Why not use a phase angle control method with a DC choke (its the same way
as most industrial charging systems work) where you have two diodes and two
thyristors to form a full wave bridge. This way you can sample the DC
voltage and control the voltage supplied to the battery and hence provide a
continuous trickle charge if required.

Steve

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Tobias Gogolin
Sent: 26 March 2009 05:53
To: Microcontroller discussion list - Public.
Subject: [EE] Charging a 120V Battery Bank : PFC ?

Hi happens that I find the piclist to be the community of the fittest
electronic engineers that I know on the web, that's why I ask here and not
on some of grid living list...

I may have mentioned before that I use 10 pc. 12V car batteries at my of
grid ranch, and that I charge those using a simple rectifier, either Bridge
from 120V AC or 2 diodes using half of each of the 2 120V outlets around the
center of my generators 240 V AC output (I do that to reduce the chance of
any one of the automatic breakers of the 2 120V circuits from tripping).

This seems to work quite good, but I just read that it is not advisable to
charge Car batteries on pulse current, and since they would be charged only
when the generators output voltage reaches above their current charge
voltage, it definitely is pulse...

So I have been toying with the idea to try a different circuit, and I would
like some comments and hints on dimensioning the circuit!
=== here it goes ===

If I use a circuit like they use on computer power supplies that double the
voltage using 2 diodes and 2 Capacitors, but hooked it up to the battery
bank, the capacitors would have to discharge completely every cycle (maybe
even reverse polarity, which I could prevent with another diode per cap),
but since last half waves capacitor starts out with minimally the voltage of
the bank, the new half wave charging the next capacitor would push up that
voltage and therefore start discharging the Cap to the Battery starting from
0...

I know it may be difficult to describe in words, but its a simple enough
drawing!
I wonder though would kind of capacitors would stand this type of abuse and
how I would estimate the current that would be required?
I figure there must be a possibility to develop a formula using the Coulombs
at max voltage, and then average out this number of electrons over the cycle
to get an estimate for the produced, now less 'uncontiniously' pulsing!

Thanks for any hints or help to express this better so more responses are
possible!




-- 
Tobias Gogolin
skype: moontogo
messenger: usertogo@hotmail.com

You develop Sustainable Ranch Technology at
http://tech.groups.yahoo.com/group/SURA-TECH
an Open Source Electric Motor/Alternator at
http://groups.yahoo.com/group/Performance_Axial_Flux
and an Open Source Motor Controller at http://groups.yahoo.com/group/GoBox
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