Need USB battery help

I need some advice with a project I'm planning on undertaking.

I've read through Sitnalta's tutorial (, and think it's a great idea, but I'd like to be able to charge anything that can charge via USB.
Because of that, I want to know if fitting a voltage regulator fitted into the same basic concept would improve the design.

I'm only asking because, if I connected my PSP or iPod to this sort of thing without regulator, is it likely to fry them because of the 6v going through it?


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lightpacker10 years ago
everyone needs help once in a while sitnalta's usb charger delivers 5.4 for me at the most (verified) because his design is STRICTLY and ONLY to be used with RECHARGEABLE BATTERIES (sorry for all the capitals wanted for it to stand out) and ive made it and i doesnt seem to charge ipods because of something in their circuitry but psp should work fine(ive heard that soldering the data and white and black ground together will work but not sure if you use alkalines which peak to 1.9 volts sometimes when brand new which will provide 7.6 it will definetely fry the psp not sure about the ipod so if you do decide to make his wonderful charger just make sure to get some good or at least average RECHARGEABLE batteries it really is a great little battery pack use it to charge my psp all the time. ALSO about the regulator i tried it as well and the voltage goes down to 4.2 volts if you use the 7805 regulator because it needs from 7-18 volts to provide at least 5 volts or basically a solid 5.0 volts but a series of resistors might work.
To allow a battery pack like this to charge an iPod (5th generation and possibly others) through a USB adapter, you must connect a 10k ohm resistor (1/8 watt will do) from the power (+) pin to the DATA (-) and a 10k ohm resistor from the power (-) or GND pin to the DATA (+) pin. This tells the iPod that it's connected for charging. This mod would not effect charging any other USB devices either.

I do suggest that you use only rechargeable batteries in that circuit. 1.2v * 4 = 4.8v which would charge a USB device safely.
ian LasVegas10 years ago
Lightpacker is right, the 7805 will drop several volts below five with only a 6v input. Rechargables are a good solution - planet friendly and all. Since the NiMH batteries came out a few years ago I haven't used anything else. If you have to use dirty disposables, you could: A) run the + straight through a big diode. That would drop the voltage by .7 volts, much closer to what you want. B) get a big 5.1 volt zener diode and make a regulated power supply. Zeners don't drop voltage like 7805s do, they just shunt away extra voltage to ground. You might need a really big zener and resistor depending on your current requirements, but you can get quite a bit if the drop isn't big.
WildBlueRhino (author)  ian10 years ago
Thanks very much. This might be exactly what I'm after :D
What would you say about these?:

So can I just use this in series to the battery just as I would if if were like a resistor, or do I have to connect it to the ground as well?
ian WildBlueRhino10 years ago
No. A regular diode (say 1n4148) can be put in series to the battery and that will give a v drop of ~ 0.7 volts. You also need to know how much current you will use or the diode will get hot and eventually release its magic blue smoke. What you found is a zener diode. With the zener, you need to design a zener power supply. That is a resistor from the battery, then a zener from the resistor to ground. The zener acts like an overflow valve, shunting the extra voltage to ground. You need to find a zener calculator on line because you have to calculate how much current will be going through the resistor and diode to calculate their value and (rated) wattage. GOOGLE FOR THIS. You will find nice zener power supply calculators online - they will also show how the supply gets wired up if my description is not clear.
WildBlueRhino (author)  ian10 years ago
Can you recommend the values and power rating of the resistor and zener diode please? I'm just not sure what values to use in these zener calculators
WildBlueRhino (author)  ian10 years ago
Ahh right, I didn't realise it was a release valve like that. just thought it went in series. Makes much more sense to how I had it planned out :) I found a zener calculator like you recommended, but what would you say the maximum voltage and current output by 4 AAs would be? Also, would a zener based power supply always be around 5 volts, even when the voltage may drop below 6 volts? Or, because of the fact that there has to be a resistor in the way, is it always going to drop the voltage/current? Basically, all I'm asking is, is there a way in which the batteries could provide a contant 5v, even when they're running low? (ie: <6v) Also, what sort of output current could I get from this? I know that usb gives 500mA, but is it possible for it to give out 1000mA like my ipod wall charger? I do realise that this would drop as the batteries start to run down.
lightpacker10 years ago
no the question mark is for the entire question about the age and lasvegas advice and the regulator etc. When did you start to Diy
WildBlueRhino (author)  lightpacker10 years ago
Haven't been doing it for long really. Been good with a jigsaw for a while now, and a few months ago thought electronics would be an interesting thing to get into. Especially when I saw this usb battery project. I wish there'd been the option to study it when I'd been at school. Never mind :)
WildBlueRhino (author) 10 years ago
Ok, based on what you two have told me, I've come up with this idea. The idea being, that if I'm using rechargeables/low alkalines, I could switch off the voltage regulator. Let me know what you think. (Image courtesy of TinyCAD)
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