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 accumulator manufacturer Peto & Radford discussing battery charging currents and potential overcharging issues.
| Identifier | ExFiles\Box 51\1\ Scan178 | |
| Date | 18th July 1923 | |
| Y4383 Works, Dagenham Dock. Essex TELEPHONE VICTORIA 3667. 4 LINES. PRIVATE BRANCH EXCHANGE. TELEGRAMS: CONCENTRATION, SOWEST, LONDON. Manufacturers of P&R Accumulators. Established 1889. PETO & RADFORD Proprietors - Pritchett & Gold and E.P.S. Company Ltd. 50 GROSVENOR GARDENS, LONDON. S.W.1 DIRECTORS: SIR ARCHIBALD G. {Mr Griffiths - Chief Accountant / Mr Gnapp} GOLD F.C.GRAHAM MENZIES C.R.D.PRITCHETT G.R.N.MINCHIN T.W.PRITCHETT WILLIAM PETO YOUR REF. OUR REF. H {Arthur M. Hanbury - Head Complaints} /C.187 18th July, 1923. Messrs. Rolls Royce Ltd., Nightingale Road, DERBY. Dear Sirs, With further reference to your letter of the 13th inst., EFC {E. Fowler Clarke - Electrical Engineer} 3, enclosing curve of charging current, we have now submitted this to our Works. They point out that the peak of the curve, which must occur on a large proportion of the running of the car, gives, on your showing, a nett charging current of at least 9 amperes and we cannot help feeling that in practice more is given to the battery. This means a charging current of 3 amperes per positive plate and our Works say that this is too much and that if the battery gets a great deal of this it will not have a very long life and the plates will shed the active material owing to the overcharging. The normal charging current of this battery is about 5 to 6 amperes with a maximum of about 7½ amperes, and our Works do not think you ought to go above that figure. Cannot the peak of the curve be reduced by about 1½ amperes? We are aware that possibly during a night run with the head lamps and tail lamp and ignition running this might possibly impose a drain on the battery. Even if it does, is this very serious? The battery might be losing 1 to 1½ amperes for, say the worst case, 8 or 9 hours. The next day's running would surely restore this and it is our opinion that there would be less risk of battery trouble under these conditions than having a charging current which is capable of giving the maximum output to cover the demands on rare occasions but which would result normally in overcharging the battery. | ||