Long-range FPV drone flying requires batteries with high energy density for extended flight time, Li-ion batteries are an excellent choice for this purpose. In this tutorial, we will discuss the pros and cons of using Li-ion battery packs compared to LiPo batteries, focusing on flight performance, weight, flight time, and cost. Additionally, we will explore the options of purchasing a ready-made Li-ion battery or constructing one yourself using high-discharge 18650 or 21700 Li-ion cells.
Further Reading: Here are my tips on long range FPV flying.
Table of Contents
Differences Between LiPo and Li-ion Batteries
Lithium-ion (or Li-ion) battery packs serve as an alternative to the more common LiPo batteries.
Left: LiPo 4S 1500mAh; Right: Li-ion 4S 3000mAh (18650)
Three main differences distinguish these battery types:
- Energy density
- Discharge rate
- Lowest safe voltage
LiPo batteries have a much higher discharge rate than Li-ion, meaning they can provide a significantly higher current output. For example, a LiPo battery typically has around a 50C continuous discharge rate, while Li-ion batteries only have around 5C (Learn more about C rating here: https://oscarliang.com/lipo-battery-guide/#C-Rating).
Here’s a demo of my 4″ Flywoo Explorer achieving 30 minutes of flight time using a 4S 18650 Li-ion pack:
Another distinction is the safe discharge voltage. You can generally discharge a LiPo battery down to 3.5V per cell safely, whereas Lithium-ion batteries can go much lower, e.g., 3.0V per cell. Both battery types can be fully charged to 4.2V per cell.
Pros and Cons of Using Li-ion Battery Packs
Increased energy density and flight time
Li-ion battery packs offer higher energy density than LiPo batteries, meaning they store more energy per unit of weight. This results in longer flight times for long-range FPV drone flying. Comparing similar size packs, Li-ion has about double the capacity than LiPo.
For example, a 4S 18650 3400mAh Li-ion battery weighs around 200g, while a 4S 1600mAh LiPo has nearly the same weight. On paper, you should get double the flight time!
Lower discharge rate
Li-ion batteries typically have a lower discharge rate (C-rating) than LiPo batteries. This means they may not be able to provide the high current demands required for aggressive, high-performance flying and punches. While Li-ion batteries are not a popular choice for freestyle and racing, they are an excellent option for long-range that don’t require a lot of amp draw, such as cruising and relaxing flight. If you use an efficient power system, Li-ion cells can sufficiently handle the demands.
Higher initial cost
Li-ion batteries are more expensive to purchase. However I personally found them to last much longer than LiPo. Firstly, you crash less with Li-ion because the flight you do with them tend to be slow and steady. Secondly, they have metal housing which make them a lot more robust against physical impact. So in the long run they are actually more econmical.
Understanding 4S1P and 4S2P
If you’re not familiar with LiPo battery terminology from our beginner’s tutorial, let’s revisit the meanings of S and P in battery specifications.
The S in 4S represents the number of cells connected in series. Conversely, the P in 2P signifies how many cells are connected in parallel. A 4S1P configuration consists of 4 cells connected in series, while a 4S2P configuration contains 8 cells in total. Although both configurations have the same nominal voltage, a 4S2P battery can deliver double the current, capacity, and weight compared to a 4S1P battery assuming they are using the same cells.
Buying Ready-Made Li-ion Battery Packs
Ready-made Li-ion battery packs are available for purchase, providing a convenient option for those looking to quickly incorporate Li-ion batteries into their long-range FPV drone setup.
2S
2S 2500mAh 18650 (25-30A):
2S 3000-3500mAh 18650 (10-30A):
- BuddyRC: https://oscarliang.com/product-m2c8
- GetFPV: https://oscarliang.com/product-pnk
- NBD: https://oscarliang.com/product-92oh
2S2P 5000mAh 18650 (50A):
- BuddyRC: https://oscarliang.com/product-qffk
3S
3S 2500-2600mAh 18650 (25-35A):
- BuddyRC: https://oscarliang.com/product-84m2
- GetFPV: https://oscarliang.com/product-ai6h
3S 3000mAh 18650 (30A):
- NBD: https://oscarliang.com/product-syqo
- RDQ: https://oscarliang.com/product-8po5
- GetFPV: https://oscarliang.com/product-goi0
3S 3500mAh 18650 (10A – for fixed wings):
3S 4200mAh 21700 (45A):
4S
4S 2500-2600mAh 18650 (25-35A):
- GetFPV (Auline): https://oscarliang.com/product-3lok
- GetFPV (Dark): https://oscarliang.com/product-vrl0
- RDQ: https://oscarliang.com/product-o0ug
- BuddyRC: https://oscarliang.com/product-gxdy
4S 3000mAh 18650 (30A):
- NBD: https://oscarliang.com/product-7dno
- GetFPV: https://oscarliang.com/product-c0ng
- RDQ: https://oscarliang.com/product-a5x6
4S 3500mAh 18650 (10A – for fixed wings): https://oscarliang.com/product-l8h0
4S 4200mAh 21700 (45A): https://oscarliang.com/product-j0br
4S 5000mAh 21700 (10A – for fixed wings): https://oscarliang.com/product-idr5
4S2P 8400mAh 21700 (45A): https://oscarliang.com/product-ir4q
6S
6S 2600mAh 18650 (35A):
- NBD: https://oscarliang.com/product-81wt
- GetFPV (Auline): https://oscarliang.com/product-gtu2
- GetFPV (Dark): https://oscarliang.com/product-ehyj
6S 3000mAh 18650 (Max 30A):
6S 4200mAh 21700 (45A): https://oscarliang.com/product-3fvc
6S2P 5200mAh 18650 (70A): https://oscarliang.com/product-i6gr
6S2P 6000mAh 18650 (30A): https://oscarliang.com/product-ws6b
6S2P 8400mAh 21700 (45A): https://oscarliang.com/product-qu7g
Building Your Own Li-ion Battery Pack
DIY Lithium-ion battery packs with individual 18650 or 21700 cells can be a cost-effective and customizable solution. By choosing specific cells and assembling the battery pack yourself, you have full control over the battery’s quality, capacity, discharge rate, and overall performance. However it requires decent soldering skills.
Below is a wiring diagram for a 4S Li-ion battery pack with XT60 and balance connectors.
Pay close attention to the wire order on the balance connector.
FPV pilots commonly use two types of Li-ion cells: 18650 and 21700. They are the same type of battery, just different in size. These numbers represent the dimensions of the cell, with 21700 cells being heavier and larger but offering greater capacity and discharge rate.
To ensure optimal performance and safety, select high-discharge 18650 or 21700 Li-ion cells from reputable manufacturers.
Molicel P45B 21700:
Popular 18650 cell choices include Molicel P30B, P28A, Sony VTC5A and VTC6. Here is my testing and comparison of these cells and which you should get: https://oscarliang.com/best-18650-li-ion-battery/
Molicel P30B:
Molicel P28A:
- AE: https://s.click.aliexpress.com/e/_De9xMd7
- RDQ: https://oscarliang.com/product-6ohi
- GF: https://oscarliang.com/product-u8yp
VTC6:
VTC5A:
You’ll also need wires (I recommend using 16AWG for the discharge lead and 20AWG or 22AWG for the balance lead), a 5-pin balance connector, and either an XT30 or XT60 connector. The XT30 is an excellent choice due to its lighter weight and capability to handle the low amp draw. Choose an XT60 if that’s the connector type used on your drone, or use an XT30 to XT60 adapter if needed.
XT30 Connectors
- RDQ: https://oscarliang.com/product-6gvi
- GetFPV: https://oscarliang.com/product-0ipn
- Amazon: Amazonhttps://amzn.to/3l8PdY0
- Banggood: http://bit.ly/2zTIRD6
- AliExpress: https://s.click.aliexpress.com/e/_DkJfemp
XT60 Connectors
- RDQ: https://oscarliang.com/product-xzn1
- GetFPV: https://oscarliang.com/product-hwx7
- Amazon: https://amzn.to/3l6oonc
- Banggood: http://bit.ly/2AuxHnC
- AliExpress: https://s.click.aliexpress.com/e/_Ddy57H7
16 AWG Wires
- AliExpress: https://s.click.aliexpress.com/e/_DFtzaZX
- Amazon: https://amzn.to/3Jfu0DE
- Banggood: http://bit.ly/2ALByxa
- GetFPV: https://oscarliang.com/product-z3it
- RDQ: https://oscarliang.com/product-wj65
Balance Connector Here
- Aliexpress: https://s.click.aliexpress.com/e/_DezrpZB
- Amazon: https://amzn.to/2AlClFK
- GetFPV (4S): http://bit.ly/2K01jtT
- GetFPV (6S): https://oscarliang.com/product-8nsa
Heatshrink Tube (86mm for 4S 18650)
- AliExpress: https://s.click.aliexpress.com/e/_DcuF3S1
- Banggood: https://bit.ly/2JTOgLy
XT30 to XT60 Adapters
- AliExpress: https://s.click.aliexpress.com/e/_DdqQ2Qd
- GetFPV: https://oscarliang.com/product-ly7o
How to Make a DIY Li-ion Battery
Disclaimer: Soldering on batteries can be dangerous. If you decide to follow the instructions in this post, do so at your own risk.
Start by soldering wires to the connectors, using longer wires than necessary so you can trim them to the desired length later.
Next, solder the wires to the 18650 cells according to the provided wiring diagram. Use good quality solder with flux core, avoid using additional acid based flux (solder paste) as it will corrode the connection/battery in the long run. See my solder recommendation here.
Before soldering, use sandpaper to scratch the top and bottom sides of the cell. This will help the solder adhere better.
“Tin” both sides of the batteries with a small amount of solder, allowing it to cool down before soldering the wires.
Keep the time your soldering iron touches the battery terminals to a minimum. The longer the iron is in contact with the battery, the more heat will build up. To accomplish this, use a powerful, temperature-controlled soldering iron. A less powerful iron won’t maintain its temperature as effectively since the heat will be absorbed while soldering large pieces of metal. I personally use the TS100 iron, which works exceptionally well.
Here’s the top side.
Here’s the bottom side.
Cover all solder joints with electrical tape, and then wrap the entire assembly in heat shrink. While you could use a shorter discharge lead to save a couple of grams, I made mine longer on purpose.
The finished 4S 18650 battery weighs around 200g and provides over 30 minutes of flight time on my Flywoo Explorer LR 4″: https://oscarliang.com/flywoo-explorer-lr/
Betaflight Misreading Cell Count on Li-ion Batteries
A common issue with Li-ion batteries is that their voltage can drop significantly lower than traditional LiPos, leading to Betaflight sometimes misreading the number of cells.
This becomes problematic if you’re monitoring voltage per cell on your OSD. Take a 6S Li-ion battery as an example: when its voltage falls below 18.0V (3V per cell), Betaflight may mistake it for a 5S battery, showing an incorrect per-cell voltage of 3.6V. This misleading readout could tempt you to fly longer than you should.
To prevent this, you can lock the cell count in Betaflight by using the CLI. Simply enter:
set force_battery_cell_count = 6
save
By doing this, you’ll ensure Betaflight keeps a consistent cell count during your flight.
Conclusion
Li-ion battery packs offer significant advantages for long-range FPV drone flying, such as increased energy density and extended flight times. Despite some trade-offs like lower discharge rates and a higher initial cost, the benefits often outweigh the drawbacks. Building your own Li-ion battery pack can be a cost-effective and customizable solution for those looking to optimize their drone’s performance. However, for those who lack soldering experience, purchasing ready-made battery packs off the shelf may be a safer and more convenient option.
Edit History
- Aug 2020 – article created
- Mar 2021 – added product links to where you can buy Li-Ion packs directly
- Apr 2023 – updated tutorial and product links
69 comments
I told my friend that i will make 3s li-ion battery pack for my rc plane that is using 2200kv motor and 30A esc but he told me that it would not work, please what is the truth
Oscar – can i use my Venom Produo dual power charger to chardge li-Ion batteries? As usual , excellent technical article. I plan to purchase Li-Ion batteries – i do not have a spot welder to make my own. The increased flight time compared to LiPo batteries is the reason to switch to Li-Ion. Thanks
Is soldering the lithium ion battery pack is better than spot welded pack ?
Spot welding is better as it dost not cause high temperature buildup on the battery which may affect performance, but not everyone have access to battery spot welding equipment.
I build 21700 packs using Molicel P42A cells. Here are my recommended tips:
Don’t use sandpaper to rough up the cells, use a diamond ball burr in a Dremel:
amazon.co.uk/SmallLeft-Sphere-Diamond-Grinding-Dremel/dp/B013FLZZ32
Use this soldering iron (or it’s bigger brother):
amazon.co.uk/Weller-Heavy-Duty-Soldering-Iron/dp/B0001P17A6
amazon.co.uk/dp/B0001P17AQ/ref=twister_B07428R8M4
Use pre-tinned braid to link the cells:
copperbraid.co.uk/product/flat-tinned-copper-braid-6-mm2-10-mm-wide-x-1-mm-thick-63-amps/
Use gel flux, of the non-corrosive no-clean kind, but clean it off anyway with a proper flux cleaner:
amazon.co.uk/MG-Chemicals-Pneumatic-Dispenser-Dispensing/dp/B00425FUW2
cpc.farnell.com/electrolube/flu400db/flux-cleaner-fluxclene-brush-flu/dp/SA02331
You could save two wires in the balance lead, if you could bridge the XT-connector’s positive and negative wire internally to the balance port, couldn’t you. Why is that not already a standard?
I made a li-ion for my long range. Are there betaflight settings to change when using these batteries as I was suffering glitches. GPS rescue didn’t work and video was dropping out where it shouldn’t have.
Product links need updating. Thanks – great post.
Do they use all power suddenly under 3V in the osd per cell?
Why is nobody using liion pouch cells for fpv ?
They have even higher energy density, are lighter and have a higher discharge rate.
Seems absolutely perfect to me. Am I overlooking something?
My FPV batteries have 120C discharge rate (nextfpv.com.au/collections/lipo-battery/products/fmr-1550mah-4s-120c-extreme-lipo-battery-pack). Are you sure you’ve got your C ratings right?
Nice little walk through. I’ve gone with molicel batteries for my builds as they are rated at 25a discharge. They are pretty much the best 18650’s out there at the mo. I’ve also gone with a 21700 4s 2600mah with 30a rated for an extra 60 grams, which should perform pretty well. I would at very least buy the cells from a reputable seller, like 18650uk or fogstar as there are a LOT of fake cells that have just been rebranded with a different wrap on them!
The most you’ll get from an 18650 is 3500mah which is a LGMJ1 cell but, these are only rated for 10amps so not really any good. So many companies claiming that they can get more are just bs to be honest. The smallest cell I’d use would be the samsung 25r or the sony vt5 but, the best by far are the molicel p26a at 2600mah and 25a if anyone else was thinking of making there own :)
Thanks for this guide, however I was a bit too quick and bought the Panasonic NCR18650B cells and built a 6S battery. I was just going to charge it when I decided to double check its C-rating, only to discover that it is 2C… I’m guessing this battery is pretty much useless for even an efficient 5″ LR build? What would even happen if I were to try and fly it, would the batteries overheat pretty much instantly? I’m probably better off taking it apart and using it to power my goggles…
The molicel site lists the P26a at 35 amps and the p28a at 40 amps.
Oscar,
Why don’t you use protective circuitry? Thank you
Charging is protected by the charger and discharge by the flight controller setup,. No need to carry additional weight and potential source of troubles.
Hi Oscar.
I am using a 2s Li-ion with a drone very similar to the Flywoo Explorer LR (4″, 1404 motors).
Although for BLHeli32 there is no option for low voltage cutoff, I am unable to take-off at voltages below 3.3V/cell. Any idea of why this is happening?
Today I built a 4s and a 6s pack using Sony VTC6D 2800mAh cells. I discharged the packs to 3.0v/cell and then charged them to 4.2v/cell (ISDT 608AC charger). Both packs took around around 2600mAh which surprised me. I was expecting the 6s to have a higher capacity (expecting 6s to take approximately 1/3 more mAh than the 4s). What am I missing?
Or is that the amount “per cell”? If so that would make sense. If that is the case I also assume that betaflight reports consumption on a per cell basis. I wondered why my 4s and 6s lipos are only showing around 700-900mAh used when I get down to landing voltage.
I guess this link sort of answers my question but I must still be missing something because I don’t fully understand the benefit of adding more cells. I know the voltage goes up but if the capacity isn’t increased what’s the benefit? https://electronics.stackexchange.com/questions/20701/adding-mah-when-wiring-battery-cells-in-series
Aha! What I am really interested in is “Wh”! You had the answer to my question right here: https://oscarliang.com/6s-mini-quad-racing-drone/
Hello, I did a 4s with VTC6 18650 Li-ion (3000mAh) and I am able to fly 29 minutes with my HGLRC Rekon5 HD (6s version), so cool. I will also try to fly with a 4s 5000 21700 that I am doing for my DJI Googles, but it is 100gr more than the 4s 18650…
Those panasonic cells get really hot easily.
Assuming we use a 5 inch drone that fly on 4S LiPo’s using a Mamba 35A Stack and 2207 motors.
Now is it possible to fly the same drone using Li-Ion 18650 4S packs ?
1. What is the pre-condition checks for the existing drone if we should attempt to fly using Li-Ion packs ?
2. What is the precautions to take before and during flying the drone so as not to burn / damage the stack ?
1. how much amp is required to take off, hover and cruise? is the Li-Ion pack able to handle that current?
2. You won’t burn or damage the stack using Li-ion 18650 pack, worse scenario is that you couldn’t fly with it.
If things go wrong while soldering, how bad can the explosion get, assuming the battery has been discharged as recommended?
Do Li-ion batteries need to be kept at a specific voltage for storage? Similar to Li-po batteries (3.85v)?
Yes, similar to LiPo, at around 3.8V.
I wanted to take a crack at doing this project, but i used some cheap batteries i got from bangood on sale. They said it was 4000 mah but i highly doubt they really are. Put the entire thing together using a plain old solder at high temp and short periods of heat exposure. The final product looked pretty impressive. Charged the cells using a LI-ON setting on my charger and got a few messages indicating that the battery had been disconnected (without touching anything). After i got a good charge, tried using the 4s LION battery on my new Flywoo Explorer 4 and as soon as it took off maybe 1 foot of the ground, the whole thing would shut down. I guess the batteries are just not supplying the load needed.
Any suggestions as to what’s happening here ? Thank you in advance. BTW I just got the panasonic batteries that you are recommending for this project.
There’s no 4000mah 18650 battery, it’s just not a thing, so I think you got the fake cells.
Get them from a well known local vapor shop! I found it to be the best way to get 18650. Too many fakes cells online.
Hi, is it possibile to use two Lion batteries, one 4s 4000mah (vtc6a) and 6s 3000mah (vtc6) in the same time? How to connect it
Not a good idea. Use the same cells in the same battery.
That is exactly where I find mine! They work great. Thanks for the write up. Very helpful.
hello and thanks Oscar,
I bought a flywoo explorer and for it made my pack of Li ions. 4s 2200 mAh was the best I could get. Is that enough?
and more importantly until what voltage do you continue to fly?
for me the quad was alarming under 14v and I got nervous and landed.
That’s a bit low for 18650 cells. You will probably only get 15 mins or so with that.
I normally land when it gets to 2.8V per cell, some even wait until 2.5V which I think is a bit risky.
You can set minimum voltage and warning voltage in Betaflight lower so it doesn’t alarm too early.
I have yet to find anything on the discharge rating calculation for lion batteries. Do i take the discharge amp rating per battery and multiply that against the Mah of the battery like we do with c ratings on lipos? So I am looking at 45amp 4200 molicel 21700 battery and as far as I can calculate a 6s can handle 189 amp max discharge. or slightly under 48 amps per motor if i am not mistaken. Is this correct?
No, for Li-ion battery they should state the max discharge current in the data sheet?
Lets say if it was 30A, if you connect 6 of them in series to make a 6S pack, the max discharge current is still 30A.
I want ask u… I have quad wizard x220.. not flywoo.. i have tried make 3s lithium ion battery..but my quad cannot fly for long time.. it less than lipo battery.. why my 3s battery lithium ion not effective to me?? I want to use lithium battery because i want more fly time.. 3s lipo only 5minit.. can u tell me why the reason…. Tq
Old battery? fake capacity? You can test capacity, drain them down to 3V/cell, then charge them back to 4.2 and see how much mAh is put back.
If capacity is too low, maybe get some new ones, I posted a link to them in the article.
It would be awesome to get more photos or a better diagram of how you have the balance leads wired up. Other than that this is a fantastic, easy to digest, guide.
I’m assuming you did not read the disclaimer…..
What is the best way and best settings tocharge this battery?
I just charge them like lipo but with a low current (e.g. 1C), but this is just my way, not saying this is the right/safe way.
Do the same rules for charing lipos apply to liion?
Like what rate should I charge at? 3,000 mah 4d liion okay to charge at 3amps?
What’s the best storage voltage?
What’s the land voltage?
What’s the max voltage?
How long does yours take to charge?
I built this and all the connections are good, with each cell showing as it should on the charger.
I set my charger for Lithium Ion balance change, maximum 2 Amps. However it seems to be taking a very long time. Is this normal, or did I somehow overcook the cells?
The problem with using other cells is that is very difficult to find such with high “c” rating, let say 35-40Amps for Ok performance. I mostly use 21700 , they are as popular as 18650.
Oscar is well known in the quad/drone World and knows what he is talking about. I stand by his word!
Hey if I were to wire the balance lead reversed would it make my isdt charger give an error code? It’s giving balance lead voltage too high.
Hello I’m starting too, I don’t know much about it, but I would like to know if using the 3400 mha 3.7 battery, I can use 9900 mha 3.7 to further increase the autonomy of flight
Hey Oscar, thank you for the write up! I am impatiently waiting for my explorer LR HD to be delivered. Plan on assembling a few of these packs and had a few questions:
1) Should I be looking at protected or unprotected 18650s? I plan on assembling just as you did in this tutorial.
2) what is the lowest amp rating for a 4s 18650 pack you would run on the explorer? As I understand, there is a trade-off between a higher mAh vs discharge amperage. I am willing to sacrifice a little flight time if it means that performance will be unaffected vs running a lipo. I’m totally new to FPV so pardon my ignorance.
Thanks!!
1) unprotected 18650
2) maybe just get the cells I linked in the articles, these have been tried and tested :)
Things I thought about, maybe someone can help:
1. How much is the current-draw difference between 3s and a 4s battery for 3″ quads. Lower voltage->more current (p=u*i). But also lighter. Any experiences?
2. Do you think that 0.1*7mm nickel-strips and the spot-welded “spots” will sustain the ~10A current. Not sure if i should spotweld or solder the batteries…
Happy flying together
What is your best guess at the “C” rating of this pack and is the balance lead used when you charge on your ISDT in Li-Ion mode? I have a Hitec X2 that has a Li-Ion mode. Do you know if it will work the same way as your ISDT?
If you do not want to solder the cells then you can buy assembled packs and attach you own lead and balancing connector. Here is a link to AliExpress using the 18650 VTC6 cells rated for 30A. I have ordered two packs and will try them out on the Explorer that I just ordered.
aliexpress.com/item/4001140540403.html
Thank you so much for your content, Oscar.
This was just what I needed in preparation of my Explorer, while it makes it’s way through corona-slowed international post. I have started backing you on Patreon, because your content is truly remarkable. Also enjoy it’s written.
TO ALL WHO USES OSCARS CONTENT: Back him on Patreon. It must require tons of work, which saves us tons of time and mistakes. Goto: https://www.patreon.com/oscarliang
Thank you !
Your balance lead diagram needs to be much clearer than sending wire to middle of another wire
Hey Oscar, thanks for this article! Very interesting.
Question, being that this li-ion 4s battery build has an XT-60 connector, can you charge this on the typical chargers we normally use for Lipo (assuming the charger has a li-ion setting) or do you need to use a different type of charger?
Thank you
I personally use iSDT chargers, and they have Li-Ion mode.
I see people charging them in LiPo mode, but do this at your own risk :)
Agree, you should at least put BIG red disclaimer about risks of doing it.
Other than that, nice article .)
There is disclaimer
do same for 6s batteries! haha
only for 1806 motors or below for 5 or 4 inch, and very light weight quad. More than 20 mn flight time, with all my own packs since 2 years. 2.9v max low limit. Works fine, but very gentle on the throttle.
hi Oscar.
I have a doubt about the discharge current, I bought the following batteries from TBS to make a 4S2P 18650 battery. But it only has 10A drain current. is it enough or should I consider a more current one.
team-blacksheep.com/products/prod:lg18650
Depends on how much current your model draws when cruising.
For example my quad draws 6A and 10A con. discharge should be fine.
Why you building 4s Not 6s?
because my quad takes 4s only.
And now people will solder 18650s “because Oscar did so”.
How irresponsible of you.
It’s true li-ion shouldn’t be soldered, but all you’ve done is leave a nasty comment to a guy who provides a lot of great free content.
People, heating up li-ion can permanently change their chemistry and impair their ability to charge/discharge. Instead of soldering, please use a spot welder.