From: Johannes Wolf (mp2100_at_mail-gw.estec.esa.int)
Date: Wed Apr 06 2005 - 23:40:26 PDT
Frank, sorry to correct you here:
as I already stated: the very main driver for the charging current into the
Newts internal rechargeable batteries is the voltage difference between the
actual voltage of the rechargeable pack and the external supply voltage
(from the ac adaptor or a power pack).
This is the very reason why with ONLY 6V external voltage you will never be
able to drive a high current into the battery pack.
Thus: as long as the external power supply (ac adaptor or battery booster
pack) provides a voltage of max. 6V there is no problem.
Since the standard ac adaptor provides 7.5V, the chargin current could
theoretically very well raise above 1.2 Amps and therefore the standard
power adaptor provides current limitation where the Newt relies on for
charging.
In fact that is a smart way to implement the charging control halfway
outside the Newt in the power adapter and therefore keep the power losses
and heat outside the Newt.
Cheers
Johannes
> -----Original Message-----
> From: newtontalk-bounce_at_newtontalk.net
> [mailto:newtontalk-bounce_at_newtontalk.net]On Behalf Of Frank Gruendel
> Sent: Wednesday, April 06, 2005 10:50 PM
> To: newtontalk_at_newtontalk.net
> Subject: Re: [NTLK] External Power Packs for Newtons
>
>
> > I'm just fiddling around with a pack I bought and
> > testing it out to see how long it lasts. My only
> > concern is to understand the caution statement made
> > by others regarding the recharging of the Internal
> > Rechargeable Pack by this External Rechargeable Pack.
>
> In a nutshell, there are two reasons:
>
> 1) Charge current
>
> Newton AC adapters limit the maximum charge current for
> a reason. Charging with more than the maximum current
> can fry the cells and the Newton.
> The power pack is, if I remember correctly, wired in a
> way that you have to sets of four serially-wired batteries
> that are wired in parallel. Such a setup can for a short
> time provide a couple of dozens of amperes as charge
> current, which both the cells and the Newton do not like.
>
> 2) Discharge current
>
> Even if the current sucked from this battery pack was
> limited to a value healthy for the Newton and its internal
> battery, which it isn't, this would mean that around 1.2 Amps are
> sucked from the pack until the Newton's internal battery is
> fully charged. At that current, it'd take but a few hours
> until the 8 batteries are a case for the trashbin.
>
> Frank
>
> -- Newton software and hardware at http://www.pda-soft.de
>
>
> --
> This is the NewtonTalk list - http://www.newtontalk.net/ for all inquiries
> Official Newton FAQ: http://www.chuma.org/newton/faq/
> WikiWikiNewt for all kinds of articles:
> http://tools.unna.org/wikiwikinewt/
>
>
-- This is the NewtonTalk list - http://www.newtontalk.net/ for all inquiries Official Newton FAQ: http://www.chuma.org/newton/faq/ WikiWikiNewt for all kinds of articles: http://tools.unna.org/wikiwikinewt/
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