(a) Because the positive active material does not stick together well, but drops off, or sheds easily.
(b) Because the positives warp or buckle, this causing most of the battery troubles.
(c) Because the positive plate is weaker and is ruined by freezing.
When the Old Plates May be Used Again
1. If one or more plates are broken from the plate connecting straps, or the joint between any strap and the plate is poorly made. If plates are in good condition, reburn the plate lugs to the straps.
Fig. 212. Element from a "Slopper." Element was Loose in Jar and Jolting of Car Caused Paste to Fall Out
2. Straight Rebuild. If the general condition of the battery is good, i.e., the plates straight or only slightly buckled. only a slight amount of shedding of active material, no white sulphate oil either plate, the grids not brittle. active material adhering to and firmly touching the grids, the positive active material of a dark chocolate brown color and fairly hard (as determined by scratching with blade of a pocket knife), the negative active Material dark gray in color and not blistered or granulated, and the plates not too thin, make a straight rebuild. To do this, charge the battery, remove any sediment from the bottom of the jar, wash and press the negatives, wash the positives, clean the parts, insert new separators, and reassemble as directed later. The only trouble may be cracked sealing compound, or a broken jar. Broken jars should, of course, be replaced.
3. Badly bulged negative plates, Fig. 213, cause lack of capacity because the active material is loose, and does not make good contact with the grids. If the active material is not badly granulated (having a grainy appearance) the plates call be used again. Sulphated negatives have very hard active material, and will feel as bard as stone when scratched with a knife. Hard negatives from Which active material has been falling ill lumps Oil account of being overdischarged after having been in in undercharged condition may be nursed back to life, if too much of the active material has not been lost.