Thread: An efficient 100Amp low voltage cut out?

Manic, when you set up your voltages, the minimum cut-out ( turn off ) voltage should be no lower than 11.6v.

All new deep cycle batteries, AGM or wet, can be safely cycled down to 20% SoC or 11.58v.

The minimum cut-in ( turn on ) Voltage should be no lower than 12.5v.

If you set the cut-in voltage any lower, you will risk suffering from oscillation, where your device will continually turn on and off, if you have a large load connected.

not sure if still needed or not after reading all discussion.

but i have used this device before (in race car to stop everything but starter motor draining tiny lithium battery too much).

Zero Emission Vehicles Australia

It can be abused a fair amount without killing it (ie don't jump start your car through it more than a few times or the smoke will come out). But I was drawing about 70 amps through it with all lights and thermo fans and fuel pump etc and it survived for a few years before I killed it with stupid placement of jumpstart cables.

The only downside is once it is tripped (low voltage) it requires a manual button press to start again, but not sure how you can get around that and still have 0 usage when tripped.

Also the manufacturer has awesome support (I sent a unit back to him twice for repairs after I killed it) and he refused to charge me.

Originally Posted by mattims

not sure if still needed or not after reading all discussion.

but i have used this device before (in race car to stop everything but starter motor draining tiny lithium battery too much).

Zero Emission Vehicles Australia

Looks decent for the price. 5mA whilst active is not going to make a difference to capacity when camping and you can't beat a 0mA draw on the battery when isolated. I could reassign my voltage detection circuit (powered only on ignition) to detect when the alternator kicks in and use that to reset this Zeva LVC. The alternator detection could also be used to trigger DRLs which would be a bonus.

I can't see my aux accessories pulling more than 50 amps continuous. So whilst I have two 50amp fused lines running to front and back, for now they could be fed by the Zeva on a 50amp circuit breaker (have one on the shelf). If I get to a point where I start popping the circuit breaker I can upgrade to a more expensive 80-100amp feed+disconnect. This could save me around $250 dollars over the sterling product or end up costing me $50 more in the long run should I have to upgrade.

Hi Manic, and what size cabling are you running now.


50 amp fuses and circuit breaker should not be used for anything smaller than 6B&S ( 13.5mm2 ) cable, with the maximum being 60 amps for 6B&S.


For 8B&S, 40 amp protection, but you could stretch to 50 but not really that good a choice.


And for 6mm AUTO, 30 amp protection is the max size.

Originally Posted by drivesafe

Hi Manic, and what size cabling are you running now.


50 amp fuses and circuit breaker should not be used for anything smaller than 6B&S ( 13.5mm2 ) cable, with the maximum being 60 amps for 6B&S.


For 8B&S, 40 amp protection, but you could stretch to 50 but not really that good a choice.


And for 6mm AUTO, 30 amp protection is the max size.

My fear of electrical fire runs deep, all my fuses are calculated for the cables they protect. This of course considers cable length and acceptable amount of voltage loss. I put these cables in and fused them a fair while ago now, probably overkill - they are bigger than 6B&S. 100amp supply wire to fuse box is only ~20cm long so much thinner.

Originally Posted by manic

Looks decent for the price. 5mA whilst active is not going to make a difference to capacity when camping and you can't beat a 0mA draw on the battery when isolated. I could reassign my voltage detection circuit (powered only on ignition) to detect when the alternator kicks in and use that to reset this Zeva LVC. The alternator detection could also be used to trigger DRLs which would be a bonus.

I can't see my aux accessories pulling more than 50 amps continuous. So whilst I have two 50amp fused lines running to front and back, for now they could be fed by the Zeva on a 50amp circuit breaker (have one on the shelf). If I get to a point where I start popping the circuit breaker I can upgrade to a more expensive 80-100amp feed+disconnect. This could save me around $250 dollars over the sterling product or end up costing me $50 more in the long run should I have to upgrade.

Yes just be careful, it does not isolate in the reverse direction (and has some resistance to reverse current when off). So if your alternator starts charging batteries through it and it is off it will get quite warm pretty quickly. This is explained better in the pdf from his site. But you want to make sure it is on either before or pretty soon after your engine starts.

Originally Posted by mattims

Yes just be careful, it does not isolate in the reverse direction (and has some resistance to reverse current when off). So if your alternator starts charging batteries through it and it is off it will get quite warm pretty quickly. This is explained better in the pdf from his site. But you want to make sure it is on either before or pretty soon after your engine starts.

Yeah I saw that, not a problem in this case as it will only be isolating an auxiliary circuit.

I've been in touch with Ian at Zeva to query the reset trigger function. Its designed for a momentary pulse, so I asked what would happen if the trigger was held constant. I don't think its a use case he considered but it turns out it would work as an override and the unit would supply current regardless of battery voltage. So you could set up a MOM/OFF/ON switch, using MOM to reset the device and ON to effectively disable/override the low voltage cut out. This means I can disable the cut off automatically when the alternator is on without having to set up a pulse timer/circuit, and it will resume normal operation when the engine is off.

Should have one arrive in the post soon.

I think I have it all sorted now. I still had over 150mA unaccounted for on the main battery, so I pulled every fuse and relay to see where the remainder was coming from and found a fan relay was consuming 170mA! The coil could not have been energised because the fans were not running, and the relay does work when switched, so I have no idea how this relay managed to eat juice whilst doing sweet f-all.

With the fan relay replaced and the new low cut out relay/configuration I should get:

MAIN BATTERY
- 35mA (previously ~200mA)

AUX
- 5 or 6mA before low cut out (previously ~190mA)
- 0mA after low cut out (previously 4mA)

That would be problem solved.

Cheers