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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 vehicle battery life, overcharging, and dynamo performance on the New Phantom.

Identifier  ExFiles\Box 54\1\  Scan062
Date  2nd December 1925 guessed
  
-2- Contd.

I have at home a six-volt Exide battery which is six years old, and has always been properly treated, and which is still quite good, but I have not the slightest doubt that if I pulled the elements out the positive plates would fall to pieces, and one could say of it, on the supposition that it was only a year old, that it had been overcharged.

Any batteries which have been on a car for, say, three years, if taken to pieces, the positive plates would probably fall to pieces, even though the charging had been quite moderate. Perhaps, therefore, you judge by the negative plates; in any case I would like to know. Is it not a fact that even with the most meticulous care of a battery, the positive paste would gradually be lost ?

I am asking the above because you say that the batteries you have examined show every appearance of being overcharged, and I wondered what that really meant, or whether the judgement was merely made on the time they were known to have been in service. If you had no other means whatever of knowing the age of the battery, could you then tell if it had been overcharged ?

As regards our output curve, I agree that generally speaking the dynamo output on the cars for reasons already explained is somewhat larger than the curve sent to you. As previously stated, however, I have not yet seen one on a New PhantomCodename for PHANTOM I which is higher than 13.6 amperes, the minimum specified peak performance being 11 amperes.

As regards the output when the dynamos are cold, I think this is of very little import, because usually when it is cold the starter had just been used and a good deal of current needs replacing. I am still awaiting information from our Test Dept. about the various outputs, but there is this disadvantage, of course, that we do not have on these cars the actual batteries that the customers will have, and in fact the same batteries are used from chassis to chassis. Therefore, if the variation is with the batteries, and not with the generators, as most of it appears to be, the information we may get will perhaps not prove of very much value after all.

Since writing to you last, we have made some tests with a standard New PhantomCodename for PHANTOM I dynamo in a warmed up condition and running on the actual chassis wires, in

Contd...
  
  


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