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).
Car dynamo output and potential solutions for undercharged batteries in winter.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan290 | |
| Date | 3rd December 1929 | |
| EFC. } FROM R.{Sir Henry Royce} HS{Lord Ernest Hives - Chair} Copy to PN.{Mr Northey} ORIGINAL. CAR DYNAMO OUTPUT. My impression is that we shall always get complaints of undercharged batteries, and some users, who in winter use their cars for so much night standing work, and traffic work, must, whatever we do, get the condition of their battery run down, and should, in their London garage, arrange for a small trickling charging current by the switchboard connecting socket. At the same time we can easily - (1) Alter the characteristic of the dynamos to fall off less with speed, and so meet a few of the complaints. (2) Next we must make standard the dynamo winding of the intermediate type, cutting in a little later, but giving 20 to 30% greater charge. It is no use having alternate windings: we never get the right one on a suitable car. They must be all alike, and an increase on our present. It is probable that we are cutting in at an unnecessarily low speed, since traffic, when it is moving, is going more quickly than in the past, and also cars are geared lower, so that to cut in 25% later is quite likely early enough. So that the matter seems quite easy to get an increased margin, and it leaves us with the summer risk of overcharging, there being no satisfactory indicator of charged conditions which will justify its complication. In fact, the only way seems to depend on indications by gassing, as I did one year at Le CanadelHenry Royce's French residence. We could arrange the switches so as to reduce the charging current,unless the headlights were on, so that the maximum battery charging current would be less, and hence average winter output of dynamo would be greater than average summer, and the battery would be less damaged by being overcharged by a large current. This would however reduce the daylight winter charging. Really, the only solution that appears entirely satisfactory is the trickling charge while in garage. Here we meet the difficulty of the lighting current being alternating, requiring a rotary transformer. Is there nothing easily procurable. PN.{Mr Northey} and EFC. will perhaps kindly tell us if they know of anything good enough to recommend. R.{Sir Henry Royce} | ||