kCap Ultracapacitor Module – High-Performance Power for kWeld
Over 1300A of pulse current. Modular, reliable, and ready to weld.
When powering your kWeld Spot Welder, you have a few great options—but the kCap Ultracapacitor Module stands out for its ability to deliver over 1300 amps at 8.2V, enabling rapid, repeated welds with minimal delay.
This high-current module contains six ultracapacitors in a 3S2P configuration, offering ultra-low internal resistance and exceptional energy delivery—up to 5,000 watts of output power.
Need more throughput? Run two kCaps in parallel to boost your productivity. Contact us for wiring instructions. (See charger requirements on p.11 of the kCap manual.)
🔌 How to Use
Connect a suitable current-limited power supply to the module’s input terminals, and your kWeld to the output. This creates a high-performance, plug in the wall solution when paired with the kSupply (and a suitable PSU).
⚠️ Power Supply Recommendations
For rapid recharge and high-frequency welds, we recommend the kSupply module, which delivers up to 70A of charging current. For slower charging (lower duty cycle), the following options are also compatible:
- Meanwell RSP-150-7.5 – available from Digikey (1866-4228-ND). Adjust output to 8.2V. ⚠️ Be sure to protect the AC input from electrical shock risks!
- Any current-limited lead-acid battery charger with 13.8V output
- Any bench power supply capable of 20A+
Important: Avoid transformer-rectifier PB chargers (no current limit), and do not connect directly to a battery, as this can cause uncontrolled current flow and damage.
📊 Key Specifications
- Input voltage: 8.1V – 14.0V
- Max input current: 70A
- Reverse polarity protection: Yes (ideal diode circuit)
- Output voltage range: 8.0V – 8.3V (power supply disconnect logic)
- Ultracaps: 6x Maxwell BCAP0310 (3S2P)
- Pack capacity: 206F / 6780Ws
- Internal resistance: 3.3 mΩ
- Short circuit current: ~2400A
- Max power output: 5000W
- Advanced cell balancing: ±50mV accuracy at all levels
- Temperature monitoring: Supports optional 120mm fan
- Terminals: Separate input/output terminals with M5 mounting holes
- Indicators: LEDs for charging, balancing, and temperature sensor
- Protection: Fully protected against voltage spikes from inductive kickback
- Dimensions: 110 x 110 x 74 mm
🔥 Performance When Paired with kWeld @ 50J
- Without fan cooling: 1 weld every 4 seconds
- With 120mm fan (e.g., Scythe SY1225SL12SH): 1 weld every 2 seconds
⚙️ Typical Welding Capability
- Welding current: ~1200A
- Max pulse energy: 100J
- Max nickel strip thickness: 0.2mm
📦 What’s Included
- Assembled kCap module
- 2x short AWG8 cables with crimped lugs (replaces stock kWeld battery cables)
- Required nuts and bolts.
Whether you’re building battery packs professionally or as a hobbyist, the kCap module is a powerful and reliable way to supercharge your welding workflow.