Making battery packs is a common pursuit in our community, involving spot-welding nickel strips to the terminals on individual cells. Many a pack has been made in this way, using reclaimed cells taken from discarded laptops. Commercial battery spot welders do a good job but have a huge inrush current and aren’t cheap, so it’s not uncommon to see improvised solutions such as rewound transformers taken out of microwave ovens. There’s another possibility though, in the form of cheap modules that promise the same results using a battery pack as a power supply.

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With a love of putting the cheaper end of the global electronic marketplace through its paces for the entertainment of Hackaday readers I couldn’t resist, so I parted with £15 (about $20), for a “Mini Spot Welder”, and sat down to wait for the mailman to bring me the usual anonymous grey package.

This Welder Promises much…

What arrived seemed promising, a “Portable Transistor Mini Spot Welder” along with a pair of battery cables and some cables terminated with spot welding electrodes.

The module itself is a sandwich of PCBs on metal standoffs, with a main board holding power electronics and a daughterboard with part-number-sanded microcontroller and small OLED display. There are some control buttons and a power switch on the board along with a socket for a foot pedal, and the main board has screw terminals, a row of hefty MOSFETs, and a large electrolytic capacitor.

Along with the unit was a set of leads, the welding leads being terminated in a set of insulated except for their tip copper probes and the battery leads being unterminated. I fitted a pair of crimp eye connectors to fit my battery terminals. Also in the box was a piece of paper advising on the type of batteries suitable for the task, which boil down to something close to a car battery. I had a suitable sealed lead-acid battery to hand as well as a few dubious cells of the extremely lightweight obvious fake variety, so taking a short piece of nickel strip I set out to weld cell and strip together.

Powering up the device and experimenting with the buttons, it became apparent that there were two modes: an Auto mode that would operate it when it detected something to weld, and a manual mode for operating it via a foot switch. I happen to have a foot switch from another piece of equipment, so opted for that.

Otherwise there’s a power setting calibrated in “E”, with no explanation as to what an “E” is. In fact it’s a measure of energy in terms of the length of the power pulse pulse delivered by the device, and on power-up it’s set to the low end of the range at 5E.

I first tried to hold the two probes in one hand and apply them to strip and cell with the other, but found I lacked the dexterity to pull this off. Reaching for a small bench vice, I was able to position them both such that I could hold cell and strip together against their tips and operate the welder via the foot switch.

… But Delivers Little

Starting at 5E and setting out to find the point at which the device would do a successful spot weld, I increased the power in steps of 5E and tried a weld at each level. The lower levels made the two stick together but only to the point that I could easily pull them apart, so I continued. Sadly I never found the level at which it worked , because at 25E one of those MOSFETs failed to a short circuit with the usual magic smoke smell, and I was unable to continue.

The process of reviewing very cheap electronics of this type is something like playing a one-armed bandit. Sometimes you win the jackpot, but at other times the device turns out to be no diamond in the rough. It’s usual though for it to at least do the job albeit in an entertainingly bad way, so this case of it failing to destruction before I had even managed to get it to perform is particularly disappointing.

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Calendering & Slitting All-in-one Machine Introduction

The Calendaring and Slitting Integrated Machine, as detailed on the website of China GMK, is a state-of-the-art piece of equipment that merges the precision of a roller press with the functionality of a slitting machine. This integration eliminates the need for additional winding devices, streamlines the production process, and reduces the workforce required, thereby enhancing efficiency and product quality. The machine is adept at handling the continuous calendaring and slitting of both positive and negative electrodes for a variety of lithium batteries, employing a constant pressure and limited gap rolling method to improve material density. It is equipped with a sophisticated system that includes a constant tension unwinding mechanism, roller press, thickness measuring device, slitting and winding mechanism, electronic control system, hydraulic system, and a correcting device. This machine stands out for its variable speed adjustable calendaring, precise roll gap adjustment, and high consistency in thickness after plate calendaring.

Calendering & Slitting Machine Working Principle

The Calendaring and Slitting Integrated Machine operates on a principle that combines the rolling and slitting processes into a seamless workflow. The constant tension unwinding mechanism feeds the material into the roller press where it undergoes calendaring to achieve a uniform thickness with a precision of ±2um. The roll gap can be adjusted from 0-2mm with an accuracy of 1um, ensuring the material's density is optimized. Post-calendaring, the material enters the slitting mechanism, which is controlled by an automatic control system. This system manages the tension of the pole piece, allowing it to be automatically cut into the required specifications as it passes through the circular slitting knife. The machine is designed to handle materials with a maximum rolling force of KN, making it suitable for a wide range of applications in the lithium battery industry.

Calendering & Slitting Machine Maintenance and Upkeep

Maintenance and upkeep are key to ensuring the long-term stable operation and extended lifespan of machinery. Here are some general maintenance and upkeep suggestions that apply to most industrial machinery, including the calendering and slitting integrated equipment you mentioned:

Regular Inspections:

Perform routine inspections to ensure all fasteners are secure and detect any worn or damaged parts.

Lubrication

Apply lubrication to all parts that require it in accordance with the manufacturer's guidelines.

Cleaning

It is important to regularly clean the machine to prevent overheating or damage caused by dust, debris, or other materials.

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Replace Worn Parts

Replace worn parts such as bearings, belts, and blades promptly to prevent further damage.

Check Hydraulic Systems

If the machine has a hydraulic system, ensure that the hydraulic fluid level and quality are adequate, and replace if necessary.

Electrical Systems

Inspect electrical connections for tightness, look for any damaged wires, and ensure all safety devices are functioning properly.

Calibration

Regularly calibrate the machine's measuring equipment to ensure production accuracy.

Operator Training

Ensure operators are properly trained in the correct operation and safety procedures of the machine.

Maintenance Records

Keep detailed records of maintenance, including dates, work performed, and parts used.

Professional Services

Consider hiring professional technicians for regular inspections and maintenance.

Manufacturer's Guidelines

Always adhere to the maintenance and care instructions provided by the manufacturer, as different machines may have specific requirements.

1.Emergency Plan: Develop an emergency maintenance plan for quick response in case of machine failure.

2.Spare Parts Inventory: Keep an inventory of critical spare parts for quick replacement when needed.

3.Environmental Control: Ensure the operating environment of the machine meets the manufacturer's specifications regarding temperature, humidity, and dust levels.

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