, or just a reliable source of power w/o worrying about starting later. If it was originally wired to run an isolator, I would replace it. Last edited by LONGHAIR; 07-06-2008 at 07:40 AM.

07-06-2008, 08:23 AM	#5
retodd7711 chrome makes it go FASTER! Join Date: Feb 2007 Location: Cleveland Tennessee Posts: 2,884	Re: dual battery question It just keeps getting better After replacing the isolator(thanks guys, good advice) I still had a no start condition. Tested both batteries, one is bad. 1000 CCA Deep cycle marine battery. Can you say cash drain? __________________ She can't cook and she won't clean. But she looks good in a skirt and she brings me beer. She can stay for now. EDIT:: But she left me anyway, So forget her. 1962 GMC Stepside V6 4 speed My rolling resto thread http://67-72chevytrucks.com/vboard/s...d.php?t=324226 My old farm truck http://67-72chevytrucks.com/vboard/s...=1#post3465005

07-06-2008, 10:37 AM	#6
Mickey_D Dirteh Kitteh Join Date: Nov 2006 Location: Mormon country Posts: 2,484	Re: dual battery question Check if there's an electric golf cart servicing place around you. They quite often use marine deep cycle batteries for the traction motor and replace them every two years whether they need it or not. You could possibly pick up a darned good battery for pennies on the dollar that way. __________________ Darrin 1955 Willys CJ-5 all original and the oldest CJ-5 on the road. 2001 Dodge Neon (wife's car) 1995 Jeep Grand Cherokee Limited Edition SOLD 1981 K15 Custom Deluxe 4X4, rusty but trusty wood hauler. SOLD 1993 S-10 4X4 Tahoe SOLD Sign up with the Contact List RIP ESLL

07-06-2008, 11:24 AM	#7
retodd7711 chrome makes it go FASTER! Join Date: Feb 2007 Location: Cleveland Tennessee Posts: 2,884	Re: dual battery question One last question. How do I check if both batteries are charging? I can borrow a multi-meter, but I'm not 100% what I'm looking for. __________________ She can't cook and she won't clean. But she looks good in a skirt and she brings me beer. She can stay for now. EDIT:: But she left me anyway, So forget her. 1962 GMC Stepside V6 4 speed My rolling resto thread http://67-72chevytrucks.com/vboard/s...d.php?t=324226 My old farm truck http://67-72chevytrucks.com/vboard/s...=1#post3465005

07-06-2008, 03:12 PM	#8
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,238	Re: dual battery question check the voltage ont the battery not running then you should see and increase to like 14 volts running __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

07-06-2008, 03:24 PM	#9
screwballl Tonawanda 454 Join Date: Mar 2004 Location: Liquid Sunshine State Posts: 2,754	Re: dual battery question BOAT: device designed to take your money __________________ 91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. -------------------

07-06-2008, 11:47 PM	#11
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,887	Re: dual battery question There's some info here that's pretty interesting; http://www.tmcowners.com/teamtalk/sh...t=dual+battery __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.



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