Pressure cast lead‐calcium alloy positive grids for float applications can cause some unexpected service failures due to abnormal growth. Such failures have been interpreted as a result of irregular grain structure and weaker grain boundaries. Since lead‐calcium is a prcipitation hardening alloy, either heat‐treatment or controlled solidification can yield favorable grain size and distribution of Pb3normalCa precipitates in the matrix. The present investigation shows that controlled solidification of pressure cast grids can produce physically sound grids which are corrosion and growth resistant. Differences between industrial and automotive SLI grids cast by gravity and pressure casting techniques are revealed. The effect of casting temperature on the microstructure and anodic corrosion characteristics of lead‐calcium alloys ranging from 0.01 to 0.1% calcium content is also presented.

Actual conversion based on AgO is 70% since some Ag + and Ag ~ remain during charging to Ag + +. Therefore 1.4 X 70% ~ 0.98 A-hr is actually expected to force discharge 1.0g of fully charged silver. Testing commences by charging at a 5 hr rate until oxygen evolution. The charging current is decreased to 25 hr rate until oxygen evolution once again occurs.Currents would be 0.98 A-hr = 0.196A~5 hr rate charge 5 hr 0.98 A-hr --= 0.039A--25 hr rate charge 25hrTesting continues by discharging at a 1 hr rate until hydrogen evolution 0.98 A-hr 0.98A discharge 1 hr Note that the discharge time is such that, in 1 hr, 70% efficiency based on Ag ++ would be achieved. Theoretically, the longest discharge would be 1.4 A-hr• 60 ~ 85.8 rain at the 1 hr rate 0.98A

Unter Druck gegossene positive Gitterlektroden für Bleiakkumulatoren aus Pb‐ Legierungen mit 0,1% Ca zeigen gelegentlich Quellungserscheinungen, die zum Ausfall der Akkumulatoren führen.