Hi group,
Whatever the Batteroo team have done or do, they will not be able to overcome the effect that I described in reply 3322 almost a year ago.
To save you looking for the message, I will reproduce it here:
Maximum Power Point Measurement - Duracell AAI have just finished an experiment to measure the Maximum Power Point of a Duracell AA cell.
ProcedureA HP6060A electronic load and HP3478A DMM were controlled using HPIB.
The cell was discharged using a constant current of 200mA for 30 minutes, 100 mAh.
Then the load was switched to Constant Resistance mode and the load resistance was stepped from 1 Ohm to 0.2 Ohms in 50m Ohm steps.
After the sweep to determine the maximum power, the load was returned to constant current. Then the cycle was repeated until the battery was depleted.
The cell voltage and current was measured at each step. The load power was calculated. The results were stored in a CSV file for analysis.
Maximum Power Point ResultsThis graph shows the maximum power that can be extracted from the cell at each step. The horizontal axis is the load resistance required to extract that power.
This is the absolute maximum power that can be extracted.
So to get 1.5V at 1A the battery must have been discharged by less than 300mAh (which is about 15%)
It doesn't matter what the Batteriser guys do, they can not exceed the power available from this set of curves.
This graph shows what is happening during a single MPPT sweep, this is after the cell was discharged by 200 mAh:
To get 1.5W you need draw about 2.2A from 0.7V, and at this point 1.5W will dissipated in the cell.
Additional comments 20161) You have to stay on the high resistance side of the maximum power point. If the integrated circuit increases the duty-cycle till you end up on the left side of the maximum power point, there is a phase reversal in the control loop and you end up shorting the battery.
2) If you are operating at or near the maximum power point. It is very inefficient. At the maximum power point 1/2 the power is in the load, the other half is in the ESR of the battery.
3) Since the ESR of the cell increases as the battery is discharged, The increasing ESR prevents the depleted battery from being able to deliver power to the load.
I did not order any
Batteriser Batteroo products, but I would love to repeat this test with a Batteroo.
Regards,
Jay_Diddy_B