In this post I will test various 18650 Li-Ion batteries and decide which one is the best to use for low current equipment in drone racing and FPV, such as your FPV Goggles and radio transmitters.
Since I will only be using these 18650 batteries for low amps applications, I am not too concerned with max discharge current as long as it works well under 5A current draw, and I will focus on verifying the actual usable capacity of the batteries. I try to test at least two different samples for each battery to get a better overview of the quality.
Further Reading: What’s the best battery for FPV goggles?
18650 Battery Testing
There is discussion of what’s the best method to test batteries and represent the result in the comment. Please note that I did the test just to find the best 18650 batteries FOR MY OWN USE, I am only sharing my experience as I thought some of you might find it useful. Please do you own research and testing, and take my words as a grain of salt.
I have selected these batteries because of their popularity. I will surely test more batteries in the future, please let me know what you want to see tested in the comment.
|Panasonic NCR18650B 3400mAh||Amazon||$7||45.8g|
|LG MJ1 3500mAh||Amazon||$7||46.2g|
|Samsung 30Q 3000mAh||Amazon
I will charge these batteries to 4.1V, then discharged them down to 3.1V with a constant 2.3-2.4A current. Data is recorded every 3 minutes, including the voltage and “mAh drawn”.
Why 4.1V and 3.1V?
For some reason my iSDT SC620 charger only allows to charge Li-Ion batteries to maximum 4.1V. I understand that 18650 can be charged up to 4.2V, I am not an expert on 18650 batteries but I think this is for safety reasons (to avoid overcharging them?).
3.1V is the recommended “safe minimum” voltage.
Results and Findings
I seemed to get more charge out of the Panasonic than the LG despite the lower rated capacity. And as expected, the Samsung 30Q provides the least usable capacity.
Note that we are not getting the advertised capacity because we are not charging and discharging the cells to their maximum and minimum voltages.
The Panasonic lasted the longest until the voltage reached 3.1V.
|Rated Capacity||mAh bet. 3.1V-4.1V||Duration|
|Panasonic NCR18650B||3400mAh||2447mAh (72.0%)||64mins|
|LG MJ1||3500mAh||2377mAh (67.9%)||62mins|
|Samsung 30Q||3000mAh||2212mAh (73.7%)||58mins|
Interestingly, the cells with higher capacity appeared to have the worse voltage sag during discharge, i.e. lower C-Rating. (Maybe that’s why 18650 batteries with high discharge current are usually lower in capacity?)
While the weights and prices are very similar between these batteries I tested so far, purely base on the result of this test, I personally prefer the Panasonic NCR18650B cells for low current application in FPV, because of its highest usable capacity. But the LG MJ1 is not bad either, given the higher “C Rating”.
Beware of Fake 18650 Batteries
Some batteries can have exaggerated capacity, it’s rare to find batteries with capacity over 4000mAh. If you find a battery that claims to provide 10000mAh, it’s mostly likely to be fake (in some cases these turn out to be only 500mAh :) )
- Buy from reputable sellers, check out reviews before purchasing
- Fake 18650 batteries generally weighs less! The good ones I have come across all weighs around 40-50 grams while the fake ones weigh only half of that at around 25 grams
Charging 18650 Batteries
It’s recommended to charge your 18650 Li-Ion batteries with a dedicated Li-ion battery charger, like the iSDT C4 charger: http://bit.ly/2G6k2Ce.
However you can also charge them with a LiPo charger if they support Li-Ion battery. In order to do that, you can connects the cells in series, this will allow you to charge multiple batteries at the same time – just less hassle and faster.
Don’t Solder Directly on Batteries
However, I don’t recommend soldering directly on the battery’s terminals, because overheating batteries can result in fire and explosion.
Build a DIY Case
Instead, get a battery holder and solder the connectors to it.
For example, here is how to make a case to connect 2 individual cells in series, and turn them into one single 2-cell battery. Parts list:
- 2-cell 18650 battery holder: Amazon | Banggood
- XT60: Amazon | Banggood | GetFPV
- JST: Amazon | Banggood
- 5.5mm Barrel for FPV Goggles: Amazon | Banggood | GetFPV
- 2S Balance Lead: Amazon | Banggood
Pick whatever discharge connector you prefer, but you must connect the balance lead for charging. You can actually use this case to power your goggles!
You can use larger cell holder and build a 3S or even 4S case, it’s all up to you.
When charger, remember to…
- Change battery type to “Li-ion” before charging
- Only charge at 0.5C or lower to minimize the risk of fire