Page:Motors and motor-driving (1902).djvu/178

146 Installation.—If a supply of electricity is available in the house there is a very easy way of charging off any wall switch (see diagram below).

The cell may be left on all night and found charged in the morning. No fear need be entertained of charging the accumulator too long. When fully charged the liquid in the cells assumes a milky appearance, and gives off a sound like gently boiling water.

Avoid Over-discharge of Batteries. Great care should be taken to see that an accumulator is not discharged for a longer



period than its rated capacity. The pressure of an accumulator keeps practically constant at two volts per cell throughout the period of discharge. Immediately a drop in pressure is observed the cell should be recharged. Nothing ruins accumulators quicker than discharging them after the voltage falls. In no case should they be discharged to such an extent that the pressure of each cell falls below 1·85 or 1·9 volt per cell. The pressure may be conveniently ascertained by means of the instrument known as a 'voltmeter,' which will show at a glance the condition of any cell.

Care should be taken that the liquid in each cell well covers