Everything you need to know about 9V Li-ion batteries: Full review & teardown 

You can learn more from these little teardown vids then you can watching the product video. 💯

Great, I especially liked the bit at the end about the two different voltage models, super helpful

Seems that these will be my new source for cheap project cells. Thank you for this video. ❤ that !

VERY INTERESTING AND INFORMATIVE! THANKS, I ALWAYS ENJOY YOUR PRESENTATIONS AND LOOK FORWARD TO MANY MORE.-----MAYBE DO SOME MORE DUMPSTER DIVING TO REPLENISH LOW VOLTAGE/AMPERAGE CUBES? TELL ME WHERE TO GO AND I WILL FIND SOME FOR YOU?

Placing two batteries in series appears to be more efficient than using a boost converter. But it won't be 9 volts, it will be a maximum of 8.4 volts.

Good video and very informative THANKS

Thanks for this review as I've been wondering about these products. Rated capacity is always lower, sometimes a lot lower, than the actual mAh capacity it takes to fully charge due to inefficiencies in the discharge process from internal resistance and switching regulators. For example, you might purchase a Li ion pack rated at 10,000 mAh which has an efficiency of 60% due to regulator losses and actually get 6,000 mAh out in use. The efficiency of the series 2-cell model is pretty high at 82%. I'm guessing the efficiency of the single cell w/ boost converter would be quite a bit lower; typically as low as 65% in my experience. So, for example, if each of the two types is rated at 900 mAh, one would deliver 738 mAh of useable current and the other only 585. Despite the higher price, I like the constant voltage feature of the USB version and convenience of charging, but I'm just wondering how these two would compare in efficiency -- actually mAh out versus what is put in to charge them. I may by one of the USB from Amazon and measure it, and if so I'll send you the results.

Very interesting analysis.....thank you.

I like this one! Good review on this particular brand. what made you choose this brand? Are there others that are not so good?

Interesting, it looks like 2 of my cheap drone batteries. I wonder if i could use them as replacements for it.

If the protection chip is indeed equivalent to the DW01, then these batteries are not safe. The DW01 is only suitable for protecting a single cell (1S battery) as mentioned in its datasheet. It cannot provide per-cell protection from overcharge and overdischarge in a series battery. It may at best be providing protection for the 2S pack as a whole using a voltage divider, or for just one of the two cells. So it will not prevent each individual cell from being overcharged or overdischarged unless both cells have exactly the same voltage (which is unrealistic in the long term). There is no balancing circuitry either so the cells will become more and more unbalanced as the battery is charged/discharged. In the test you made with the intention to verify the overdischarge protection, you actually triggered the overcurrent protection. You can usually tell the difference by checking the open circuit voltage of the battery. In case the overdischarge protection is active, you will get no output from the battery, even for a tiny load such as your voltmeter. In case of overcurrent protection, the output will shut off only once you connect a large enough load. Perhaps consider making an update video to clarify these errors so that your viewers are better informed. Thank you for your effort to make an informational video and have a great day.

BMS always saves the battery

you got 517mah capacity but the label on the outside of the battery pack says 600mah with 9 VOLTS!

Ur so cool, man!