Modified Bad Boy: was: Where did I go wrong ?

[Michael Everett <michaeleve@yahoo.com>]

Hi all - 

I've been playing with this for the last several weeks to try and come up
with a charger I can use at work (I'm dreaming that an external plug may be
put in this year...) and have come to the conclusion that the nominal line
voltage needs to be about 20V +/- 5V above the nominal battery voltage for
this type of charger to work well. I have somewhat the same setup: a GFI
breaker feeding a 1000 watt fan cooled dimmer feeding a 2mh choke feeding
the 40 amp bridge. This works well for a 96v pack and OK for a 108v but is
borderline for a 120v and I could imagine pretty useless for 144v though I
haven't tried that. I suspect you'd need at *least* a 24v 'boost' transformer
to do the 144v pack and 36-48 would be more likely usable.
To use this thing you manually 'ride the gain' on the dimmer during the first
minute of charging to keep from blowing the breaker (seems to be the wall
breaker that goes first) and then set it for a current that you know from
experiance won't cause thermal trip and over time, current will taper nicely.
Fairly easy to kill even the heavy duty dimmers this way.
I'm working on a charge point 'trip' circuit and a finish charge stage to add
into this thing and will post more and/or do a website once I know more.

Lee Hart's 'Divide and Conquer' approach may well be best for 144 and up.
A 12v 'boost transformer is cheap and easy to get, not so for 36 or 48v.


And yes, I know all about the 'absolute need' for an isolation transformer...

Michael Everett   R5EV


-------Original Message---------
From: "Scott Hull" <scott@m-cad.com> 
To: "EV Mailing List" <ev@listproc.sjsu.edu> 
Subject: Re: Where did I go wrong ? 
Date: Mon, 30 Jul 2001 11:46:09 -0000 


Tom Martin wrote:

>...This device would require perhaps three or four
>days "past forever" to recharge my simple 144 system....

You need a 12-18 volt boost transformer (steal one from a 12v battery
charger). Hook the secondaries in series with the 120 volt AC (before the
bridge rectifier). Hook the primaries up to a light dimmer and connect them
to 120VAC. Now you have an adjustable charger that will be able to charge in
a reasonable amount of time.

Valuable options - AC amp meter, DC output amp meter, digital voltmeter on
output, input GFCI, output fuse, etc.

Scott Hull



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