Outback FX voltage fun [RE-wrenches]

[Hugh Piggott]

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Hi Wrenches,

I have recently got a VFX 3048 50Hz and installed it in my own home. 
Very solid and quiet.

Here on Scoraig we use a lot of big standby cells that we get 
secondhand from telephone exchanges and power stations etc. 
Originally glass (up to around 1980) then clear plastic cells, big 
and heavy, that can last twenty or thirty years.  My son found me 
24 at 200Ah, year-2000 cells that had not been used.  They are a bit 
obstinate.

I find that I can get some current into them if I push the volts up a 
little. They are actually working better now.  I charge them with a 
variac off my old 12 volt Trace U-series.

Anyway I also wanted to try out my 5 kVA  diesel generator (also 
recently acquired, secondhand) to stuff some charge into the battery. 
I found that it could only get about 7 amps charge rate at 58 volts. 
So I decided to push the batteries a bit with a 66 volt EQ.  The got 
the current up to about 15 amps.  A bit noisy though, so I did not do 
it for more than a few minutes.  Seemed to cheer the batteries up.

Later my wife asked me if I knew why the TV was not working.  I 
didn't know - presumably because the power was off in that room. 
Before putting the generator back down to the workshop I did one more 
EQ charge, and while that was gong on I checked out the power in the 
bedroom where the TV was.  TV didn't work.  Power seemed OK but just 
to be sure I tried out the VCR.  Very dramatic sudden death with 
smoke and small popping noises.  hmm....

I put my graphing multimeter on the supply and found the the diesel 
was producing a normal looking sine wave with a dirty great peak on 
the top of it extending to just over 600 volts.  Normal peak is just 
over 300.  That explained the carnage.

I am not exactly blaming the Outback, since it was the generator that 
produced the waveform (actually I was pleased still to have an 
Outback) but I was very surprised.  These Pramag diesels with Yanmar 
engines are not the most expensive but neither are they cheap.  I 
guess the AVR does not like whatever game the Outback plays to 
regulate charge at 66 volts output.  I will be watching the waveform 
anytime I synch with that generator for the next while and being 
careful what I have connected.

Anybody had a similar experience?  Any suggestions to safeguard my 
loads?  I need to get a 48 volt stator into my AWP and a 48 volt 
solar array going.  But I would like to be able to fall back on the 
diesel.

all the best,
-- 
Hugh

Scoraig Wind Electric
http://www.scoraigwind.co.uk/


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