Cupcar#12

wrong...DNA?
interesting statement since it is a USA Cup (i.e. RS) - pointed at a normal C2 i see your point.

Cupcar

Rob-

To test the factory supplied DNA of your car, I weighed a brand new Porsche supplied "RS" 36 AH battery that I have here in my garage and it weighs in at 19 pounds. I suspect the electrolyte would add around 3 pounds for a total of 22 pounds, so the saving will be more like 16 pounds for you with the trick battery.

Your Cup is an ideal candidate for a light battery because it has no superfluous electrical devices and has a switch to disconnect the battery easily when the car is stored.

The stock C2 battery is a 75 AH battery that weigh in at around 40 pounds.

Given that the battery is on the same side as the driver and affects corner weighting, any mass saved here is a good piece of mass

Cupcar#12

my wife is going to hate me but i will probably go for it and see what happens to it.
16lbs is worthwhile nonethe less (esp since my car was weighed at the stated weight w/ a heavy optims gell battery - red top-

btw did you see my thread on the wheels? 36 lbs savings! (BBS MS Mg 18" vs. the stock et68 & 52 Cup 1's, 10mm smaller tire all around however, i am changing the fronts to 235mm soon though )

Cupcar

I could not find the wheel thread in a search.

One thing came to mind with the small, super light battery and mounting it in a Cup or RS body shell; I wonder if mounting the battery to the alternate ABS brain mount or mounting the ABS brain on the alternate mount and the battery where the ABS brain normally goes using those studs would work. This would improve the corner weights since there is already a lot on the left side.

tonytaylor

I'm using the Odyssey 680MJ and have been using the same one for the last 2 years. At 6kg it's usefully lighter than the stock or cup Porsche batteries. There's little electical drain on my car since it's track orientated however I've had no real problems with it. It's been flattened a few times but charges up OK and I now "condition" it by having it jump lead attached to the stock battery when the cars not in use.

Point being at £150 for the battery and mount and terminals ( IIRC) it's a cheap way of saving 25+lbs or gaining 3hp depending on your POV.

DrJupeman

Interesting and fwiw my Cup's ABS is in what you call the "alternate" location as noted by your arrows. Otherwise, interesting idea. I put my lightweight battery in the stock location.

Cupcar#12

yes your cups ABS controller should be there - better position from a crash perspective.

Bob - it is under my thread for CCW C10's - on the - i'll send you a picture

HiWind

I see the old hands were on this story right at the beginning ...
seems Not much has changed really .. Voltphreaks have added mgmt so draws don't flatten the battery when engine off
And their prices have moved up 25% ... Normal for 7 years?
Or not considering the economies of scale in LI-on batteries over that period?
Weights have fallen below 5lb too.

Where too now? And over next 5-7 yrs?

Raceboy

Todays standard in lightweight battery is LiFePo4 cells and these can be had for very good price.
Here's my 20Ah DIY LiFePo4 battery that uses A123 prismatic cells. Can crank Porsche 2.5liter 944 motor for half an hour easily and have been proven over our winter on a Jaguar S-Type R 4.0 supercharged V8:



Total cost of the battery was ~150 euros and the 20Ah capacity is fully usable making it similar capacity as regular 60Ah lead-acid battery (because the latter is usable just 30% of its rated capacity, it will not start the car when already 40 ah is left).

Balanced charger cost just 30 euros and I have verified the balance once during winter (end of 2nd season, runs like a champ).

HiWind

Thanks race boy ... Yes the thread is 7 years old in case you missed that

But I was looking at the a123 DIY yesterday ... Did you write yours up?
How do you balance the cells when charging - sorry I'm not experienced
and did you add any 'smart' circuitry re auto cut off etc..?

Raceboy

I saw that, that's why the post starts with words "todays standard"

Did not write mine up but here's a Pelican thread where Steve Wong shows how to do it: http://forums.pelicanparts.com/porsc...-875lbs-2.html

HiWind

Aha! I missed that the first time .... Thanks for the link!