Recent content by TDA78

The kWeld will work with up to 30V but 12V is ideal. Here's a quote from the designer on this subject: "Desired current is 1500A. The resistance of the kWeld system is roughly 3.2 milliOhms (stock cables). The weld spot itself contributes another 1 milliOhm typical. This gives 4.2 milliOhms...

The Drain to Source voltage is not 12 V when the MOSFETS are fully on. They would measure about 0.183 V @ 2000 A (2000 A / 6 FETs * 0.00055 Ohms). You should be looking at the "limited by Rds(on)" part of the graph.

Circuit board trace width calculators are good for this. I'd keep the internal layer temperature rise under 20°C for the hottest days. Trace Width Calculator

Read and understand the power supply requirements detailed on page 7 of the operating manual.

I see the gold coloured negative terminal on pictures of protected NCR18650B cells. Are your cells 70 mm long instead of 65 mm? If so, you're trying to weld to a printed circuit board. It would be very thin copper plated with nickel, then gold.

You could use the contacts from an EC3 connector and insulate them with heat shrink tubing. Similar 3.5mm bullet connectors are available without a housing but they often don't list the maximum AWG.

Even if a 10A cell doesn't overheat, the voltage may sag too low when the blade spins up. The BMS low voltage cutoff may be triggered or the guidance processor may lose power.

I would assume the designers had a good reason for choosing a 20A cell over higher capacity. The EVE 25P is a good budget replacement. I'd go with Molicel P30B if money was no object, they were available, and they fit in the cell holders.

There are some transistor shaped solder pads missing components near the switch input, so I'd say the switch capability is missing from this BMS. I'm never going to recommend cutting a safety monitoring feature to disable the output.

From estimating the dimensions, it could be any one of these: https://www.digikey.com/short/qf3rpvzb

50 amp output is not 50 ah capacity. This battery is available in lead-acid with 20 ah capacity.

The bare minimum is 800 A for proper functioning. 1200 to 2000 A is the recommended range. 496 A is inadequate. That battery is very tired.

The 50E is perfect for this use case. I pull peaks of 7.5A from the 50E in an e-bike (30A @ 4P) and they don't even get warm. The cells go in and out of stock all the time. At least you know you are getting fresh ones!

I use a trace ampacity calculator for high current printed circuit board design. You may find it useful. The source code could probably be modified for nickel or steel as well.

It's an unusual approach. I mentor budding electrical engineers who ask the wrong questions all the time. I always appreciate too much information over what they think is a concise question.