diy professional 18650 battery pack

The world is moving away from fossil fuels and will one day be fully electronic.
In today\'s world, lithium
Ion is the most promising chemical in all batteries.
Most of the battery packs used in laptops, RC toys, drones, medical devices, power tools, electronics
Bicycles and electric vehicles (EV)
All based on 18650.
It\'s the most mature Li.
The ion format is available, large in size and low in cost per Wh.
You can be at: 18650 (
18mm in diameter and 65mm in length)
The size of the battery is lithium-ion batteries.
It\'s in the same shape, but it\'s a bit bigger than the AA battery.
In contrast, AA batteries are sometimes called 14500 batteries because they are 14mm in diameter and 50mm in height.
I did a solar generator earlier and have worked very well so far.
But the main problem is its weight, it\'s really heavy.
The main weight of the solar generator is due to the heavy lead-acid battery inside.
So I decided to make a lightweight compact 18650 lithium ion battery pack.
In this Instructable, I will tell you how the application of the 18650 battery is condensed, such as: mobile power supply, solar power generation, e-
Bicycles, electric walls, etc.
The basic principle is very simple: just connect the number of 18650 batteries in series and connect them together to make a larger package, and finally add BMS to it to ensure safety.
At the end of this project, I made a custom 3D print case for the battery pack.
Statement: I do not take any responsibility in case of property loss, damage or loss of life involved.
This tutorial is for those who have an understanding of rechargeable lithium ion technology.
Please do not try this if you are new. Stay Safe.
Required parts: 1. 18650 Battery (
GearBest/Amazon)2. BMS (
Amazon good/Amazon)3. Ni Strips (
Amazon good/Amazon)4.
Battery Indicator (Banggood )5. Rocker Switch (
AliExpress/BangGood)6. DC Jack (
AliExpress)7.
Battery stand 18650 (Banggood )8.
3 m x 10mm screws (
AliExpress)Tools Used 1. Spot Welder (
Amazon good/Amazon)2. 3D Printer (GearBest )2.
Stripping/cutter (Amazon )3.
Hot air blower (GearBest )3. Multimeter (Amazon )5.
Lithium ion charger (GearBest )
Safety equipment: 1.
Google security (Amazon )2.
Electric gloves (Amazon)
You will find that there are many types of 18650 batteries on the market in the price range of 1 to 10 dollars, but which one is the best?
I highly recommend buying 18650 batteries from brands like Panasonic, Samsung, Sanyo and LG.
These batteries have good recording performance features and excellent quality control.
18650 of batteries from well-known brands are usually expensive, but they are worth having if you consider using them for a long time.
Don\'t buy cells with the word fire in any name, like Ultrafire, Surefire, and Trustfire.
In fact, the batteries were simply rejected by the factory, purchased by companies such as Ultrafire and repackaged on their own brand covers.
Many old batteries are repackaged as new and Whitelabeled.
They sell batteries by marking capacity up to 5000 mAh, but actually their capacity is between 1000 and 2000.
Another major problem with these cheap 18650 batteries is the high risk of exploding when overheating during charging or discharging.
In this project, I used GearBest\'s green Panasonic 18. 0b battery with a capacity of 3400 mAh.
To make a battery pack, you have to connect 18650 batteries together via a nickel strip or a thick wire.
Generally, nickel bars are widely used here.
Generally speaking, there are two types of nickel bars on the market: Nickel bars
Plated steel strip and pure nickel strip.
I suggest buying pure nickel.
It is a little more expensive than nickel plated steel, but its resistance is much lower.
Low resistance means that less heat is generated during charging and discharging, which results in a longer battery life.
The size and length of the nickel bars are different.
Select the band according to the current level.
You have two options, and the two connect 18650 cells together: 1. Soldering 2.
The best option is always spot welding, but spot welding is much more expensive than a good quality soldering iron.
Welding: you should know why spot welding is more popular than welding, the problem with welding is that you apply a lot of heat to the battery and it won\'t dissipate very quickly.
This enhances the chemical reaction in cells that destroy cell performance.
In the end, you will lose the ability and life of some cells.
However, if you are not interested in buying expensive spot welders, you can weld the nickel label to the battery with some of the following precautions and tricks: 1.
In order to minimize the contact time of the soldering iron on the battery, make sure that the surface wear is large enough and that enough flux is used to allow rapid welding flow. 2.
It\'s better to have a high wattage of high quality (min 80W )
The iron has a good heat capacity, so it can quickly transfer heat to the joint, so you don\'t have to keep the iron on the battery for a long time, let the heat penetrate into the battery, causing damage to the battery.
Spot welding: the reason for our spot welding, because it firmly connects the battery together without adding too much heat.
At present, there are two levels of spot welders in the market: hobby level and professional level.
The price of a decent hobby spot welder is between $200 and $300, while a good professional level can cost about ten times more.
So I would suggest buying a hobby-grade spot welder from any online store such as: Banggood, AliExpress or eBay.
I am using SUNKKO 709A 1.
Banggood\'s 9kw spot welder.
Before connecting the battery in parallel, check the individual battery voltage first.
For parallel batteries, the voltage of each battery should be close to each other, otherwise a large amount of current will flow from the battery with higher voltage to the battery with lower voltage.
This can damage the cells and even cause a fire in rare cases.
If you are using a brand new battery, the battery voltage is close to 3. 5 V to 3.
7 v, you can connect them without worrying too much.
However, if you are going to use the old laptop battery, make sure the battery voltage is almost the same, otherwise, charge the battery to the same voltage level with a good lithium ion battery charger.
Before connecting 18650 batteries together, I charged them with my Nitecore SC4 charger.
To make a battery pack, you must first determine the nominal voltage and capacity of the battery pack.
Whether it\'s voltage, mAh/Ah or Wh.
In order to achieve the required capacity, you must connect the unit in parallel (mAh )
And series such a parallel group to achieve the nominal voltage (Volt ).
Our requirements for this project are: 11.
1 V and 17 Ah battery packaging specifications for 18650 batteries used: 3.
7 v and 3400 mAhCapacity (mAh)
: Expected capacity of Battery Pack = 17 AH or 17000 mAh.
Capacity per unit = the number of units required for a 3400 mAh parallel connection = 17000/3400 = the abbreviation for 5 noscommon parallel units is \"p\", so, this package will be called \"5 P package \".
When 5 units are connected in parallel, you end up making a unit with a higher capacity (i. e 4. 2 V, 17000 mAh)Voltage(Volt)
: The expected nominal voltage of the battery pack is 11. 1V.
Nominal Voltage = 3 per battery.
The number of cells required for 7 V series = 11. 1 /3.
The cell in the 7 = 3 nosCommonly series is abbreviated as \"s\", so this package will be called \"3 S Package \".
So we\'re going to put three parallel groups (
5 cells per group)
Connect the battery pack in series.
The final pack configuration is specified as the \"3s5 p pack\" with the final specification of 11 \". 1V ,17AH.
As can be clearly seen from the previous steps, our battery pack is composed of 3 series parallel groups (3 x 3. 7V = 11. 1V )
There are 5 cells in each parallel group (
3400 mAh x 5 = 17000 mAh).
Now, we have to arrange 15 batteries correctly in order to make an electrical connection between them and the BMS board.
Place the first group of parallel cells (5 nos)
The positive side is up, then the negative side of the second parallel group is placed up, and the positive side of the last parallel group is placed up.
To stand better, you can see the picture above.
You can make the packaging by assembling the battery using hot glue or using a plastic 18650 battery bracket.
I used the plastic 18650 battery holder/gasket to assemble 15 batteries.
The main advantage of using this cell scaffold is 1.
You can customize the packaging of any size according to your requirements.
It\'s like solving a problem. 2.
It provides space between the batteries, allowing fresh air to pass through, and the batteries are easily cooled. 3.
It makes your battery pack solid and reliable. 4.
It provides safe anti-vibration function for your battery packNow. Now it\'s time to know the procedure to use the spot welder (
I\'m talking about the spot welding machine I used in this project).
Spot welding machine has three welding options: fixed welding head, movable spot welding pen with foot switch.
I prefer to use the second option.
You must have the nickel bars and welders ready before welding.
Cut nickel strip: place the nickel strip on top of 5 batteries (parallel )
, Make sure it covers all battery terminals, leaving more than 10mm pieces for connecting it to BMS and cutting.
Used to cut small nickel bars in series as shown in the figure.
The parallel connection requires 4 long bands and 10 small bands for the series connection.
Connect the first parallel group negative end to the positive end of the second group, and then connect the negative end of the second group to the positive end of the third group.
Welding battery strips: This welding machine can be used to weld pure nickel and nickel-plated steel bars.
You have to adjust the welder pulse and current knob according to the thickness of the nickel strip. For 0.
15mm nickel bar, press the pulse knob 4 p and the current knob 4-5. The same is 0.
2mm nickel bar, press the pulse knob 4 p, 6 p and current knob to 7-8.
Make sure to compress the solder pen with nickel bars and battery terminals and press the foot switch.
You will notice a small spark with two point marks on the stripe.
Welding success: you can bring inspection welding quality by pulling nickel.
If it is not pressed down with a hand or requires a lot of strength, then it is a good weld.
If you can peel it off easily then you have to increase the current.
Safety: Be sure to wear safety goggles before starting welding.
Battery Management System (BMS)
Is any electronic system that manages lithium batteries, the main function is 1.
Monitor all parallel groups in the battery pack and disconnect from the input power supply when fully charged (near 4. 2V )2.
Balance all battery voltage 3.
Packages from over-are not alloweddischarged.
Two important parameters required to purchase BMS are: I)
Number of series units-
2 S/3 S/4S ii).
Maximum discharge current-
Like 10A/120a/25A/30 A for this project, I used 3 s and 25A BMS boards.
These are the specifications of BMS: The overvoltage range: 4. 25~4. 35V ± 0.
Discharge voltage range above 05 volts: 2. 3~3. 0V ± 0.
Working temperature:-05 v maximum working Current: 0 ~ 25
40 ℃ ~ How to connect 50 ℃?
Connect BMS as shown in the wiring diagram.
There are four pads in BMS: B-,B1,B2 and B+.
You have to connect the first parallel group negative terminal bus to B-
The positive terminal bus to b1.
Similarly, the third parallel group of B2 has a negative end bus and a positive end bus of B.
You can weld the nickel bars to BMS or you can weld them to the PCB pads.
For a strong connection, I prefer to weld the nickel strip to the PCB.
First apply flux to the end of PCB pads and nickel bars.
After that, through a small amount of welding, they are then welded together and all the pads are welded together.
Credit: the wiring diagram is taken from the Banggood product page.
To avoid any accidental short circuit, there are exposed nickel bars around the battery pack, I designed a shell for it.
I designed the case for my battery pack using Autodesk Fusion 360.
The shell consists of the main body and the top cover.
You can download.
The Thingiverse STL file.
I use my creative CR-
10 s 3D printer and 1.
75mm green PLA filament for printed parts.
It took me about 6.
Print the main body for about 5 hours.
Print the upper cover in 2 hours.
My settings are: print speed: 70 mm/s layer height: 0.
3 fill density: 100% extruder temperature: 205 degC bed temperature: 65 degC usually the standard battery has only two terminals for connecting the load and charging the battery.
In addition to that, I have added a battery level indicator to view the battery level when needed.
I used a 5mm DC jack (12V /3A )
For input/output, the 3 s battery indicator module can view the battery status and turn the battery indicator on/off.
Now, let\'s go ahead and discuss the wiring of the components.
I have prepared this simple wiring diagram for all components.
This is very simple!
I used a heat shrink tube to insulate the conductive parts.
Note: Do not Weld wires (P+ and P-)
Please connect to BMS before installing the component to the enclosure.
First install the component into the corresponding slot in the 3D print enclosure.
You can see the picture above.
Welding positive (red wire )
From the DC Jack and rocker switch to the P of the BMS, from the DC Jack and battery level indicator to the P-of BMS.
Then apply hot glue to the bottom of the battery box, and then fix the battery pack.
Therefore, it will be firmly fixed on the seat to prevent loose wire connection.
Finally, screw the top lid in place!
I fixed the lid with 3 m x 10 screws.
The battery pack is now available.
Charge the battery pack: you can charge the battery pack 12.
6 v DC adapter like this.
You can get it from AliExpress or eBay easily.
Hope you enjoy reading my project as much as I do.
I will encourage you to do this if you want to do it yourself and you will learn a lot.
If you have any suggestions for improvement, please comment below. Thanks !