Power bank circuit

Homemade Powerbank using Li-ion 3.7v Battery

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Power bank For Mobile/Smartphone

What is a Power bank

When we go away from home then I face a very common problem, that is power backup of mobile phones. During travelling, it is a very common problem to get regular power backup.  If you’re traveling or out you won’t have a chance to recharge your device, simply plug in your power bank and charge it right back up again.

Powerbank is a good solution for portable mobile or other electronic gadgets charging without an AC adaptor when we out of the home. Powerbank is a portable DC power source to provide a backup for your electronic gadgets. The power is stored in a power ban by charging and it can be used when you need,  In any power bank, A battery or combination of some small special batteries (cells)  used to produce the power source to provide for mobile or other electronic gadgets battery charging.  The USB port is used to input for charging and also for output. It has a circuit to control the power flow to provide a regulated supply.

Very different types of power bank available on the online and local market, but the quality which i need they don’t provide us. When we get any branded product at which we can trust that brand, the quality is good but these branded power banks are very costly.

Power bank used mostly Li-ion battery -Li-ion battery has very good power density and also cheap in cost.

some power banks used Li-Po (lithium-polymer battery) – Li-po is a better choice than Li-ion battery but it has higher manufacturing costs.

How to Make A Power Bank At Home

When we think to make a power bank then first of all we need a battery that is also rechargeable for charging many times as per requirement. The second thing is to maintain the power capacity (mah).

Rechargeable battery

voltage Regulator


USB socket

You can also use any old battery cell from a laptop battery or other, but that can no sufficient charging ability. In the regulator circuit for this power bank I use 5v regulator ic L78S05, This is not a normal LM7805CT ic, but the pinout and looking size are the same as any 78xx regulator ic. So I suggest using only this ic. But if you use LM7805CT then the output current is not more than 1 A, in this case, your mobile battery takes more hours to get charged.

The L78S05 provides up to 2A current at the output with 5v. L78S05 is a three-terminal Fixed voltage regulator that can deliver output current over 2A.



In this circuit, there is a total of 4 batteries are used. Two batteries are connected to each other with a series connection to increase voltage. Two other batteries are also connected in series to increase voltage. As we know that in the series connection of the battery, only the potential difference (voltage) increased but the Current is the same. So For increasing of current both (which are connected in series) batteries are now connected with parallel connection. 

First combination of 2 series battery make 3.7 + 3.7 = 7.4v (current is equal to one battery)

The second combination of 2 series battery also make 3.7+3.7 = 7.4v ( current is equal to one battery)

Now Both outputs of 7.4v are connected with the parallel that produces 7.4v But the Current is Equal to increased by adding both 2 outputs. it means now the output is 7.7v and the current capacity is  Double (if each battery is of 4000 mah then the overall output power is 4000 +4000 = 8000mah). Because in the parallel combination of batteries voltage is the same but the current is equal to adding of both batteries.

how to make Power bank circuit with aa battery

how to make power bank circuit

usb socket pin

usb pinoutmicro usb

What is the meaning of 5000mah, 8000mah, etc 

1000 mah = 1 Ah (Ampere per hour)

For example

if you have a 5000mah power bank then this provides continuously 1 hour with the 5-ampere current if your device consumes 5 A.

If you have an 8000 mah power bank – it means it provides continuously 8 A current till 1 hour, if your device consumes 8 A.

Components List

Rechargeable Battery 3.7v (minimum each 2000mah) – 4

IC L78S05 (5v 2A Regulator)-1


Capacitor 0.33uf-1 (334), 0.1uf-1 (104)

Connecting Socket Micro USB and USB 2.0 cable

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3 thoughts on “Homemade Powerbank using Li-ion 3.7v Battery”

  1. Wow, this is a very detailed and helpful post! I’ve been looking for a circuit diagram for a homemade power bank and this 10000mAh one is perfect. I was wondering if you could provide some more information on the voltage regulation and charging circuits, I’m still a bit unclear on how to implement those parts. Great work and thanks for sharing your knowledge with us!

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