Re: (ET) Using Fair Radio charger on ET?

["Paul Heinzerling" <pheinzerling uakron edu>]

Bruce,

The only gotcha using the Fair Radio Charger is that you have to do some
babysitting.  If it's the one I have, you can't set the current above 15
amps or the output breaker will trip.  You have to monitor the charge
voltage with a good voltmeter and keep notching the charger up to keep the
current at 15 amps as the battery charges, and as it gets close to full
charge, you have to start notching it down  to keep the voltage from 
getting
too high.  One quick and dirty method for finishing the charge and
equalizing the batteries is to keep the final voltage at about 44 volts and
keep turning the current down until it stabilizes.

Remember that the output is unfiltered full-wave DC, so if you measure the
output voltage without it being connected to a battery, you will measure
only .707 of the voltage that will be present when you filter the output by
connecting it to a battery.

There are also two safety issues:  1.  It's possible to get about 135 VDC
(nasty!) at the terminals if you have the tap switches set too high.  Start
at 1-1 and keep moving the coarse tap switch up until you get some charge
current and go from there.  2.  The bananna plug output connection is not
the world's greatest.  If you use it, make sure you have a good low
resistance connection between the plug and the wire and a quality plug.
Otherwise the plugs get really hot!

Actually probably the worst safety issue is throwing your back out trying 
to
move the thing around!

P.S.  I set my input switch to 240 volts and operate it on 120.  This gives
you 144 switch positions between 0 and about 70 volts, which gives you very
fine control, although still unregulated.  It's possible that this approach
may stress the transformer, but the thing is so overbuilt that it's never
been a problem for me.

Paul Heinzerling
Hudson, OH


----- Original Message -----
From: "Bruce Conner" <bconner mediaone net>
To: <elec-trak cosmos phy tufts edu>
Sent: Friday, September 07, 2001 2:09 PM
Subject: (ET) Using Fair Radio charger on ET?


> My E12M charger decided to blow a diode and I wanted to charge up the
> pack using my surplus charger from Fair Radio while I wait for parts.
> Anybody used one of these before and are there any gotchas involved?
> What's the charge rate?
>
> Just because I'm paranoid, I'll ask the following as well.  With the
> charger taken out of the ET, which of the wires is the positive and
> which the negative?  Is the positive the one that connects to the
> heatsink of the diodes?
>
> Bruce Conner
>
>