Calcium Maintenance Free(Mf) Batteries ??

[Shri]

Does anyone know the difference between Ca-Maintenance free(MF/SMF) battery and a General Lead acid Battery?

Plas advice beacause now a days most of the batteris comes with this Calcuim thing.

Anyone know the chemistry behind this?

[Rumesh88]

Both are essentially lead acid batteries. Lead in its pure form is a mechanically weak substance. What you find as soldering lead in fact is an alloy of 60% tin and 40% lead (there are other proportions as well). Hence in the construction of a lead battery electrode, lead is mixed with another substance such as antimony, calcium, or even silver (too expensive for practical use). Most commonly used substance is antimony but the manufacturers use calcium for MF batteries because of certain qualities such as higher cold cranking amperes and low self-discharge rate. However, use of calcium is expensive and calcium batteries are difficult to recharge once fully discharged. Although there are pros and cons in the use of both of these two substances, manufacturers favor calcium in MF batteries.

[Shri]

Thanks for the clear explanation.

And also we can see calcium addition in some Dry Charged batteries( Nomal Lead Acid batteris where acid needs to be filled) as well.

[Rumesh88]

Thanks for the clear explanation.

And also we can see calcium addition in some Dry Charged batteries( Nomal Lead Acid batteris where acid needs to be filled) as well.

I do not find a direct connection between the use of calcium and dry charging. In dry charging the cell plates are assembled with spongy lead and dried in an oxygen-free environment and then sealed. This is why you should always ensure that the battery seal is intact before you purchase the battery. Ideally the battery vendor should show you the battery with the seal before you purchase it and then break the seal in front of you and fill up with acid. Never buy a battery with shelf life exceeding 2 years or with the seal broken. Prolonged exposure of dry charged cells to oxygen degenerate the cells quickly.