I'm putting in a second Optima into the LWB while I'm in there fishing around with hoses and such and have run into a decision about how to wire it that I hadn't really made up my mind about.

I am really not a fan of isolators, and run the dual batteries in the CrewCab wired in parallel. I was originally thinking of doing this on the LWB, but was thinking of running it in parallel but with a disconnect switch on it (a simple marine screw down switch) disconnected until I really needed it. Keep a full charge and then only use the second battery when the first one is dead or winching, or what have you.

Whaddya think?

:flipoff2:

If you don't have it connected to the rest of the system for at least some of the time, it will not have the full charge you want when you want it!

Just put a Sorenson solenoid in there and be happy that should the primary battery die (headlights on, etc and no, don't ask me how I know about this), the secondary is ready to go.

If you wish, you can switch the solenoid manually from a switch inside the passenger compartment, or just hook it up to some other circuit that is hot when the key is on.

I believe this topic has been discussed and I provided specifics on the solenoid and its ratings, etc.

I can highly recommend the Hellroaring Isolator/Combiner (again :D ) It keeps your back-up fully charged and will combine the two batteries with the remote switch.

http://www.hellroaring.com/4wheel.htm

SC

Still doing research...

The Hellroaring isolator has me very tempted, but this looks almost simpler/better.

BEP Automotive Switches (http://www.bepautomotive.com/showproduct.cfm?productid=1024)

Hmmm......

:flipoff2:

Michael,
I have 2 yellow tops in my Rangie. I just connected them in parallel and put one of those quick disconnects on the second battery. Seems to work fine. Word of caution (common Sense) if by some stupid act you manage to completely discharge both batteries, recharge them with a proper battery charger or plan to by a new alternator.

I haven't experienced this one first hand but it takes about 8-10 hours to fully charge each yellow top. They hold tons of juice.

Slade,

Your buddy at wranglernw has what you need. Switch, 200 amp solenoid, etc.. I just did the same thing on another vehicle and it worked out fine. His switch with LED is a nice system.

Ali

I just ordered the BEP isolator and cut-off switch.

The isolator is rated for 300 amps continuous, 750 amps for 1 minute and 1200 amps for 15 seconds.

The switch is rated even higher.

These are for the CrewCab. For the Range Rover I'm going to go the ultra simple route and just use a cut-off switch like LWG did. I figure on the Range Rover I'll just leave them connected all of the time, ensuring I have a topped up charge on both batteries, but when I go out into the bush, I'll disconnect the second battery for insurance.

Ironically I left the 1000 watt inverter on over the weekend with the CrewCab and both of the Oddessey batteries were DEAD this morning.

Had to use my back-up to get it started, trickle-charging them right now.

The chances of me leaving something on inadvertently on the CrewCab is MUCH higher than on the Range Rover.

If you're planning on using a deep cycle as the second battery, remember to "top" it off with a charger at home monthly.

I would pass on over-priced gimmick isolator jobbies as well. I don't know what a Sorenson Solenoid is but when I put the second battery in the Tonka I used the tried and tested cheap and easy solution of using a big f-off solenoid and 70 amp relay that a bunch of guys in the Gulf use. Very reliable and cheap Whole thing is about $35.

Basically the solenoid clunks in once the alternator is up to speed and delivering current, the second battery will only take charge if needed. Will only draw current with the vehicle running and sufficient juice to kick in the solenoid, thereby avoiding frying your alternator. If you want to wait a bit, I think I have the wiring diagram in the Tonka still and can fax it/e-mail it but it is currently undergoing minor surgery and I won't have it back until at least next week. Worse case I can always try to track down the the "inventor" or someone else with a diagram fro you.

I know you seem to have already decided but I will throw in my 2c worth.

A friend devised a cunning isolator that connected the 2 batteries with a high current relay (the 2nd battery was not for starting though, just for the fridge). The feed to the relay was provided by the auxillary feed on the alternator (not normally used) - so the batteries were only connected to each other while the engine was running AND the alternator was producing charge.

I believe the auxillary feed is usually marked with an "F". On Bosch and Lucas alternators it is 12V and on Japanese alternators 6V. Don't know about others.

Michael, the BEP looks cool, let's hear how it works out.

SC

******Non-Rover Newb Input WARNING******

Here's a write-up on a Land Cruiser site that may be of interest; kinda in line with what some people were suggesting.....

Write up (http://www.sleeoffroad.com/technical/tz_dual_batteries.htm)

Schematic (PDF File) (http://www.sleeoffroad.com/technical/images/dual_batteries.PDF)

What I want to understand is why people don't want to just install a simple isolator?? Simple, keeps the batteries separated, no moving parts, cheap, only needs to be sized to match the alternator.

Michael,

I have e-mailed you the wiring diagram for the solenoid and 70 amp relay twin charger.

Cheers,

Originally posted by Serious One
The isolator is rated for 300 amps continuous, 750 amps for 1 minute and 1200 amps for 15 seconds.

Now this gets interesting. If you are winching with your winch drawing it's stall load of say 450 amps, will you fry the isolator? I couldn't figure out if I would wreck my hellroaring doing this so I added a separate, manually switched, heavy duty bootie fab wire from the 2nd battery to the winch bypassing the isolator. Thoughts?

Yeah, that is where it gets interesting.

I don't think I'll stall out my winch (12,000 Warn), and if I do I doubt it will get over 12000 amps for longer than 15 seconds (I think the winch motor would fry first).

The higher loads of the marine isolator led me to choose it (plus it looks sexy when mounted in a location that no one will see).

Time will tell.

One thing I have learned is that the Hella/OMP cut-off switches I was using did end up frying and I believe that my starting and winching problems I had at the National Land Rover Ralley in Moab last fall were a result of those switches.

Gonna switch the switches now.

:D

12000 amps

shit - I guess Coop got that nuke->LT230 conversion kit wrapped up! LMAO :flipoff2: :flipoff2:

We found out the hard way during the winch challenge that the standard red handle hella switches are not up to winching loads. They get fried.
Earthing the winch back to the body is also not a good idea - we now run heavy duty cables back directly to the batteries with no switches - which is fine for a winch challenge truck (where you take the batteries out afterwards) but no good for a touring set-up.
But the fact remains that when you do need your winch, it will pull 300 - 500 amps when the load is on. If your switches, isolator, cable, earths etc aren't rated at that level for continuous use then you will get problems.

The worst bit is that these problems don't show up when you are testing the system at home (with no load on the amp draw is light). In fact, they don't show up until you start using the winch seriously - like when you are stuck. Then the parts start burning out and you may or may not reach the point of failure in one pull or two or... This is how we burn out our earths, they basically burnt themselves off the part of the truck they were bolted to, giving more and more resistance (and poorer and poorer winch performance) until they failed completely.

Given that most winches are used as a very occasional use insurance policy (when travelling solo for example) it may be better to simply run good cables (with no switches, or failure prone gizmos) directly back to the batteries but leave them disconnected until they are needed.

Whoops. One too many 'zeros'.

:flipoff2:

A normal isolator goes between the alternator and the batteries. All LOADS draw directly from the batteries. The isolator should only see what the alternator can supply.

This is why it is cheap, safe and simple. I'm still waiting for the reason why people don't like this method.

http://www.surepower.com/images/g_isofig.gif

In my RRC, I’ve got my winch wired directly to my second battery being kept charged by an isolator rated a little above the max output of my alternator. All heavy amp draw is thru heavy gauge welding cable style leads directly to the winch. My winch safety cutoff is in the standard solenoid control circuit back to a switch on the dash. No problems after four years.