MintyBoost! - Small battery-powered USB charger

Step 26 Done!

That's it...go forth and boost!

Comments

[bodybuilding_mike]

with the step up design, isn't the current being pulsed into the ipod...is that bad for the ipod battery?

[Mavamaarten]

500 Hz...
Your iPod won't even notice it :P

[pjax]

actually, because of the filter capacitors, the output doesn't pulse

[krrish009]

thanx.....  a lot........

[svarc]

soo if i add 4XAA batteries 2 of them serial and 2 of them parallel then i would get 3V and 6000mAh ? Then on 100mAh i will get 60h ? Is this theoretically true or not?

[cegu]

If we ignore aesthetics,... could't I just use 4X recargable AA batteries (4*1,2V=4,8V)...connect them to USB extetensior and plug that in iPod(or whatever)?

[damasta]

i think the amps wouldn't be right, you need 100 mA and 4 batteries provide much more

[wackyvorlon]

A key principle is that current is drawn, not pushed. As a simple example, if we have 1 volt, and 100mA current flow - E=IR, giving us R=E/I or R=1/.1, or 10 ohms. The only way I can increase the flow of current through our ten ohm resistance, is to increase the voltage. Even if we have a 1 volt source that can provide 100 amperes, our ten ohm load will never draw more than 100mA. If we increase the voltage to ten volts, we get I=E/R or I=10/10 giving us 1 ampere. It cannot draw more than one ampere. The only way to change the current flow, is to change the resistance and/or the voltage.

nota bene: the subject of current draw is much more complicated than I've explained, but this should convey a basic idea relevant to the circuit being discussed.

[rusty0101]

Actually the amps is related to the load on the power supply. The solution of using 4 AA batteries 'works' for a while, but you run into problems over time as you drain batteries below the input threshold for your device. Some electronics are sensitive to this loss, and either degenerate, or provide 'interesting' results such as distortion, etc. Batteries are generally related in amp hours, which allows you to calculate approximately how long the battery will last under a given amperage load. As noted earlier in the article, AA batteries supply approximately 3000mAh, or potentially 30 hours at 100mA. (drawing over an amp does not always give linear results, 3 amps may last 15 min or less, rather than the 'hour' you might suspect.)