just a quick answer will help me.
do most dual batteries run a fuse in the positive cable that parallels the two batteries? if so, what amperage?

thanks

 

Most of the time I don't think so, because of the amperage that can be pulled from the batteries. I would just route the wires so they don't get pinched or anything like that and you should be good.

 

more people with some experience please.

 

no fuse, amperage draw is too high to make one worth while....... on the painless system there is a fuse going to the solenoid, so if there was a short the power gets cut off to it......

 

I have a battery isolator between my two batteries. Alternator is connected to both batteries, but the batteries can't backfeed to each other, so if I drain my aux battery, my starting battery is still good. I have a 50 amp automatic reset circuit breaker on the positive lead from the isolator to my aux battery.

 

Vehicles that come with dual batteries from the factory usually don't run fuses in between batteries. This is sort of ok because they are close to each other, and the factory most definitely thought about how catastrophic it would be to have a short...

If you are planning on adding another battery, like in the trunk, then I would definitely fuse the wire on both ends. Fusing one side will only open the circuit from one of the batteries, and the wire will still be live from the other battery, and if there's a short, that wire will burn up and probably cause a fire in your car.

A lot of people don't know this, but a fuse at the battery is for the WIRE, nothing else... A lot of people think it's to protect the amps, but it's not. The fuse you see ON the amp is for the amp itself... The fuse is determined strictly by the gauge(size) of the wire, and the length it's running. (I would definitely run at least a 1/0 wire)

In your case with the batteries, there are many other things to consider. It is ideal to have all the batteries new, made around the same time, the same size, and the exact same voltage. It's not a myth, mixing new batteries w/old just isn't good.

Do your research before you plan on just adding batteries. As far as a short answer to your question about fusing the wire, yes if they are far from each other and no if they are close.

 

its about 15 ft of 1/0 between them, and theyre in parallel, with no isolator, just a disconnect in the line between.
the disconnect is the red plug type you see on race cars, and it has a max amperage of like 250 or something so wouldnt it just act like a fuse if the draw was too high?

seems like everyone else is saying no fuse. hmm

 

Is it a circuit breaker? If it is, you need one at each end of that 15ft wire...

here, i found the perfect link... note the fuses at each battery.

http://www.bcae1.com/battiso.htm

 

not a breaker, a quick disconnect.