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Subject: RE: Battery FAQ #12

RE: Battery FAQ #12

From: Dave Jones <>
Date: Thu, 19 Feb 2004 09:05:53 -0600

In my long term recording sessions (multiple weeks of continuous recording)
I've been estimating about 3.2 Ah per day of recording. This is using an
external power supply and tapping directly into the battery leads of an
AJBR20, bypassing the charging circuitry entirely. The power supply is a
switching regulator with an efficiency of around 85% or so.

I generally get just less than 4 days of recording out of a Alkaline D cell
battery pack (approx 12 Ah)

Of course, this is continuous, 24 hour stereo recording with relatively
high quality settings. I'm sure your use will be somewhat different....

Interestingly, if you use Bjorn's 110 mah estimate for current draw, for 24
hours gives you 2.65 Ah per day. With 85% power supply efficiency, that
gives you 3.1 Ah per day for an external battery pack. Very similar to my
field testing experience.


At 08:26 AM 2/19/2004, you wrote:
>Thanks that should help.
>Any figures on "normal" mA usage / hour?
>-----Original Message-----
>From: []
>On Behalf Of Björn Stenberg
>Sent: Thursday, February 19, 2004 9:16 AM
>To: Rockbox development
>Subject: Re: Battery FAQ #12
>David Reis wrote:
> > Is "HDD on,reading, backlight off 600 mA"
> > "HDD on, backlight on, play 230mA"
> > What is the difference between "play" and "reading" ??
>If I recall correctly, during 'play' the disk was not accessed, i.e. it
>was just spinning idly. During 'reading' the disk was actively reading
>data into the buffer.

Dave Jones P.E.
Senior Project Engineer
HFP Acoustical Consultants Inc.
6001 Savoy Dr., Suite 115
Houston, Texas 77036
713.789.9400 (phone)
713.789.5493 (fax)

Received on 2004-02-19

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