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 test chart recording amperage and ampere-hours over time.
| Identifier | ExFiles\Box 58\3\ Scan195 | |
| Date | 31th December 1929 | |
| 31-12-29 224 P&R & Exide V61 111lls 75-s. Average amperes: 6.4 Hours: 9.75 Ampere Hours: 62.4 .56/ 1.80w TRADE MARK 'MEGGER' | ||