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Show POCKET AMMETER CAJHD DAMAGE Will Test Dry Cells Excellently, Excel-lently, but Works Havoc With Batteries. (I can test dry cells with a pocket ammeter. "Why can't I test my storage battery the same way1?" This question is frequently asked by automobile owners, many of whom have learned through bitter experience that there must be a reason why the familiar little pocket ammeter, used to tell whether dry cells are weak or strong, will cause considerable damage to . a storage battery. To the average automobile owner a battery is a good deal like a Greek puz- zle. It is hard for him to appreciate that a storage battery is a purely chemical chem-ical device. And so, a battery is a battery.' But there is a big difference between the chemical and electrical natures na-tures of the dry cell and the storage battery. Both dry and storage batteries operate oper-ate by chemical action when "the circuit cir-cuit is closed." The dry cell, when it is exhausted, is done; the storage battery, bat-tery, when exhausted, can' be recharged. re-charged. The ordinary dry cell has a comparatively high 1 ' internal resistance, resist-ance, ' ' which permits only a certain amount of electricity to be discharged at one time. But just the opposite is true of the storage batterv its "internal "in-ternal resistance" is very low, and it can discharge a tremendous amount .ot current when given an opportunity. When the pocket ammeter is used on a dry cell, the amount of current liberated liber-ated is small, doesn 't in -jure the drv cell and doesn 't injure the ammeter. But the same little instrument, placed on a cell of a storage battery, will in most cases be burnt up by the tremendous tremen-dous current discharged, "and at the same time the storage battery cell is permitted to discharge itself all at once, with a ruinous result upon the battery bat-tery itself. The same thing occurs when tools or other metal objects are carelessly placed on top of the batterv. |