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KB2VXA > TECH 16.08.04 00:31l 54 Lines 2478 Bytes #999 (0) @ WW
BID : 26394_WT3V
Read: GUEST OE7FMI
Subj: Re: G8MNY > lead-acid batts
Path: DB0FHN<DB0MRW<DB0ERF<DB0ROF<DB0AIS<DB0SIF<HB9EAS<HB9AK<K1UOL<K1UOL<
WX1CT<WA2PNU<KC2COJ<WT3V
Sent: 040815/0356Z @:WT3V.#CNJ.NJ.USA.NOAM #:26394 [Lakehurst] $:26394_WT3V
From: KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
To : TECH@WW
Hi John and readers,
Just to elaborate on what Tony G8TBF had to say about "recovering"
batteries is that method is sipmply a "poor man's charger". A long time
ago the company I worked for needed a charger that would handle any kind
of cell and in multiples since the mechanics were eating batteries like
candy. I wired up a line isolation transformer, a 100 Ohm 2W carbon
resistor and a 1uF capacitor in series and a whole lot of battery clips,
also in series. You don't need a print, everything on the secondary side
is connected in series. Oh, forgot the bridge rectifier, hi. Since in the
US the peak mains value is about 160V any number of cells in series may
be charged up to slightly less than that value. All unused battery clips
were bridged by short jumper (crocodial) clips.
The key to Tony's charger and mine is it's the CURRENT that charges the
battery, the only consideration given the voltage is that it must be
above the fully charged, open circuit battery terminal value so that
current flows. In both cases current limiting must be provided because
depleted batteries almost look like a dead short to the power supply. The
higher the open circuit charger output voltage, the more current limiting
must be provided in accordance with the rating(s) of the batteries being
charged.
Since this is a high voltage method it must be compared to the low
voltage method for current limiting to be fully understood. Start with
Ohm's Law and you're off BUT still some form of limiting must be
considered with low voltage. There are two ways of doing it. In high
current chargers a split core (saturable) transformer is used while the
typical home charger uses the DCR of the secondary winding. In other
words the transformer design is the key here, no external devices are
needed.
Yes, the beauty of the poor man's charger is twofold, it's simplicity and
versitility. You can charge from one to as many cells as you want
totalling up to only slightly lower than the open circuit charger output.
Just watch your fingers, it bites even when unplugged, the cell voltage
DOES add up.
73 de Warren, KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
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Message timed by cesium laser: 04:05 on 2004-Aug-15 GMT
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