Batteries for Uniden radios, BP-38 BP-40

Not long ago, I was asked to buy some batteries for radios. It seemed simple enough: I found a suitable listing on AliExpress, placed the order, and picked it up at the post office a while later. But was everything really as good as it seemed?
Today’s review is a “micro” one. I’ll try to keep it short and stick to the facts.



These batteries are designed for some fairly popular Uniden radios, like these.


List of compatible radio models:
GMR3689, GMR3699,
GMR1838, GMR1038, GMR1048, GMR1438, GMR1448, GMR1558, GMR1595
GMR2238, GMR2838, GMR2240, GMR2872, GMR2875, GMR2059, GMR2089, GMR2099, GMR2889
GMR635, GMR638,
GMR645, GMR648, GMR680,
GMR855, GMR885, GMR895, GMRS380, GMRS680, TR640

I haven’t actually held one in my hands; I ordered it just by the name. But as far as I can tell, the original batteries look something like this.


People sometimes modify these a bit, printing an adapter for the battery compartment and connecting it to a power bank. But in my case, I needed to buy the batteries themselves.



And this is where the story really begins. I initially needed 10 batteries, but they were sold in lots of 12. I figured, fine, I’d have two spares. No big deal.
But something went wrong when I placed the order. Maybe the payment didn’t go through at first, or maybe it was something else—I don’t remember now. In the end, I accidentally placed two orders.
This has happened to me before. The solution is simple: cancel the order, selecting “other reasons” or “I no longer need this order,” and that’s it. Sometimes I also message the seller to say I accidentally ordered one lot and ask them to cancel it. The seller has always canceled the order in question.
This time, I thought I’d done the same thing, but when I checked my orders the next day, I saw that it was still marked as awaiting shipment. I canceled it, and to make absolutely sure, I messaged the seller: “I placed order 12345789 by mistake. Please cancel it.”
No reply. Two days later, both orders changed status to “Shipped.” I messaged the seller again: “Why did you ship it? I asked you to cancel it. I only need one order :(


In the end, I picked up two parcels at the post office. The packaging was certainly better than in the photo: wrapped in bubble wrap, with each battery in its own bag. But still, I’d only ordered one...


I’m now the “happy” owner of 24 batteries instead of 12, even though I only needed 10. And I paid for all 24—about $80 in total.


The batteries—or rather, battery packs—look pretty good. I’ve ordered ones like these before, but that was quite a while ago.


The product page and the battery label specify the type, a voltage of 4.8 V, and a capacity of 700 mAh. Each battery has four terminals: two to power the radio and two for connecting the charger. They’re different from each other.


What pleased me even more were the specifications listed on the product page:
1. 100% compatible with the original battery manufacturer.
2. Microprocessor-controlled charging.
3. Reverse-polarity protection.
4. Chemistry: Ni-MH
5. Voltage: 4.8 V
6. Capacity: 700 mAh
7. Weight: 100 g

I’ve bolded the most interesting claims :) The “reverse-polarity protection” is just protection against connecting the battery backwards. As for the rest—what microprocessor are we talking about, not to mention a weight of 100 grams...


About half the batteries have a little “nub” in the middle of the back. The battery shown above has one too.


The “reverse-polarity protection” is a diode connected between the positive terminal on the side and the positive terminal on the end. It’s there to prevent a short circuit between the exposed terminals used to connect the charger. And that’s the whole protection circuit.


So, what about one of the battery’s main specifications—its capacity? (I can’t test its longevity yet.)
I grab the first battery out of the box, connect it to an electronic load, set up the test program, and start it.


The test program was as follows:
1. Green — pre-discharge at 150 mA down to 0.9 V per cell.
2. Blue — charge at 150 mA to 5.72 V (1.43 V per cell), with cutoff when the current drops to 100 mA (the load won’t let me set it any lower).
3. Red — discharge at 150 mA down to 0.9 V per cell.
4. Blue — charging at 200 mA to 5.72 V, to compare the capacity change after one cycle.

In the end, before even reaching step 4, I got 230 mAh from the battery, while the pre-discharge removed just 1 mAh.


I stopped the test and ran it again. Since the battery had been only lightly charged, the first discharge came out to 19 mAh, which is normal in this case.
I ran the test a second time to see if the battery might “wake up”; unlike lithium batteries, nickel batteries can show this effect.

Unfortunately, instead of 230 mAh I got just 246 mAh, and judging by the capacity used during charging, it won't get any better: the first and second charges both took the same 280 mAh.


Feeling pretty disappointed—after all, I paid 80 dollars and ended up with 24 batteries whose capacity is three times lower than advertised—I take a second battery from the box and run the same test.
This one is a completely different story: the pre-discharge took 204 mAh (the charge it came with from the factory), and the capacity delivered was 458 mAh. I think it would actually be closer to 500 mAh, since the cutoff should clearly be set below 100 mA.


I take a couple of batteries from another box. The results are about the same as for the second battery in the previous test: 456–469 mAh. As far as I know, this is perfectly normal for non-brand-name batteries, and as I wrote above, their actual capacity is closer to 500 mAh.



After the tests, I decided to check the internal resistance. The first four batteries are labeled according to the tests above; the last two were picked at random from the box.
Surprisingly, the first battery has the lowest internal resistance, 148 mΩ, while the three good ones measured 157–170 mΩ. A pair of “unconditioned” batteries measured even higher, up to 190 mΩ, but that's perfectly normal here: a couple of full charge/discharge cycles should improve this characteristic a little.


That's it for the tests. All I can say is that for relatively little money, you get a clone—though who would have expected otherwise? The actual capacity is around 500 mAh, versus the advertised 700. That's low for a genuine battery, but perfectly normal for a clone. Still, you might get a defective one. In my case, it was 1 out of 24; I checked the other batteries by loading them at 0.5 A and watching the voltage sag, and they all behaved like batteries 2, 3, and 4.

That's about it. I hope you found the review useful. As usual, I'm happy to answer questions. I'll try to get the seller to address the out-of-spec parameters and defects.