Question Dealing with Different Voltages

Discussion in 'Wii' started by rcb123, Mar 28, 2019.

  1. rcb123 .

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    Note: This is essentially a condensed and less convoluted version of my first post (in the Console Modding section). If you want a full description of the situation go there.

    My question is, given three different voltage sources (around 0.1-0.2V difference), how would you balance/equalize them so that under a load the higher voltage source won't be the only one having current drawn from it.

    Setup uses three separate rechargeable batteries, but diodes prevent voltages from equalizing.
    Edit: Just for clarification, this is used in a Wii battery pack of sorts.
     
  2. cheese the tallest memer in town Staff Member . . .

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    Is there a reason you are using three separate packs? An easy solution would be to combine all the packs together into one larger one
     
  3. rcb123 .

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    I'm using a 6 layer Wii (where can I find a 4 layer Wii, no luck on ebay) and the charging board that comes in each pack can only supply 2.1 A at 5 V. Thought that this might be easier/cheaper than ordering another board.

    These are also suspiciously cheap, 8 18650s for 15$.

    I've attached a picture of the board. This one is dead (I suspect from overcurrent, explained in my other post), but the three working packs are identical to this one. Each pack has 8 18650s in series being boosted to 5V. The total rating at 5 V is 20,000 mAh (I know its excessive, but for long drives I thought it would be nice).

    Should I just take the output of the cells directly and only use the circuit for charge? If so I would need to put two packs into series for the output, as my boost converter is unstable around 3-4V (even though its rated for 3-30V) and will spike to high voltage (~30V) at the low 3 V range.
     

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  4. rcb123 .

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    So, a quick test with the output of a good battery pack (before it goes to the board) led to the Wii not powering on. I don't know why, as the 8 batteries in parallel should have provided more than enough current even after the boost converter. I tested the Wii to draw around 20W peak (with disk drive) and at a voltage of ~12.46 on the boost converter and more than enough current, the Wii only made small clicking noises.
     
  5. Stitches 2 and a Half Dollarydoos Staff Member . .

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    Yeah, that plan is not going to work out. You need a properly built and rated 12.6v or 14.8v pack to do what you're trying to do. Those 5v battery banks are generally the cheapest shit chinesium that can exist without spontaneously combusting, and they're definitely not designed to be run in series like that.
     
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  6. rcb123 .

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    I understand that, but cheap is the point here.

    They don't need to be run in series, but as I stated above, one battery pack going through one boost converter was unable to power the Wii, can anyone explain why.

    Also, can anyone actually answer my original question.
     
  7. GingerOfOz no wario Staff Member . .

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    To answer your original question:
    You shouldn't use any part of this pack at all. Sketchy batteries are a bad idea. Boost converters are a bad idea. You need to get some legitimate 18650 batteries (These will run you $20-$25) and a protection/charging circuit for said batteries. Boost converters are temperamental and are not meant for boosting voltage/current to the levels that an untrimmed Wii needs. Nothing good can come of trying to use this setup.

    So yeah, Stitches is right. Cheap and portablizing are an explosive combination, and I mean that literally, not in a good way.
     
    Last edited: Mar 30, 2019
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  8. Stitches 2 and a Half Dollarydoos Staff Member . .

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    Because when you double the voltage, you halve the current, and lose a chunk to heat inefficiencies. An untrimmed Wii needs way more current that one of those power banks can supply, even if you have a 5v to 12v boost converter. Especially if you have a 5v to 12v booster. Those power banks already boost the 2.7v-4.2v range of the cells to 5v, so you're boosting twice and losing a huge chunk of power to it. Even if you ran the 3 banks in parallel to get enough current, you'd still have poor results at best.

    As for your original question: The tiny voltage differences between the bank outputs won't affect the draw, you don't need diodes, they'll all be pulled from equally assuming they can all output the same current. But as I said before, it's a bad idea. You'd be better off buying some cheap 18650 battery holders from ebay, putting the cells from the banks in them, and then wiring them up to a 14.8v BMS.

    (And as Ginger said, cheap and portablising do not go together. Just ask Mumble)
     
    Last edited: Mar 31, 2019
  9. rcb123 .

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    Ok, well thank you, especially Stitches. New plan is a 4S 4P 14.8 V 18650 pack. I'll order a BMS online, will probably use a boost converter to get the voltage needed for charging (from a 9v dc supply), and use a buck converter on the output to the Wii and the monitor. I'll get new cells, unless I can use ones from a laptop battery. I'm also going to borrow some actual equipment for this as well (like a soldering station as I'm currently using a Radio Shack soldering iron). Anything seem wrong with this? I'm not concerned about the size of the battery pack as much as I am the playtime. Also, are all colored Wii's 4-layer. I think I've just been dumb by only looking at the bottom label (rvl-001) and I'm wondering if these Wii's in color (ex. black) may actually be 4-layer.

    (sorry if I seemed stubborn earlier, and when I referred to the battery pack in my previous post, I was talking about the output of the cells themselves. I now realize that my boost converter was set to too low of a voltage anyway, and under load that would drop to under what the Wii could tolerate)
     
  10. GingerOfOz no wario Staff Member . .

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    Stop with the boost converters. Boost converters are bad. You may need a specialized smart charger to use with your 14.8v pack, depending on what protection circuit you end up using.

    Other than that though your plan sounds good. Check the guide section for an in depth explanation about how to identify 4 layer motherboards, it'll do the best job of explaining
     
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  11. Stitches 2 and a Half Dollarydoos Staff Member . .

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    Yeah, just get a proper 14.8v smart charger off ebay and do it right. Lithium batteries MUST be charged by a matching smart charger unless the BMS specifically states that it handles charging off dumb DC. And even then don't use boost converters for that, they aren't very safe for the purpose.
     

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