Thread: Which dual battery setup?

Redarc is another option apart from Traxide. Works slightly differently, as per how much of your cranking battery gets used for the fridge etc, but both are a class act.

Smart Start® SBI | Redarc Electronics

cheers, DL

ok...

the main flaw in the system lies in the control for the aux relay (the little one in the right of the wiring diagram thats in the blurby PDF. In its unpowered state it connects the load to the batteries.

if you have a control unit failure (say a bad earth) it will drain the aux battery to dead.

ok so thats liveable whats not liveable is if you have a main battery failure or leave the lights on or the vehicle accessories on when the main battery voltage drops below about 9V the unit wont be able to drive the AUX relay any more and once again the aux battery will drain down to 0V.

you're now down to nowhere near enough power available to do anything but a push start or crank start of an old school engine. Something new that has a cut out voltage on the ECU of 10V just aint going to play and you cant even do the old trick of running 2 batteries in series for "one last shot" at a start.


The not so big problem is the unit lists as being able to deal with 80Amps which is nice but lets look at the amps that are going to be involved if you have a large dead flat battery, a nearly fully charged one and a decent alternator call it 120 Amps worth. when you hook the dead battery in parrallel to the charged one it will immediately begin to drain (which in some cases may be enough to kill your ability to start if the main battery isnt the greatest) into the flat battery. When you get the engine started and the alternator starts to crank out you now have a higher voltage to help push the power along and it all goes through the one relay.

as a "lets just see" I've hooked a new but dead flat N70 size battery (which is the standard battery size for all Td5 engines and all shed class rovers) to a fully charged one using my "jump start a small planet" grade jumper cables and had a current draw that pegged my 100A mini clamp meter for nearly a minute. now chuck some alternator amps on top of that... how longs that 80A relay going to last and what happens if it spots its contacts in the closed position so that both your batteries are hooked up all the time?