So I keep hearing my alternator whine when the rpms drop and I'm using my lights and my radio or both sets of lights, or all three, it's just annoying and I'm gonna need to upgrade my alternator and go to dual batteries when I get a winch anyway so I figure I can go ahead and get it set up. I'm looking at the Roadless Gear GM alternator kit, then putting in another battery. How would I wire the second battery into the system so I can run my off road lights to it, and the winch when the time comes, I know I'll have to do some wire splicing and a custom mount for the extra battery. Ideas? Pics?

I would use a good battery isolator so both batteries will get fully charged and it will only pull off of one battery until it gets low, that way you can start you rig! They come with directions, they aren't real cheap but worth it.

Kj

check out a marine supply for a dual battery switch and power post.
i have some circuits on one battery (some radios, inverter), post powered by either or both batteries.
mostly run in "both" mode.
my stock alternator puts out 60-65amps(according to spec.sheet that came with it).
my driving lamps are 100W units.
i'm using 2 of those little stock batteries.
power post under hood

marine switch on side of dash, 2nd battery(+inverter) is behind where passenger seat woulda been

fine so far. just an idea.

The 'correct' way is an isolator as mentioned above. Switchology is cool but gimmicky, K.I.S.S. (Keep it Simple Stupid!)

I have run several dual battery setups in parallel and had no problem. Start with identical new batteries for the best results. Look at diesel trucks that have dual batteries, all that I know of run their batteries in parallel, only time people have trouble with them is when one battery wears out (5-10 years!)

The 'correct' way is an isolator as mentioned above. Switchology is cool but gimmicky, K.I.S.S. (Keep it Simple Stupid!)

I have run several dual battery setups in parallel and had no problem. Start with identical new batteries for the best results. Look at diesel trucks that have dual batteries, all that I know of run their batteries in parallel, only time people have trouble with them is when one battery wears out (5-10 years!)

That's exactly how I did mine and have had no issues.

The 'correct' way is an isolator as mentioned above. Switchology is cool but gimmicky, K.I.S.S. (Keep it Simple Stupid!)

I have run several dual battery setups in parallel and had no problem. Start with identical new batteries for the best results. Look at diesel trucks that have dual batteries, all that I know of run their batteries in parallel, only time people have trouble with them is when one battery wears out (5-10 years!)

If you're not going to use some form of isolator, and preferably a smart isolator - identical new batteries is pretty much a requirement for trouble free performance - the only advantages of such a dual battery system over a single battery of comparable reserve capacity is that it offers the possibility of better weight distribution, and perhaps easier installation in that it's easier to find space for two smaller batteries rather than a single large one.  Both the dual battery and the single larger battery will provide increased cold cranking amps.

The primary reason these systems are common on diesel trucks but not on gasolene ones is because of the cold cranking requirements of the diesel and as mentioned above it's easier to find space for a pair of smaller batteries.  There is no advantage from a charging stand point and because there is no isolator any load drains both batteries simultaneously, making it quite possible to end up with two flat batteries - if the load requirement is greater than the alternator output.

If you run dissimilar batteries - whether it be dissimilar capacity, dissimilar chemistry or dissimilar age - the end result of a parallel system with no isolator is reduced battery life.  The lack of an isolator can make detection of a failed battery difficult and will also allow that failed battery to discharge (and destroy) a perfectly healthy battery that it is in parallel with.

The decision to isolate or not should be dictated by the intended usage - if the additional capacity is going to be used whilst the engine is running, an isolator may be considered optional; if the additional capacity is going to be used with the engine off, an isolator is recommended; if there is any desire to have one battery kept in reserve for starting purposes an isolator is required.

For the original posters stated requirements - radio, lights & winch - which will presumably be used with the engine running, an isolator is optional, but identical new batteries is strongly suggested.

Edit.

I forgot to mention one thing ...

For best results - not only do you need to start with identical new batteries, you also need to replace them in pairs, with identical new batteries.

i think isolators are a good idea for charging dissimilar batteries, 'specially if one is a deep cycle "cabin" type battery as used in boats or motorhomes.
i do use one battery for circuits i keep live most of the time, and the other i consider responsible for running the vehicle.
my "isolator" is a switch.
it is possible to drain both batteries completely.
i haven't done it yet.

Good tips!

Just one thing would like to add for this.  From personal experience I can tell you that you do NOT want to have an CS-130 alt set up with a 180A capacity if you need it to charge |removethispart|@ idle.  Even with the smallest 6 rib pulley it mine will not charge unless I have it above 950RPM.  Would recomend going with a 140A set up and go ahead and use a pigtail adaptor to keep wiring issues down to a minimum. 

Brad

Opps.  alsmost forgot.  Make sure you bump up the ground circuits and add a power supply line from the alternator to atleast one of the batteries.  The stock power is limited to 80A and you can easily blow that fuse.

Mine won't start charging until I blip the throttle to get the alt excited. Sort of like my wife.