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  • tomzarbo
    replied
    Thanks for the good info, Ben.

    I admit, I didn't know what I was doing, I was just experimenting a bit, and flying by the seat of my pants. I wasn't aware that it could be dangerous.
    Didn't get a chance to open up the radio and try some of my caps in action on the actual radio itself. I will be careful when doing so looking at voltage ratings as I go. Thanks for the warning.

    TomZ

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  • 1100xxben
    replied
    Umm, Tom... You don't ever want to exceed the voltage rating of a capacitor! If you were putting the 12V output of your converter on a 2V supercap, I'm honestly surprised you didn't literally blow the thing up. When electrolytic capacitors get high voltage or reverse polarity... they typically are destroyed in grand fashion and will literally explode like a party popper. Jump to about 1:10 in this video, for example: https://www.youtube.com/watch?v=dja1CrpJxXc. Honestly, a good electronics design will also de-rate the capacitors so that you will never exceed 70-80% of the rated voltage (I prefer 50-60% if physical/cost constraints allow). If you're using them on your boosted 12V rail, you should have at LEAST 15V rated capacitors, and I would personally look to use 25V rated caps. Depending on how well designed and stable your boost converter is, you may have small spikes that exceed 13-14V.

    Putting capacitors in series can be a bit of a task too. Yes, you could put ten 2V caps in series to have a "20V" rating, but you divide the capacitance when doing that. For example, ten of your 1F caps in series will only yield 0.1 F of capacitance. The bigger issue though, is that the voltage will not be equally spread across the capacitors unless the ESR and capacities are matched perfectly, so the 20V rating isn't legitimate. You need to use resistors in parallel with the capacitors to balance the voltage. Just search for "series capacitor balancing resistors" for more information on that.

    Another thing to keep in mind here is that adding massive amounts of capacitance to the output of your boost converter may cause instability. If you start reading through power supply spec sheets of well developed designs, they will specify a maximum amount of capacitance for the load. Also, a large capacitance load on a power supply may cause issues at start-up since you're essentially applying a short circuit in the short term.

    But, I will reiterate... do not EVER exceed the voltage rating of a capacitor. It makes them VERY unhappy!

    -Ben

    P.S. Resistors dissipate power and create heat. As long as the circuit is designed properly, resistors getting hot can be normal. Capacitors should not be dissipating power (the reality is that there are losses in the ESR, but this should be minimal). If your capacitors are getting "DANG TOASTY", as you put, then something is very wrong (probably either exceeding the voltage rating or polarity is backwards).

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  • tomzarbo
    replied
    Well that didn't go as expected.

    I ordered several different caps in varying ranges to test this out.

    Sort of.

    I hooked the same battery charger/booster board to another of the same amp board on the bench and hooked it up to a set of Neo Nano speakers as well as trading off with one of the NN's for a subwoofer. I did this rather than take the whole shebang out of the tiny radio as it's not so easy for your fine, fat-fingered friend to do this. I figured a set of Neo Nano's and a 7" subwoofer would tax the setup more than a pair of DMA45's, especially since it was the bass hits where the issue showed up.

    Sheesh, I had the entire room shaking with the bass at medium to nearly loud volume and it wasn't even breaking up until I got into the semi-loud territory. I was just shocked how much "Ooomph" this setup had running off of 2 18650's boosted to 12 volts.

    I did 'test' out some of the caps with this setup. I went + to + and - to - on the amp voltage input. I ended up getting a 1 farad polarized cap that was rated at like 2 volts or so. That got DANG TOASTY pretty quick, I have multiples of those so I could add a few to bolster the low voltage rating if that ends up being a good value. I also used a 1000, 2200 uF and 3300 uF with higher voltage ratings if I'm not mistaken.

    I had to get it cranking uncomfortably loud to get any breakup going on without the cap to see if adding any of them helped any. Honestly, I couldn't tell if any of them made any difference at all.

    Guess I'll have to pull the guts out of that tiny little radio and do my experimenting that way.

    I'm so surprised how loud this little setup got before 'crapping out' so to speak. I almost want to build a little box for this combo and hook it up to some of my 'big boy' speakers just to see what it could do with those.

    Well, more testing to come tomorrow (probably) on the real thing.

    TomZ

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  • tomzarbo
    replied
    Originally posted by 1100xxben View Post
    Tom, If your boost supply can only supply 450 mA, that means it can only supply 5 Watts of power, and that might even be a peak number. I'm guessing you can EASILY exceed that, and no reasonable amount of capacitance is going to allow you to make it through any kind of long, loud bass hit.

    Also, when you mention your battery-direct solution of "1300 mA", I'm assuming you mean they are 1300 mAh capacity. That is how much total energy the batteries hold, but they will likely supply several amps of current, especially in short-term bursts.
    Good points Ben.

    I suspect your estimations are pretty close. My back of mind guess was similar. And yes I was speaking of the mAh capacity of the batteries I previously used.

    I'll experiment with the caps for the fun/education of it, but it very well may just have to be this way. It's fine, the output is loud and clean... just that last bit of volume is now "clicky" instead of slightly distorted, but at least my niece will know when to back it off a bit.

    My wife thought it was much more loud than our niece could play in in a NYC apartment without bugging her neighbors anyway..

    I'll report back with any results..

    TomZ

    Leave a comment:


  • 1100xxben
    replied
    Tom, If your boost supply can only supply 450 mA, that means it can only supply 5 Watts of power, and that might even be a peak number. I'm guessing you can EASILY exceed that, and no reasonable amount of capacitance is going to allow you to make it through any kind of long, loud bass hit.

    Also, when you mention your battery-direct solution of "1300 mA", I'm assuming you mean they are 1300 mAh capacity. That is how much total energy the batteries hold, but they will likely supply several amps of current, especially in short-term bursts.

    Leave a comment:


  • 3rutu5
    replied
    Originally posted by tomzarbo View Post
    Well I don't have a single polarized cap in that value range, heck not even in any range. I was looking for some old electronic equipment to salvage one from possibly, but nope.
    If I want to play around with this idea, I'll have to order a few then.

    So I have suggestions of 50-100 microfarad and 2200 microfarad.

    PE has these polarized caps: 470 microfarad... 470uF 100V Radial Mini Electrolytic Capacitor (parts-express.com)
    and these 680 microfarad ones: 680uF 16V High Temp Radial Electrolytic Aluminum Capacitor (parts-express.com)
    They have a larger 100 microfarad unit but it's huge and $5 so...

    neither get close to the 2200 used in the setup shown by 3RUTU5.

    PE just doesn't have many polarized caps as they aren't used in crossovers.

    Edit: Just ordered an assortment of larger values to play with. 100, 1000, 2200, and 3300 microfarad. I'll test it out when they come in.

    TomZ
    I went down to my local hobby electrical mob and picked it from a box. I also did something similar originally and tried to go janzten but the values didn't get higher enough.

    I did literally no research, just copied what was being discussed as I was using the same amp, booster, battery arrangement, so don't know the theory behind it.

    Leave a comment:


  • billfitzmaurice
    replied
    In a situation where a stiffening capacitor works, auto sound, the typical minimum size used is one farad. That's usually with high power amps, but still that's one farad, which is a million microfarads.

    Leave a comment:


  • tomzarbo
    replied
    Well I don't have a single polarized cap in that value range, heck not even in any range. I was looking for some old electronic equipment to salvage one from possibly, but nope.
    If I want to play around with this idea, I'll have to order a few then.

    So I have suggestions of 50-100 microfarad and 2200 microfarad.

    PE has these polarized caps: 470 microfarad... 470uF 100V Radial Mini Electrolytic Capacitor (parts-express.com)
    and these 680 microfarad ones: 680uF 16V High Temp Radial Electrolytic Aluminum Capacitor (parts-express.com)
    They have a larger 100 microfarad unit but it's huge and $5 so...

    neither get close to the 2200 used in the setup shown by 3RUTU5.

    PE just doesn't have many polarized caps as they aren't used in crossovers.

    Edit: Just ordered an assortment of larger values to play with. 100, 1000, 2200, and 3300 microfarad. I'll test it out when they come in.

    TomZ

    Leave a comment:


  • tomzarbo
    replied
    So I'll try a high microfarad polarized cap if I can find one, and connect to the amp power in. It will be interesting to see if it helps or not.

    Thanks for the input.

    I'll let everyone know if it helps or not.

    Tom/Z

    Leave a comment:


  • 3rutu5
    replied
    another thing i just thought of, the DC-DC converters? I've seen people incorporating these into the input lines to remove static noise, and i think even on power lines after the buck converter to take the signal, filter it and output it as a clean version (well that was my take on it). I havent yet tried this so could be so far off the mark it isnt funny and i dont think i could find one at the time that had a 5v to 5v with 2A output

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  • 3rutu5
    replied
    Looks similar to what this little Bose kit would do as well
    something else I just noticed.....a separate charging board to the 1S BMS?
    Attached Files

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  • DeZZar
    replied
    Originally posted by tomzarbo View Post
    So if I wanted to try a cap, it would be across the amp power terminals?
    this is how it's done in car audio installs.
    Click image for larger version

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  • billfitzmaurice
    replied
    Originally posted by tomzarbo View Post
    This setup worked previously with the same amp running off of 12 volts from three Lion batteries outputting the same 12'ish volts with no clicking or any funny business, the amp seemed to be doing fine. I was able to overdrive the speakers before the signal got ugly.
    In that case I'd say the power supply you're using isn't adequate, and I doubt that a cap will help. It can't increase the available current from the batteries.

    Leave a comment:


  • tomzarbo
    replied
    Just to clarify... This setup worked previously with the same amp running off of 12 volts from three Lion batteries outputting the same 12'ish volts with no clicking or any funny business, the amp seemed to be doing fine. I was able to overdrive the speakers before the signal got ugly.

    Now with the booster board, it's clicking at high-ish volume on power-hungry bass hits. The booster/charger board can only deliver 450 mA I think I read, so that's a lot less than the other battery-direct setup of 1300 mA or so. I suspect that's the issue. The batteries are two 2100 mA 18650's so they by themselves have enough amperage to deal with these speaker/amp combo I would think. It's just that they are being 'boosted' to 12.1 volts instead of running direct.

    So if I wanted to try a cap, it would be across the amp power terminals? I was thinking inline with the positive, but I've never really looked into it... well, whatta-you-know? Just learned something That would be a Non-Polarized cap then. I think I may have a few smaller-sized caps in that value range. I'm going to try it sometime this weekend if I get time.

    Thank you all of you for your input, comments and thoughts on this. I know there are fewer of us on here the past few years, but you guys are really great and most helpful when trying to figure out stuff like this.
    I really appreciate it.

    TomZ

    Leave a comment:


  • devnull
    replied
    Tom.
    in your post you said wired in series, it should be wired in parallel across the amp power terminals. I'm going to guess 50-100 uF should help.

    Leave a comment:

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