# Keeping a ZEVA Fuel Gauge Driver powered 24/7



## dtbaker (Jan 5, 2008)

EscapeVelocity said:


> ... I imagine that it would be very inefficient to continuously run a 200W DC/DC converter for a 1/4 watt load.



the dc-dc really doesn't use very much.... unless you let it sit for DAYS. you might want to consider wiring a tiny little rechargable in parallel on the output side. I found a little 12vx1.2ah for $20.... it does a good job for me of filling in the voltage sag from the dc-dc when the vacuum pump kicks in at night when I have headlights on too.


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## EVfun (Mar 14, 2010)

That's funny Dan. I have that very battery on a bracket that was going to end up in my Buggy. Instead, I created a soft start system for the headlights consisting of an NTC and a headlight relay to bypass it after about 1 second (after the head lamp filament resistance goes up and the NTC resistance goes down.) I don't have a vacuum pump to satisfy.


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## dtbaker (Jan 5, 2008)

I never had a problem with my old Curtis 1400 dc-dc, which I think had lower output, but the new Chennic I think is 'cheaper', and I was getting a serious 'blink' when driving at night, radio on, and the vacuum pump kicked in.


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## EVfun (Mar 14, 2010)

For me, the Zilla was getting pissed at the "blink" when the headlights where switched on. Sometimes it would just light the warning light, other times it would shut down due to low 12v supply voltage.

This brings up another (on topic) thought. What else might be contributing to the standby 12 volt loads? The fuel gauge driver is one, but how about the controller? What is the standby load of the DC to DC converter? 

Also, you shouldn't run the ZEVA fuel gauge driver off the traction pack. If you do you will connecting the traction pack to the vehicle 12v frame ground system through the ZEVA gauge driver. The fuel gauge driver measures current with a hall effect sensor to maintain isolation between the traction pack and the 12 volt system.


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## dtbaker (Jan 5, 2008)

EVfun said:


> This brings up another (on topic) thought. What else might be contributing to the standby 12 volt loads? The fuel gauge driver is one, but how about the controller? What is the standby load of the DC to DC converter?



I don't think the controllers have a standby load if the KSI is 'off'.... but I would guess the majority os the dc-dc, and probably different by brand and capacity. I thinkn the chennic is ALWAYS warm to touch, and I don't recall that with my old Curtis dc-dc.

quantitatively, I left the car sit for a week last summer while on vaca, and plugged in to top off the charge, with a kill-a-watt meter attached because I was curious what the drain would be... almost 2 kWhr/week!

so, fine overnight, but long vacations should probably disconnect traction pack...


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## EscapeVelocity (Nov 12, 2010)

It looks like I need to build a ~1-Watt 72V to 12V isolated DC/DC converter. Possibly a 96V to 12V version as well for a higher powered scooter I'm looking to building. Does anyone have a good reference for DC/DC converter schematics?


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