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 discussing the performance and over-charging issues of car batteries and dynamos.
| Identifier | ExFiles\Box 54\1\ Scan055 | |
| Date | 27th November 1925 | |
| PETO & RADFORD. CONTINUATION 2. E.{Mr Elliott - Chief Engineer} Fowler Clark Esq., 27th November 1925. batteries except the one that you returned, and no batteries have come back off any Phantom cars. The one you returned did undoubtedly do very well and I am glad to know that it will do so well. It would, however, have done even better if it had not had so much charging, as its condition proved. I should like to modify my statement to the fact that the batteries in the past were undoubtedly over-charged, and I think that even with the present arrangement, they still run a serious risk of it. The output curves you send are of course much better than the Lucas. I should like, however, to have seen each of them brought down by fully an ampere all along the curve, and probably the Exide Company would agree with me in that, but one of my points is that the dynamos actually in use on the cars do not conform to these curves in practice. When they are cold they give very much more and they take some time to come down in output. I was in Mr. Sopwith's Phantom the other day and this has (I believe) an Exide battery on it and the dynamo seemed to me to charge just as highly as the one does on my car with a P. & R.{Sir Henry Royce} He told me he never ran on one ignition only, and I think you will find practically no owners who will do this to help their battery, in spite of what they may be told in the instruction book. I dont think your own Officials do when driving. I think the solution lies in the suggestion of having a lower charging current normally, which is increased when the head lights are switched on and I am very interested to see that you suggest this. It is excellent. If only you could get it agreed to I think you would have the finest electrical system of anyone in the world and get most wonderful results and the batteries would last perhaps 5 years. You say it could not be agreed to because it would be different from the 20 H.P. Its as desirable for the one car as the other. Both ought to have it. All the rest of your system is so perfectly designed and worked out and made, but to me it all seems marred by this high charging rate of the dynamo and the unliklihood of it ever getting a decent rest. | ||