Hey guys (or should I say "hoyi" to emulate Dave. :p)
I've been into electronics for a couple of months now, and I decided to make my first project a battery power pack after having wasted $15 on one of those cheap 18650 single cell powered jobs from Kng Soopers.
Anyway, I salvaged some 18650s from a laptop battery and hooked them up in series for a hefty 10800 (ish) mah of 3.7 to 4.0 volt goodness, enough to last through even the longest time away from a plug.
The second thing I needed was a boost converter, so I grabbed one of the following:
http://pages.ebay.com/link/?nav=item.view&id=161841071025&alt=webI made sure it was what I needed. Input voltage correct? 2v < 3.7v < 5v, check. Output correct? 5v, check. Hell, it even had the USB plug.
So I get it ordered and since it was from china, it took like 3 years to arrive, but it finally did and I wired it up. Didn't work. I checked everything with a DMM. Input voltage: 3.86v. Output voltage: uhh... 3.62v? WTF?
I assume the thing is defective and since I did not want to spend another 28 months waiting for mail, I just opted to get different ones from adifferent seller. I grabbed these:
http://pages.ebay.com/link/?nav=item.view&id=401015693773&alt=webI wired the 18650 pack up to the input side, andnat this time their voltage was an even 3.7v... Aaaand the output was 3.67v. Sigh. I even messed with the potentiomrnters, which didn't change the output voltage -at all-
I finally obtained a couple of these:
http://pages.ebay.com/link/?nav=item.view&id=400544557141&alt=webThe input voltage was 3.6v, and as a test I set the output voltage to an even 3.0v and cranked up the current limit to 3.0a. I connected up the boost converter with the potentiomrnters mentioned above and got 0.6 volts output. Oddly enough, it was pulling 2.5a at 0.5v and the converter got very hot. I swapped it out for the other identical converter with the same results. I also tried the first converter with the USB output, same results.
So there are basically two choices:
1. All three converters are defective, or
2. I am using them incorrectly.
Any insight?