Re: (ET) Aaargghh!!!!

["David Roden" <etpost drmm net>]

On 25 May 2017 at 22:20, jlantonucci comcast net wrote:

>     The charger is hard wired to the battery pack like Jim said. 
>  Turning off
>     the power disconnect does not disconnect it

Interesting.  My HSM shows the E15 charger going through the main
disconnect.  Dunno if my own E15 is wired that way though.

Also, Michael didn't get his fireworks until he engaged the disco.

Maybe this is another of those things that varied with different production
runs.

The symptoms described suggest at least one shorted diode in the charger, 
though since it apparently sent out smoke signals, it might be open now.

The original factory diodes were 1N3493, press-in DO-21 case, 25 amp, 200
PIV.  Here's the datasheet:

http://www.alldatasheet.com/datasheet-pdf/pdf/76661/MICROSEMI/1N3493.html

Jim Coate sells equivalent diodes as spare parts.  A pair is $12 plus
postage.  He also offers "heavy duty" versions (difference not stated) for 
a
little more $$$.

Looks like you'll have to remove the heatsink, press or hammer the old
diodes out, press in the new ones, and put it back.  Jim mentions that the
aluminum may stretch so that the new diodes fit loosely, don't dissipate
heat well, and fail.  He has a point.

Jim conveniently offers a complete heatsink and diode assembly which is no
doubt the easy way to go.  It is of course quite a bit more expensive.

I tend to take such challenges as inspiration to my hacker side (the "make
it work" kind, not the "wreck someone's computer" kind).  The nice thing
about this route is that if you can find diodes locally, you're back up and
running that much sooner.

Some possibilities that occur to me:

1. Find something with the same size / style case but at least 50% higher
current rating. That way they don't have to fit quite as snugly.   Make 
sure
the case is the cathode, or bad things will happen.

Heat the heatsink with a hot air gun before trying to press the old diodes
out and the new ones in, in the hope that you won't stretch it as much.
Don't overdo the heat.  Maybe chill the diodes themselves with dry ice?

2. Easier: drill the heatsink and use equivalent or better stud-mount or 
TO-
220 case diodes.  As above, make sure the mount is the cathode.

3. Easier still: at least double the current rating (50a+) and let the
diodes, whatever mounting they have, hang in free air (make sure they won't
touch something with vibration).  Add a muffin fan if you're worried.

4. Replace the entire charger with something more modern (as we've recently
discussed).


David Roden - Akron, Ohio, USA

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