Thread: BATTERY CHARGING in 4WDs–How to get it right - What do people reckon of?

Tim, what is a 'smart' alternator? I'm running a 175 amp Reece Neville to charge 4 x N70 in series/parallel, it takes a few minutes for the volt gauge to recover from twenty V. The last batteries only just made warranty.

Originally Posted by V8Ian

Tim, what is a 'smart' alternator? I'm running a 175 amp Reece Neville to charge 4 x N70 in series/parallel, it takes a few minutes for the volt gauge to recover from twenty V. The last batteries only just made warranty.

Hi Ian, can you post up more details of your setup and how it operates?

Originally Posted by V8Ian

Tim, what is a 'smart' alternator? I'm running a 175 amp Reece Neville

Reece or Leece?

My old D2a has a 130a alternator and it easilly runs 2x 12v fridges and keeps 3x batteries topped up.
I recently added a fridge and 80ah battery to my boat the alternator also easilly runs this as well as the 2x fridges, cranking and 2x 110ah deep cell batteries while i am travelling.
I don't have any flash dc to dc charger or any other isolator gizmo fitted I have simply added cabling from the cranking battery to an Anderson plug at the rear of the truck and via a daisychain of anderson plugs i run the whole shebang directly from the cranking battery/alternator.
The only thing I have to do when I pull up is to disconect the daisychain from the rear anderson plug to make sure that the cranking battery isn't affected.
A very Very simple setup and it works

Originally Posted by DAMINK

Ok i stand corrected man. Its all a gimmick and my isolator does not isolate rather just charges both batteries all the time.

your isolator does isolate. when you turn your car off, it isolates/seperates both batteries, which is the intended design

Originally Posted by DAMINK

Yes true. But the isolator reads the batteries charge not the alternators. The starting batteries charge and if that is below the threshold then it will take all the charge until the charge battery is full.
Then when the charge battery gets low again it will take all the charge and leave the second battery out of the loop.

Thats my understanding of the units and i thought that was why they call them isolators. Isolating your charging battery from the aux so that your charge battery will always be full regardless of your aux.

well your crank battery is connected to your alternator. so, if your alternator is putting out 14.0, your battery should be showing 14.0 too (minus any small loss due to cable size).
to complicated matters, just because the voltage at the battery is 14.0volts, doesnt mean it is full. it could be full, or it could be half full and charging.

you're so close to getting this right

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Thanks for the correction, Ron.

Originally Posted by DAMINK

Thats all i was trying to say mate. That they isolate the cranking battery to protect it from discharge. During start if the cranking battery is low it will charge first. Or if the battery is below a threshold the isolator will separate them.

your correct, the isolator is to protect the crank battery from discharge.
when the alternator is spinning, the battery is being charged, and there is ample capacity to charge both batteries. so why not do it?

Originally Posted by DAMINK

Also i was under the impression an alternator charge rate was determined by the engines revs? So at idle your alt will not put out as much? I could be wrong here but just something i recall.

yes but no. its nowhere near dramatic as that.
depending on the alternator, lets take a 100amp alternator for example. 700rpm (idle) might be capable of pushing out 80amps and 1000rpm is capable of the full 100amps.