This smart charger brought my dead camera batteries back to life – here’s how

The XTAR L4 Pro Pro is a USB smart charger that has been designed to work with AA and AAA batteries, as well as 18650 cells. What marks it out from other chargers of this type is the fact that it not only charges your AA and AAA batteries, but also has the additional functionality of being able to fully discharge the batteries as well as recharge them.

The reason it does this is essentially to help keep your batteries in good condition. Normally, when you put your batteries into a standard charger, they all charge at the same time, and the charger’s job is basically just to balance out the speed of the charging. With this particular charger, what you can do is discharge all of the cells and then recharge all of them. In doing so, it helps to keep the batteries fresh, as well as being able to highlight if there are any issues with a battery. In such cases, it actually shows an error with that particular battery.

Another nice touch is that, rather than just having an indicator or status LED that shows whether the batteries are charging, charged, or there’s an error, you get a very simple LCD that shows each of the batteries’ status. Once charging is complete, the charging icon changes from an animation with simple levels to a solid icon, showing that the charge has finished.

The LCD display also shows the charge level of each battery, with a maximum of five bars down to zero, showing what percentage of charge the battery has, either 20, 40, 60, 80, or 100%.

Obviously, if you’re out in the field taking pictures and you need to refresh your flash batteries, this is really useful, because you can quickly look at the display and pick the batteries that are up to 60 or 80%, so you know you’ve got a good few charges left.

So, whilst the XTAR L4 Pro is primarily an AA and AAA battery charger, with the added functionality of being able to refresh and discharge your batteries, it adds extra usability to this otherwise simple device.

First and foremost, this is a compact AA and AAA charger, and its size means it will easily fit into a side pocket of your camera backpack without adding too much bulk or weight.

It weighs just 88 g (without the AA batteries or the USB Type-C cable), and its dimensions are 10 cm × 8 cm × 2.5 cm.

The body of the charger is made entirely out of plastic, which is of decent quality. I wouldn’t say it’s high-end, but it’s a good mid-ground. On the front, you have the LCD that gives you all the display information, and just below the LCD is the function button. A longer press on this will switch you between the modes to charge, discharge, or refresh your batteries.

Below this are the four slots where you can insert either AA or AAA batteries, and it doesn’t matter what order you put these in. Placing the batteries into the charger, they are instantly recognised and appear on the LCD.

It’s also worth noting that, unlike some other chargers, the slots for the AAA batteries hold the batteries securely; they’re nice and tight and hold firmly in place.

On the back, there are four small feet that hold the charger a millimetre above the surface to allow some airflow through the system while charging. However, these feet are made from the same plastic as the outer casing, and when using the charger in the field, if the surface isn’t quite flat, the charger can slip because the feet aren’t rubber. This isn’t a major issue, but it’s worth noting.

The casing itself is made out of ABS plastic, essentially the same material as Lego, so when it comes to durability, it’s ideal. If you do drop it, it’s unlikely to have much of an effect.

One of my worries about AA and AAA chargers is that I have collected a vast range of different AA batteries over the years, and not all are the same chemistry or even charge rate. I have some Ni-Cad, some nickel metal hydride, and a few lithium iron AA batteries, all with their own separate chargers. However, with this charger, it doesn’t matter. As soon as I place any of those batteries into the charger, the chemistry of that particular battery is recognised, and the charger is smart enough to adjust the charge rate to match that battery type, even if all the other slots are filled with different chemistry batteries.

When it comes to more modern batteries like lithium-ion, if you don’t use them and they fully deplete, the battery can become useless. This charger is able to help revive overly discharged lithium batteries, which is extremely useful, as these rechargeable batteries can be expensive compared with standard nickel metal-hydride batteries.

To give the charger a test, the first thing I did was use another charger to charge up four AA batteries. Once they were fully charged, I put them into a flashgun and fired the flash at full power until the batteries were drained enough that the recycle time had extended to well over three seconds. As the batteries were relatively old, this happened after about 50 full-power flashes.

I then took the batteries out, put them into the XTAR charger, gave them a full charge, and then transferred them back into the flash. Again, I fired the flash at full power until the recycle time was over three seconds. I then put them back into the XTAR L4 Pro for another full charge, and this time I managed almost 64 full-power flashes, which is quite an improvement compared with the standard charger.

After a full discharge and recharge with the XTAR, I saw a significant uptick, with over 70 full-power flashes before I noticed the recycle time starting to slow down.

I also tried this with some old alkaline batteries that I have had for years, and again, I saw a marked improvement once they had been through this charger. This shows just how effective the refresh feature is.

When it comes to actually charging AA batteries, this charger performed exceptionally well. What I really liked, aside from the fact that it gave a bit more life to some of my old batteries, is that you have those three distinct functions: standard charge, refresh, and full discharge before charging. This gives you confidence that your batteries are in top condition before you head out.

The small LCD display is simple but useful, showing all the information you need, such as battery level rising or falling depending on whether you’re charging or discharging. It displays this information individually for each battery, so you always know which battery has reached full capacity and can be removed and used. Each slot operates independently, not as part of a pair like many other chargers.

Another advantage is that it’s a USB Type-C charger, which means you can take it out in the field without needing direct AC power. You can plug it into a power station or your computer if necessary. While it does take up to five hours to reach a full charge, I think that flexibility is more than worth it.

At the end of the test, I’m impressed with the feature set that the XTAR L4 Pro packs into such a small form. Considering the price and what you get, it is an extremely valuable package, offering higher-end features at a relatively budget price.

The build quality is okay, but the ABS casing does give it a good, solid feel, and the matt texture adds a little to the look and feel of the charger.

At this price, one thing really does stand out, the fact that it has those two additional features, refresh and discharge. These are features you would have paid quite a lot of money for in the past, but now you can get them for just under £15 or $15, which is incredible. What these two features do is help keep your AA and AAA batteries in top condition.

The fact that this charger will charge both your older NiCads, as well as more modern nickel metal hydride and lithium iron batteries, means you’re essentially getting three chargers in one, plus a charger that will show you the health of those batteries or even revive them in some cases.

While a charger might not be the most exciting accessory ever made, the L4 Pro certainly does the job and, for my money, is probably one of the best options at present for the price.