Warning - some insurance companies may not understand the technicalities and consider this to be a performance modification. All a supercapacitor does is to improve the starting capabilities in cold weather and improve the action of the gearchange slightly.
Elderly or tired battery? - fit a high capacity capacitor across the battery.
Solon Wu shared his finding about the sluggish gear change on his auto:
"My battery works very well and engine fires up at the very first compression. However, as I cannot capture the lowest voltage at start up and I do think Jim's suggestion about battery quality is vital, I ordered a super capacitor of 83F/16V and wired it parallel to the battery. Just finished a test drive and the sluggish gear change problem solved like magic!"
"The capacitor just fits inside the battery compartment. Leakage current of the capacitor is less than 50 mA (but see below) so it won't drain the battery even the car is not used for a month.
This is a supercapacitor board with thick leads and substantial clips added for testing:
It is made up of six 2.7 volt 500 Farad capacitors in series; equivalent to 83 Farad @ 16 volts.
. . . . . . and the supercacitor in place on my elderly battery.
I simply pinched the wires into the battery clamps and held the board in place with a piece of double sided tape.
The supercapacitor was fitted across the battery in March 2018 and extended the battery life by about two years.