TrustFire 14500-size batteries and a little DIY.

At work, we have quite a few portable radios, powered by Ni-MH batteries. They’re charged any old way, so the batteries fail quickly. We ordered lithium batteries as replacements; if you’re interested, read on.

At first I looked for replacement batteries made from prismatic cells, but then I happened to notice that 14500-size lithium batteries are available, and they’d fit in place of the Ni-MH batteries of the same size. So I decided to order some and try the swap.
More on the replacement later; first, the usual introduction and description.

The batteries arrived pretty quickly (I’m waiting for another package that was sent a week earlier, but it still hasn’t arrived, while I’ve already had a chance to use these batteries)—in about 18 days.
They came in a regular yellow envelope.


Inside were a bubble-wrap bag and a zip-lock bag, though I don’t think these batteries are all that easy to damage.


The batteries are packed in pairs (I ordered 2 lots, but more on that later).
There’s a holographic sticker; everything looks nice and branded.


The batteries don’t just claim to have protection circuits—they actually do.


And now things get more interesting.
To start with, the batteries differ slightly in color. One pair is darker, the other lighter. You can’t see it in the photo, so I’ll show the other differences below.



In short:
First pair — 51.7 x 14.3, pair weight 40 grams.
Second pair — 51.0 x 14.0, pair weight 42 grams.

There’s a clear difference, even if it’s small.
But dimensions are one thing; what’s much more interesting is their actual capacity.
Remembering the questions and doubts readers raised during my previous battery review, this time I decided to take a more serious approach.
I took the batteries to a friend who does this professionally. He labeled them and took them away for testing.


In short, testing showed the following capacities.
1 — Fail! Low capacity; Capacity=640.6 mAh (71.2% rated)
2 — Fail! Low capacity; Capacity=666.3 mAh (74.0% rated)
3 — Pass! Capacity=787.7 mAh (87.5% rated)
4 — Pass! Capacity=779.3 mAh (86.6% rated)

Batteries 1 and 2 are larger and lighter, while batteries 3 and 4 are smaller and heavier.

That brings me to what I actually wanted to use them for.


Next, some photos of the process with comments.

Here's the radio battery itself.


Inside are 6 Ni-MH cells connected in series, providing 7.2 V. The voltage is close to that of two lithium batteries, which is what gave me the idea to replace them.


Since I needed somewhere to fit the charge-control board, I decided to use 4 cells instead of 6. The board goes in the space left over, which is why I made it as wide as the battery.


The board is made, and the components are selected.


Here’s what it looked like after soldering. The inductor is a bit oversized, but I used the one I had on hand.
These inductors and diodes have already appeared in one of my reviews.


I took out the old batteries, soldered wires onto the new ones, and got them ready to install.
A separate note on choosing cells for the pack.
I had two possible combinations of battery pairs.
Either 1445 mAh + 1427 mAh, or 1453 + 1419. I chose the first option because the capacities are the closest match (the closer the capacities in a pair, the better the balance in the battery).
I also removed the diode that protects against a short circuit at the charger terminals; the charging board now provides that protection.


The terminals that power the radio itself are on the back cover.
I don't know what the assemblers were thinking, but the black wire goes to positive and the red one to negative.


Since I thought that was wrong, I rewired it in what seemed like the more logical way. It was also more convenient for me given the wire lengths.


I installed the new batteries. They fit very tightly, even though when soldering I chose them so that one battery in the pack would be longer and the other shorter; otherwise they wouldn't fit. I tried to solder them without increasing the overall length of the pack.


With the board held in the air, I soldered all the wires: the input from the charging terminals, the wires from the battery packs (positive, negative, and midpoint), and the output to the radio terminals.


Then I put the board back in place. The inside of the case is lined with double-sided tape, so the board is simply stuck on. There are no components on the back, but it's best to wipe the board with alcohol so it sticks better.


That's it. Close the case and put it on charge.


After the modification, I got a capacity of about 1430 mAh. The battery is labeled 1500, but I think the actual capacity was lower, so formally the battery's capacity hasn't changed. It should, however, be less fussy about improper use.
The battery is also lighter.
Before —


After


I also want to say a few words about the charger.
I've never seen such cost-cutting. Imagine an “intelligent” charger built from a diode, an LED, and two resistors.


The back is completely blank.


Although I wasn't planning to modify the charger, I think I'll rework it to provide a proper charge-complete indicator. But that's a whole other story.

Datasheets, schematic, circuit board here.


Summary.
It's hard to say whether these are good batteries or not.
The first part of the review was originally going to be shorter, but since I ended up with different batteries, I had to include more photos and descriptions.
The first pair isn't very good quality (capacity is under 75%), but the second pair is quite decent, with capacity at almost 86% of the rated value. Still, the batteries in each package have very similar characteristics.
So they can certainly be used in pairs, but batteries from different batches should only be used after testing.
The batteries have a protection circuit board, as claimed.
All in all, I tried to provide as much information as possible. Whether to buy them is up to you.

I hope this information is useful.
The batteries for testing and review were provided free of charge by the chinabuye store.