When we go away from home then i face a very common problem , that is power backup of mobile phone. During travelling it is very common problem to get regular power backup. If you’re travelling 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 AC adaptor when we out of home. Powerbank is a portable DC power source to provide a backup for your electronic gadgets. The power is stored in 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 . USB port is used to input for charging and also for output . It has circuit to control the power flow to provide regulated supply.
Very different different types of power bank available on 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 bank 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 bank used Li-Po (lithium-polymer battery) - Li-po is better choice than Li-ion battery but it has higher manufacturing costs.
When we think to make power bank then first of all we need battery that is also rechargeable for charging many time as per requirement. Second thing is maintain the power cappacity (mah).
You can also use any old battery cell from 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 pin out and looking size is same as any 78xx regulator ic. So i suggest to use only this ic . But if you use LM7805CT then the output current is not more than 1 A, in this case your mobile battery take more hour to get charge.
The L78S05 provide upto 2A current at the output with 5v. L78S05 is three terminal Fixed voltage regulator that can deliver output current over 2A.
In this circuit there are total 4 batteries are used. Two battery connected each other with series connection to increase voltage. Two other batteries are also connected in series to increase voltage. As we know that in series connection of battery only potential difference (voltage) increased but Current is 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)
Second combination of 2 series battery also make 3.7+3.7 = 7.4v ( current is equal to one battery)
Now Both output of 7.4v connected with parallel that produce 7.4v But Current is Equal to increased by adding both 2 output. it means now output is 7.7v and current capacity is Double (if each battery is of 4000 mah then overall output power is 4000 +4000 = 8000mah). Because in parallel combination of battery voltage is same but current is equal to adding of both battery.
1 mah = 1 Ah (Ampere per hour)
if you have 5000mah power bank then this provide continuously 1 hour with 5 ampere current if your device consume 5 A.
If you have 8000 mah power bank - it means it provide continuously 8 A current till 1 hour , if your device consumes 8 A.
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