Hi All, I am planning to build a Lithium (LiFePo4) pack as a replacement starter battery for my
Cayman S
. Does anyone know what is the peak starting Amperage? I have been on the internet for over a couple of hours and found very widely varying results. I live in India and Lithium battery dealers are not willing to ship by air. It is possible to find plenty of source for 3.2V cells around and hence I am planning to DIY.
Thank you for your replies
I'm not sure this will help you but here's some information about the
Porsche
motosport unit. In the photo of it you can see some performance related data on the top of the battery
Porsche AG: World Debut: Starter Battery in Lithium-Ion Technology - Porsche USA
Stuttgart. Dr. Ing. h.c. F. Porsche AG, Stuttgart, is the first car maker in the world to offer a starter battery in lithium-ion technology. Weighing...
www.porsche.com
Replacing the lead-acid battery with a lithium battery is more complicated than just hooking up a bunch of cells in a series-parallel fashion to get the desired voltage and current. The cells need to be balanced when building the pack and equalization circuitry needs to be used when charging. More circuitry needs to be added to prevent the voltage on any cell from going below about 2.5 V when discharging. Without these protection features the battery pack will have a short and/or dangerous life.
Yes. I do understand the added complexity. I have been reading up on this subject for sometime now. Constant current charging, with cell balance circuitry and Amperage control both while charging and discharging, trickle charging whilst parked at home, etc.. But , like most things, plenty of guys doing it as a hobby with loads of info and assistance on the internet. Ideally, would just like to buy a 12V off the shelf "Antigravity batteries". Just not doable due to shipping constraints.
Thank you, the article kinda gives an indication , but not a specific number to the peak (cold cranking) cracking Amps for the 6 cylinder boxer engines .
Denso lists the starter (9A160410300) as 1.8Kw, so at 12v you're looking at ~150A draw.
Please note that I am not responsible for any outcome using the information below.
while I can confirm the starter model and spec which was installed on my
987.2
2.9, I thought that the max supply was determined by the battery size and rating? I recall batteries ranging from 60-80Ah were recommended for the 987 range. From what I can tell, the CCA ranges from 750-780A based on battery recommendations for my car. The one in my car now has a 12V/74Ah/750A rating.
I've attached a pic of the specs extracted from a document for
987.1
model as reference. Hope that helps.
Also FYI the car may need additional power once turned off for engine bay cooling fans so the solution you come up with may need to cater for that as well.
A battery does have to deal with a lot including bumps/shock, charge/discharge cycles, ambient heat + charging heat which are quite harsh conditions so please do consider those factors.
starter pic
Thank you all for the replies.
The Lead acid specs on the stock battery might not help as a reference, cause the efficiency of a lead acid is quite low. Hence trying to find the actual data. The
Porsche
Lithium Motorsports battery is interesting , 18Ah, 480A (Pulse discharge or CCA I believe). That battery was designed for a larger capacity engine 3.8Litre (
911
GT3
RS)
The Denso starter is rated at 180 Amps. ( for
987.2
)
So I am assuming if I built a pack 12.8 V, 30 Ah, 300A (Pulse discharge), 90 A (continuous discharge), it should be more than adequate, so long as i have a Lithium
battery tender
hooked up in the garage. Crucially, with the electronics modules (BMS, cell balancer, blue tooth) ,Tabs, wiring, and case, the overall weight would be 4 Kg (8.81 lbs) or less. My Lead acid battery is at 18.5Kgs.
With all the DIY information (exhaustive amounts) on Youtube, this is a 250-300 $ project.
