[OLPC-devel] Battery Charge End Sensing

[Jim Gettys]

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