Thread: Decisions, decisions, which dual battery system??

Originally Posted by Vern

What isolator do you use, and/or recommend?

I'm not having a dig, but I'm not exactly sure what your point is about the 10v/8v bit is, i understand it, but just not sure what the point is, are you saying tims isolator won't do the job?

That the isolator will drop out the second battery during high current demand/voltage drop below 10v...the solenoid cut out point as it will be seeing 8V due to voltage drop

The problem with a smart isolator is that it switches under load, that destroys the solenoid contacts, DC is extremely aggressive, a solenoid itself will usually handle much higher current draw than rated, as that what it is rated to switch not rated for constant draw

I was under the impression that once in "winch" mode it won't drop out. Switching dc under load is not good for a lot of isolators, unless designed for it, am aware of that, in the past I always used a 200a continues duty iso, will see how long the 160 lasts then. Am sure tim can fill us all in about it

Originally Posted by Vern

I was under the impression that once in "winch" mode it won't drop out. Switching dc under load is not good for a lot of isolators, unless designed for it, am aware of that, in the past I always used a 200a continues duty iso, will see how long the 160 lasts then. Am sure tim can fill us all in about it

Originally Posted by drivesafe

When you select WINCH mode, the USI-160, automatically resets it’s cut-out voltage level from 12.0v to 10.0v, to allow you to discharge your auxiliary battery to a much lower level during the high current draws that occur during winching.
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Sounds like it drops at 10V, which is easily going to happen with a big motor and sustained winch

But, for 95% of people it sounds pretty much ideal in its functionality

I like to think I am in that 95%😊

Hi, I work with batteries and have done so for 25 years now. That makes me look old hey! Having batteries of the same type is the best option if you can because they will have the same internal resistance. Electricity is like water and will take the easiest path to get where it's going. If you have a flat battery which will have high resistance along side a charged battery which will have low resistance then most of the power will go to the charged battery till they equalize. The spiral cell types are a good choice because they have both low internal resistance to start with and good starting and cycling capabilities

I don't know whats being used to do the job as such, if there is hysteresis built in or just simple volt sensitive relay, but by having 2 modes I'm guessing its got a bit more logic than vault sensitive relays, or it could just be 2 with different set points

My setup on my dual cab will be factory battery, then charge controller to 2 optimas under tray which will provide for usual dual battery crap and 8274, aside from engine load and maybe a bit of lighting, the main should stay topped up enough to feed enough charge to the rear 2 whilst winching

To much effort and no need to think that much, all I know is that with 2 optima's, linked with a solenoid I could comfortably winch myself or others out of anything needed, and that's spending time looking to get into trouble

So 2 at the rear with the winch being the sole draw whilst winching....maybe fridge but meh, will be heaps, feeding from the cranker is good theory to get the most from the alternator, but If I've flattened 2 optima batteries, including the dregs of what comes off the alternator winching, its time to stop for a beer anyway

Which is why I recommended 2 optima batteries linked with a dumb solenoid, this means to batteries linked for winching, also has the advantage of leaving the aux disconnected and can be run flat and the cranker still charged, pretty clever hey

It was the best method I ever used for someone who used a winch a fair bit and run a fridge and big stereo....I used a lot of battery controllers and killed a lot of batteries over the years until I did exactly as above

It also means both batteries get exercised

Worst thing that can happen is you let the cranker flatten, single jumper cable fixes that