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rectifying generator 120AC output?

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Posted by gotomytekdigital.com on February 7, 2004, 3:52 am
 
Hello

I'm attempting to built a diesel powered generator which will be
charging a 120 VDC or 144VDC battery bank of 10-12 batteries connected
in series. This will be used to power an electric motor.

I was wondering if there was an easy way to convert a single face 120VAC
RMS generator of approx 12kW to a battery charging device by somehow
rectifying/regulating its direct output.

If I simply put diodes on the output I'll have a rectified sinewave
output of peak amplitude of 170 V and RMS of 120V. What do I do with
this to obtain sophisticated battery charging w steps so the battery can
be charged frequently without damage?

Thanks for any clues

Regards

M


Posted by Eric Sears on February 9, 2004, 10:31 am
 
Hi M
Just briefly, yes it can be done but you need to limit the current
that can flow. The simple way is to use either some light bulbs or
maybe something like a 1000 watt heater element (depending on the
amp-hour capacity of your battery).
If your used a 400v, 25 amp bridge rectifier (overkill) on a heatsink,
and put a 1000 watt element in series with your battery, you might get
somewhere around 2 to 5 amps into your battery (I am used to working
with 230 v in NZ so I am taking a stab at it).
If you are using a battery of 60 amp-hr or bigger, probably a 2000
watt element or heater would be better. I am presuming you are talking
about wet cells  -  you don't have any regulation with this simple
circuit  -  merely a current limiter.
If you really want "charging steps" you are probably in for big money
unless you know how to build a regulator.
However, you COULD use a simple switching regulator to read the
voltage of one or two representative batteries in the group (ie either
12v or 24v), and use it to either disconnect or reduce the current
into the total battery (using a relay).

And remember  -  DANGEROUS VOLTAGES!

Eric

On Sat, 07 Feb 2004 03:52:52 GMT, "gotomytekdigital.com"



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