I love mine

I wrote the following to a friend, with regard to an Italian car, but the advice should be applicable to German vehicles too. :-)

[snip] Then, always, and I mean always, use a battery tender. The "Battery Tender" by Deltran, and sometimes marketed under other names, is intended exactly for this purpose -- to maintain the battery. I've used one on my motorcycles for several years, and my cars as well with no problems. More info can be found here: http://www.batterytender.com/ If you're going to park it for more than a day or two, just plug in the charger and voila.

It comes with two methods of attachment to your battery -- regular alligator clamps (like on jumper cables), or a connector where the ends terminate in metal o-rings (like a washer). Each method connects to the charger through a little plug-together connector. The o-ring connectors, intended for semi-permanent mounting, slip right through the bolts used to attach your terminals to your battery. Then simply tie down the length of the wire, until you have only the other connector poking out into the trunk. Thus, when you're in the garage, pop the lid, snap the two connectors together, and voila! Or buy the cigarette lighter attachment, if your car has a "live" power adapter when the key is out.

Alternatively, one can get a charger that attaches, piggyback style, to the battery (the most popular is manu. by Schumacher, and sometimes marketed as a "factory" charger, e.g. Ferrari); the 120v plug is located inside the car; you just have to connect an extension cord when needed.

Why do I consider the Deltran method better? Well, I'm presuming that the Schumacher is also a computer controlled charger like the Deltran. The primary advantage, in my mind, is that you don't have the charger sitting in the car -- only the wiring. Thus, (a) it's lighter, (b) you can use one
charger for more than one vehicle if you alternate, (c) the wire coming out of the trunk is thinner and you can in fact close the lid with the wire dangling out, if you wanted to do so, you can put the cover over the car, (d) I guess if the car gets stolen, you didn't lose the charger as well, (e) if the circuit breaker (or whatever) inside the Schumacher fails, it melts INSIDE the car, right next to your battery; I'd prefer to have the thing melt down outside my car, not in it!!, and (f), the Deltran is only $30 or $40 on Amazon, versus the $700 the dealer wants for the Ferrari-branded Schumacher.

Oh, should add that the "Jr" version is available on Amazon for $23, with free shipping for orders of $25 and over.
http://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S

Vty,

--Dennis

Worth mentioning - before starting the car it might not be a bad idea to pop the bonnet aka hood and VENT it. Paulie found out the hard way that any lead acid battery charging, no matter the charger, creates hydrogen gas. He used a lighter charger, didn't vent, and the hydrogen exploded - it made a mess. A good idea to have the vent tube hooked up too I might add! Gels and sealed aren't supposed to do this but hey venting is free....

Good point and if iam not mistaken this problem with hydrogen gas is described in the manual of the charger, and it states that the chargeing should take place in a well ventilated environment.

As Paullie found out - they were serious about that recommendation!

Agreed. I've used it on multiple cars for multiple 6+ long overseas deployments. Perfect.

This battery tender is what I use for my bike and tractor batteries. I use the Porsche cigarette lighter charger for the turbo and leave it plugged in all the time.

I have a Porsche Techquipment cig lighter charger for my 04 tt. First season using it but it seems to work great!

I have used the Porsche Techquipment lighter version for over three years. So far, so good.

I use the battery tender plus on the TT and the battery tender jr on my
S4. They both work great. The only problem I have had is with the tender plus after a near by lighting strike. The tender plus fried and the jr was fine. They were both on the same circuit. I did get a new replacement at no charge. The jr was able to withstand the power surge with no problems.

Have used a Battery Tender Junior on all my cars. Even keeps the Vipers alive and they are known for killing batteries in as little as a few days.

I have the battery tender plus. do not know what the diff is between the Jr. an Plus.

I have used the Porsche tender for several years, never vented before starting and never had any problems. After reading about Paulies experience, when starting recently, I popped the bonnet and let it air out for a few minutes first. I thought better safe than sorry, as that battery explosion looked pretty nasty.

I got mine (Porsche Brand) from http://www.automotion.com/default.asp? and just plug it in till Spring!

The lighter circuit apparently is always hot.

99C2

I use the Porsche tender unit on the TT and a more elaborate device on a truck I use a few weeks a year (no issues almost 4 years now)