Thread: D4 dual battery isolators - what options

Hi Ray, battery capacity while winching is dependant on the output capacity of your alternator and whether you are competition winching.

The D4 has a huge output capacity so it's fine, the only other consideration is how you plan to you your winch.

For now I will work on the premise that your use is recreational and not competition ( correct me if otherwise ).

As best practice while winching is to have your motor on high idle and winch for 60 second and then rest for 90. Repeat until winching is completed.

With the 180 amp D4 alternator, you can keep auxiliary battery size down, particularly if you use a high current charging battery like an Optima.

With exception to running your winch into stall, where the current demands are very high, most of the time you are unlikely to draw more than 300 amps, peaking to under 400.

But you can go well over 400 amps and still be with in the operating limits of your D4.

You would also tolerate a stall current of up to 600+ amps, for a short time.

These sorts of currents are easily maintained when one of my USI-160 isolators is use to like the auxiliary battery to the cranking battery during winching.

Ray there are three D4 Dual Battery kits designed around the USI-160 isolator, and if you want additional battery capacity, either to assist with winching and/or for additional accessories battery capacity, there are there Triple Battery kits that will fit "MOST" D4s.

Thats fantastic,
thanks heaps Drivesafe!
yeah only rec winching here and hoping to put a fridge/freezer in the rear for camp out trips when fishing etc

Have been checking out the optima batteries,
whats the typical Ah people install for dual battery systems?
i see the 55Ah seems to be an affordable price, but i dont know if this would be enough for a 60ltr fridge?

looks like the USI-160 is the one for me

Originally Posted by apachefreak

Thats fantastic,
thanks heaps Drivesafe!
yeah only rec winching here and hoping to put a fridge/freezer in the rear for camp out trips when fishing etc

Have been checking out the optima batteries,
whats the typical Ah people install for dual battery systems?
i see the 55Ah seems to be an affordable price, but i dont know if this would be enough for a 60ltr fridge?

looks like the USI-160 is the one for me

The 55AH Yellow Top will be fine. Remember you're also scavenging some reserve out of the primary with the USI-160, so in reality it's closer to a standard system with a 90AH second battery.

Cheers

Gordon

Originally Posted by drivesafe

.....These sorts of currents are easily maintained when one of my USI-160 isolators is use to like the auxiliary battery to the cranking battery during winching.

....

Hi Tim,

Is the SC80 also able to tolerate these amps while winching or should I be thinking of upgrading?

Cheers,
RickO

Hi Rick and sorry, the SC80 is not designed for use with winches.

BUT, there are two options, and one is to replace the SC80 with a USI-160.

Or a cheaper operation is to keep the SC80 and add a bypass switch, a 250 amp ( or higher ) marine battery switch. See the diagram below.

Either way, don't forget to upgrade the cabling between the batteries from the standard 6B&S ( 13.5mm2 ) to at least 3B&S ( 25mm2 ).

Again, there are two cable upgrading options.

You can either replace the 6B&S with 3B&S.

Or you can run another length of 6B&S in parallel with the existing 6B&S and this will give you roughly 27mm2 cabling.

NOTE, remember you have to upgrade all negative ( - ) cables as well as the positive ( + ) cables.

Hi Drivesafe

Just saw this post about NOT running a winch through the SC80 that I have installed.

My car has a winch and I've had no problems winching, admittedly I've only ever used it to pull the van into position

What would be first to fail?

Also, the diagram you posted doesn't actually explain what I connect to the switch. I assume its the main positive cable from the main battery to the SC80.