Originally posted by: Omegachi
but some devices don't rate their power use by mah? some just say it draws 9v .5ma
Originally posted by: Heisenberg
So if it draws 0.5 mA, then 2000 mAh/0.5mA = 4000 hours. The mAh rating is the product of the current draw and time.
Originally posted by: So
Originally posted by: Heisenberg
So if it draws 0.5 mA, then 2000 mAh/0.5mA = 4000 hours. The mAh rating is the product of the current draw and time.
Well...it looks like heisenberg has this well under contol.
<wanders out casually>
Uh, no.. it isn't.Originally posted by: cavemanmoron
mah?
Cold Cranking Amps is better.
Originally posted by: Heisenberg
If you use it in a device that draws 1000 mA, then it will last 2 hours. It it draws 500 mA, it will last 4 hours, etc. Just divide 2000 by the current draw in mA.
Originally posted by: Heisenberg
So if it draws 0.5 mA, then 2000 mAh/0.5mA = 4000 hours. The mAh rating is the product of the current draw and time.
Yeah, I realize that the produced voltage falls as the battery discharges and so will effect how long you can actually run something at a certain current draw. I was just trying to give him a simple answer.Originally posted by: KMurphy
Originally posted by: Heisenberg
If you use it in a device that draws 1000 mA, then it will last 2 hours. It it draws 500 mA, it will last 4 hours, etc. Just divide 2000 by the current draw in mA.
Not quite. The battery manufacturer claims the battery can output 2000mA down to a certain per cell voltage. They have different curves published for varying discharge rates. The requirements of the OP may be such that if he put a constant load of 1000mA for two hours, then the per cell voltage would drop so low that the device would not stay powered up. It would be best to consult with the battery manufacturer to find out the discharge rate to 80-85% of the nominal cell voltage.
The rating of 2000mAh is probably based on a cell voltage drop down to the 60-70% range which is not sufficient for powering most equipment; especially for electronics with a significant inductive makeup (small motors, transformers, etc.).
Originally posted by: KMurphy
Originally posted by: Heisenberg
If you use it in a device that draws 1000 mA, then it will last 2 hours. It it draws 500 mA, it will last 4 hours, etc. Just divide 2000 by the current draw in mA.
Not quite. The battery manufacturer claims the battery can output 2000mA down to a certain per cell voltage. They have different curves published for varying discharge rates. The requirements of the OP may be such that if he put a constant load of 1000mA for two hours, then the per cell voltage would drop so low that the device would not stay powered up. It would be best to consult with the battery manufacturer to find out the discharge rate to 80-85% of the nominal cell voltage.
The rating of 2000mAh is probably based on a cell voltage drop down to the 60-70% range which is not sufficient for powering most equipment; especially for electronics with a significant inductive makeup (small motors, transformers, etc.).