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# 1   2007-10-29 16:55:36 Battery Charging

ThomasScherrer
Member
From: Denmark
Registered: 2007-10-29
Posts: 64
Website

Battery Charging

The battery was close to flat when I got my primer,
Charging is done from USB either ports will charge it,
but the current is limited by a 1R R6 resistor and series diode D3 from a 3.5V supply.
too me it seems like the cells will newer be topped up 100% ! ??
how many mAh are those cells actually ?
and are they nicd or nimh ?


Thomas Scherrer Denmark webx.dk

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# 2   2007-10-29 18:34:40 Battery Charging

iotize
Administrator
Registered: 2007-07-09
Posts: 30

Re: Battery Charging

Hi Thomas,

You will find the battery datasheet on this page http://www.stm32circle.com/resources/stm32primer.php.

The STM32 Primer uses 2 x 1.2 400mAh Nimh batteries (NiCd is now forbidden).

Regards,

Ben.

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# 3   2007-12-05 21:20:49 Battery Charging

eeroasarlin
New member
From: Espoo
Registered: 2007-09-26
Posts: 1
Website

Re: Battery Charging

Hi Benoit, Thomas
Actually the datasheet quite clearly states that battery nominal capacity is 300mAh
it is not big difference, but unless the production units use different battery than the LPH44AAA300 as pointed by handmade  arrow in
http://www.stm32circle.com/projects/fil … attery.pdf
the battery is indeed 300mAh

largest claimed (quoted) capacity in this formfactor is about 900mAh, so if you need to extend usagetime by factor of 2-3, it could be one solution. one such cell albeit without soldertabs is Tenergy-AAA-1000 and other Brands
who claim 1000mAh are  Ansmann Sanyo and Mercury.
My Experience is that the true capacities are invariably smaller than claimed, but that is another subject.

since the charging circuit is 3.5V regulated source and 1Ohm resistor, you can not expect many hours of lifetime
for the batteries if the STM32 Primer is forgotten to an externally powered USB Hub for extended periods of time.
the D0 power state used by (at least my primer) limits current to 500mA max and the 1Ohm resistor to even lesser value after battery voltage is above 1.5V per cell.

Many NiMh cell manufacturers specify maximum charging current as 0.1C (30mA for these cells)
Eero A. Sarlin
Finland


Benoit :

Hi Thomas,

You will find the battery datasheet on this page http://www.stm32circle.com/resources/stm32primer.php.

The STM32 Primer uses 2 x 1.2 400mAh Nimh batteries (NiCd is now forbidden).

Regards,

Ben.

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