dual battery switch

[SkippyThBushKangeroo]

Benny, if you just have two dissimilar batteries running in parrallel they will try to find a common level, so the lower charged battery will draw power from the other battery 

 thanks warren  within that beutifully worded statement u have dropped th penny rite on the question mark  wot has hung over my pondering of me mitsi 4x4 which had a 2 batt setup which woz in short shytefull always drainin not behavin itself ,took second one off an ran fine,but always wondered why when second batt was workin ok on own too.. 1 was from hz v8 wagon the other woz off a vile little barina thingey.. enlightenment is such a fortifying emotion    thanks again bloke for answering a mystery WTF? which has mellowly haunted me ,when the missin green van hasnt been 



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[ShaneJ]

You don't have to worry about overloading an alternator. Its not possible. Unless of coarse the battery is a dead short and in which case your fusble link will blow.

With my setup you also don't have to worry about a sad deep cycle battery draining the crank battery. Your alternator regulator is going to force out charge voltage when the engine is running so the crank battery will always charge. When you turn the engine off the crank battery becomes isolated.

[MaTTe]

Shane, thanks for the insight.
I had been thinking about getting a dual battery setup along the lines of the 4wd type setups, they are generally costly and in some ways sophisticated - however some reviews make this sophistication out to be a draw back rather than an advantage.

You say not to run a Redarc, which seems to be a fairly common brand. Are you able to recommend any other brands that you think/know are worth the time effort and money? If you have tried any and have part numbers that'd be even better 
Cheers
Matte

[delrazor]

So just to complicate matters, is it possible to incorpotate this relay system into the manual switch setup?
ie. use the relay setup, but be able to isolate the batteries if one goes funny.

I just woke up so ignore if this doesn't make sense. derek

[Warren]

Um depends on how you wire it wired

If you had another relay from the house battery to ground (like shane has on the cranking battery) you could add a manual switch in the control wire that comes from the ignition to the relay, giving you a manual over ride.

The simplicity of Shanes layout is that its all automajick

Warren
 

[ShaneJ]

Shane, thanks for the insight.
I had been thinking about getting a dual battery setup along the lines of the 4wd type setups, they are generally costly and in some ways sophisticated - however some reviews make this sophistication out to be a draw back rather than an advantage.

You say not to run a Redarc, which seems to be a fairly common brand. Are you able to recommend any other brands that you think/know are worth the time effort and money? If you have tried any and have part numbers that'd be even better 
Cheers
Matte

Mate don't worry about those complicated systems the 4WD joints try and sell you. They provide no extra benefits over my set up apart from some of them having a voltage meter on them.
The redarc relays just disconnect the deep-cycle battery from the main battery when the voltage drops to a certain point. So you are still able to flatten your main battery by leaving your lights or stereo on. People rave about them because they are a neat little automated package that is easy to install. Problem is they are more expensive than a standard higher amp rated solenoid relay and they just don't last that long. I have one here which I trialled in my 4x4 for a while.

I recommend you get your hands on just a standard high amp solenoid relay. One that looks just like this:


I use a 400amp one in my 4.2D 4x4 and I think it cost me between $70-80.

If you guys are interested I'll try to find and buy some at trade price? I would need to order a few though.

[MaTTe]

Hey Shane, yeah i had thought the same about the 4wd setups, and then i saw the simplicity of your design..

Looking at that photo i have seen something similar kicking around my grandads shed somewhere, but i'm not sure of the amperage.

Would you get a 400amp relay for a 400cca battery, therefor a 600amp relay for a 600cca battery? or a 400amp relay is fine for a 600cca battery?

I'm pretty keen on the idea as i'd like to be able to run a few different things while parked without risking being stranded.
If you can get some high rated ones at a good price i'd be keen, if we can't get enough together for it tho, i can probably get trade for myself.

Cheers
Matte

[ShaneJ]

A 400amp relay is pretty large and would only be required for high compression diesels or V8's. A 200-300amp will be fine for your average little holden 6.

[MaTTe]

Shane, i've got a 350, and the 540cca battery has trouble starting when the motor is hot, so i'll look at going back to a 620+cca battery. will i need the relay to match the cca rating of the battery? is what i was asking in a round-about way 

[ShaneJ]

No. Infact I don't think you would even find a 600amp relay. I guess you could run two in parallel.