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).
Comparing the P & R BD.11 battery to the standard, detailing differences in plate thickness, separators, and overall weight.
| Identifier | ExFiles\Box 38\5\ Scan238 | |
| Date | 27th July 1922 | |
| To R & E.{Mr Elliott - Chief Engineer} from EFC. c. CJ. & PN.{Mr Northey} c. By & EP.{G. Eric Platford - Chief Quality Engineer} c. Rg.{Mr Rowledge} & Da.{Bernard Day - Chassis Design} X 3398 EFC1/T27.7.22. X.3398 - P & R BATTERY FOR 40/50. Further to our EFC2/T25.7.22 and in amplification of remarks contained in our long paragraph on page 2, referring to the size and weight of the P & R BD.{Mr Berend}11 battery. Messrs. Peto & Radford have now written us that this battery should not be looked upon to any extent as a larger battery than our present standard, but rather an improvement on same. They point out that both batteries have eleven plates per cell and that the area of the plates is the same in each case, the only difference as regards plates being that the positives of the P & R battery are thicker to stand the overcharging and give it a longer life, also to avoid the shedding of the paste which we get at present, and further there is a decent amount of acid in the cell, reducing the necessity of topping up so often. Again the separators are thicker and stronger and double ribbed. These factors make the battery a little bit larger (but not much) and as we are not tied to room this does not matter. The battery is rather heavier, of course, but as mentioned in our note, the battery does not require a box. Previously the comparison has been made between the two batteries, but if we add the lid{A. J. Lidsey} to the P & R battery and the battery box and lid{A. J. Lidsey} to the present Exide, the net increase in weight is actually nil. We admit that this is the way in which it should originally have been given on the standardisation sheet. | ||