isolator for dual battery help/info? [Archive] - JKowners.com : Jeep Wrangler JK Forum

: isolator for dual battery help/info?


mcnaught6
03-24-2008, 06:57 PM
is there anyone that knows something about isolators for dual batteries? i'm working on trying to build a dual-battery tray for under the hood.

i want to get an isolator to use with my dual battery set-up i'm working on, but don't really know what i should be looking for.

i know i want one that is automatic and doesn't require the use of a remote. i'd like to be able to isolate my starting battery from the accessory battery that runs the winch, lights, cb, etc....

if anyone can give me some info on what i should be looking for and where i might be able to get this, i would greatly appreciate it!

venom
03-24-2008, 08:21 PM
I've heard a LOT of good things about these guys
http://www.hellroaring.com/
prob who I will go with when I go dual

skydyvyr
03-24-2008, 08:47 PM
I'd sure love to see pictures of what you come up with... I've been toying with trying to work a dual setup (without going to motorcycle/golf cart batteries), but can't find the space I need. That power distribution center (or whatever they call it) takes up a ton of space under the hood that could otherwise handle an extra battery.

--Sky

mcnaught6
03-24-2008, 09:50 PM
if you remove that HUGE plastic battery tray, you free up a lot of room. that plastic takes up a lot of space that could other wise be useable. i'm also planning on moving the fuse box forward a couple inches and mounted to the new battery tray. the tray will be made to specifically fit two optima batteries, so it will also be more narrow, leaving room for something like a winch solenoid to be mounted back there.
whatever i come up with should be fully bolt-in and i might look into having a guy manufacture some if he's interested and things work out.
the metal has been ordered, so we'll see what we can come up with.

i'll keep you posted on what happens.

i still need advice on how to wire the batteries. should i go with an isolator, or just wire them in parallel?

gcg
03-24-2008, 10:35 PM
if you remove that HUGE plastic battery tray, you free up a lot of room. that plastic takes up a lot of space that could other wise be useable. i'm also planning on moving the fuse box forward a couple inches and mounted to the new battery tray. the tray will be made to specifically fit two optima batteries, so it will also be more narrow, leaving room for something like a winch solenoid to be mounted back there.
whatever i come up with should be fully bolt-in and i might look into having a guy manufacture some if he's interested and things work out.
the metal has been ordered, so we'll see what we can come up with.

i'll keep you posted on what happens.

i still need advice on how to wire the batteries. should i go with an isolator, or just wire them in parallel?
I definitely would not wire them in parallel. I have a dual battery setup in my XJ and went the isolater route. I ordered the isolater itself from Wrangler Electronics (or something like that). It's basically two diodes with their anodes connected together. This common point is where you connect the alternator "charge wire". One of the cathodes goes to one battery (call it the primary) and the other one to the second battery (call it the secondary). I ran all the original equipment off of the primary battery and all the accessories (winch, compressor, CB, inverter, etc.) off of the secondary.

With this approach the two batteries are charged in parallel but cannot discharge through eachother. You can completely discharge one and the other will stay fully charged. I liked this setup except for one issue. I ran Optima yellow tops, which are way expensive. I found that I had to replace one of them every year (at about $200 each these days). I don't know if this is typical or not, but is somewhat prohibitive on a cost basis.

One possible explanation is that this particular way of wiring the batteries adds a diode drop between the alternator charging output and the battery. In effect, the charging voltage to the battery will be about 0.7 volts (or more) lower than it would be if the isolater weren't in place. Perhaps this charges the batteries in a less than optimum way and may account for what seems like a short life. I honestly don't know, this is just a thought. Maybe someone else knows and can reply.

Other than this issue, the isolater approach is pretty nice. I do like the Hell Roaring Technologies products and they appear to use a FET switch instead of a diode and claim that it has a very small voltage drop so it might eliminate the problem I mentioned.