Thread: USI-160 160/240 AMP ULTRA SMART DUAL BATTERY ISOLATOR.

Hi Ron and an interesting use for the USI-160.

Because the USI-160 monitors both the input ( from the cranking battery ) and the output ( from the auxiliary/house battery(s)) you can’t simply swap the cables around.

The USI-160 is designed to go into a low power mode if no auxiliary/house battery is detected or if the auxiliary/house battery is below 8v.

With the USI-160 set in the IGNITION Mode ( switch towards the LED ) the isolator will go into low power mode when the cranking battery voltage drops to 12.6v. So if you were running a few accessories and didn’t have the auxiliary/house battery connected, the isolator would go into low power mode after just a few minutes.

BUT, if the USI-160 was set to the SHARED Mode ( switch set away from the LED ), the isolator not only would not go into low power mode until the cranking battery voltage dropped to 12.0v, but after turning the motor off, once the cranking battery voltage dropped to 12.75v, one of the two relays in the isolator would turn off.

This is done to reduce the amount of power being used by the USI-160 to helps to extend the operating time before the battery(s) needs charging.

So if you leave the USI-160 set to SHARED Mode, it will do exactly what you are after. It would provide accessories power off the cranking battery but would isolate the cranking battery leaving you heap in the cranking battery to be able to start your motor.

The only catch is that if the voltage dropped to 12.0v and the USI-160 went into isolate mode, as there is no auxiliary/house battery connected, within 60 seconds, it would also go into low power mode.

Normally the only way to get the USI-160 out of isolated mode is to connect an auxiliary/house battery but you can “trick” the isolator into thinking there is an auxiliary/house battery connected by starting your motor and bridging the two main terminals on the isolator for 8 seconds.

While you could achieve the same thing by installing a push button switch in the cab of your vehicle, the push button switch and the wiring between it and the USI-160 would have to be big enough to carry the current load of your accessories while it is pressed.

Note, again if you did fit the push button switch in the cab, all you would have to do is press the button and watch the LED on your In-Cab module. This will flash for the 8 seconds and then come on solid to indicate when the USI-160 has turned on.

Originally Posted by drivesafe

...
Because the USI-160 monitors both the input ( from the cranking battery ) and the output ( from the auxiliary/house battery(s)) you can’t simply swap the cables around...

Thanks for the info. What I was trying to ask is how difficult would it be to modify the unit to only monitor the cranking battery terminal voltage? That is, move the auxiliary battery voltage sense wire to the cranking battery terminal.

If that was a possibility, I could then use a change over switch to select either the aux terminal to monitor when a aux battery was connected (normal operation as designed ), or the cranking battery terminal when operating without a second battery. (Ron's devious way of tricking the 160 into believing that a second battery is installed.).

Hence the switch in this case could be another toggle switch similar to the control switch.

Cheers
Ron

Hi Ron and the more I think about it the less I like the idea of an independent switch set up.

Even the Push Button suggestion above requires fuses being fitted to each wire at the isolator.

While this set up won’t cause any harm if something goes wrong, it’s still not the best way to achieve what you want.

As for tapping into the internals of the unit, that’s just not an option.

BUT, I may have a way to achieve what you want with a few changes to the microprocessor’s program, adding an extra feature to the operation of the unit and allowing the existing switch to carryout the additional feature.

Leave it with me for a while as I’m flat out with another project at the moment.

Thanks Drivesafe,

I can wait awhile and am happy to be the first test customer. I will be running my power line down to the back soon as my interior trimmings are still out due to a skinny dip on New Years Day... I'll leave a loop in a convenient place.

Cheers
Ron

any reason you cant fit a semi decent sized capacitor to trick the SC160?

tap the solenoid-startermotor winding to get the initial spot charge to the capacitor then the sc160 can read the capacitor voltage and then hook up to the load. you'll then run in shared mode till the battery voltage goes low and then it'll drop off the aux load.

Hi Drivesafe,

A question about putting the batteries on mains charge when connected with the USI-160.

If the USI-160 is in shared mode, then the mains charger will see one battery? If they are isolated then the mains charger will only see the battery it is connected too?

Otherwise, am I right in thinking that if I switch to 'jumpstart/ignition' mode they batteries are joined and the charger will charge both batteries equally? And is this the 'mode' to use for charging?

Looking at your diagrams on the first page - does it matter which battery is connected to the mains charger? Aux or main?

Rgds
Willie

If in shared mode AND the relay has both batteries connected (voltage of the starting battery is above 12v - the LED is fading in/out) your charger will be charging both batteries simultaneously as they are both connected together by the relay.

If in ign' mode, the relay will be disconnected when the engine stops (or after a short while when the surface charge on the batteries drops below 12.75v I think) ... your charger will charge the starting battery only UNTIL it's voltage rises to 13.2v (i think) at which point the relay will connect both batteries, and both will be charged as they will then be connected together.

Regardless of where the switch is, when a charger is connected to the starting battery, BOTH batteries will eventually be fully charged. (Starting first & until voltage rises to cause the relay to connect both batteries)

If you connect the charger to the aux' battery, BOTH batteries will be charged IF the relay has both batteries already connected (voltage of the starting battery is above 12v - the LED is fading in/out) . If in shared mode & the voltage has dropped to 12v or below, both batteries are disconnected from each other, and the charger connected to the aux' battery will ONLY charge the aux' battery.

Connect your charger to the starting battery. That way, BOTH batteries will get charged up.

Hi Drivesafe,

I know your install manual touches on this, but i was looking to install the incab control via a latching SPDT 'arb' style rocker switch from custom rockers. Will this retain all the features of the original in cab module? Your install manual just refers to an on/off switch rather than a SPDT switch.

cheers
Chris