Thread: Dual battery system that always works

i think the SC-40 does just that......it charges the aux battery off the main one........
till the main starts to drop.......then it isolates it.......

so the main is always charged.........with more than enough power to crank the engine over.......



being connected to the main battery.....it will also use some of the surplus power from that......
which will give you power for longer than just the aux battery can supply on its own......

Hi Defenderzook,

The problem is that as Drivesafe says, some modern charging systems provide only about 13.2 volts under some circumstances. The second battery needs about 14.5 volts to charge quickly and completely.

Thus what is needed is a controllable voltage step-up device capable of pumping 20 to 40 amps, and that's the expensive bit. It also needs the usual isolating circuitry but with adjustable voltage levels to suit personal needs.

Cheers,

Paul

Originally Posted by Wilbur

Hi All,

The current thread on dual battery problems shows that there is a real need for a proper system, one that will work whatever the charging voltage of the car system is without affecting the car charging regime, and give proper three stage charging to the second battery.

It would need to have a user-selectable cut-out voltage so that the user could decide how low they woud allow the car battery to drop, and a user-selectable second battery type to optimise the three stage charging for the particular battery.

This is all easy, known technology but it would not be cheap. It could cost around $400 for a 20 amp system, and maybe $600 for a 40 amp system.

The big question is, would anyone pay that much? It seems unlikely, or there would be some on the market already.

Any thoughts?

Cheers,

Paul

Piranha quoted over $1000 to fit a dual battery system so i think, yes, people do pay for a good system. Or are you saying that it would be $400 on top of the $1100 Piranha Unit

No, I was thinking it would cost around $400 to $600 all up for a complete unit, boosting output volts to 14.5 volts regardless of input volts, and including the usual isolating cut-outs etc.

That is probably not a retail price - I looked up retail prices of the appropriate bits on the net as a DIY project. I guess in commercial production they would sell for more - but not $1100!!!!

Do you know if the Pirhana system includes voltage step-up?

Cheers,

Paul

And Pirahna systems are crap.

I have 2 in the shed 1 with a burnt circuit board from running the fridge, they said thats normal and just run a wire over it and solder it on and the other is a smaller unit that they dont recomend you use if you have a winch as the voltage drop can damage it apparently.

Im going to build my own basic simple system and just give the aux battery a full charge on the plug in charger before we go away anywhere.

Originally Posted by Wilbur

No, I was thinking it would cost around $400 to $600 all up for a complete unit, boosting output volts to 14.5 volts regardless of input volts, and including the usual isolating cut-outs etc.

That is probably not a retail price - I looked up retail prices of the appropriate bits on the net as a DIY project. I guess in commercial production they would sell for more - but not $1100!!!!

Do you know if the Pirhana system includes voltage step-up?

Cheers,

Paul

No the old ones that I have dont, they are just battery voltage but I dont know about any new ones they could have.

Voltage sensing solenoids (not relays) do the trick fine. They parallel the batteries if and when the reserve battery needs it and separates them otherwise. The auxilliary battery(ies) get(s) the full charge when needed. Batteries in parallel last longer and give more power than separate batteries. We do this on our boats at work all the time with zero problems. We use the Sure Power Smart Solenoids ex. USA that ARB used to retail. Redarc (Australia) do them as well. My Defender and SIII both use these so does the ute at work with an electric/ hydraulic crane on it. A piece of cake to install and an absolutely bullet-proof solution.

Originally Posted by Dunnie

Voltage sensing solenoids (not relays) do the trick fine. They parallel the batteries if and when the reserve battery needs it and separates them otherwise. The auxilliary battery(ies) get(s) the full charge when needed. Batteries in parallel last longer and give more power than separate batteries. We do this on our boats at work all the time with zero problems. We use the Sure Power Smart Solenoids ex. USA that ARB used to retail. Redarc (Australia) do them as well. My Defender and SIII both use these so does the ute at work with an electric/ hydraulic crane on it. A piece of cake to install and an absolutely bullet-proof solution.

It's Redark that Im getting, I cant remember the Amps but I will be isolating it when winching anyway with a big red key switch but at around the $100 from my auto elec mate it is a much better and simpler system for me.

Electrickery is never great on things like 4wd's that get used in extreme envioroments (for electronics that is) I have found.

They dont like dust, vibration, oil and fumes, heat and water and then it still is meant to work.

If you were not using your 4B of road all that much and mainly towing or the like then it wouldnt be much of a problem.