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).
Letter from an accumulator manufacturer discussing celluloid battery specifications, features, and charging procedures.
Identifier | ExFiles\Box 38\5\ Scan016 | |
Date | 7th March 1919 | |
Manufacturers of P. & R.{Sir Henry Royce} Accumulators. Established 1889. Victoria & Greville Works, Ashtead, Surrey X. 3398 THE NEW PETO & RADFORD ACCUMULATOR CO LTD Electrical Engineers 12. HEDDON STREET REGENT STREET LONDON-W TELEPHONE REGENT 2576 TELEGRAMS 'CONCENTRATION REG. LONDON' REF M/C 73. 7th March. 1919. MANAGING DIRECTORS WILLIAM PETO M.I.E.E. G.R.N. MINCHIN M.A. [STAMP: RECEIVED] [STAMP: S.D. 18 MAR 1919] Messrs. Rolls-Royce Ltd., Nightingale Road, DERBY. Dear Sirs, In reply to yours of the 1st inst. (received only this morning) ref.EFC2/AT, re celluloid battery, we shall be interested in your further examinations and tests. We are expecting almost daily the ebonite boxes which are on order for making up the ebonite set and within 3 or 4 days of receiving these we can send you the ebonite battery. One feature of our battery which you may not have noticed is that we have put the acid level high up above the plates, in fact level with the top of the separators. This is so that the acid will not continually be topping up owing to the level getting too low. We believe that this is found to be an irksome job and will not receive the attention it should do, so we have provided what we consider enough margin to let the owner wait for about 6 months or a year without having to fill up with acid. The separators are raised up to the level of the acid, so that they can stop any tendency to "wash" that there may be owing to the free volume of acid at the top of the cell. The capacity of about 45 ampere hours that you obtained for the first test is about what we should expect, though when the battery is in condition we think you will find it will give 60 ampere hours at the 10 hour rate, i.e. 6 amperes for 10 hours. We are glad to hear that you will require only 120 amperes and this being the case, if you consider the battery too large we can supply a smaller one that would easily give 120 amperes for the best part of a minute. Perhaps taking into consideration the lighting and other services, the present size of the battery will be about right. With regard to the query raised in your post-script about renewing the acid after the first or second charging, the point is this: There may be certain chemical differences in the celluloid boxes that one might almost call impurities and certain slight differences in the plates, separators etc. These are unavoidable. When the battery has had a long slow steady charge, such as is necessary to bring it into condition at the start, the current passing will have the effect of loosening, and so to speak, dislodging all these various things and the result will be that certain cells which had more in them than others will differ electrically and also from the point of view of acid gravity than the others. This is not so noticeable in 4 volt 2 cell batteries, but in 12 volt 6 cell batteries it is more noticeable. This is the reason why we recommend that after the first charge the acid should be emptied out, and fresh acid put in. After this everything should equalise itself. Some makers say that this process should be repeated twice; it certainly should be done once with every starter battery if the full results are to be obtained. | ||