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).
Potential causes of failure in Exide batteries, comparing overcharging with over-discharging.
| Identifier | ExFiles\Box 46\3\ Scan071 | |
| Date | 1st June 1922 | |
| To BY.{R.W. Bailey - Chief Engineer} from EPC. c. EP.{G. Eric Platford - Chief Quality Engineer} X607. EFC2/T1.6.22. X.607 - EXIDE BATTERIES FROM PARIS. In further answering Mr. Parsons note Fs{F. Steele}9/JP18522, we consider that, as discussed in conversation, the following further points should be enquired about :- (1) Judging from their first paragraph describing the condition of the various batteries after failure, it would appear that failure is not so much due to over-discharging as to overcharging, and we think this is much more like to be the case. Overcharging as we know may cause the positive plates to buckle, and particularly in the unmodified batteries to cause short circuits in the cells. The battery would then be found to be 'down' and they might consider that this was due to insufficient charging. If a battery is repeatedly overcharged and the cells are not short circuited, then it would be expected that all the cells were found to be in approximately the same condition electrically, but in the case of overcharging and shorting, the shorted cells would be found to be dead down, whilst the others would still give their full voltage, so that detailed information from them on this particular point should apparently be obtained. (2) If on the other hand the failure is truly due to overdischarging, then we venture to suggest that the batteries for some reason or other might not have been correctly charged in the first instance. The correct initial charge is of the highest importance and if not carried out properly we know from definite experience that a battery will not give its proper capacity, even though the plates appear to be in perfect order. We wish to make the point that it is of the highest importance that a battery be correctly charged in the first instance. Overcharging on the first charge does not do a battery any harm, it is only after repeated charges and discharges when the grids themselves have been eaten into to some extent, that overcharging is deleterious, but on the first charge we know from very definite experience that this is not. Therefore there should be no hesitation about continuing the first charge until it is absolutely certain that the battery has received at least three times its ampere hour capacity, and preferably more to be on the safe side. We would like them to say whether they can really guarantee that the first charge in this instance has been | ||