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G6KUI > HELP 22.03.05 18:06l 56 Lines 1830 Bytes #999 (0) @ WW
BID : 90697-G6KUI
Read: GUEST
Subj: Re: Cheap n nasty gel cell chgr ?
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Sent: 050322/1645z @:GB7DBY.#23.GBR.EU NPF2.54c [G6KUI PMS Alvaston Derby]
Harry M1BYT wrote.......
}
} GM7HUD Opined with considerable skill:-
} >> If you want cheap and dirty.... 13.8v power supply, with a car headlamp
} >> bulb
} >> in series to restrict the charge current.
} >
} > Wrong!
}
} Why?
}
} It is cheap, exactly as requested. The headlamp bulb will restrict the charge
} to at most 2amps or so. I appreciate it will not achieve a full recharge,
} because to achieve that would require 14.4v.
}
If I read the TITLE correctly, we are talking about GEL Batteries, not
normal lead-acid batteries.
Of course Andy GM7HUD is perfectly correct in what he is saying.
The *BEST* charger for Gel cells is a constant Voltage charger.
There is absolutely no need to "restrict" the charging current, in fact it
can be detromental.
Info from the RS data sheet for their RS A200 Dryfit batteries gives very
detailed info.
The copy that I have before me (Data sheet 2854 issued March 1984) is what
I based my portable DX-operation on - namely 13.8 volts Continuous charge.
The charging voltage is CRITICAL - the data sheet gives an absolute maximum
of 14.10 volts for non-constant charging.
The data sheet states :-
"It should be noted that with constant voltage charging the charge current
is regulated automatically by the battery.
To avoid reaching the temperature-dependant gassing voltage, the charging
voltage, including any ripple should not deviate by more than +/- 30mV. "
I'm led to believe that later versions of this data sheet had a LOWER voltage
~13.5 volts, but as I was using batteries that dated prior to 1984 ( still
working ) then the 1984 data sheet is ok for me.
13.8 volts ( ie the shack power supply ) is something that we all have
readily available in the shack, so why use something inferior when you can
use the best.
73, Pete G6KUI
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