[Review] XTAR 1.5V AAA rechargeable batteries

Batteries and Chargers Rechargeable Batteries
1

Alkaline batteries easily leak unexpectedly and are bad for the environment. NiMH batteries (preferably the LSD variants) are better in almost all aspects: Rechargeable hundreds or thousands of times, higher current and they don’t leak. But the downside is that their voltage is more around 1.2V instead of 1.5V. This causes some devices to show an early battery warning or to not work at all.

Li-ion based 1.5V batteries try to fill this gap: They are rechargeable Li-ion cells with an integrated step-down converter to provide constant 1.5V over the full capacity of the battery.

XTAR has sent me a set of their new 1.5V AAA batteries for a review.

This review is also available in German on my website: SammysHP Blog › XTAR 1,5 V Akkus



Overview

The set contains four 1.5V AAA batteries, a “charger”, a USB-C cable and a “manual”. The batteries were rattling in the box when they arrived.



The “manual” includes ten languages (EN, DE, FR, IT, ES, GR, TR, RU, CN, PL), but not much content. If you skip all parts about warranty and where to find the USB-C port, it is basically: Plug in the USB cable, put in the batteries and they will charge.


The batteries

They look like regular AAA batteries: flat negative pole, button-top positive pole. Hidden at the positive side is the step-down converter providing constant 1.5V from the 2.8–4.2V of the Li-ion battery. It also includes the charging circuit and a green status LED.

As an example I tested the XTAR batteries in my UNI-T UT210E clamp meter. While it works with NiMH batteries, it will show a battery warning even with almost full NiMH batteries. Because the XTAR batteries deliver 1.5V all the time, the battery indicator will not be shown. Great.

But you still get a battery warning for the XTAR batteries at the end. How is that possible? When the batteries are almost empty, the voltage will jump from 1.5V to 1.08V – what a great addition!



Another device I used for testing is a radio clock with external temperature sensors. At about 1.3V the display starts to fade, at 1.2V it is almost unreadable. And that’s the normal voltage of NiMH batteries. With the XTAR batteries the contrast is always perfect. At the end of discharge the display would be unreadable, but the alarm would still work.



But there is a problem: The clock signal is only received when I bring the clock outside and the temperature sensors are not received at all! There must be some kind of interference with the batteries.

When checking the noise of the voltage with an oscilloscope at different loads it becomes obvious. I guess there was not enough room for proper filtering, but this limits the use of the batteries. It is likely they will cause trouble when used in something that receives radio signals.



I tested the discharge at currents ranging from 600mA to 1600mA. Even at the highest load they provide 1.5V, but they will also heat up significantly. My test was open on the bench, so it will become a much bigger problem enclosed in devices.

The claimed capacity of 1.2Wh is mostly achieved, depending of the discharge rate. When the battery is empty, the voltage will slowly toggle between 0V and 1.08V and the indicator LED is blinking.



I was not able to measure the self discharge in the short time. Unfortunately XTAR doesn’t provide that information either.


The charger

You cannot charge the XTAR 1.5V batteries in a normal charger. You have to use the official XTAR LC4 “charger” – more or less just an adapter from USB to the battery terminals.

All positive and negative contacts are connected in parallel and are at 5V. There is a USB-C port at the back of the device.



The actual charging circuit is integrated in the batteries themselves. It charges the battery at 250mA in about 1:15h. During charging the status LED blinks green, which gets annoying when you charge all four batteries at the same time. Better place the charger not in direct sight.



A hole in the underside of the charger allows for an easy removal of the batteries. Its construction is solid and well made. I was not able to open it because it is either welded or clipped together.


Conclusion

The XTAR 1.5V batteries fill a gap between Alkaline, NiMH and Li-ion batteries. They are a good solution when you want to use rechargeable batteries in a device that has trouble with the lower voltage of NiMH batteries.

But you have to be careful if the device is compatible with the noisy voltage of the XTAR batteries. It is likely they will cause trouble when used in something that receives radio signals.

Product description at xtar.cc

2

I would have maybe been interested in AA version for handheld Garmin GPS, but that interference looks like it would cause havoc with the GPS signal.

Apologies if I missed the info, but do XTAR provide max rated discharge current?

3

That works pretty good with NiMH in my experience.

It’s not mentioned on the box, manual or battery itself.

4

Thanks for the sophisticated review. Any idea how they compare to TenaVolts 1.5v AA Li-Ion cells & charger?

slmjim

5

These are the first batteries with integrated step-down converter that I’ve got. Here is some good info about the TenaVolts: https://www.reddit.com/r/AAMasterRace/comments/chzxhv/review_teardown_tenavolts_aa_size_15v_liion/

6

Not that it should interfere but did you test the clamp function but did you test the clamp function on AC and DC and the non-contact function. I have the same meter and it sits in the truck year-round most of the time. I have to do something other than alkaline. Either energize lithium or something like this. I think these would make sense for people that are dealing with a lot of constant heavy use.

7

Yes, everything seems to work fine.

I have lithium primaries in devices that require very little current or that I use very rarely. They also have benefits if you use the devices below 0 °C (the step-down converter Li-ion batteries will suffer from the same issues as regular Li-ion batteries).

I had hoped to use these Li-ion based AAA batteries in devices that I use often and which have issues with regular NiMH batteries (which are by far less expensive).

8

Interference due to the voltage converter is common in this kind of battery. I’ve not heard of your Garmin application, but for regular audio application (radio, microphone and similar) they don’t work. I’d be skeptical. Also, see below about capacity. Know what you WANT vs NEED.

I’m AMAZED they handled 1.6A current. I have tried several (3 brands actually) 1.5v AAA and they start to fail soon after 0.5A, usually not making it past 0.7A. XTAR is a bit more ‘solid’ than a lot of these ‘no name’ Chinese companies but I wouldn’t believe marketing specs until verified. The claims on these 1.5v batteries are generally very inflated.
I have a dozen Tenavolt AA that I generally like, and they pretty much max out at 1.6A and 1600mAh.

Generally they don’t give mAh, instead mWh. Best case scenario:
1200mWh/3.7v = 325mAh
I’m going to give these 1050mWh from the graph: 1050/3.7=285mAh
An average NiMh = 700+mAh. There is simply NO WAY to put the same kind of capacity in that little can with the electronics as a NiMh.
So….useful if you NEED 1.5v. Otherwise, not so sure.
The cost premium is also an issue.

9

At high discharge they were able to deliver about 1000 mWh, on very low discharge probably almost the claimed 1200 mWh. A 750 mAh NiMH has about 900 mWh. So the Li-ion based batteries have even a higher capacity.

Charging was almost 300 mAh, so even that makes mostly sense.

10

I wonder how they will behave in rc toys, those things suck up batteries pretty fast. or walkie talkies, wonder if they interfere with their operations.

I've tried similar AA, no names, just got them on ebay and amazon, was pretty much disappointed, they either did not last long, or had horrible self discharge rates

11

Wonder what the conversion loss is? I think an issue is the usable energy for the desired application.
I’ve found a few useful applications for the AA Tenavolt. I haven’t found any “real world” uses for the 1.5v AAA. So far they just end up in remotes as I don’t have anything that requires the sustained voltage in that size.

Very good review. Don’t see many for this kind of battery.

12

Yeh, I got a clock/thermometer that takes 3 AAAs. 1 is for something and 2 are for something else. Forgot which is for the backlight-only and which is for the digital innards.

Either way, the backlight always works fine, as it’s not picky, but when I switched from alkaleaks to… think they were Tenavolts… the buttons to set the clock, etc., just plain wouldn’t work. It kept time, starting from 12:00:00 of course, but you couldn’t set the time, switch from C/F or F/C, nuttin’.

Just checked, my wx base-station has 3 alkaleaks that haven’t exploded yet, and I think the remote has NiMH cells in it, which is why it always had a reliable connection.

Still, these doodads are good for teevee remotes, wireless mice, etc., as they usually work fine in those kinds of things.

13

Can these AAA batteries be completely drain or like Li Ion there’s a low voltage limit that can’t go under?

14

Internal electronics include overcharge+undercharge protection, and voltage conversion. So no, if the electronics are working properly, the Lion cell is protected.
The “charger” is merely USB 1.5v input (some of them have a USB port built in). The actual charging is handled with the battery electronics NOT the external ‘charger’.
One of the problems is the electronics take up space, so……less space for the actual battery.

IMO, the versions WITHOUT a USB port (Tenavolt, XTAR) might/maybe be a little better simply by having a bit more space to put actual battery chemicals inside. That doesn’t meant they DO that, but they can’t if there is a USB port in the way.

15

Oh right, totally forgot to mention that! I noticed as well that the buttons worked unreliable in the clock with the XTAR batteries.

16

What if the protection circuit fails, and the device drains the battery(ies). Is there a chance for a fire or worst? I don’t want to constantly check with a DMM for a voltage reading.

With the charging circuit in the battery. Will it fit (Due to size) in all devices the accepts AAA batteries?

17

IF it fails. It’s also possible that the charging circuit won’t work anymore in that case. But this can happen with any device that uses Li-ion batteries.

The XTAR batteries have a length of 44.5 mm, the same length as my other AAA batteries. The diameter is 10.3 mm, exactly like other AAA. So yes, they fit all devices that accept other AAA batteries.

18

If you DRAIN the battery completely, there is no energy to start a fire.(I don’t suggest throwing it in a fire though to check. :person_facepalming: ) I have not heard of any problem of this sort associated with them.
Charging is a larger potential risk. Then you are putting energy IN. ANY Lion with protection (or not) plus charger that you rely on without any oversight at all has a similar risk associated with using it.
Note - the amount of lithium in a AAA is……tiny……Probably 1tsp of gasoline is more dangerous.

Size should be fine, but I haven’t used this brand. All the other ones I have seem well made and don’t have a fit problem.

FWIW I have a bunch of 9v (2S) PowerUS batteries that have been used HARD for over 10 years and are still working fine. They use a similar circuit. I’ve had one fail. No danger, it became a ‘dud’ and would no longer charge.
I also have a few 9v EBL. They simply aren’t as good (worse capacity and losing it faster), but I don’t consider them more dangerous.

19

I have used li-ion cell step-up voltage to 9V in my IR gun, but the battery lasted way lower than I expected.

I suspected it may be due to combined effects of the following two:

  1. inefficiency in the step-up
  2. parasitic drain of my IR gun.
    I thought the drain was small enough, but the battery had to consume power to step-up the voltage causing overall inefficiency.

For the same reason, I think these step-down batteries may be good for med-to-high power applications, but not very good for low power applications, such as clocks and remote controllers. What are your thoughts?

20

The step-down converter is running all the time. Depending on the load it fires more often. So I’d say it doesn’t matter much if the batteries are used at low power or just sitting on the shelf. Question is, how long will they last if not used at all?