Dual Batteries for dummies

[outbackjoe]

you need a relay with two contacts, one normally open and one normally closed, and of course rated at high enough current

[aandy]

I don't think you need to disconnect the Ctek at all, of course it will be useless as long as the batteries are paralleled. It doesn't know its 14V input is actually the same 14V it is pumping out. Probably not something Id leave and forget long term but I don't see it as an issue for short term use.


I have used my parallel switch for jump starting after leaving the stereo on all day and half a night on Australia day with no problems, it would also be useful if the Ctek ever died as I could still charge both batteries the old fashioned way.

[outbackjoe]

Yeah maybe, I worry the ctek may not like its output clamped down to 12V when its trying to make 14, especially for long periods, good practice is to isolate it, although I have never asked ctek, maybe check with them.

[cuzo4x4]

started my install today, was going well untill naubours come down with beers will try and finish it during the week.



I have a question though - I have a manual cut out switch that I want to put in to isolate the back tub if need be but should i install it before the relay or after ??

Also see the Toyota denso thingy in the bottom right corner of the first pic this was mounted were the battery holder is now, does this need to be earthed as I have only cable tied it in at the moment, and the mounting bracket seemed to be powder coated right through so it didn't seem to be earthed any ways. ??

[aandy]

Yeah maybe, I worry the ctek may not like its output clamped down to 12V when its trying to make 14, especially for long periods, good practice is to isolate it, although I have never asked ctek, maybe check with them.

Yep fair call. What can I say, Im a risk taker and like livin on the edge.. haha hardly

[10 luxxxx]

G'day I have just picked up a redarc Smart start isolator to replace my current setup and after a search on google I came across a few people that say there is no need to run a fuse between the battery's and redarc.
My last isolator did not have fuse much like Cuzo4x4 pictured above.
Also was mentioned that a 60 amp circuit breaker would do the job instead of a fuse.
Any help or feed back would be great I will put fuses in just to protect it all and be safe. Also any links to builds or pictures where you have installed you redarc smart start.
Cheers

[wayn05]

Hi Fella's

Putting all of the battery management systems and isolators aside, has anybody done a direct parallel connection between their two batteries (i.e two batteries exactly the same size)?
I have been looking at this method as my old man has had this setup on multiple cars for years (40 series, 60 series, 100 series and now his 79 Ute), and my brother has gone with this method on his new 76 wagon, all without any dramas, and still getting great life cycles out of both batteries.

Any comments from anyone that has installed or attempted this system, and what auxiliary battery they used would be much appreciated.

Wayne

[Alby]

What is the advantage in doing it this way?
I can think of some disadvantages:
If one battery collapses it will pull the other one down too, if lights or something are left on accidently all of your batteries will go flat
Keen to hear the upside though

[wayn05]

The upside i guess is the initial saving (not forking out for the system, redarc or similar).
Also, if you do have 2 drained batteries, you can always disconnect the second battery manually, wrap it up in a rag or something, and get a jump off your main battery.
Another reason i am looking at this is i have heard of management systems failing to disconnect and burning out etc.
Just thought id ask out of interest as i have always been taught, since i was a wipper-snapper that its the best way to do it, but everyone seems to be hell bent on electronic systems and chargers.
Any thoughts?
Thanks

Wayne

[2007Lux]

G'day I have just picked up a redarc Smart start isolator to replace my current setup and after a search on google I came across a few people that say there is no need to run a fuse between the battery's and redarc.
My last isolator did not have fuse much like Cuzo4x4 pictured above.
Also was mentioned that a 60 amp circuit breaker would do the job instead of a fuse.
Any help or feed back would be great I will put fuses in just to protect it all and be safe. Also any links to builds or pictures where you have installed you redarc smart start.
Cheers

[outbackjoe]

The biggest disadvantage with direct connection is you will deplete your starting battery and risk being unable to start your vehicle. This is the main reason for voltage sensing isolator.

[Qwerty]

The upside i guess is the initial saving (not forking out for the system, redarc or similar).
Also, if you do have 2 drained batteries, you can always disconnect the second battery manually, wrap it up in a rag or something, and get a jump off your main battery.
Another reason i am looking at this is i have heard of management systems failing to disconnect and burning out etc.
Just thought id ask out of interest as i have always been taught, since i was a wipper-snapper that its the best way to do it, but everyone seems to be hell bent on electronic systems and chargers.
Any thoughts?
Thanks

Wayne

Advantage : Cheap and Nasty way of doing it.

Disadvantage : Cheap and nasty way of doing it.

Sure, it'll work mate. Til it doesn't work.

Same can be said of any system I suppose , all boils down to what kind of safeguards and functionality you wish to have, and what you deem to be "good enough" / professional solution.

I run a starter battery that is for engine and the car (ie dash, headlights, fuel pumps, ECU etc), and that is ALL it does. It gets charged by the alternator as normal.. When the key is off, that sucker is untouched (well unless i leave headlights on of course).

My auxillary outputs (2 x ciggie and 1 x anderson plug), stereo amp, stereo deck are all wired directly to my auxillary Battery, and ONLY my auxillary battery. It is charged by a DC-DC charger , which in turn gets power from the alternator when engine running, triggered by ignition wire (it is also voltage sensitive, so if for some reason my alternator is not working, it will disable itself and prevent draining from the starter battery ... same logic as an isolater I guess).

The Auxillary battery is designed to be discharged a little more deeply than a starter ... and has a higher AH capacity. It gets raped on camping trips ... lots of discharge and re-charge ... exactly what it's designed for. That said, I never auxillary go below 12.0v ... as that's starting to get into sub 50% territory and do chemical damage to the battery (which is OK if you "had to", but i avoid it).

My aux battery is probably going to have a shorter life than the starter.

If and when I need to bridge my two batteries, I have a set of jumper leads, as yet have never had to (leaving headlights on would be the only real thing I can think of). Some blokes have a switch that bridges them for winching .. i dont know much about that.

It's the same on boats ... you maintain a bank of batteries for engine and critical nav systems, and a bigger bank of batteries for house duties / inverters etc.

Exhausting auxillary power , whilst may result in warm beer, is no biggie ... exhausting starter batteries and having a disabled engine is a bigger deal.

No matter what system you use mate, so long as you keep an eye on it, know its limits... and work with them, you'll be fine.

[Alby]

The upside i guess is the initial saving (not forking out for the system, redarc or similar).

Wayne

Redarc isolator is about $80

[wayn05]

Thanks for the feedback gents

[2007Lux]

G'day I have just picked up a redarc Smart start isolator to replace my current setup and after a search on google I came across a few people that say there is no need to run a fuse between the battery's and redarc.
My last isolator did not have fuse much like Cuzo4x4 pictured above.
Also was mentioned that a 60 amp circuit breaker would do the job instead of a fuse.
Any help or feed back would be great I will put fuses in just to protect it all and be safe. Also any links to builds or pictures where you have installed you redarc smart start.
Cheers

Dam I just lost my reply to you so here we go again. I mounted my BCDC1220 on the side wall of the engine bay beside the cranking battery. You'll have to drill two small holes in your beloved car to achieve this but it's right out of sight so who cares? Face the unit upwards so you can see what part of the charging cycle it is on. See my comments above regarding the circuit breaker issue you are asking about.

[Wing]

Thanks for the feedback gents

If I can choose again, I would just install your proposed system but with two dual purpose battery (optima or century marine) and connect them in parallel. You will be like having 2 ancillary batteries. Simple. The fridge will cut off under a certain voltage. Head light chime will prevent draining. Two half dead century should be able to start the engine. And for me, under most circumstances, there should be always another 4WD nearby. Worst case, use the solar panel and spend an extra day there.

[Anth D]

My heads spinning fellas, but I'll be going Redarc! I guess the main issue at hand as to whether I mount in the engine bay or take it back to the tray? I'll do a search and see if I can find any issues with the wheel arch cracking.

[Wing]

both have cons, in tray can save the arch but you may need long heavy duty cable fused at both ends and the batteries occupy some space. If you can weld, cut and fabricate, there is space under the tray and in front of the LHR indicator lights where you can mount an optima upside down.

I put mine on the front LHS arch with same rubber washers sitting between the tray and the arch. I don't think many people have cracking issues. Install a lighter battery if worried.

[Anth D]

I did a search and all I could find is blokes recommending the use of the ARB battery tray to try and prevent it. Washers are a good idea, cheers!

[2007Lux]

The ARB tray is a must IMO. Reason will become clear when you do it as it slots in nicely and has holes for the things you move off the firewall.