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).
Dynamo fuse blowing intermittently on a Grylls, GXO-46 model, potentially due to overcharging.
| Identifier | ExFiles\Box 47\3\ Scan111 | |
| Date | 29th June 1931 | |
| 84117 FN.10/WT29.6.31. S/W. {Sales / Derby Works} Copy. from FN. Copy to Messrs. Hs. {Lord Ernest Hives - Chair} Hx. Hh. Grylls. GXO-46. Referring to this owner's complaint recently that his dynamo fuse has blown intermittently three or four times, but apparently it has not given trouble during the last week, and to Hd {Mr Hayward / Mr Huddy} /SB {Mr Bull/Mr Bannister} 14/HW.26.6.31. in which it is suggested that this trouble may have been caused by the battery on the car already in a charged condition being still further charged, enabling its voltage to rise to 18, and pointing out at 18 volts the fuse covering the field circuit of the dynamo will be blown. Keeping in mind that the dynamo fitted to this car is of the higher output type, it does not appear at all a satisfactory condition of things that this owner should be written to warning him that unless he remembers that his battery is already sufficiently charged, his whole charging circuit will become dead. In any case, whilst we are looking for an adequate cause for the trouble complained of it must be remembered that a P.D. of three volts per cell is very seldom experienced, a rise to 2.75 volts per cell under such conditions being a fairly high estimate of the back E.M.F. likely to occur. It has frequently been our practice to advise owners to take reasonable care to switch off their charging circuit in order to safeguard the battery plates from being worn out, and also to avoid the loss of electrolyte, but we have not had to consider that there should be a necessity for switching off in order to prevent either the fuse blowing or the dynamo suffering from overheating. * We could of course not reasonably be satisfied in having to give a warning in respect of either of these possibilities; the latter trouble of course being quite likely in the event of the fuse being made sufficiently heavy to overcome the difficulty which has given rise to this discussion. We should like to have the view of the Experimental Dept. on the whole subject because it would appear to be far from satisfactory at the present time. X In the absence of some indication as to the state of battery charge. FN. | ||