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How to Charge Lithium Batteries

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44 Comments on "How to Charge Lithium Batteries"

  1. Louis Derry says:

    Sorry if this is a stupid question I have a charger which outputs 25 volts = 0.5a 12.5va from a hoover – from the same hoover i have 5 of what looks like the Lithium 3.7 batteries (green once cylinders) . Would the charger be safe enough on its own? When I times 4.2 (the safe amount to charge a 3.7 battery too) by 5 – (the number of batteries) it gives me 21Volts- the charger puts out 25 ? they're from the same device but im confused if it will overload the batteries.

  2. highdesert50 says:

    Thanks for sharing your adventures, to include both your wins and fails.

  3. Arek R. says:

    Nope, nominal voltage for li-on is 3,6V…

  4. Arek R. says:

    What about current control?
    Discharged cell is almost like a short, so if the power source is capable of 10A it will push it into cell, cell will overheat and explode.
    But that module isnt, it will overheat and thermal shut-down will occur, then cool down, turn on again, etc.
    So no current control is bad.
    Pay extra 1$ and you will get similar module that is capable of delivering adjustable constant current and constant voltage, so everything we need for battery charging.

  5. Arek R. says:

    Holding cell at 4,20V decreases its life, proper chargers stop charging at 10% of set charging current.
    So if the charging current is 1A, we should stop at 100mA.
    You build EV and you dont know all these basic things????

  6. mosfet500 says:

    Hi Jehu,
    Thank you for the video, lots of fun!
    I understand the principle of slowly charging batteries for safety but I'm not sure about your charging. How are you regulating charging current which is a very important thing to do?
    Also have you checked individual cells to see if they balance out to relatively the same final voltage? How does Tesla, for example, charge a string of series batteries, is there concern for individual battery hogging? Also do they current limit?

    Thanks for your time,

  7. MrBrymstond says:

    For your 12v Samba You have 3 batteries in a series and 33×3 wired in parallel to get the most Ah, correct? Then you wire the positive on the series to the positive on the 33 cell in parallel. Then you wire the negative to on the series the negative on the 33 cell in parallel, correct???

  8. If you guys enjoy building battery packs and Messing around with electric bikes then I recommend you checking out my channel. Not trying to be annoying, just giving you guys a source for more cool videos you can watch. Anyways thanks for reading.

  9. Wayne Manzo says:

    Ok rocket scientists if they are using the same Li-ion battery
    technology and they are squeezing the most Lithium and other chemicals
    in that little 18650 shell__and only getting say 2000MAH out of that how
    in the world do you think they can get 6000 or 9800MAH out of the same
    dimensions using the same technology! Ah, you are finally saying to
    yourself I don't even have to test this__this is impossible from a
    chemistry and manufacturing point of view. The 18650 cells would have to
    be the same diameter as a "D Cell" flashlight battery!
    Ha Ha Ha! That's a little thought experiment that would make Esienstein blush!

    The Universal Brain( The Information Black Hole ) has turned out little walnut
    into mush!

    So, when I wired eight of these into the case of my old Dell Inspiron 300m notebook
    battery and plugged it in I notice an incredibly fast rate of charging and in about
    20 minutes the battery was fully charged. So, I knew something was fishy because
    the regular 2000MAH take about two hours and give you about two hours of usage.
    With fully charged 9800MAH batteries I was able to squeeze 1 hour of usage
    with a 1.8" Toshiba Hard Drive. Hmmmmm? If the Chinese are using Capacitors
    instead of Lithium maybe something can be learned here. Charging time was
    really fast and but the time was only 1 hour. If, they could design these capacitor
    batteries to give 2 hours at only 30 minutes charge time they would be worth
    paying a premium price of say $20 for eight batteries.

  10. my calculation:

    one cell is 3.7V @ 1.8A;
    there are 3 parallel circuits;
    each parallel circuit is composed of 33 cells.. so each parallel circuit is 3.7V @ 59.4AH (Calculation is 1.8X33)
    the 3 parallel circuits are connected to make 1 series… so the entire battery pack is 11.1V @ 59.4AH (Calculation is 3.7X3) at NOMINAL.

    when we calculate its Wh… it's 59.4AH X 11.1V = 659.34 Wh
    when we calculate is kWh…. it's 659.34 / 1000 = 0.659 kWh

    can someone confirm if my calculation is correct? thanks!

  11. Jehu, how much current each battery draw when charging? When it's fully discharged…

  12. if you connect 2 batteries in series then the voltage is 8.4 not 7.4 that you told at 5:30 in this video.

  13. NBX MASAWAT says:

    Hi, I have one question, I made 5 cells in parallel and 3 groups in series to be 12v pack and I agree with you to be not use the BMS to charge my pack so should I charge it with 12.2v cv/cc power supply or separate to 3 of 4.2v cv/cc power supply ?
    thank you.

  14. Danijel9616 says:

    greetings, one question,i make battery for elektrobike from old batteries in laptops,i produce battery 36v 10A and i dont have BMS on that battery,can i charge that battery with tipical (Chinese)charger for that battery(42v 2A) without fear that battery will explode(because there is no BMS on it)?i.e.will charger stop charging when the battery is full? Excuse on my bad English

  15. Dylan T says:

    how do you charge your diy Tesla battery?

  16. Thanks man. This was really interesting and straight forward!

  17. ArcAiN6 says:

    Yea… NO!

    If you charge a lithium ion cell without doing it properly, you can damage the cell, as well as run the risk of fire, explosion etc..

    The proper way to charge a lithium ion cell, is to start off with constant current, while the voltage ramps up, once the voltage reaches the proper voltage, you then cycle to constant voltage process, where the voltage remains the same, and the current drops over time until the cell is completely charged, at which point the charger shuts off.

  18. Awsome but I think its not safe to charge lipo battery's in series connection with high voltage, it can be so dangers if one of the cells die, BMS is a better way

  19. 4.2v x2 = 8.4 not 7.2 ;)

  20. iYammmzTV says:

    AWESOME VIDEO, +1 SUB… but please for the love of God stop jump cutting

  21. can i parallel the charger? for example i use 50W power supply and i parallel it just to make it become 100W, is it possible?

  22. Alan Brown says:

    Why not bring the balance lead out of the box so you don't have to keep opening it?

  23. Hi Jehu. i still don't understand how to charge this 18650s. please explain more detail on this topic

  24. pirucreek says:

    If one of the cells goes bad in the 33 cell parallel area, and it drops in voltage, won't the other cells send power to the dead cell like over 100 amps?

  25. What a refreshing change on Internet to find advice from somebody who knows what he's talking about. Believe me Jehucarcia, there are SO many who DON"T but that doesn't stop 'em!
    Thank you….Love the dogs…Only once a week to the park? Send me the air tickets..I'll do it for the rest of the week and get further training from you while I'm there.
    Thanks and good luck from Brexit land.

  26. 9:51 so you charge at 12V, but at what amps? Seems using 0.5-1.0 amps would be painfully slow… What's the recommended ratio of charging amp to total Ah/capacity?

  27. Mr Garcia, you obviously have lots of hands-on experience charging lithium battery. The important details left out are:

    Find those switching regulators which:

    – limit the voltage to some adjustable value (4.2 volt for 1 cell, 12.6 volt for 3 cells)
    – limit the current to some value specified in Amps
    – when current limit is hit, must not go in shut down mode, like most computer power supply do ; instead, it must continuously adjust the voltage to keep the current at the limit

    In other word, the power supply will start at the same low voltage as the battery discharge state. As the battery is charging, the voltage will raise while the current will remain at the fixed maximum allowed.

    When the voltage reach 4.2 volt, the power supply automatically enter in the second mode of operation, which is regulating the current to maintain that fixed 4.2 volt.

    The battery is still charging when reaching 4.2 volt, but it consume less and less current. It is really the battery that "decide" how much current it want, the power supply just try to keep the voltage at 4.2 volt and provide as much current as the battery want to keep that voltage.

    Now, to speed up charging, we want to provide a voltage slightly higher than 4.2 volt (or 12.6 volt for 3 cells). The extra voltage is provided to counter act the loss in the following components:
    – loss in wires
    – loss in connectors
    – loss in batteries

    The loss in wire can be decreased by using thicker wires. But bigger wires are more rigid, less flexible and get damaged faster from constant flexing. Typical cable in USB charger with a current of 1 amp waste from 0.1 to 1 volt.

    The loss in connector is often in the same range of 0.1 to 1 volt. Even when the exposed metal on the connector appear shiny yellow, imitating the look of gold, they may still waste part of the energy, which imply absorbing part of the voltage. Those bad quality connector become warm to the touch.

    The battery itself, particularly as they age, waste a portion of the charging energy. An old battery that waste part of the charging energy is exactly equivalent to a very good battery with a small resistor added in series ; both located physically inside the batteries.

    Let's take a real example : suppose the battery has an internal resistance of 1 ohm and we provide 1 amp of current. The ohm law allow to find the voltage across a resistor:
    V = RI = 1 ohm * 1 Amp = 1 volt
    The battery itself takes from 3 volt to 4.2 volt as it charge, and the internal resistance take 1 volt.

    We can also find how much energy is wasted by the internal resistance as follow:
    P = VI = 1 volt * 1 Amp = 1 watt

    Suppose that the battery charge level started at 3 volt and is now at 4 volt. Our charger is still pushing 1 amp since we are still below 4.2 volt. The total energy provided by the charger is:
    P = VI = 4 volt * 1 Amp = 4 watt
    The energy wasted by the internal resistance (assuming 1 ohm) is:
    1 Watt, as calculated above

    Brief, 3 watts are used to charge the battery and 1 watt wasted as heat

    All the long text above is to explain what make a battery to become hot during charging. The lithium battery are strong when delivering high current, but they easily get damaged by silly little thing such as overcharging them or discharging them too much.

    All lithium battery designed by an company, not just professionals equipment, but every device (even the cheapest Chinese clone and the cheapest child toy) include a temperature sensor which is used during charging.

    The charger inside your cell phone does the following test:

    – refuse to charge if temperature already too high
    – start in fixed current mode, with voltage increasing slowly
    – monitor for "fast" temperature change with high precision (down to 0.1 degree Celsius or about 1.5 F) and stop charging if increase "fast"
    – while charging, stop if temperature exceed some threshold
    – when the voltage reach a limit, switch to fix voltage (the current is decreasing slowly)

    The end of charge is determined by:
    – current below a fix value while voltage already at 4.2 volt (for example)
    – temperature suddenly raise at any time during charging

    When the battery get old, it may accept less total energy and may decrease the maximum voltage to a value below 4.2 volt. By monitoring the temperature raise with high precision, the charger can stop charging and avoid damaging the battery.

    This precise temperature monitoring technique is what allowed old battery to keep working for many months after the voltage started to drop. Somebody got a patent for that and that company probably still get large amount of royalty for allowing all of us to use the same cell phone with the original battery for a few years.

    The battery exploding in recent Samsung cell phone is probably caused by an engineer who wasn't not very clever. He didn't read the patent explaining how to charge a lithium battery correctly and use the temperature sensor in a smart way.

  28. blueckaym says:

    I got the rest, but just one (newbie) question 🙂
    If I have two Li-Ion cells (3.7 2000mAh) in parallel and each can safely charge with lets say 1A (0.5C), then can I pass 2A to both of them (being linked in parallel) without risking to overheat eventually blow them (or the least evil to reduce their life)?

    Or to be specific if I have 3.7 3400mAh 10A, with charge recommendation of 0.5C (ie 1.7A) in a 3p6s config.
    I'll obviously need 25.2V (4.2*6) to charge them, but what about the current?
    If I leave it only 1.7A and it splits between the 3 cells in parallel, it would take about 3 times slower wouldn't it?
    But is it safe to just dump 5.1A (3*1.7) directly on them?

  29. So… If I want to charge 3 cells connected in series and another 3 cells (same series connection) with the 2 groups connected in parallel, and if each cell can except 1.5 amps, how many amps would I need to charge all 6 cells?

  30. Hey
    Can you do a video on how to "wake a dormant lithium hoverboard batterie back"?
    I have like 9 boards that the batteries is not taking charge. Its been sitting for a year now. Thx

  31. cody perret says:

    where can I get the 18650s cheap in bulk

  32. Neal Van Dam says:

    how i charge an AA battery with 1.5V a made a battery pack from 10 of these battery's but i dont know how to charge this battery pack , it are reachargeble battery

  33. asc556 says:

    Hi. I would like to know if you wanna balance that pack how you do that? with bottom or with top balance?

  34. Leonardo Po says:

    dis silly ass nigga aint even got BMS
    he aint even balancing the charge
    nigga go buy a battery management system FOO
    power supplies only regulate voltage, doesnt even limit current which will over charge that shit homie
    i bet dis wack azz nigga is a house contractor and probably wants to have your houses burned down to increase sales

  35. TheDano1947 says:

    4.2®4.2= 7.4? Not = 8.4?

  36. Tony W says:

    Sorry but that looks dodgy af

  37. JPAG0806 says:

    Thank you for this video.
    I just toke 9 pieces 18560 batteries from my Dell laptop. All batteries are dead: 0,0 volt.
    All tricks I found on YouTube, I tried in order to get them running. Unfortunately without any result.
    I fear that I have to throw them away, or you you have a last advise ????
    Jan, from the Netherlands

  38. K Jensen says:

    These are step up modules, or buck converters, they will supply voltage and current regardless of cell capacity and voltage, i think you missed something, because in addition to that, you will need a cell protection charging module, such as the tp4056 for charging a 18650, or a 3,7v lipo battery. I would never replicate this method to charge my batteries.

  39. vishal singh says:

    do u not balance the series cells

  40. i always enjoy your videos 💯 thank you so much

  41. RixDobbs says:

    Excellent education Jehu. Thank you. I NEEDED that.

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