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).
Performance test chart for Ediswan 6-volt units.
| Identifier | ExFiles\Box 52\4\ Scan062 | |
| Date | 2nd April 1930 | |
| 2-4-30 221 Ediswan XSB557-1-2 (2, 6 volt units) 92 lbs 90 a.h. Average amperes = 6.40 Hours = 12.1 Ampere hours = 77.5 .841 1.80w | ||