Porsche Battery Maintainer

[teacher]

Originally Posted by MNBoxster

Hi,

It depnds on your starting point. But, usually, only about 4-6 Hrs. But, the maintainer keeps the battery from discharging by sensing a current drop and bringing the charger online to charge it back up. Because of this, the maintainer doesn't need the 3-10 Amps a Normal Charger uses and this is beneficial to the battery by eliminating the possibility that lead-sulphate crystals are permanently formed on the plates.

Sulphation is the formation of lead sulphate on the plates. As a lead acid type battery discharges, lead sulphate must form. There can be no discharge of such a battery without the formation of lead sulphate, it is the natural product of the chemical reactions by virtue of which current may be drawn from the battery.

When a battery has been discharged until the voltage per cell has fallen to the voltage limits, considerable portions of the lead peroxide and spongy lead remain on the plates. The sulphate which is then present is in a finely divided, porous condition, and can readily be changed back to lead peroxide and spongy lead by charging the battery.

If the discharge is continued after the voltage has fallen below it's voltage limits, an excessive amount of sulphate will form. It will fill up the pores in the active materials, and covers up much of the active material which remains, so that it is difficult to impossible to change the sulphate back to active material.

Plus, the expansion of active material which takes place as the sulphate forms is then so great that it causes the active material to break off from the plate. It is for this reason that sulphated plates should be charged at a low rate. A standard Charger (3-10 Amps) will get the battery up to charge faster, but at the expense of the battery's overall health and prolonged life.

Finally, there is a tendency for lead sulphate crystals to "tree" over from the negative to the positive plates, especially in an idle battery. Treeing will occur through the pores of the separators and as there is no flow of electrolyte in or out of the plates, the lead "trees" are not disturbed in their growth. A freshening charge causes this flow to take place, and break up the "trees" which would otherwise gradually short circuit the cells. This is another reason why using a maintainer is preferable to letting the battery sit for the off season and then recharging it in the Spring. Hope this helps...

Happy Motoring!... Jim'99

hi, you sound like you know your stuff, what is the best maintainer to buy? I need something that lasts at least 3 weeks...last time I went on vacation I had to buy a battery, and you know that ain't cheap! Any ideas?