best battery charger for all types of batteries

Being able to charge all of my different types of rechargeable torch batteries were beginning to be a hassle. I have AA, AAA, lithium-Ion 18650, and the smaller LC 17500 batteries which all have their own chargers. So I needed a smart battery charger for all different types of batteries.

I had been using the world-renowned older Lacross smart BC-9009 charger which was great for the Eneloop AA and AAA batteries until it failed. Being able to see and set the charge rate is a real bonus. So I wanted something similar, that can also charge lithium-ion batteries as well.

This is when I came across the Opus BT-3100 Version 2 battery charger, and wow I am really impressed with it. So after a few months of use, I decided to do this review on the best AA, 18650 smart battery charger of 2018.

Best AA lithium battery charger

As a prepper, I just need a 12v Li-ion aa battery charger that has slots for multiple different types of batteries. This is where the Opus BT-C3100 version 2.2 comes to the rescue. The 12 volts input is the holy grail of usability. I can charge straight from a car battery or many other 12v sources as long as they can deliver 3 amps.

AA lithium battery charger
Opus battery charger in operation with AA, AAA, and 18650 lithium batteries

In the picture above we can see that we are charging 4 different types of batteries at the same time.

  • AAA Low discharge LSD NiMh 1.2 Volt
  • AA Shine NiMH 1.2 Volt
  • Lithium-Ion 18650 TrustFire 3.7 Volt
  • UltraFire 17500 Lithium-Ion 3.6 volt

Opus BT-C3100 Review- Battery charger for all types of batteries

AA lithium battery charger
Click for more information and specs over at Amazon

Compared to my older AA smart charger this one is slightly larger in size. This is due to the increased battery capacity slot needed for the larger TR18650 Li-ion battery. There is also a small internal fan which helps keep the electronics cool. But don’t worry this fan only kicks in at 40’C, and it’s very quiet.

There are 4 buttons on the front of the BT-C3100 used for displaying and setting various charge rates, voltages, etc. There are:

  • Mode – Selects what we want to do, charge, discharge, or refresh.
  • Display – Toggle between voltage, current, and time
  • Current – Set the desired charge or discharge current.
  • Slot – Used for selecting a battery to adjust charge rates. See voltages and capacity.

It all sounds complicated but it really is easy. Most times I just push in a battery, select current of 500mah and wait a few hours for the charging to finish.

Charging Cell Type:

The big selling point of this smart AA – 18650 charger is the fact that it can juice up so many different types of cylinder batteries.

  • Ni-MH, NiCd, Lithium-Ion.
  • Designed for AA ( LR6 ) and AAA ( LR3 NiCd, NiMH)
  • 3.7V Li-ion rechargeable batteries in size type of 10440, 14500, 16340, 17335, 17500, 18490, 17670, 18650

Charging Rates:

The charging current can be user selected with the following presets 200mA, 300mA, 500mA, 700mA and 1000mA. There are also higher charge rates of 1500mA and 2000mA but these can only be selected when slot 1 or 4 is used. I guess this is for heat dissipation.

If you don’t select anything the default charging current is 500mA and I find this a great compromise of fast charge vs heat build up. Because as most of us know batteries will fail with extreme heat. A few fast charges above 500ma won’t immediately destroy your battery but don’t do it too often.

When we pay good money for quality batteries like eneloops for our high-end electronics like Cannon camera flashes we want them to perform at their best. So stick with the slower charge rates.

How to charge a battery with the Opus BT-C3100

Opus BC-3100 Ver 2.2 AA lithium battery charger

First, plug in the power cord to a wall outlet or use a 12v power source like a car battery or Lithium-Ion Mini Jump Starter. With a 100-240V operating range, you can use this charger all around the world.

The Opus charger will cycle through the LCD display and will be ready to accept any battery size or type.

Inset an AA or 18650 battery making sure it goes in the right way. Once a rechargeable battery is detected its voltage will be displayed on the screen for 3 seconds. Then the default 500mAh charge rate will be displayed for another 3 seconds.

If Mode or Current is pressed within this time frame you will be able to change the values.

Amp Current Selection

If you press current within 6 seconds of inserting a rechargeable battery you will be able to charge the milliamp-hour charge rate for that battery slot.

The charge rates are 200, 300, 500, 700, 1000, 15000 and 2000mAh

Discharge rates are 200, 300, 500, 700, and 1000mAh

Discharge, Refresh, and Testing of your Torch Batteries

The Opus BT-C3100 also has a special feature called Discharge, Refresh, Quick test, and Testing. These features are designed to test your AA, AAA, and lithium-ion batteries for full storage capacity.

Say you have a 2000mAh AA NiMh battery you could press discharge and see how much true capacity you have.

If you find that your batteries don’t last as long you can try the refresh feature. This will cycle the charge and discharge rate a few times to hopefully refresh the battery.

BT-C3100 Charge Mode:

This is the normal charging mode and will set the optimum high capacity with the smart charger will detect when you insert the rechargeable battery. For NiMh and Nicad batteries, a trickle charge will be applied of 10mAh to keep them topped up once they are fully charged.

Discharge Mode:

Opus display discharge li ion AA battery charger

This can be used to reduce the memory effect. Especially useful for Ni-CDs. Its preset discharge stop points are.

  • 0.9 volts for NiMh and NiCd
  • 2.8 Volts for lithium-Ion
  • Once the discharge is complete the LCD will display the total energy consumed. Great for working out the true capacity of new batteries or working out when old ones go bad.

Refresh Mode:

Opus BC3100 18650 aa charger LCD display refresh battery

This is when the rechargeable battery is repeatedly charged and discharged for 3 cycles. This can take a day or two depending on the capacity of the battery.

Its been proven that regular refreshes will bring a battery back to life and extend its usage. I like to refresh AA and AAA NiMH and eneloops once a year. Never had a failure yet.

Test Mode:

Opus battery charger for all types of batteries display testing

The C3100 charger will discharge the battery fully to determine if the capacity is the same as the charge capacity. This will determine if the battery is failing internally and losing energy via heat or electrical leakage.

Quick Test:

Basically, the smart AA charger will use a combination of voltage, current, and internal resistant checks to determine the quality of the rechargeable battery. The lower the internal resistance the better for high current loads like digital cameras and flashes.

As you can see the display reading of 150 milliohms above is for an IKEA NiMH battery that is around 2 years old at the time of writing. It’s still perfectly fine to use.

  • 20-80 milliohms is a perfectly good quality battery internal resistance.
  • 100-500 milliohms are still ok to use but the maximum current output will be slightly lower.
  • 500-2500 milliohms are only good for low-power devices and are best used for clocks and tv remote controllers.
  • 2500 + milliohm and above means the battery is failing and should be replaced.

Always use battereis with the same internal resistance together in pairs.

Because of all these extra features, the Opus BT-C3100 is considered one of the best battery chargers for all different types of batteries. At a very affordable price.

18650 battery vs AA battery

Many high-power survival torches nowadays use Cree LEDs for their light. These are high-power draw globes that need usually 3 triple-A (AAA) to deliver the right amount of volts.

These AAAs are wired in series to provide around 4.5 volts of power. But the downfall is they quickly run out of internal capacity. This is where the 18650 lithium-ion battery comes in.

The EBL 18650 is my Li-Ion battery of choice. It has a normal voltage of 3.7v and an internal capacity of 3000mAh. You can get higher capacity up to around 5000mAh Li-Ion depending on the design but they start to get expensive.

So this is where the 18650 battery can quickly be so much more powerful than the AAA. In fact, it is starting to become the standard in survival and law enforcement torches.

As this charger is so popular and successful its also been rebadged, branded, and sold as Zeepin and Floureon.

What is a 18650 Battery?

These are lithium-Ion batteries with a very high capacity and high discharge rate. They have a size of 18mm by 65mm so they are much larger than a normal AA. A quick bit of history is that the 18650 battery is designed for early laptops the lithium batteries were soldered in series or parallel to provide usually 12v -21v of power for laptops.

Most of these cells are designed with low and high-voltage cutouts to protect the battery. They are usually rated at over 500 charge cycles so they will last a very long time if cared for properly.

Some people tend to break open the older laptop battery packs that fail after 5 years and recover most of the Lithium-Ion batteries that are still good. This way they have cheap battery cells for torches. Not to mention that the Opus charger should bring a lot of the older failed cells back to life with the refresh function.

Check out this full list of different types of rechargeable batteries.


If you could only take one battery charger to your survival shelter, then this Opus BT-3100 smart AA, AAA, 18650 battery charger is the way to go. It gives you future-proof options to charge the newer lithium-ion cells that are becoming very popular due to their low price and high energy delivery.

I like the internal fan as this will keep the internal components cool and it is very quiet. The 12v supply is perfect for taking out on field trips to use remote control cars, drones, or airplanes. Someone always has a flat battery on these weekend meet-up groups.

12 volts is easy to find nowadays so you aren’t restricted to direct 110v or 240v wall power. So you can be fine taking it on a field trip or storing it in your bug out bag rucksack.

Being a smart charger means that it’s plug and play or you can dive into more extreme settings if that interest you. Trust me this is the best battery charger for all types of batteries.

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