DC boost converter not boosting - Page 1
Forum section: electronics / beginners

author: Lycaon
author_rank: Contributor
timestamp: December 19, 2015, 08:32:30 pm
content: 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, or2. I am using them incorrectly.Any insight?

author: Simon
author_rank: Unknown
timestamp: December 19, 2015, 08:48:42 pm
content: Quote from: Lycaon on December 19, 2015, 08:32:30 pmI think you mean parallel. Step ups are a nuisance, might be easier to put batteries in series and have 7.2V stepping down if your trying to get 5V output.

author: Lycaon
author_rank: Contributor
timestamp: December 19, 2015, 10:21:33 pm
content: Yeah, I did mean parallel. Sorry, been up for like 35 hours heh

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: December 19, 2015, 10:32:06 pm
content: Quote from: Lycaon on December 19, 2015, 08:32:30 pmThis doesn't make any sense.If its set to 3volts, you're not going to get 0.6volts output.How can it be pulling 2.5amps at 0.5volts, if there's no load on the output, there will be little current going in to it, and you're not measuring the input voltage, you're measuring the output?Are you using your multimeter with the probes in the "current" sockets, and simply shorting everything out?Post pictures of what you've done.

author: langwadt
author_rank: Super Contributor
timestamp: December 19, 2015, 11:05:33 pm
content: Quote from: Lycaon on December 19, 2015, 08:32:30 pm0.6V sound like a diode, have you swapped plus and minus ?

author: Lycaon
author_rank: Contributor
timestamp: December 19, 2015, 11:43:11 pm
content: I'll get comprehensive pics of everything for you guys this evening. I have a cheap multimeter that is probably one step up from a harbor freight one, but it tends to agree with a quick arduino based voltmeter made from a schematic I found on the net.