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Not so sure on the relevance of that plot. This is what Samsung say: So after just 300 cycles, capacity is down to ~70%. 4.1 V charging would be a lot better than this after only 300 cycles. However, as I have said previously, unless you are sufficiently technically minded, have the time and...

Early batteries were not made so consistently, so balancing was more of an issue. These days, cells can go hundreds of cycles without going out of balance and I have observed this myself. It doesn't mean the balance function is redundant, it is an insurance policy.

Because if you start with quality matched cells it can take hundreds of cycles for them to go out of balance. Also, he has already said he checks for balance regularly with his set up.

But how do you know that it's high if the DVM isn't calibrated? The charger may be fine and your meter could be out.

Storage isn't the issue, we were talking about charging?

There are some fancy ones around, some where you can even customise your own voltage for balancing with an app etc, but most don't. Look at the specs of your average BMS. Balance starts at 4.18 V. Why don't you pull a pack apart, deliberately discharge one bank slightly, charge the pack to less...

No, you do need an absolute, not relative value. You have only a 200 mV window between not balancing (less than 41.8 V) and cell overcharging (over 42 V). My feeling is that you want an accuracy of at least 40 mV to be confident you are in the right range. So then if your DVM measures a reading...

Can you give an example of a £20 to £30 DVM with 0.01% accuracy in the 200 V range?

I haven't looked for a while. When I get the chance I'll dig out the scope and look into it. From memory, when I last looked it was quite small. Chargers have inbuilt filtering to remove most ripple. Won't get a chance this week though.

Not in my experience. Lots of multimeters I've tested from a range of manufacturers are not accurate enough for our purposes over the 200 V range, regardless of the number of digits. +/-1% is a typically quoted accuracy level, which can be 0.42 V at 42 V. Some are only +/-2% and some I've tested...

Interesting to see how the accuracy varies over a range of just 10V. How did you set the charger 0.5 V lower? With the voltage 0.5 V lower, it's likely that you will not get to 4.18V/cell needed for balancing to occur. Are you worried about that?

From the chargers I've looked at, ripple hasn't been such a problem, drift has been more noticeable, especially in conditions where there is no load, but only around 50 mV or so. If ripple is a concern you could always put a capacitor of a reasonable size across the output.

One of the most important tools in an e-biker's toolbox is a multimeter (aka Digital Volt Meter or DVM). It is sometimes needed to be used to measure voltages with a high degree of accuracy, for example looking at the output of a charger to tell if it is set up to the correct voltage or not...

You mentioned in one of your posts squirting WD40 into the motor. Don't ever do that, the risk is you will dissolve the grease in the bearings, leaving them to run dry.

It seems unusual to have just a single BUS line. Most protocols normally have at least two connections. I wonder if it is some form or variation of 1-wire coms: https://ww1.microchip.com/downloads/en/appnotes/01199a.pdf

Nope, that's nonsense. You'd get a different answer every time, depending on the size of the load (in terms of what you would measure between 4.2 and 4.1 V - the discharge curve is highly non linear in this region and what you see under load is highly impacted by the size of the applied load)...

It's a discharge test, not a charge test?? Discharge curves are produced under load. They do not stop at 4.1 V/cell and wait for the battery to equilibrate. Capacity under open circuit conditions between 4.2 and 4.1 V is not something they are interested in showing.

My guess is that the board waits for a high signal on the BUS, then transmits some data, then waits for the BUS to go high again and then sends updated data.

Not that simple unfortunately :(

Might be worth replacing the thermistor temporarily with a potentiometer so you don't have to keep heating it. If you need to encode a range of say 100 C with 1 Deg resolution, you'd need at least 7 bits? Or maybe it doesn't even need to measure the actual temp and it just gives a good/no good...