# ZEVA Fuel Gauge driver help... (polarity)



## lowcrawler (Jun 27, 2011)

I'm having a heck of a time getting my ZEVA Fuel gauge driver to work properly.

I use POT 1 to set the 'full' point -- relatively easily setting the needle to 'full' on my 1970 VW's stock gas gauge with the pack fully charged.

But the state of charge never goes down during use.... in fact, the more energy I use, the needle pushes up beyond 'full'. According to the instructions you can use POT 2 to set the size of your pack to between 200ah and -200ah. My pack is 100ah. If I set it to 100ah or -100ah, I get the exact same results.

Any help or thoughts? It's extremely frustrating....


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## Ivansgarage (Sep 3, 2011)

Is the batt cable going in the right dirrection..Throught the ZEVA


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## lowcrawler (Jun 27, 2011)

Yessir it is.

Even if it wasn't, you'd simply expect that the pack polarity could be changed... right?


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## MN Driver (Sep 29, 2009)

I'm assuming it goes down when you charge it right now, right?
You wouldn't change the polarity of the pack, you'd just flip the driver coil so it is facing the other way. So lets say it is facing a battery terminal, make it face away, but otherwise in the same place on the same battery cable.

Have you tried that?


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## lowcrawler (Jun 27, 2011)

Sadly, with my config, that's a long process... so I have not. I think I will though.


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## mizlplix (May 1, 2011)

It sez which way to face it in the instructions.......

If you followed them and it is backwards..please tell us. Some of us have one and have not as yet powered it up

Miz


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## piotrsko (Dec 9, 2007)

comments: if you are running a bug, you need the "diode" breaker unit as part of the circuit since the gauge seems to require a intermittent voltage source. I'd have to get mine out of storage, but I recall they seem to peg at full when you apply a constant voltage without the "diode" thingey. They also run at only 5 vdc max. Never tried them like this, BUT I suspect that you could wire them with your source instead of battery (still through the "diode") and use a 10 ohm resistor on the return side.

BTW I know it isn't a diode, but that is what my reference stuff calls it.


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## CrunchTime (Feb 13, 2009)

Have you asked EVWorks and/or ZEVA about this directly? I found them both very helpful (and I asked many questions before I got mine working (only on the bench as yet))...


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## lowcrawler (Jun 27, 2011)

I guess that's what I'll have to do.

When ordering they were extremely unresponsive, so I didn't expect much help -- which is why I came here first.

I'll report back with any fixes or changes...


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## lowcrawler (Jun 27, 2011)

I have finally gotten around to spending the 2 hours required to flip the device around... again.

No luck - I still get the exact same results.... driving the car results in the fuel gauge 'filling up'.

Turn the #2 pot 12 turns the other direction (which should keep me at ~100ah, but flip the polarity) and the needle doesn't move; it stays 'above full'.

Any thoughts or help?


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## lowcrawler (Jun 27, 2011)

The guys at Zeva got back to me straight away and gave me some tips on finding the right polarity and direction for the cable.



Ian from ZEVA said:


> After setting the Full position as you have, I'd recommend trying Pot 2 at the two extremes of the 25-turn range, i.e turn clockwise until you can feel faint clicking from the pot (or just give it 25 full turns to be sure), spin up the motor briefly and see what direction the gauge moves. If it's wrong, turn the pot the other direction 25 full turns, and the needle should go to Empty.
> 
> The other possibility is that the device is physically backwards on the power cable. You'll know this if, after a reset, the needle doesn't move when you run the motor regardless of Pot 2, but does move when you charge. (When first powered up, the device resets to 100% state of charge. If the sensor is backwards, running the motor will just be trying to increase charge that above 100%. Then charging current will be seen as discharging the pack below 100%...)


I _think_ I have things going in the right direction right now ... but I want to tweak the 'quantities' before I call it done.


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