Connect with us

Boost low volts at a few amps

Discussion in 'General Electronics Discussion' started by Nick Lee, Mar 4, 2018.

Scroll to continue with content
  1. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
    Hello,

    I am a general amateur in electronics.

    I have a bluetooth speaker i made myself but i have an issue, it is powered with two 18650 cells in parallel (parallel for charging via a 1s micro usb charger) they go through a eBay boost converter, thus going from 3.5-4.2 (1s LiOn voltage) to the minimum required voltage for the amplifier, around 7.5 volts. The problem is that the converter only delivers about 700mah max. With heavy bass the converter doesn't match the current requirements and it pops loudly. So i need a a boost converter that can boost the cell voltage and deliver 2-3 amps successfully.

    Please let me know. Thanks, Nick~
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,660
    2,696
    Nov 17, 2011
    Have you searched online? Suitable converters can be had from many sources.
    Before you buy a new converter, try adding a large buffer capacitor to the output of the present converter. E.g. a 2200 μF / 16 V electrolytic capacitor. This capacitor will be charged by the converter and will deliver peak current for the bass.
     
  3. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
  4. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    What is the speaker impedance? If you are using 8Ω speakers and it is a class D amp, the maximum current will be just under 1A. For 4Ω iw would be 7.5/4 = 1.875A. If it is a class AB amp running from 7.5V, those numbers would be half of that, so, I am assuming class D or bridge tied class AB.

    You will need twice the current from the batteries, so something like 4A.

    What is is the capacity and discharge rating of the 18650 cells. You should be okay with even 2 paralleled for 4A, but it is worth checking. If you are buying these off Ebay, derate by 50%, and even that might not be enough.

    Also, check the max power rating of the booster. For the 4Ω case you would need 15W. And watch out, the cheap Ebay ones often require an add on heat sink to get to their max power rating.

    Bob
     
  5. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
    i have two 8ohm 15w speakers but i connected the amp to my bench power supply and it went up to 1.7+ amps easy with kicking bass and without distortion or popping. Also the capacity of the batts is around 2.3AH and can probably deliver 15+ amps in parallel.

    Another question, If i raise the input voltage will the amperage go down because A=w/v
     
  6. AnalogKid

    AnalogKid

    2,515
    718
    Jun 10, 2015
    1. Large capacitors as close to the boost converter input as possible.
    2. Search ebay for a larger boost converter module. You cannot possibly build one for less than you can buy one.

    ak
     
  7. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
    are there certain chips i should be searching for that will deliver
     
  8. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
  9. AnalogKid

    AnalogKid

    2,515
    718
    Jun 10, 2015
  10. Nick Lee

    Nick Lee

    9
    0
    Mar 4, 2018
    lol what do you mean by overrated
     
  11. AnalogKid

    AnalogKid

    2,515
    718
    Jun 10, 2015
    To reduce heating problems, use a module that can deliver twice your required output current. If you need 3 A out, use a module that can deliver 6 A. Several reasons for this, but #1 is that the #1 killer of electronics is not plugging it in backwards, or static electricity, or even power-on transients - it is heat.

    Heat weakens things to the point that other things that should be well-tolerated, such as a power-on transient, kills a part that worked fine for years. It is a long, slow thing. You know that standard little box fan in your computer? Fan bearing life increases 50% for every 10 degrees C below the max rated operating temperature. This is a good rule to apply to all electronic components.

    ak
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-