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Subject: Re: Shamingly obvious question about NiMH vs NiCad chargers
From: Chris Holt (amiga2k_at_cox.net)
Date: 2002-11-26


----- Original Message -----
From: "George Michaelson" <ggm_at_apnic.net>
To: <rockbox_at_cool.haxx.se>
Sent: Monday, November 25, 2002 6:52 PM
Subject: Shamingly obvious question about NiMH vs NiCad chargers

>
> God, how embarrassing not to know these things.
>
> If one owns an older tandy (blush) NiCad charger, is this 'safe' to use to
> re-charge NiMH or are they radically different and require a different
charger
> and current?

Yes, they are different enough that you take a chance on destroying your
NiMh cells. Luckily AA/AAA 4 pos. chargers start at around $20.

> Also, I spoke to a source of AC/DC plugpacks yesterday and he was pretty
> adamant that the current limiting requirement to 600ma from the 9v pack or
> 1.2a from the 12v pack was meaningless, it was the device which determined
how
> much current was drawn. I didn't buy this, but also I don't *understand*
this
> area.

Yes, that is where the expression "drawing current" comes from. The device
draws what current it needs from the power source. Like replacing your 10
gallon gas tank with a 20 gallon one is not going to flood your engine. The
voltage (sort of like "pressure") is the important thing to get right, the
device will take care of the current (sort of like "flow").

> I'm not an electrical engineer. I don't even play one in Soap Operas. I
don't
> intend risking my device either, so I'm sticking to my US charger in a
> 240v->110v stepdown unit until I can get a regulated 9v/600ma DC block. I
> tried one rated to 300ma, it didn't charge, but it does trigger the
poweron
> behaviour of the volts-in, I guess thats a mechanical switch right?

Yep, I belive it is. Can be demonstrated by plugging into the Archos but
not into the wall. (0v/0ma) :)

BTW: it could in fact be dangerous to use a severely under rated
transformer, as they don't have much protection built in, so I wouldn't
experiment too much with them.

Chris



Page was last modified "Jan 10 2012" The Rockbox Crew
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