144vdc charging [RE-wrenches]

[Ray Walters]

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At 11:53 AM 7/20/2004, you wrote:

>This one being discussed happens to be a "real" 144 vdc battery -
>
>You can argue that any battery is hazardous - but I prefer working on
>batteries which won't bite you if you brush a terminal post.
>
>Christopher Freitas
>OutBack Power Systems, Inc.

Hi All;

I've been playing with a 144 vdc battery bank in my EV, and considering a 
PV charging system. Chris is right: high voltage DC definitely has a lot 
more bite. I'm floating the ground of course (EV), so normally you don't 
get zapped. But I had a damage battery case allowing a cell to bond to 
ground, and when I touched my arm to the chassis while my hand brushed the 
battery terminal: I got 90 v hard. Based on that voltage, it was easy to 
count cells till I found the bad one.
A few months ago, I had a relay( to a 144 vdc heater) fry in the most 
spectacular way. It drew a sustained 1/2" arc, while only pulling 10 amps 
(I was able to watch it on the E meter). It never blew the 20 amp fuse, but 
threw enough sparks and molten contactor to definitely be a major fire hazard.
However,  I can see the Aussie reasoning for high voltage ,too. I can pull 
30,000 watts out of a single string of golf cart batteries. Don't try that 
at Home Kids....
On the original thread of controllers for 144 vdc, has anyone talked to BZ 
products? They have made odd voltage controllers for me before. Another 
possibility is to use a voltage sensing  device like an E-meter and then 
have it switch a relay rated for high voltage like a Kilovac. Check out 
<kta-ev.com> or <evparts.com>.
BTW, what were the Aussies using for controllers Chris?



Ray Walters
ray at solarray.com
President, SolarRay, Inc.
NABCEP Certified Solar PV Installer
BS Mechanical Engineering, UT Austin 88
Returned US Peace Corps Volunteer 

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