Battery amp rating

[Paul]

Hi,

How does the battery amp rating work? I have the a 2000 mA rechargeable
battery. Does it mean that it can supply 2 amps in an hour? What about
charging these. The charger puts out 140 mA at 2.4 volts, if I divide the
2000 by 140 i'll get the suggested 14 hours of charge. Why is the charging
voltage doubled though? This Ni-Cad battery regulary puts out 1.2V.

 

[John Popelish]

Paul wrote:

Hi,

How does the battery amp rating work? I have the a 2000 mA rechargeable
battery. Does it mean that it can supply 2 amps in an hour? What about
charging these. The charger puts out 140 mA at 2.4 volts, if I divide the
2000 by 140 i'll get the suggested 14 hours of charge. Why is the charging
voltage doubled though? This Ni-Cad battery regulary puts out 1.2V.

That rating is in milliamp hours, so you divide this rating by the
load current in milliamps to estimate the operating time before the
battery is depleted to some cut off voltage. If that time is less
than 10 hours, the estimate is optimistic. In other words, the rating
is usually based on a 10 hour discharge. So your 2000 mAHr battery
should last 10 hours with a 200 milliamp load.

Charging is not 100% efficient, especially when done quickly. I think
it typically takes about 120% of rated milliamp hours to fully
recharge a battery, and there is a limit on how fast this can be done
without damaging the cells. It also takes more than discharge voltage
to force the internal chemistry to run in reverse. The battery makers
usually have detailed data sheets for their products that spec all
this.
--
John Popelish