Is a batt tender necessary?

[MNBoxster]

Hi,

A battery maintainer is necessary for any seldom driven car. You do not want to cause Wear & Tear to the engine by using it to charge the battery. The engine doesn't deep charge the battery, and you're using about $0.30 in fuel to do so where a maintainer would use about $0.02.

Every time you wear down your battery, it loses 15% of it's ability to hold a charge due to sulphating and scaling (so you get about 6 discharges and the battery will be shot). Sulphate crystals form on the plates insulating them from the electrolyte, reducing the chemical reaction and the power it can produce(and/or reducing the contact area of the plates) and pieces of the plates fall off (scaling) which also reduces the area of the plates in addition to collecting in the bottom of the battery case, in which case, it may short circuit between some of the plates reducing the battery's capacity. The same thing is true (though to a lesser degree) for a battery which isn't up to full charge. It too will sulphate and scale at an accelerated rate.

Get a quality maintainer (not recommending Porsche - the Cig lighter attachment may be convenient, but I'm not sure it's the best maintainer for your battery) of 1 to 1.5 Amps max. Also, be sure it has a Float circuit which will turn the charger off once the battery is fully charged and come back on if the battery experiences a one volt drop. Avoid using high amperage chargers such as 10-15 Amp or more. These get the battery too hot and can cook-off the electrolyte. Hope this helps...

Happy Motoring!... Jim'99