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).
Procedure for testing battery performance by taking voltage readings under a specific current load.
| Identifier | WestWitteringFiles\C\May1919\ Scan38 | |
| Date | 26th April 1917 | |
| Contd. -3- EFCL/T2.5 19. We did not use the starter motor but we arranged a group of resistance wires in parallel of such a resistance as to take about 100 amperes at about 11 volts. We would have each battery fully charged and with correct densities and connect each on in turn through a switch to this resistance wire, with a voltmeter across the battery terminals. If the open circuit voltage was above 12.5, we would allow current to flow until the steady open circuit voltage was brought down to 12.5, then we would commence taking readings. We would switch on the current and when a steady reading was indicated by the ammeter, take the terminal voltage of the battery with current on. At the instant of taking the reading, the current was switched off, and the instantaneous reading of the voltmeter taken immediately after switching off. This last reading is less than the steady open circuit voltage, because there is a gradual subsequent rise of open circuit voltage to a figure which is rather less than the 12.5 at which we originally started. The point was that we wanted to get the change in terminal voltage due to the current alone and not due to an alteration in E.M.F. We actually took three readings on each battery, but in the table below, we are giving one average reading only for purposes of comparison. It will be noted that the value of the current given is itself to a great extent an indication of the battery internal resistance, (it would be exactly so if the battery E.M.F's were all the same). Contd. R.R. 235A (500 T) (S.D. 408 26-4-17.) Bm 2/156/13. | ||