I tend to agree that all I really need is a balancer, but my challenge has been finding one that works.
When I started learning for this project, I didn't want to spend much before I knew what I was doing. I started with four mismatched cells from a blown pack and started experimenting. I bought a MK3x4SMT Digital Lithium Regulator from Manzanita Micro for around $200. While I wished I could have made heads or tails out of it, I couldn't figure out how to talk to it through a PC or get the settings right. The online video explains how to connect wires in order. The printed documentation is pretty sophisticated. My missing knowledge fell neatly between those cracks. After beating my head against the technical documentation gap and online forums for far too long, I gave up on it.
Next, I bought a simple Capacitor-4S-30A-BMS from EVAssemble. It cost $27 plus about twice that in shipping and a month of waiting. No adjustments, it just worked perfectly. After hooking up an old laptop power supply to the pack and watching the voltages from the CellLog8s, I was amazed to see all four wildly mismatched cells come into alighnment and settle in within 10mv of each other and stay there. Now that I had spent some education money to get up to speed on what balancers would work for me, I was ready to spend the real money on my pack. Based on my experiences, you can guess what I bought:
16 x 40152 Headway cells from Manzanita Micro. Given the shipping costs and wait time from China, Manzanita Micro was far cheaper and faster than any Chinese alternative, and they brought them to the Seattle Electric Vehicle Association meeting so I didn't have to pay for shipping or wait anyhow. Big win.
Next, I bought a Capacitor-16S-30A-BMS from EVAssemble. While the BMS arrived in a few weeks, the charger took another month to arrive. Good thing this is a side hobby project and not transportation I need to depend on. After connecting everything according to the diagram, the BMS turned out to be a dud. A few of the cells shot up far far beyond what Headway would ever warranty. I caught it before anything exploded and pulled the plug. The BMS failed to do any part of it's job. No balancing, no overcharge cell protection, failed the undervoltage test. Given the perfect performance of the Capacitor-4S-30A-BMS from EVAssemble, I was hoping for equally great performance from the 16S-30A-BMS, but luck wasn't on my side this time. Given the shipping costs and lead times, it wasn't even worth attempting to begin a conversation about warranty issues. Buying directly from China without a US intermediary for warranty coverage is buyer beware. I lost on that gamble, but only $100 or so including shipping so it's pretty cheap as far as life lesson expenses go.
Given that this scoot project is going to see some heavy real-world use, I couldn't afford to fry my pack because I saved a few bucks on a BMS. While the Manzanita Micro had baffled me earlier, it was worth doubling down on them. So, I bought the two MK3x8 Digital Lithium Regulators, the Dongle Terminator and some harnesses for about $800. About 8 times the price of the EVAssemble equivalent, but clearly more sophisticated and with higher component quality and much more rugged construction with real screw mounting options. After almost frying my 16 Headway cells, I couldn't risk it again.
It took a lot of hours to figure out how to send commands to the MK3x8 Digital Lithium Regulators correctly and get the monitoring working right with a laptop computer, but eventually I figured it out. Perhaps one day, I'll make a YouTube video so others can learn how to talk to them too.
So, you are correct in that I only need something like the Headway or EVAssemble balancer. That would be my preference due to the price, size and heat challenges with the Manzanita Micro BMS units. But my bigger need is for a BMS that is of high quality, can be bolted down properly so it doesn't come loose on a bouncy two wheeled jalopy, and is dependable enough for me to risk my investment in batteries and not burn down my house. Given my short history in these lessons, I can't say I'd make different choices than the Headway40162 Cells, the CellLog8s and the Manzanita Micro MK3x8 Digital Lithium Regulators. I reserve the right to keep learning as time goes on and change my mind.