[BC] Lead acid batteries.

[Cowboy]

On Monday 01 November 2010 11:04:01 pm Steve Lewis wrote:
> SO... What you're telling me is that the battery in my van is going to...
> Go dead?  Wear out sooner?  Blow up?

 Wear out sooner.

 Briefly.........

 Depending on how deeply discharged, and how many times,
 it may be the difference between the battery lasting 4 years
 instead of 6.
 Run it dead often enough, and it may not last 1 or 2.

 Every time the battery is discharged, sulfate from the acid is absorbed
 by both plates, making them physically larger. The sulfate is returned
 to the electrolyte during charge, and the plates shrink back to normal.
 This physical change stresses the mechanics of the plates, and is a
 primary reason they wear out eventually.
 Hence, the less discharge, the less often, the less physical stress, and
 the longer the battery will last.
 If the discharge is shallow enough, the physical change may be
 confined to the surface only, and do little harm at all. Still, flexing at
 the surface will eventually cause material to be shed off the plates.

 So called "deep cycle" batteries merely have more lead, but less surface
 area, so a greater total energy capacity. ( much thicker plates )
 Start batteries have less total lead, but much more surface area on much
 thinner plates. Higher "high current" capacity, but less total energy, and
 more physical stress for the same energy removed and restored.

 Lead acid cells have lower energy capability than most other types, but
 much higher current, so higher power capacity per unit volume/weight.
 Great for starting your car. Not so great for an emergency flashlight,
 or smoke detector over the long term.


-- 
Cowboy