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).
Battery comprised of two 6-volt units.
| Identifier | ExFiles\Box 168b\3\ img001 | |
| Date | 15th September 1926 guessed | |
| 7535 BATTERY IN TWO 6-VOLT UNITS. WWV (Lo-Exg.) to be used (perf-e) on R.R. | ||