dual battery hook up

I have a good size battery in my pro street car, but would like to
set it up with two batteries..Could some one tell me the proper way
to hook this system up, and the necessary hardware envolved.
thanks rdobbs

Well, you are going to want to hook them up in parallel, not in series. Parallel is where the two batteries negatives are grounded, and the positives run to some sort of a selector switch so you can choose one battery or the other, or both at the same time. With this arrangement you only get 12 volts out of it.

Series is where you take the negative of one battery and connect it to the positive of the other battery, then ground only one battery and run the positive lead from the second battery to your load. With this setup you get 24 volts, because the two 12 volts add up to 24 that way.......you do not want the series setup for your car.

Essentially you can do it like we do it on boats, where you either use a manual selector switch, or you can rig it as a "paralleling setup" where you have a toggle switch on the dash and you use Ford starter type relays to electrically link the two batteries together when needed.

What is your reason for wanting to do the two battery routine? Having trouble cranking your engine? The reason I ask is that generally one BIG battery with lots of CCA (cold cranking amps) will start most engines and eliminates a lot of extra weight and hookups that can cause problems.

Just curious.

Don

Instead of two batteries I would suggest this one battery. Look at the specs below, it even replaces an 8D battery that is used in trailer trucks and yachts!!
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Product Description
ODYSSEY PC2150S <br>Group 31 1370 MCA <BR> Marine, Heavy Duty & Trucks / Fleet Applications
<--Click here for terminal diagram
***1/2 OFF SHIPPING ON THIS BATTERY***
ODYSSEY PC2150S
12V 100.0AH 1370 MCA
*4 year warranty full replacement
*2150 cranking amps , 240 minute reserve capacity on a 25 amp draw.
*Group size 31, for the serious boater. Replaces Thermo King Eon Battery PN# 203-550
CATALOG# 0790-2020


PC2150S Design:
Absorbent glass mat (AGM) technology. Rugged construction 3/8 inch corrosion-free brass stud terminal. Can be mounted in any orientation. Suitcase lifting handle. US DOT and IATA certified non-spillable. Shipped fully charged - just install and go. Container and cover made from oil resistant plastic.

Performance Features:


PHCA: 2,150A at 80°F (27°C); for 5 seconds
PCCA: 1,500A at 0°F (-18°C); for 5 seconds
CCA: 1,090A at 0°F (-18°C)
CA/MCA: 1,370A at 32° (0°C)
HCA: 1,545 at 80°F (27°C)
Short circuit current: 5,000A
Deep cycling capability: 400 at 80% DOD
Design life: 12 years
Typical service life: 6 to 8 years
Length 13.00" Width 6.80" Height 9.41"
Weight 78.0lbs
4 Year warranty


APPLICATIONS: Marine: Ultra Heavy Duty & Fleet Applications, Group 31

This powerful group 31 can even be used as an 8D replacement

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I am using their SMALLEST battery that they make for BMW motorcycles, and it starts my 350 Chevy like gangbusters. This group 31 would crank even a fuel dragster and is very compact.

Don

interesting battery Don...i had to parallel two small gel cell batteries in my coupe...just behind the seat...gas tank is in the trunk and theres very little room between the tank and the back of the seat

The guys are right, one big battery is better. Two are only as good as the poorest one, and the extra connections are a headache. If space makes it necessary, pay special attention to all connections, keep everything bright and shiny.

Guys, thinks for the info...I have a 468 BB and it seems to be a little
hard to start when it's hot, plus the electric fan, and fuel pump has a
draw on it. I am currently using a long Interstate, don't even know the
amp size, but I think you have convinced me to stick with just one battery
to eliminate weight and confusion....rdobbs