Building Batteries with 1 Port Play and Charge

Discussion in 'Guide Submissions Archive' started by Miceeno, Aug 25, 2017.

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  1. Space Puppy .

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    Miceeno, have you had a chance to test two Red Boards in parallel? I would imagine this would work just like two battery cells in parallel. I saw you mention this in your thread about your portable N64 and didn't even think to do that. This is a much better and cheaper option.

    Great portable by the way, love the 7" screen. Is it widescreen?
     
  2. Stitches 2 and a Half Dollarydoos Staff Member . .

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    Why would you use two red boards? You only need one.
     
  3. Space Puppy .

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    More current with a faster charge time. I would use a 2s2p configuration and one red board as Miceeno did but a charge time of ~6 hrs is not ideal. Since the red board can only deliver 1A of charge at a time, connecting multiple boards in parallel would yield the ability to charge in ~3hrs, but still double your current. One could indefinitely put however many red boards in parallel you want. Voltage regulators are commonly put in parallel, I would imagine this is no different.
     
  4. Stitches 2 and a Half Dollarydoos Staff Member . .

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    Plain protection circuits yes, but the red board is more complicated. The rear board would be trying to pass power to the front board, which has a minimum input voltage of 9v so I don't know if it'd even accept the power in. It could just sit there doing nothing and wasting space and money.
     
  5. Miceeno .

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    @Space Puppy I haven't made it around to testing two boards in parallel, like I said I've been too busy for this. As for the theory behind it, I think it could be done safely but you are limited to one Red Board for every 2s1p set. So in your case you'd have two separate 2s1p batteries that you'd run with one Red Board per set. Then run these two Red Boards in parallel to the portable. The way the Red Board isolates a battery from load while charging makes me believe it can isolate parallel batteries from each other to while charging. I would NOT use this theory in a series set up because protection boards are dangerous to use in series.

    Not possible, the smart chargers would confuse each other's CC/CV cycles.

    -------------------------------------------------------------------------------------------------------

    Look, I understand you want to build the most functional portable possible but here's the simple truth with battery powered electronics. You are in the presence of electricity almost 90% of the time in your day to day. And anywhere you'd want to SIT down to play a portable you'll have access to a charging source. The only place I can think of that you wouldn't have access to power is if you take public transit or are at school/college. If you are taking public transportation your commute will be short enough you can go 30 minutes without playing if your battery dies. And at a college, you can go to the library and plug in. The only time I'm personally not in the presence of electricity is when I'm dirt biking or skiing. As you can imagine when I'm doing either of those activities I'm not really interested in playing my N64.

    As for the other 10% of the time that you are away from electricity, you have plenty of time to get a full charge for those situations. I mean you have to sleep at some point during the day. And if you like 8 hours of sleep then that's plenty of time to charge a portable.

    Here's a quote of what I generally tell people:

     
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  6. Space Puppy .

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    I have ordered a few red boards and will run some tests to see if they can be run in parallel. Not sure if anyone is still curious about the circuit that I was planning on making but I could post that if people would like.

    I cannot see how the red boards CC and CV would get confused as it is completely regulated based off of each individual red boards input regulators. So long as each board has enough current and voltage to do what it needs to, the regulators will take care of the rest on the other end. Im sure that they would start to act weird at some point, but it probably wouldnt be until theres such a large amount of inrush current from plugging in say a 10A charger for 10 red boards and one or a few of the red boards input regulators dies because it has slightly less resistance than the others. But this could be mitigated with the right zener diode, this is how condensor microphones which operate at +48V and are interfaced with smaller signal electronics without breaking them when phantom power (48V) is turned on. I could very well be wrong about this, so please correct me if what I am saying is not true.

    Yes, we are around electricity all the time. This is why many portables don't even have a battery, because its unnecessary if you don't plan to use it away from an outlet. If at the end of all this, its just too much work and not easily done, I will likely settle for a single red board and a 2s2p configuration. That being said, I would still like to try.
     
    Last edited: Nov 3, 2017
  7. Miceeno .

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    You are asking for MY advice. I'm advising if you must run parallel boards then to run 2 cells connected to each individual board. Then run these individual boards in parallel. I haven't tested this so if you must try it be certain to test it throughly.

    As for running multiple Red Boards connected to the same set of cells, I don't think it's a good idea. If these were engineered to be stacked it would be advertised. Since these are from China and the chips have the part numbers rubbed off we can't know what smart charging IC is on board. They are already questionable enough because of this. I have tested and reverse engineered a single board enough to be confident in recommending it. You are free to try what you want. You don't need my permission to try to become a burn victim. I just can't advise you to do something potentially dangerous in good conscience.

    Did you read the part about hot swapping batteries? I had a Galaxy S3 and this was the norm for my day to day with it. It's better than dangerous levels of fast charging.
     
  8. Space Puppy .

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    I had edited my previous post, I did not initially see your first comment that you did not try them in parallel. Apologies for the misreading and any miscommunication. I hope I am not upsetting you with my questions. I was talking purely on a theoretical basis about stacking more in parallel. I understand the risks involved and that is why I am here.

    No I did not read about hot swapping batteries, Im assuming this is where you can replace the dead batteries with charged batteries? Similar to a Gameboys AA batteries.
     
  9. Miceeno .

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    @Space Puppy before you try to hook 10 of these Red Boards of in parallel on one set of cells you need to stop and think about this from all the angles.

    1. My primary concern. Even if the charging works flawlessly, the Red Board is also the PROTECTION circuit. The Red Board is rated at 3 amp max draw. If you use 10 Red Boards you've increased this to 30 amps before the short circuit protection kicks in.

    2. MOSFETs are tricky to manufacture. All the specs on them are usually listed in ranges because they vary from batch to batch. So if you have 10 Red Boards with a variance in the MOSFETs they will switch from running off batteries to charging at different speeds. (This is why when repairing a large amplifier you have to use MOSFETs from the same batch.) You could potentially (for a split second) have some Red Boards charging and some not. You'd be applying power from both the battery and PSU to both sides of the charging IC simultaneously potentially shorting it out. This may not cause failure the first time but eventually it will.

    3. The charging IC's may not play well together. They may cause a small voltage spike when they come on together. This will probably make them think the batteries voltage is high enough to switch from CC to CV. When the voltage settles they will switch back. repeat, etc. Or they could all have different tolerances on fully charged voltages causing some to stay in charging longer than others. Causing some boards to trip overvoltage protection while others are still charging.

    4. If you run the battery low enough to trigger under voltage protection then the boards probably wont trigger together potentially causing more issues.

    Do you kinda get an idea of what I mean? There's more at play here than simply increasing charge current. If you ditch the red board and build your own MOSFET switching circuit with only one protection board and multiple charging modules you'd be safer. I still don't recommend it because as stated above the charging ICs could be unpredictable when you have multiple in parallel. If you are going to build your own MOSFET switching circuit you may as well go the extra mile and build a higher output charging module.

    Here's the text outside of the quote in case you didn't find it:

    Here's an idea, use the Red Board because it can safely play and charge right out of the box. To get around the 1 amp of charge current limitation, build your battery removable. (They make very nice 18650 battery holders for this.) With removable cells you can fully "charge" your portable in seconds. When you connect external power to the Red Board it disconnects the battery from the portable. So you can swap the cells without even needing to power the portable down. And for the times you don't need a quick charge, the 1 amp charge rate is safe and sufficient.
     
    Last edited: Nov 3, 2017
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  10. Space Puppy .

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    Lol I do not plan on actually connecting 10 in parallel. I have thought about this from multiple angles, otherwise I would not be asking for others opinions :). I am purely interested in the thought process behind this discussion as I am an electrical engineer. Im guessing you have your degree as well Miceeno? Everything your saying makes sense, at that point you would likely want to have some input and output protection for each red board. But I get what you mean, at higher current ratings it would likely make more sense to design a different system that is meant to handle that much current and doesn't require a bunch of separate charge management boards.

    I did consider the thought of designing a case to hot swap. I am working on a 3D design and it could be easily implemented. Would also be able to use a standard cell charger for the 18650s instead of having to find wall power that can deliver enough current. No power or charge jack too ;). The more I talk about it, the more I am considering it.
     
    Last edited: Nov 3, 2017
  11. Miceeno .

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    Rofl no, I'm unedjimacated.

    As for the screen size question I missed earlier, its a 4:3 screen. It's sacrilegious to play old game consoles in widescreen (and possibly even on an LCD). Here's how I prefer play until I get an RGB monitor: My Multi-Console "portable"
     
  12. Space Puppy .

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    Well your a smart pup. Keep it up and soon enough you'll be in space too ;)

    The screen looks cool, never seen a non-widescreen 7". I was planning on using a 7" widescreen LCD for my portable N64. I know it is frowned upon but it looks fine and the screen can switch between 4:3 and 16:9. Plus I got the screen for $10 at a thrift store so I really want to use it.
     
  13. Aurelio The Fixer ᕕ( ᐛ )ᕗ Staff Member . . . . .

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    Miceeno is right. Any small difference between the output voltage of the two regulators would cause a very high current flowing between the two. That’s given by Ohm’s law and the resistance between the two is only given by the wire that you would use to join them, which is going to be low.

    PS: I have a degree and I’m doing a PhD in Electronics, but that doesn’t really matter
     
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  14. Space Puppy .

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    Makes sense, I mentioned that you would need input and output protection for each board. Some diodes in series could be used to make sure nothing gets shot back into each output before connecting in parallel. I would think this would work.....might even do this for two red boards in parallel to be safe.

    It matters to me! Its good to know another person here who is studying electronics. I think having a degree is important, it helps me understand circuits that I have no experience with quickly, like battery charging circuits :). Also, the more people here with degrees on this website the better. I think it helps those without who may not have the same level of experience with circuits. Aurelio, you definitely have a higher degree of education than me and every bit counts, so thank you for your responses. Hope I did not come off as pretentious by bringing it up.
     
  15. Aurelio The Fixer ᕕ( ᐛ )ᕗ Staff Member . . . . .

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    I’m not saying it doesn’t matter in general, but it just didn’t in this case. Anyway, protection diodes still won’t work because then the regulator wouldn’t take into account the voltage drop caused by the diode.
     
  16. Space Puppy .

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    Could you elaborate on this? Are you saying the voltage drop across the diode will cause too much of a drop in voltage for the load regulators (ex. 3.3V regulator for the N64)?
    Edit:
    I don't see how this would cause an issue so long as the diode drop is taken into account. The red boards should still deliver the same voltage, minus the diode drop which is ~0.6V-0.9V if you use a 1N5819. So ~6.8V-6.5V will be your new voltage which should still work for the 3.3V regulator. The PTH08080 can handle voltage down to 4.8V so I would think it is fine. Im assuming your talking about something else then?
     
    Last edited: Nov 3, 2017
  17. Aurelio The Fixer ᕕ( ᐛ )ᕗ Staff Member . . . . .

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    No, I’m talking about the voltage drop between the charger and the batteries
     
  18. Space Puppy .

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    Oh I was talking about the output voltage of the red board so that it does not send current between each unit, should have stated that more clearly. The input would be better suited with some zener diodes and maybe some resistors, assuming the extreme case of course. Two in parallel shouldn't matter as there is less current.

    Even if there were series diodes at the input, it would just drop the voltage by a little bit. You would have to account for this of course and ensure the correct power supply. Series diodes are commonly used as a reverse protection before regulators in case the wrong power supply is used. I wouldn't think this would cause any complications, but I could very well be wrong.
     
  19. nitevision .

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    Hi, thanks for the guide, can you tell me (simply!) how to reduce the amp output of the red board CX-74-2S to about 200mAh? I'm wanting to charge a 7.4V 700mAh LiPo from a 12VDC source. Or have any other suggestions if any newer cheaper boards are on the market that will do it?
     
  20. cheese the tallest memer in town Staff Member . . .

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    Please make a new thread instead of bumping a 2 year old one.
     
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