A Pair of 18650 Holders: Keystone vs. Blossom

Today I have a short review of a pair of branded holders for 18650 batteries. One of my readers sent them to me for a comparative test and review, so now I can share the test results with you.



The Keystone was purchased from Mouser, and the Blossom from Taobao in China - link.
The first came in Mouser's familiar packaging, while the second was simply in a zip-lock bag.


At first glance, I'd say they're identical twins, though it later turned out that appearances can be deceiving.


The hands-on test showed that the holders are identical to each other, but very different from the cheap Chinese version. The Chinese one is made of something resembling hard polyethylene, while the material used in the holders reviewed here is less rigid and feels like relatively soft plastic. In other words, you can deform them, but it takes more effort.
The manufacturer's website lists the materials used:
Base: High Temp Nylon 46, UL 94V-0
Contacts: .012 (.30) Stainless Steel, Gold Plate (Flash)


Another visible difference: both holders take the batteries in a head-to-tail arrangement, with the positive end of one next to the negative end of the other. But the holders are mirror images of each other, so where one has a positive contact, the other has a negative one.


Both versions have markings on the bottom, but Keystone lists the model number (1048), while Blossom doesn't. However, online stores also list it as the Blossom 1048 Dual 18650 Battery Holder, so both holders share the same part number.
You can also see that the Keystone plastic has a rough texture, while the Blossom is smoother.


Since the two holders are exactly the same size, I'll include a screenshot from the Keystone datasheet, which shows all the details.


The holders are sized to fit batteries with either a flat positive terminal or a raised one.
The second type of battery is a pretty tight fit, and protected batteries are out of the question.
For testing, I tried batteries that were 65 and 66 mm long.


There is one difference, though: the Keystone (on the left) has pins on the bottom for securing the holder to a circuit board, while the Blossom has a smooth bottom.


These holders are designed for surface mounting, but there are actually a great many different versions available: for through-hole soldering or wire soldering, with or without battery retainers, and with different contact plating options.


You can browse the full catalog via this link.
To be fair, Keystone is the original brand, while Blossom is more of a clone. That's partly why they're so similar, though they also have quite a few cosmetic differences.
That's why I was able to find almost all the information I needed about Keystone, while Blossom mostly turns up in online stores.


As the inspection showed, these models are very similar, but they also have some noticeable differences. The contacts on the Keystone (top) protrude less than those on the Blossom. As a result, the battery goes in a little more easily.


That's not all: the Blossom contact plates are C-shaped, unlike the Keystone, which has a characteristic step in the plate.
The contact point between the plate and the battery terminal is almost in the center of the terminal on the Keystone, while on the Blossom it's shifted all the way to the bottom. For example, the battery's positive terminal catches on the contact almost at its edge.
I couldn't get a photo, so you'll have to take my word for it.


At a quick glance, the terminals look identical.


But look closely or run your finger along the terminal, and you'll notice stamping defects on the Blossom (left), in the form of a characteristic ridge along the edge. A small detail, but it gives you an idea of the manufacturing shortcomings.


Also, Blossom (on the left again) has visible signs of rough finishing on the contacts, while I have no complaints about Keystone in this respect.


Just before the tests, and mostly out of curiosity, I weighed both holders. As it turned out, the right tail is longer Keystone is almost a gram heavier :)


I spent some time thinking about how to test the holders so the results would be as clear as possible and, just as importantly, accurate.
In the end, I used four 18650 batteries, a multimeter, and an electronic load. I used the load to draw the required current and the multimeter to measure the voltage drop across the contacts. Of course, I could simply have measured the contact resistance, but in my opinion, measuring under a high current is more accurate. And, to make the test even more realistic, I left the batteries installed in the holders for a couple of weeks to at least somewhat simulate the effect of "aging".
The situation was made worse by the fact that the holders' rated and maximum current capacities aren't specified anywhere.


To start with, the setup looked like this, as shown in the photo. One of the multimeter probes was clamped to the load cable with an "alligator clip".


The test was run at three current levels. First, I checked the voltage drop at the battery's negative terminal, then at the positive terminal.
So, Keystone is on the left and Blossom on the right. Three tests each, at 5, 10, and 15 A.


The same test, but at the battery's positive contact.


The test results made me question the method a little, so I changed the connection to the holder's tab, simply wrapping the probe wire around it closer to the body.
But nothing changed; the results were the same as above. At 15 A, Keystone's contacts heated up noticeably, which is understandable: in this mode, they were dissipating about 2 W! Blossom's contacts, on the other hand, were dissipating only about 0.6 W.


Positive contact.


But once I started the experiment, I decided to see it through and changed the connection setup for a third time. There was no way this one could be wrong.
One probe touches the battery's negative contact, while the other is inserted into the gap between the body and the holder's tab. This way, I almost eliminated the effect of the tab's cross-section by connecting closer to the contact point.


I didn't test different currents this time; I simply applied a 10 A load once. As they say, the results speak for themselves: Blossom came out ahead again.


Here are the brief takeaways from the tests.
Keystone is better made, although its housing material is rougher.
Blossom, on the other hand, has the telltale traits of a "clone", such as poorer contact finishing.

But the test results surprised me a little: Blossom has a noticeably lower voltage drop, which means it can handle 10 A continuously and 15 A for short periods. I wouldn't recommend using Keystone above 5 A continuously or 7–8 A for short periods.
Overloading can gradually degrade the spring properties of the contacts and, as a result, increase their losses.

If we look at why the more "branded" holder performed worse than the clone, one possible explanation is that Blossom's contacts press harder. I mentioned this near the beginning.
In my opinion, Keystone is better suited to low currents and is better made, but for higher load currents I'd choose Blossom. On the other hand, if you change batteries often, Blossom is less convenient because its contacts are stiffer.

That's all from me. I hope you found the review useful. As usual, I look forward to your comments and questions.