[OLPC-devel] Battery Charge End Sensing

[Ray.Tseng at quantatw.com]

James,
	Ambient temperature is considered.
	Quanta is working with battery cell company to implement the charge/discharge algorithm.

Ray Tseng 7/12/06 

-----Original Message-----
From: devel-bounces at laptop.org [mailto:devel-bounces at laptop.org] On Behalf Of Jim Gettys
Sent: Wednesday, July 12, 2006 9:09 AM
To: James Cameron
Cc: devel at laptop.org
Subject: Re: [OLPC-devel] Battery Charge End Sensing

On Wed, 2006-07-12 at 10:21 +1000, James Cameron wrote:

> For NiMH charging, delta-V and temperature sensing are required.  
> Having a supervisory device record amp-hours is also helpful.
> 
> Delta-V sensing often detects the fall in voltage of the first cell in 
> the pack that has reached capacity.  But if the pack is fully charged 
> already these falls in voltage may not occur and so temperature 
> sensing is used ... NiMH releases heat during charge, and releases 
> even more when overcharging begins.
> 
> Begs an additional question ... since OLPC environmental specification 
> for temperature is so wide, would it be necessary to compensate for 
> environmental temperature when measuring cell temperature?
> 

I expect so, but don't know the details.
              - Jim

--
Jim Gettys
One Laptop Per Child


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