First 3.3V battery powered design

[sinkplaat]

3.6v nicel-metal

Hi all.

I'm doing my first battery operated design and need some guidelines please.
It is a dsPIC30F voice application and current consumption is estimated at 20-100mA but needs further testing and refinement.

My main concern is what type of battery to use.
A few design constraints include:
-3.3V operating voltage
-Space limitation (cordless-phone sized battery would be ideal)
-Operating duration of about 8 hours
-Must be rechargeable.

Can anybody with some experience in battery powered designs suggest a reference design or some design guidelines?
Thanks.

 

[IanP]

AS 3.3V batteries are not common, the closest rechargable battery will be 3.6V NI-MH (nicel metal hydride). I have come accross nice little battery GP60AAH3BMX which is a 3.6V - 600mAh NI-MH battery and it looks like something similar will be suitable for your project .. **broken link removed**
(NI-MH batteries don't suffer the so called "memory effect" as the NiCAD do)

 

[ambreesh]

Dear IanP,
What I have read says that NiMH batteries are effected less by memory effect compared to NiCd.
You could visit this, my knlowedge is limited. If I have understood it wrongly please elaborate.
**broken link removed**


"How to restore and prolong nickel-based batteries

The effects of crystalline formation are most pronounced if a nickel-based battery is left in the charger for days, or if repeatedly recharged without a periodic full discharge. Since most applications do not use up all energy before recharge, a periodic discharge to 1V/cell (known as exercise) is essential to prevent the buildup of crystalline formation on the cell plates. This maintenance is most critical for the NiCd battery.

All NiCd batteries in regular use and on standby mode (sitting in a charger for operational readiness) should be exercised once per month. Between these monthly exercise cycles, no further service is needed. The battery can be used with any desired user pattern without the concern of memory.

The NiMH battery is affected by memory to a lesser degree. No scientific research is available that compares NiMH with NiCd in terms of memory degradation. Neither is information on hand that suggests the optimal amount of maintenance required to obtain maximum battery life. Applying a full discharge once every three months appears right. Because of the NiMH battery’s shorter cycle life, over-exercising is not recommended."