From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Experiment to determine the efficiency of recharging a car battery after multiple discharge cycles.
| Identifier | WestWitteringFiles\H\January1922\ Scan46 | |
| Date | 1st January 1922 | |
| Contd. -2- EPC1/T31.1.22. We had often heard it remarked that it seemed to take a very much larger quantity of ampere-minutes to recharge a battery actually on the car after using the starter motor, than were taken out. This we consider might be possible as it is conceivable that some current is not being used in producing chemical action. Or again, it is possible that chemical action might be going on at the positive elements or the negative elements only, so this experiment was carried out to determine if there was anything in this. The same process as described above of discharging the battery for 2 minutes at the high rate, and recharging it with exactly the quantity which was taken out, has been carried out 20 times in succession, sometimes with short intervals between and sometimes with longer intervals, the whole experiment extending over three weeks. After 20 such discharges and recharges, so that exactly every bit taken out was replaced, we then took a low rate discharge capacity test of the battery and found it to give 30 ampere-hours. Dividing the loss (20 ampere-hours) equally over the 20 discharges, the loss per cycle was about 1 ampere-hour. Since, therefore, the amount put in per charge is about 3 amps. ere hours, the portion of this obtained on discharge is 2 ampere-hours, the efficiency per cycle appears to be in the neighbourhood of 67% showing that it is necessary to replace about 50% more ampere minutes than were taken out on the discharge. Contd. | ||