How many of you use a battery tender on a regular basis?

My battery went dead about a month ago...

When I called the Porsche Service Department, the tech told me that the 997.2 draws something like 26.5 amps (maybe mA?), not sure of the correct term... but his point was that just about all the current the alternator generates is going to run the car during its operation and very little goes back to charging the battery.

I drive 8 miles a day total (4 to and 4 from work)... he told me that 8 miles isn't enough to keep the battery charged and when I told him when I bought the car, he said he was surprised the battery lasted that long.

His suggestion was to buy one of those cigarrette lighter battery tenders that plugs into the garage wall... and plug it in every night when I get home from work.

So, do any of you guys use tenders?

 

the batteries in these cars are such wienies that unless you drive them every day you need some kind of battery maintainer...I have a Battery Tender and it works great...I don't use it all the time especially when I can drive the car every other day and it isn't necessary...but over time the battery will run down and it will need some charging and a maintainer will not substantially charge the battery but will give it enough to get it started...when it sits longer I will leave it on overnight and that seems to give it a pretty good charge

 

I tend to agree that 2 daily runs of 4 miles each may indeed not be enough to recharge the battery and replenish the starter energy loss. I would recommend that you either get the OEM dual-mode charger or the CTek similar model. If you get the CTek do get also the cigarette lighter adapter, the easy/preferred way of connecting it.

You do not need to connect the charger everyday, but you may need to do it one full night, once a week.

 

I have the Battery Tender with alligator clips. Haven't used it with my Porsche (but should considering how seldom I drive it--comparatively with my DD). If I did, are there terminal points on the chassis to connect (like BMW)? Guess I need to buy the Porsche charger...

 

You can also get a cigarette lighter adapter for Battery Tenders.

 

Seeming non-sequitur, and I know you clarified it with the mA, but just for your general knowledge...

Voltage x Current = Power
You have a 12 volt battery, so 12V x 26.5A = 318 Watts
... and 1 horsepower = 746 Watts

I hope your car doesn't use 1/2 horsepower at rest

 

I agree (rep points added ) - the parasitic idle current is about 25 mA. But the key issue is that the energy consumed in starting the car, VIt, where I is in the 100s of Amps is not recovered by charging in a short 4 mile drive.

 

This is for the Canadians... This http://tinyurl.com/66qhlrh is what I use, works great and 20 bucks cheaper because it doesn't have Porsche stamped on it

 

Excellent point, I definitely agree!

We could estimate a high 500 amps for 1 sec, which would be:

500 A-s = 8.3 A-min = .13 A-hrs (which doesn't sound like much to me, a standard car battery is around 40 A-hrs)

But sadly most battery manufacturers no longer list a-hrs, only "cold cranking amps." Oh well ;(

And as to your point, we'd also really need to know the rectified voltage put out by the alternator and the resistance of the battery as it charges to figure out if a 4 mile run would charge it back up.

Lastly as an aside, I usually hardwire battery tenders to all my motorcycles batteries.

 

battery tender = cheap insurance

my "nice" cars are not DDs and I've always used battery tenders

 

I use a cigarette plug in tender 90% of the time. Wal Mart has them as well as the dealer. I drive my car couple days a week at best.

 

4 tips to get your battery to last to the max:

1) Use a battery tender

2) Check the water level often & add distilled water when needed. You have to remove the stickers on the top to get to the fill plugs.

3) Lock the doors. This will allow the car to get into the "sleep mode" and thus it will draw lower amps.

4) Keep the battery post clean of any acid build-up.

 

I have one of these very chargers spare now if anyone needs one. I'll stick it up for sale in the marketplace or you can just PM me.

 

+1 Battery Tender. I have used it for years with my C2S and keeps the battery always charged. You should check Amazon.com, they sell them for under $50.

 

Thanks fellas,

And Adias, thank you... I have a battery tender that I keep on my Harley, it didn't come with cigarette lighter adapter, but now I see that would be cheaper than buying another tender.

Thanks,
M.