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    li-ion battery charger

    hi guys! I want to build 24v 10A lithium ion battery charger for my own made 24v 20Ah battery pack. I also used BMS for my battery pack. Can you please guide me to build that charger?

    #2
    What is your electrical background? This is an electrical engineering project even at it's simplest - however these chargers are very simple in principal (and design) but in order to be "safe" there are criteria to meet. We need to understand your electrical proficiency in order to help though. How comfortable are you with using a device like this: http://www.vishay.com/docs/65124/sic46x.pdf ?

    10A is a high charge rate and you should ensure you want to charge your particular cells at that rate. If I was rolling-my-own I would make the charge current variable or at least multi-level. OTOH, 24V makes things pretty easy.

    What is the intended input? Do you have a DC power source or do you intend to make something that runs on AC?

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      #3
      OP, please post up what info you have so far. Don’t be afraid to post too much. Long, detailed posts with details, charts, etc. are great.

      Are you sure you want to charge lithium ion cells at 10A? What specific cells are you using?

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        #4
        first of all, I did my bachelor degree in mechatronics engineering. I made my DIY battery pack with old laptop batteries with 2200mah ratings of each cell. my BMS can withstand the charging rate of 10A continuously. here's my need is a guide to make a charger for my battery pack.

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          #5
          If you know how to build power supplies, you'll be building a constant-current supply at the desired charge current that transitions to constant-voltage when you reach the charge voltage.

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            #6
            I know only the methodologies for making a charger. my method is making a charger with flyback topologies with feedback of optocoupler for ic UC3842. guide me with any kind of circuits and links which help me to understand the charger concept for my battery pack.

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            • tklop
              tklop commented
              Editing a comment
              I have a suggestion for a possible different approach:

              I'm guessing that many people out there in the e-bike world have chargers that don't work anymore.

              Would it help you figure out exactly what it is you need to do, if you had a "dead" charger which you could take apart, analyse and back-engineer?

              Look: It seems to me, if you start out by simply copying the components, circuitry, connections, and other elements found within an existing design that's known to be effective; it will give your charger-project a solid functional platform to work from--a platform which you can then customize, adding in your own desired features and enhancements.

              I'm reminded of the saying, "There is no need to reinvent the wheel." In other words, things that already exist in the world, don't always have to be re-engineered from the beginning.

              Anyways, good luck with your charger build, Gunasekaran. I'll be interested to see how it turns out!

              Take care,

              Tklop
              Last edited by tklop; 09-19-2018, 03:28 AM.

            • Gunasekaran
              Gunasekaran commented
              Editing a comment
              Thanks tklop for your advice. Please share some links which help me to make a charger for my requirement.

            #7
            Flyback isn't a bad approach but will end up with larger and less efficient transformer than a push-pull... easier to design though.

            Not the worst approach for AC input since you'll want that isolation. If you haven't done it before flyback is reasonable...

            OTOH a push-pull or full-wave these days isn't all that bad when it's all said and done and will be smaller, more efficient and likely lower cost.... Transformer is trickier though..

            Look for parts made for this. TI website would be a good start to learn since they are strong here but there are plenty of other suppliers of parts like this and TI support these days is lousy...

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              #8
              Are you sure you want 10A for 20Ah battery? Its a little high which will reduce the battery life. We are lithium battery manufacturer, if you have any questions for lithium battery, we are glad to help! (www.vcellpower.com)

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              • Gunasekaran
                Gunasekaran commented
                Editing a comment
                Thank you for your kind response. I did my battery pack with old lithium batteries which harvested from old laptop batteries.

              #9
              TI's datasheet for the UC3842 has a constant -voltage flyback application example. If you start with that but tweak the feedback network to do both constant-current and constant-voltage then you'll be there although it might take some additional tweaking on the compensation. Nice thing about flyback is that the loop is usually fairly easy to make stable...

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              • Gunasekaran
                Gunasekaran commented
                Editing a comment
                Thank you AZguy for sharing your thoughts with me. I have attached my charger design in this command. Please find the attachment and guide me for further improvement.

              #10
              Hi guys...! Here I attached my charger design with the specification of 29.4v 10Ah. Please find the attachment and guide me for further improvement.
              Attached Files

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                #11
                You need a current sense in series with L2 and incorporate that into a constant-current into the TL431 feedback along with the existing constant-voltage. The TL431's are slick little devices but they are a little trickier to design with than op-amps and comparators though they have the big advantage of being predictable at turn-on. I'd be simulating that portion at a minimum.

                The transformer will also need to be changed in order to get the higher voltage. I don't know which one it is but you'll likely need twice as many turns (series) on the output winding.
                Last edited by AZguy; 2 weeks ago.

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