Re: How do chargers determine what battery pack is installed?

From: Steven Swift (novatech_at_eskimo.com)
Date: 07/19/04 

Date: 19 Jul 2004 00:17:24 GMT

I have designed a bunch of these while a "Fluke." I used several methods:

1: keyed terminals. different packs used very slightly different terminal
arrangements.
2: extra terminal with connection to circuitry, sometimes just a resistor.
This circuit could signal the main device or just be a programming resistor
to set charging parameters. All packes used the same terminals, but the
insides were different.
3: smart battery IC on the terminals, usually containing E^2 for memory.
4: keys on the packaging
5: then the obvious-- put in a constant current and measure the voltage
in the main device.

Depended completely on the goals of the project. What was more fun was
determining different types of batteries with the same terminal voltages
(like NiCd vs NiMH).

DaveC <me@privacy.net> writes:

>How do multi-voltage chargers (specifically, cordless power tool battery
>chargers) determine whether the battery pack installed is a 7.2, 9.6, 12,
>14.4, 18, or 24 volt pack before charging it? If any one of these is quite
>depleted, it won't register its nominal voltage until it's partially charged.

>Several of the lesser-voltage packs don't have identifying terminals on the
>pack. How does the charger determine what voltage to apply?

>Thanks,
>--
>Please, no Google links. I wouldn't ask a
>question here if I hadn't done that already.

>DaveC
>me@privacy.net
>This is an invalid return address
>Please reply in the news group 

-- 
Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC.      P.O. Box 55997
206.301.8986, fax 206.363.4367  Seattle, Washington 98155 USA

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