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).
Alterations to high-rate battery discharge testing procedures and standards.
| Identifier | ExFiles\Box 168b\2\ img063 | |
| Date | 13th September 1921 | |
| M.R. 188A (No. 7) 15.11.20-5M (A.200) EFCL/T13.9.21. -3- Contd. easily for a period of 5 minutes. Other batteries e.g. our present standard with modifications have been capable of this for 2 1/2 minutes only (onle one trial); the U.S.A. Exide 6-LXR-9-1 would only stert at 126 amperes on this test (one trial only). We have now altered our invariable resistance for high rate battery discharge tests to .100 ohm exactly, (kept to within ± .5%), so that the battery terminal volt reading is now exactly 1/10 of the ampere discharge reading. Again allowing .015 ohm as the limit of virtual battery resistance, the circuit resistance corresponding to this limit is .115 ohm, through which resistance 12.0 volts is capable of driving 104 amperes. Thus, any battery or a given battery at any time or in any condition to be suitable for the starter job, should be capable of discharging at least 104 amperes through this resistance. We say that if the battery is fully charged, it should be capable of discharging 104 amperes through this new resistance for 8 minutes or in the case of a battery taken in any sort of condition a quick and practical test of the fitness of this battery for operating the motor is to connect this battery to the resistance, switch on, and take the reading, which need not be more than momentary, unless the reading shows signs of falling away quickly. Our resistance is conveniently arranged with two electrically operated main switches and start and stop buttons, so that | ||