You're in Wearforge -> Wearhard -> DayRunnerProjectBatteryPack
The components chosen for this project were attempted to be a balance between performance and cost.
After considering the various chemistries used for batteries, we felt NiMH was the best for our purposes for primarily 3 reasons.
- Not as volatile as LiIon cells
- Not as sensitive to "memory", unlike NiCad. (NiMH can be randomly charged - with periodic maintainance discharge(~1/month))
- Reasonable energy density
The best cells we found were the Sanyo 4/3FAU(X). The energy density and size are 4500mAh/1.2V 18mm diameter, 67mm length per cell. These create 8-9 cell battery packs that are approx. 2.75"x3.5"x1.5" (43.2Wh/48.6Wh, respectively). These cells can also be rapid charged in less than 2 hours.
First, The thermistor we've choses is a embedded glass thermistor with a response of 3s. This increases the cost by a few dollars each, and certainly can be modified for using less expensive thermistors. We chose this thermistor for protection of ourselves and the battery. This system rapid charges the batteries - thus in order to not damaging the batteries from heat during charging, the thermistor stops rapid charging when the packs reach 40C. This also helps prevent the cells from exploding.
For battery monitoring capabilities, we're using the DS2438. It uses the 1-Wire protocol for communication.
-- RickJones - 07 Feb 2002
-- PaulBernard - 15 Feb 2002 - Minor correction wrt capacity of packs.
|
