The 18650 battery is probably the most used Li-Ion battery.
They’re everywhere Electric Vehicles, Vapes, Laptops, all the way to high-powered Flashlights. These fuel cells are powering everything.
Some of the top 18650 Lithium Ion Battery brands are Panasonic, LG, Samsung, Sanyo, Sony, and Toshiba.
Most of the batteries that you see on the market are rebrands or pretty packaging on top of the base batteries from these bigger brands.
The first thing to note is that with Li-Ion batteries the number names mean something.
What does the name 18650 mean? This is a direct reference to the size of the battery 18 mm diameter by 65 mm height. Since this is a fixed size it’s not like you can just increase capacity quickly without big changes in technology.
The current highest capacity 18650 battery is 3600mAh. From these you will get great battery life. But they definitely cost a premium.
One more quick note is that we are talking about Lithium Ion Technology here not just a Lithium battery. There are lots of battery types. If you buy a battery that is just labeled lithium that is a primary battery which means it is not a rechargeable battery this is an important factor to remember.
With that said, you’ll find batteries that have way higher numbers, most of these batteries are fake batteries and are just quoting numbers for marketing reasons but they do not hit the advertised amount.
The biggest issue here is that these counterfeits are selling on eBay, Amazon, and other places for much cheaper than the high-quality batteries. Also, these cheaper batteries are less stable and more likely to cause some of the bad things we’ve heard about Lithium-ion batteries.
It is easy for these companies to get away with this because not many people know how to test their batteries, they’re just looking for a good deal. Later in the article will get into how to test Lithium-ion batteries for capacity.
Another thing to consider is there is a push-pull relationship between amps and milliamp hours. If you want a high drain battery like an IMR or INR battery you will pull higher amps and get a brighter light but these higher amp batteries have considerably lower capacity. A higher capacity cell will give you long runtime but less power.
So, how to test the capacity of a 18650 battery?
As mentioned earlier, testing your batteries is something that isn’t easy to do. There are three ways, two that require some extra equipment. I’ll list them out from hardest to easiest.
You will need an adjustable load resistance and a DC power supply, using this you’ll charge the battery and fully discharge the battery. With that you’ll be able to use a simple formula of the charging current multiplied by the charging time which will give you the battery capacity. Do the same by multiplying discharge current and the discharge time to get the capacity.
The second method is to fully charge a battery which c.ould range from 3 volts to 4.2 volts the nowadays usually 4.2 volts next no discharge the battery to the rated discharge voltage and record how much electricity ty is released again using special equipment the voltage typically goes down to around 3 volts and the last step you’ll charge the battery back up to the room capacity whatever you did during that step two where you’re recording how much electricity was released that’s the capacity of the battery.
The third way this is probably the easiest way is to have at least one battery from a reputable supplier.
Then, you will do an equal test with the same electronic but with the different batteries.
So what this would look like is having a battery from a trusted supplier like Panasonic that is rated at 3500mAh and then if you have a few batteries that all have a claimed capacity of 3500mAh or much higher fake numbers you put them both in the same high lumen flashlight or other device. Real quick, they also need to have the same Amp rating. You are going to time how long it takes them to drain off the battery. You are not going to have an exact capacity measurement here but you’ll have a relative number.
The last thing to note is that when these batteries are discharged they don’t run down completely so when you’re looking for Batteries you can’t say that something that has doubled the mAh will have double the amount of life because it’s not completely at zero and actually has a pretty decent number before when it’s unable to power the electronics.
So if you’re looking for a high capacity battery, if you are looking for a great power source for a flashlight, electric bike, electric vehicle, or anything else.
First, decide if you are interested in high power with high discharge rate or discharge current or if you’re interested in something with the maximum capacity. Because, the larger the capacity or what we would call high energy density then the lower the power density because you have a higher internal resistance.
Stay away from fake cells get good name brand batteries, these high-quality battery manufacturers will be really close to their rated capacity.
Even if you know the brands to look for there will just be some counterfeit and fake batteries that are knocking off high quality brands. So in addition you should buy from a reputable online shop with reputable Brands.
Shopping for Batteries can be a little confusing.
Good job going for rechargeable batteries! if you treat these power cells right they’ll have lots of charge cycles and keep you powered for a long time.
Couple things are going to need are a good battery charger and some things to burn off that power like some great flashlights, check out these articles if you’re looking for flashlights. we recommend flashlights from Olight, Fenix, Nitecore, Surefire, and many more.
When shopping for batteries you need to decide if you want higher power which would be high amps or if you want long run times which would be a higher capacity battery cell with a lower discharge rate.
If you want a really powerful 18650 battery the high amps and a really steep discharge curve then you can expect to have a capacity around 2500mAh. Many of these are also batteries without circuit protection but in general, they’re still very safe.
At the high level, Like I said before we would go with batteries that were based on a core made by the Panasonic Corporation, Samsung, LG, Sony, or Toshiba. These batteries will give you a great life cycle and will measure up to any capacity test.
From here Brands like Nitecore, Orbtronic, AW, Fenix, Keeppower, Xtar and a few others Rebrand the batteries decide if they want to put voltage protection and a circuit board on it and ship it off. these batteries will generally match their declared capacity
If you are looking for a higher capacity battery and find what flashlights use those. Read our comparison between 18650 and the 21700 battery.