This is usually due to ‘ sulphating’—that is, the formation of lead sulphate in a crystalline form, which may be seen as white patches on the positive plates. In a charged cell at rest there is always some leakage of current, and, as in usual discharge, lead sulphate is formed. This, as first deposited, is soft, and easily altered by recharging; but if that be long postponed the deposit becomes crystalline, and is no longer altered by the current. This deposit reduces the available area of lead, and consequently decreases the capacity of the cell. Plates much affected become useless, and should be replaced by new ones.

The obvious remedy is frequent recharging*. Where insoluble patches have already formed, they should be scraped off with a piece of glass or other non-conductor.

Some try to prevent sulphating by adding 1 ounce of caustic soda to 5 gallons of the electrolyte, but careful working should obviate trouble from this source.

Treated properly, a set of accumulators should do good service for many years, but the various points mentioned must be constantly attended to.

Accumulators may be charged by—

Each of those sources of supply is discussed elsewhere in this chapter, and we need only note here their suitability and method of use for the present purpose. The foregoing notes on charging are applicable to all.

1. Primary batteries need hardly be mentioned, since no serious worker would suggest their use for other than toy installations, and even there the batteries might better be connected direct to the coil.

2. Charging by dynamo is the usual method adopted to charge accumulators where no main supply is available; and, even where the latter source is available, unless it may be ntilized without special transport of the accumulators, we recommend the former.

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