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).
Continued discussion on battery charging systems, comparing single and two-rate charge schemes.
| Identifier | ExFiles\Box 181\M13\M13.2\ img007 | |
| Date | 9th December 1930 | |
| -4- of operating voltage with ampere output in accordance with a schedule which we arranged to represent the condition of a fully charged battery and for a considerable time now curves have been comparative on this basis. The outputs shewn by such curves are, therefore, usually higher than shewn by the ammeters on cars themselves, though they may be lower if the battery is in a fully charged condition and the battery and dynamo are cold, as each of these three circumstances raises the voltage and amperage of the system. normally With the two-rate charge scheme as at present arranged, we do not ever realise as large an output as the dynamo is really capable of giving because the operating voltage is in the neighbourhood of 14. If we could say for certain that the dynamo output was always going to be limited in this way, we could fearlessly set the machine to a higher output. Owing to the possibility, however, of the field resistance being short-circuited, or the head lamp fuses being taken out and the head lamp switch put on to give full rate of charge, and the battery then rising to a full state of charge, we cannot give this higher setting because in those circumstances it could become dangerous. It will be appreciated that in a similar argument lies the one objection to the single way interconnection of the two-rate charging scheme in that it provides the possibility in normal running of overcharging the battery at a high rate of charge and therefore necessitates a slightly lower output setting of the machine. It is in the above principles that lies the great desirability of an automatic method of inserting such a field resistance, or better still, of cutting off the charge altogether by making this resistance sufficiently high, for then the full capabilities of the dynamo could be made available when needed. Reverting to the two-rate charge switching scheme, it is possible that early experience and a few later complaints have made us over-careful with batteries from the overcharging point of view. It will be remembered that our standard batteries are now very much more robust than they used to be and capable of still having quite good lives even if subject to a not unreasonable amount of overcharging. It will therefore, probably be the case that with this new system the lower values of external | ||