Hi,
I am new this forum and a software engineer by profession. But I have immense interest in electronics. I am an amateur photographer too. So being in Photography I have learnt eneloop pro batteries are best rechargeable batteries. I have around 60 eneloop Pro battery all working fine. Now I want to construct a smartphone charger which can use eneloop pro batteries (required number) and charge the smartphone efficiently using usb cable.

I need help in designing the circuit for taking the input from AA eneloop pro battery and producing output which can be used to charge my smartphone.

May I please request members to guide me in designing the circuit. Let me tell you I have only basic knowledge of Diodes,capacitor,transitors, resistance never designed any circuit earlier

 

This is the basic arrangement.
If the batteries can't produce the voltage the "Smart Phone" wants, we can design a voltage regulator.

 

I think Voltage required is 4.2V constant but each eneloop pro provide 1.2V so 4 AA eneloop pro should provide 4.8V now we need to cut down to 4.2V also I have heard tickle charging is good but how to design circuit for tickle charging.

 

A small dc-dc stepup supply is all you need for around $5. This is what I use to charge my phone using 2 rechargeable batterys. Hardly worth building for that sort of money. Most phones I know of use 5V DC as a charge voltage as the regulator is built in the phone.

 

Hi,
Thanks for the info but building is always fun.. by the way the module you have given reference out puts 5v but smartphone battery needs 4.2V and I have heard smart phone battery catches fire if wrong input voltage provided. How is your set working is it efficient. Looking afead to hear from you

 

The biggest issue I can see here already is the batteries you want to use are ~2600 mAh and a common smartphone is listed to have at minimum a similar capacity lithium battery so once conversion losses plus charging losses are factored in you would need at least 6 of your Eneloop Pro batteries to get one full charge into your phone which is something that needs to be considered for overall concept viability.

Personally I would shoot for having all 6 in series and using a buck converter to bring their voltage down the standard 5 volts any device that uses USB type power sources works on.

 

Hi,
Thanks for the info but building is always fun.. by the way the module you have given reference out puts 5v but smartphone battery needs 4.2V and I have heard smart phone battery catches fire if wrong input voltage provided. How is your set working is it efficient. Looking afead to hear from you

Usually the regulator to take the 5 volt usb voltage down to 4.2 is in the phone.

 

The unit I assembled is only for charging the phone in an emergency.

 

I think Voltage required is 4.2V

I have heard smart phone battery catches fire if wrong input voltage provided.

Just out of curiosity, how many hundred dollars worth of Smart Phone are you willing to risk for a $5 hobby project?

 

The biggest issue I can see here already is the batteries you want to use are ~2600 mAh and a common smartphone is listed to have at minimum a similar capacity lithium battery so once conversion losses plus charging losses are factored in you would need at least 6 of your Eneloop Pro batteries to get one full charge into your phone which is something that needs to be considered for overall concept viability.

Personally I would shoot for having all 6 in series and using a buck converter to bring their voltage down the standard 5 volts any device that uses USB type power sources works on.

I liked the answer can you please help me to go ahead I am ok to use 6 eneloop pro. Please help me to design the circuit.

 

Just out of curiosity, how many hundred dollars worth of Smart Phone are you willing to risk for a $5 hobby project?

I have three phone all above 300$ each but I feel if we can built a efficient charger from eneloop pro batteries no risk in it.. Thanks for your reply if you can please help me in designing the circuit

 

I liked the answer can you please help me to go ahead I am ok to use 6 eneloop pro. Please help me to design the circuit.

Not too much to design. Just put all 6 (or more) in series to make a 7.2+ volt 2600 mAh battery and use any basic premade buck conveter board that has a 5 volt or higher input rating.

Or put 10 - 12 in series to get 12 - 15 volts and use the board out of a cheap automotive USB charger adapter with a 12 - 24 volt input rating of which nearly all of them have. That would get you at least 2 full charges on your phone for every single charge of your backup pack device.

 

Not too much to design. Just put all 6 (or more) in series to make a 7.2+ volt 2600 mAh battery and use any basic premade buck conveter board that has a 5 volt or higher input rating.

Or put 10 - 12 in series to get 12 - 15 volts and use the board out of a cheap automotive USB charger adapter with a 12 - 24 volt input rating of which nearly all of them have. That would get you at least 2 full charges on your phone for every single charge of your backup pack device.

I am ok with both the option as I have many eneloop pro battery So I would like to give a try to both if you can give me link to basic premade buck conveter board that has a 5 volt or higher input rating and a link to the board out of a cheap automotive USB charger adapter . I have no experience in electronic so need your help.Kindly help me out

Also I checked my charger has output as 5v 1.2A.. now voltage is fine as we are using converter what about current (Ampere) is any ampere OK..

 

 

Find whatever car charger adapter you like that has the input and output specs you need and take it apart. Odds are you probably have a few laying around or know someone who does.

Google and Amazon or eBay can help with the rest.