Hybrid Starter Battery

Votes: 1
Views: 1948

The hybrid starter battery (e.g. CAPstart) is designed to replace a conventional lead acid starter battery.

Probably almost every car owner has faced the unpleasant situation where the battery has died after the car has been unused for a longer period. This is especially familiar to motorcycle or hobby/classic car owner in the beginning of the season.

CAPstart offers a cost efficient, light and long lasting solution. While there are numerous Li-ion starter batteries on the market, supercapacitors offer superior cranking current capability and cycle life in a lighter package, not forgetting the fact that also the Li-ion battery can be drained due to standby current drawn by the car while unused. Wait a minute! Supercaps have less energy density and higher self discharge rate compared to Li-ion or even Lead Acid for that matter. How is this going to solve anything? Here’s where the ingenious architecture of the CAPstart comes in!

As depicted diagrammatically in one of the accompanying pictures, the CAPstart incorporates a low power energy storage device, a bidirectional DC-DC converter and supercaps. There are two slots for the energy storage as depicted in the CAD illustration of the device. The other one is for a 3xAAA-battery holder such as the one you can find from your good old flash light and the other is for an 18650 Li-ion cell which can be found in various mAh ratings. Here’s how the device works: When the batteries or a single 18650 cell is inserted in the slot and secured with the cap, a red power indication led is lid and the DC-DC converter starts in input current regulation mode and charges the supercaps with a constant current drawn from the batteries or cell. When a voltage level suitable for cranking is reached, a green LED will be lid to signal the driver to start the engine. After a successful start, the alternator will charge the supercaps. This higher output voltage level will be sensed by the DC-DC converter and it will reverse the operation direction and start a constant current/constant voltage charge cycle of the 18650 cell given there is no voltage detected in the AAA-battery slot. The charging is ended when the cell is fully charged. If the energy storage device is left in place after the use of the car, the DC-DC converter will monitor the voltage level of the suprecaps and prevents the voltage level from dropping they self discharge.

The weight of the CAPstart is below 800 grams with dimensions of a conventional motorcycle battery. The cranking capability is sufficient for passenger cars and motorcycles.

The snap-in type supercaps are welded on a PCB while the Standard motorcycle battery terminals with M6 threads are off pressfit type. The DC-DC converter is assembled on another PCB. A free hanging connector is used for routing the indicator LEDs and an enable switch to a convenient location. The plastic housing is made of two parts. The whole assembly is fixed from the top with four screws.


Voting is closed!


  • Name:
    Juuso Kelkka
  • Type of entry:
  • Profession:
  • Software used for this entry:
  • Patent status: