Improve a car battery's performance with capacitors
Putting capacitors in series to add up their voltage ratings isn't very wise. Their difference in leakage current will lead to an imbalance in the voltage they'll have across them (see https://electronics.stackexchange.com/a/80589/107479), and some of the capacitors could easily experience overvoltage (especially given the low voltage ratings supercapacitors have). The solution for that would be to add a resistor ladder in parallel to compensate this, but that would increase your standby battery drain, which is not a good idea either.

Moreover, your computation is wrong, since the capacitor will be charged to the battery voltage (~13V), not the full capacitor voltage rating. And I doubt it requires less than one second to start.

And, when you say in your comment:


  The top rated answer in the post that PlasmaHH linked, suggests doing exactly what I want to do, using capacitors in addition to the batterie, so the battery can store lots of energy, and the capacitor can deliver it at high rates for short times.


you're mistaken: this answer you're referring to, when it mentions "short times", it means "a few ms", for example to smooth the big current spikes due to the inrush of the starter. Not for the starter the whole starting time. This is where it begins not making sense.

Finally, if your car doesn't start when it is -10°C outside, you simply have a problem somewhere with your car. Bring it to your mechanic. He'll fix it, and he surely won't fix it by adding capacitors. He'll find the actual faulty component (which, by the way, you don't seem to have really checked - you're assuming it's the battery, but it could be anything: glow plug/starter motor/some sensors/whatever/...) and replace it (because when such a component starts to fail, trying to fix it by adding capacitors or duct tape is futile - you replace it).