Cadmium Sulphite works well in extending the working life of lead acid batteries, more particularly those with low duty cycles. Should be installed in batts when new. Battery companies generally deny it works, or void warranties, because it ultimately means less sales. Sealed batteries [no maintenance] should not be dismantled to install it, as the battery is usually badly mechanically damaged. Car battery life have been observed to be upto 7 yrs with this additive, whereas a car battery is usually only good for 4 yrs. IE Battery warranty is a con. You pay more to get 4 yrs on the same 2 yr battery, and it's only pro-rata. Love of money........ Spending $10- on a terminal battery is rarely cost effective, IMHO.