The Supercapacitor Jumpstarter/Booster

I own a Chevrolet that from time to time tends to drain the battery even though only the alarm is enabled. At such time it needs to be charged or jumpstarted.

But what to do if you only have one car and cant wait the hours required to charge the battery?

I have been experimenting with Supercaps for some time with not so good success until I got these 500 Farad, 2.7V capacitors.

Charged to 2.4V they hold 1450 Joules of energy.Not enough to start a car but 8 in series?

With 8 of these in series they hold 11.5KJ at 19.4 Volts.That is alot of energy and enough to pull the starter engine.

But why 19.4 volts and not something like 14 volts?The excess energy will charge the drained battery faster.

Can’t have enough of them Joules!

I’m not removing the original battery like others have, just jumping it for assistance.

The booster is connected to a 12 volt/1000mA wall-wart that charges the supercaps from empty to full in just 15 minutes.

Here is the full schematic:

The 12 VAC is fullbridge rectified and feed into the string of 8 capacitors.

When you connect capacitors in series it is extremely important to balance them for not exceeding the 2.7V limit.

That is the job for the 8 zener diodes making sure that the voltage for each capacitor never exceeds 2.4 volt.

The capacitors are series connected with heavy gauge copper links to keep the resistance low.

Also connected is a cheap small voltmeter to show when the bank is full and up to 19.4 volts.

Is there any power in this?Sure is!

When testing I managed to reverse connect the clamps to the battery and a loud bang blew off all the wire links between the capacitors.

Don’t try that!

Don’t worry that the empty caps presents them self’s as a short circuit to the transformer.

There is enough internal resistance in the secondary winding to not overload the transformer the first few seconds.

I don’t know yet if it works when the battery is completely drained but it works as a booster.

Connect it to the battery and wait 30 – 60 seconds before trying to start.The voltmeter will show the energy transfered.

I’m very happy with it.