Introduction: How to Make 9v Battery Pack Using 18650
How to make 9v battery pack using rechargeable 18650 lithium-ion cells that are common and easy to reuse in a power pack, connected in series or parallel to form your desired rechargeable pack
Step 1: 9v Battery (nine Volt Battery)
he nine-volt battery, or 9-volt battery, is a common size of battery that was introduced for the early transistor radios. It has a rectangular prism shape with rounded edges and a polarized snap connector at the top. This type is commonly used in walkie-talkies, clocks and smoke detectors.
The nine-volt battery format is commonly available in primary carbon-zinc and alkaline chemistry, in primary lithium iron disulfide, and in rechargeable form in nickel-cadmium, nickel-metal hydride and lithium-ion. Mercury-oxide batteries of this format, once common, have not been manufactured in many years due to their mercury content.
Step 2: 9v Rechargeable Battery
There are at the moment some 9v rechargeable batteries but the capacity is low and the price is quite high,so in addition, we will make a simple exercise of how to wire some 18650 cells in series to form a 9v battery pack rechargeable with the capacity of 2500mA.One other method is to use rechargeable aa batteries but we have to use more,because the voltage of a rechargeable AA is around 1.2v,and the lithium ion is 3.7V
Step 3: 9v Battery Parts
Wiring the battery pack
-2x 18650 battery
-pp3 connector from an old 9v batery
Step 4: 9v Rechargeable Battery
The first step is to find an old 9v battery and remove the pp3 connector that makes this 9v battery special than the other commonly batteries. After we have the connector we will proceed in making a simple series connection,we have chosen this method of 18650 battery holder because is easier, safer and in any case, we can easily replace the cells. With this lithium batteries we try to stay away as much as possible from soldering direct on them
Step 5: 9 Volt Mith
Most nine-volt alkaline batteries are constructed of six individual 1.5 V LR61 cells enclosed in a wrapper. These cells are slightly smaller than LR8D425 AAAA cells and can be used in their place for some devices, even though they are 3.5 mm shorter. Carbon-zinc types are made with six flat cells in a stack, enclosed in a moisture-resistant wrapper to prevent drying. Primary lithium types are made with three cells in series.
So we will replicate just that but we will use more affordable and available lithium rechargeable 18650 cells
Step 6: Finishing Project
After we have connected all the wires and put some hot glue on the pp3 battery terminal we will have a fully functional 8.4 battery wich will outperform the standard 9v battery in many ways.As a method of charging this lithium battery are different then lead acid or nicd, we need a constant current source till 4v and then a constant voltage till 4.2v as recommended charger imax b6 .
Step 7: Battery Pack the Beginning
Now you have made your first battery pack ,take in to consideration that the big pack even the big powerwall from TESLA is made by lots of lithium-ion cells stacked together in multiple combinations of series and parallel but all that in a future tutorial for now engoy this small 9v battery pack and dont forget to find us on youtube.
See you there ...
4 years ago
Well, if my maths are correct, 2 x 3.7 Volts are only 7.4 Volts, not 8.4 Volts. I have not tried it out but I suppose, most 9 Volt devices will not work with just 7.4 Volts ...
Reply 2 years ago
In most basic electronics there is room for voltage difference when the 3.7v batteries are fully charged they can be over 4 volts each... I have used the 3.7v 18650 batteries in different configurations as long as your are within 10% of the required voltage there is not a problem - probably the only downside is making sure they don't run down below the minimal charge voltage. I am doing an instructable soon to outline what I now do instead of buying standard batteries and instead replacing them with 18650 batteries in series.
Reply 4 years ago
This is the nominal voltage,or reference voltage,a li-ion or 18650 is fully charged at 4.2v
Question 3 years ago
4 years ago on Step 7
Hi,18650 batterys must between 2.5/4.2 volts....if you dont use BMS(battery management system circuit) 2 possibility : under 2.5 volt, battery destroyed,above 4.2 volt, explosion....
you can use this(https://www.banggood.com/3_7V-9V-5V-2A-Adjustable-Step-Up-18650-Lithium-Battery-Charging-Discharge-Integrated-Module-p-1264852.html?) for safety usage. :)
Reply 4 years ago
With this type of batteries there are to key poits in protecting them do not overcharge them,anddo not over discharge them,and more if you will not go fullcycle they will last longer