Keeppower 18350 Battery Test

Our customers asked for an 18350. We searched. And Searched. And here it is…

This is the UH1835P – An 18350 10A 1200mAh cell from Keeppower

Why so long?

With most larger manufacturers (Samsung, Sony, LG, etc) now concentrating their efforts on 21700 form factor cells and other non-cylindrical products (so much so that Sony have now completely handed off all of their 18650 manufacturing to Murata), anything smaller than an 18650 is now almost solely manufactured by unknown, small Chinese manufacturers – and this poses a problem. Historically, they’ve never been that great. They have high production wastage (cells that come off the production line not meeting performance requirements) and are prone to change at any time. Some of this wastage can occasionally make it onto the market, leading to poor performing products being sold and damaging brand reputation for these fledgling businesses. They also manufacturer in much, much smaller volume and so where demand suddenly spikes, customers and suppliers are often left with very long lead times or not being able to get the product at all.

Why Keeppower?

Keeppower have been in business for many years and we have a good working relationship. They built a brand around supplying mostly protected cells for the torch market and are generally very up front about what cell they’re using under their own black wraps. We’ve been supplying their protected cells for a number of years without fault. Their ratings mostly run in line with the manufacturer ratings for the cells they use and their build and overall product quality is in our opinion the best of the Chinese re-wrapping companies.

The Test

This cell has done the rounds a bit and wears wraps from Efest, Aspire, Vapcell and a few others. Not surprising when you consider that as I mentioned at the start, very few companies are still manufacturing the 18350 form factor. Yong De Li New Energy Co. is the manufacturer for this particular cell. Interestingly (and perhaps very honestly), Keeppower have done the right thing in ignoring YDL’s factory rating of 15A maximum discharge and instead opted for their own 10A maximum discharge rating. It does also have a secondary “Max Pulse 15A” rating on the wrap but clearly states “10 Max Constant”. Its well known that almost all cells can handle much more than their rated maximum if used in short bursts but with a lack of international/industry standard in Pulse Discharges, we’ll leave that alone.

Despite charging to a full 4.2V and discharging at 0.2C (240mA) all the way down to 2.5V, I couldn’t squeeze the 1200mAh rating on the wrap from either of the test samples from our newly arrived stock, managing only 1,054mAh and 1,087mAh. 1100mAh would have been a better rating to place on the wrap, but expect to see circa 1000mAh in normal use.

At their maximum discharge rating of 10A, voltage drop was quite substantial. Datapoint 2 (milliseconds after start) on the test shows that discharging at 10A saw the voltage drop straight to 3.76V and continuing to drop to around 3.2V at the more linear part of the curve. Although the temperature at this point was only 59’C, this is clearly at its limit. It did however, deliver 969mAh from this test, further backing the 1000mAh true capacity rating.

Overall this is a good cell, perhaps slightly overrated on capacity. The final temperature in testing at 5A was only 45’C and 71’C at 10A. I see no issue using the cells I tested at their 10A limit although I’m aware of others (Largely mooch, having had access to the same cell in other wraps) having tested these cells and found poor cell to cell Internal resistance consistency indicative of a small Chinese manufacturer which led them to a 9A rating. This isn’t unreasonable and its worth bearing in mind, but isn’t something we’ve found here.

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