kCap ultracapacitor module

To customers from the U.S., Canada or Mexico: visit our North America reseller here

The assembly and operation manual is available on this website for download: https://www.keenlab.de/wp-content/uploads/2026/10/kCap-manual-r3.0.pdf

This module features six Skeleton SkelCap SCA0300 ultracapacitors (older modules: Maxwell BCAP0310) with ultra low internal resistance, delivering more than 1000A of pulse current to the kWeld system, but the power delivery capacity of the module of about 6kW enables the use of this module can also be used for a variety of other demanding applications.

IMPORTANT! Connect a suitable current regulated power supply to the inputs of the module, and the kWeld to its output terminals to create a stationary spot welding solution. Because it is modular, you can easily change back the system into a portable welder.

IMPORTANT! Simple transformer-rectifier based PB chargers are not usable, as they do not feature current regulation. For the same reason, do not connect the module directly to a battery, as this will lead to uncontrolled current flow and possible damage of the module. Also, most off-the-shelf power supplies are using hiccup-style overcurrent protection – these are not current regulated (ATX computer power supplies are of this type and cannot be used directly).

In order to weld with quick repetition rates, the kSupply module is recommended to power this module as it provides up to about 80A of charging current. The welder consumes up to 500W of average input power during intense use. However, when a slower recharging speed can be accepted, the following options may offer a more affordable solution. An output current of at least 20A is recommended – the kCap user manual includes a graph that estimates the achievable welding repetition rate as a function of available current.

• Any bench power supply with voltage and current regulation

The key specifications are:

• input voltage 8.1V – 13V
• charging current 0 – 80A
• input protected from reverse powering the supply (ideal diode circuit)
• charger disconnect at about 8.4V, reconnect at 8.1V; set the charger to 8.5V (8.4V minimum)
• six Skeleton SkelCap SCA0300 cells (300F / 2.85V) in a 3S2P configuration
• pack capacity 200F / about 7000Ws at 8.4V
• internal resistance about 2.8 milliOhms
• typical short circuit current about 3000A
• maximum power delivery about 6000W (into a 2.8 milliOhm load)
• advanced balancing circuit that keeps all cells within +-50mV at all charging levels
• temperature monitoring and control of an optional 120mm fan
• separate input and output terminals (for ring cable lugs, M6 screws)
• LED indication for balancer activity, temperature sensor, and charging activity
• fully protected against voltage spikes from inductive kickback from welding
• dimensions 110 x 110 x 74mm

Performance when used with kWeld:

• maximum continuous repetition rate with kWeld (50J pulses):
  • once every 4 seconds without fan cooling
  • once every 2 seconds with a Scythe Slip Stream SY1225SL12SH fan mounted (not included in the kit)
• typical welding current 1200A
• pure nickel 0.15mm at 10-20J and 0.2mm at 50-70J (user reports); pulses above about 100J heat the electrodes and the fuse
• 0.3mm nickel and copper-nickel sandwiches need two kCaps in parallel

You receive a complete board that is ready to go, including mounting hardware and two short connecting cables (AWG8 with crimped cable lugs on both ends) that replace the stock kWeld battery cables.