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).
Comparison table of specifications for Alklum and Exide batteries.
| Identifier | ExFiles\Box 164\4\ img137 | |
| Date | 6th November 1933 guessed | |
| ITEM. | ALKLUM | ROLLS-ROYCE 20/25 EXIDE 6XSM-7-1L Overall dimensions including lid.{A. J. Lidsey} | 20" long. 7 7/16" wide. 11" high. | 14 3/16" long. 6 3/4" wide. 11" high. Ampere hour capacity at 10 hour rate. | 60 (specified) | 57 (actual) Weight of battery including electrolyte. | 103 lbs. | 75 lbs. Final charge voltage. | 16.2 | 16.0 Internal resistance per cell. | .002 ohms. | .0035 ohms. Price. | £10-2-6d. | £3-5-0d. Makers Guarantee. | 12 months. | 12 months. | ||