How to make power bank with 8 rechargable AA batteries?

i'm a nobody at electronics, electricals and stufs. well i have some rechargeable batteries for some reasons,. 2 of my friend has a portable power bank for their phone. then curiously thinking if i can make that kind of stuf.. (DIY),.. if it possible please help me make this... my AA batteries is 1.5V with 500mah of power if i'm right. , then multiply by 8 so that will be 12V with 4000mah of power? right?. then i want this to charge my phone... recently searching i need to drop the voltage to 5, because if not, my phone battery will or might explode., then my phone will be damaged?.. so i need to make a circuit,, then that my problem, i dont know any thing about resistors and things like LM317, just i don't know anything about that.. i need it be able to be recharge and charge my phone,

so here's another question, expect the wee did make something like that, then how will i be able to charge it?, it's 12v right from the inside? right?..

that all, hope we can make something like this,, if there's a related post, which has been already answered, if this is not possible.. That all.. Advance Thanks for helps... 

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how can i use 12 dry cell battery for power bank for my phone

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kag4323 years ago

You need to be careful with this. DO NOT charge the battery directly this way. If you hook up the batteries to the charging port on your phone then the internal circuitry of the phone will handle the unregulated voltage, but if you hook this directly up to the battery it will likely explode. The phone battery itself cannot handle over 4V and usually around 1A, so you would have to regulate both voltage and current. If you want to charge it without a regulator through the charging port on the phone I would suggest putting 3 AAs in series like in one one of these holders, which would give you around 5V fully charged. Also, AAs are not meant to be discharged at very high currents so I would feel them for 30 seconds or so when you first hook it up. If they get too hot, disconnect it immediately. Feel free to message me if you have any questions, just remember to be safe with these things.

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No you will either wire them in series giving you 12V 500mAh or you will wire them in parallel giving you 1.5V 4000mAh.

This project may help with converting the 12 to 5V for USB. There are more efficient ways to do it but this is the least complex.

https://www.instructables.com/id/Universal-USB-Powe...

Your best bet is to put the batteries into a holder and then pull them out to charge them in their recommended charger. But if you want them to stay as a single pack then any 12V charger for whatever type of batteries they are (NiCad, Alkaline or what not) should do the job. But they all need to be the same brand and about the same age. Otherwise you won't get even charging across the battereis and will run into problems.

ZoneOne26 (author)  mpilchfamily3 years ago

Thank you for the information. not much of how i understand it before. my calculations is all wrong. hahah :D hmm. so it's not possible to charge my phone which has a 3.7V and a 2000mAh with 8 of my batteries in parallel because it will only have 1.5V.. a 12V batteries with 500mAh of power will charge it? right.? then how will it turn out?. i can only get the 500mAh of power out of the 8 batteries?.. or maybe the voltage drop of 12V to 5V will affect the mAh of the batteries, so its not 500mAh if i'm not ussing 12V?...

mAh and mA are 2 totally different things. mAh is a rating of how long the batteries will last. So basically 500mAh says the batteries will run for about 20 hours with a current draw of about 500mA on them. So your phone battery can last about 20 hours with a 2000 mA current draw. That is not how much current the phone is pulling of the battery can provide. Keep in mind those figures are maximum. Real world numbers are far different. Needless to say the 12V configuration will easily charge your phone. Yes you will loose some power through the voltage regulator but it will be fine. Also the batteries can supply more than 2000mA if needed. But it will drain them faster.