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  1. #1
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    Feeler thread about 8.4V 2A Li-Ion charger for 2SxP battery packs

    I've got the feeling there is a lack of simple chargers with higher currents in order to charge our battery packs in decent time. Mostly we can get the chargers declared 1000mA which is nowere near the truth and charging high capacity battey packs takes forever. Me personaly has also Magicshine charger with 1.8A and I'm mostly fine. Still think it's more on the low side in reality.

    I've started to find out China manufacturers being able to make good charger with some security fetures. Then if they decide so, some reseller like Gearbest would take over to distrubute them.

    Here in this thread I want to discover how much demand there would be for such a charger. We should not discuss about the features as they are mostly defined and I don't see the reason to change them significantly. No intensions to get another hobby charger.

    So here are the basic features:

    Wall plug 8.4V Li-Ion charger with:

    two phase CC/CV charging algorithm
    AC plug: US, EU, UK (AU? if does not raise the costs )
    DC output: connector 5.5x2.1mm
    true 2.0A DC output current
    regulated output voltage 8.40V
    red/green status led (switch from red to green at 1/10 ie. 200mA)

    Safety:
    Over Voltage protection
    Short Circuit protection
    Polarity error protection
    Over power protection
    20mA efectively termination current (ie. completly stops charging)

    Of course there are also other fetures like operating templ, humidty, some electrical stuff we normaly don't think off, etc..

    I'm at very beginning contacting one manufacturer, so there is a lot of work to do.....

    Now the stage is yours.

  2. #2
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    I'm not sure I really know the difference between a hobby charger and advanced single cell charger.

    On your list of things which are not already done by the Magishine charger?

    I was doing some research on advanced AA/AAA nimh chargers and one of features touted by the ability to select the charging rate. The reviewer mentioned that he prefers the lower charging rate as it avoids heat build up which degrades the lifespan of the batteries. Is this not an issue with lithium bike light batteries? What's the maximum safe charge current of the lithium batteries?

    It would like a pack charger that has a readout that shows me the charging progress as well as the total charge applied to the battery. It was also be nice if the charger could be perform an entire discharge/charge cycle and calculate the total capacity of the battery, as well as detecting a bad pack. Is that the kind of thing you had in mind?

  3. #3
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    varider, no I have in mind simple charger very similar to those you are getting within bilke light sets. The difference would be only higher current/faster charge and most important known/tested safety features. The size and the weight of the charger would be bigger up to 190gr.
    I'm not shure how much do you know about Li-Ion batteries. I recomend reading Charging Lithium-Ion Batteries ? Battery University - charging and other chapters too.

    About charging rate. Recomended for Li-Ion is 0.5C which in terms of 2200mAh cell means 1.1A. This is the lowest capacity we are using nowadays. So if you are using 3400mAh cells 0.5C would be 1.7A. Now if we apply this to the xS2P batery pack the 2.2A - 3.4A is recomended for 2 cells in paralell. With 2A we are still below the recomended charging current. 2A applies only to CC phase.

    Designing charger with readouts, charging, dischargin capacity, etc. is totaly useless. It will raise price significantly and for that price you would get hobby charger already doing all that and more. I don't say it would not be handy, it is just the price would be to high since ith as to be developed from the scratch.

  4. #4
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    If I understand correctly, the charger you're describing is essentially exact copy of already existing MagicShine standard 1.8A and 2.5A chargers. Are you sure your variant will be any better?

  5. #5
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    Well, probably yes, but should be cheaper with well known safety features. I'm not aware of 2.5A version. Can you point it out?

  6. #6
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    Does the magic shine 1,8A charger have an advanced charging algorithm?

  7. #7
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  8. #8
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    Quote Originally Posted by varider View Post
    It would like a pack charger that has a readout that shows me the charging progress as well as the total charge applied to the battery. It was also be nice if the charger could be perform an entire discharge/charge cycle and calculate the total capacity of the battery, as well as detecting a bad pack. Is that the kind of thing you had in mind?
    Well as you probaly know the XTAR VC2 does mostly all that except it doesn't perform the discharge cycle, you have to run out your batteries yourself. Maybe kinda difficult if your setups all have high over-discharge thresholds?.

  9. #9
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    Quote Originally Posted by ledoman View Post
    Well, probably yes, but should be cheaper with well known safety features. I'm not aware of 2.5A version. Can you point it out?
    It's for the 880 that uses a different plug , but I assume it could be easily modded with a standard connector ??
    Action LED Lights - Brilliant lighting for all your biking & outdoor sporting activities.

    But yes I'm all in for a simple charger like the 880 one with the standard connector .
    Every time i walk into the LBS and see the price tags on new bikes it makes me enjoy and appreciate my Ol' ride even more.

  10. #10
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    Quote Originally Posted by ledoman View Post
    Well, probably yes, but should be cheaper with well known safety features. I'm not aware of 2.5A version. Can you point it out?
    Sure:
    MJ-6072 2.5A Battery Charger | Magicshine USA

  11. #11
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    Quote Originally Posted by Appel View Post
    Does the magic shine 1,8A charger have an advanced charging algorithm?
    What do you mean?

  12. #12
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    Quote Originally Posted by ledoman View Post
    AC plug: US, EU, UK (AU? if does not raise the costs )
    IMHO, different versions of charger for regional power outlet standards is a bad thing, as well as using adapters (the're inconvenient & ugly looking).

    For me, ideal design is a replaceable power cord, as in modern MagicShine chargers: you can use one suitable for your location.

  13. #13
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    OK, I see. I thought the 1.8A is the highest.

    Archie, I can't design it. This will probably raise the price to much. I know it would be better, but the manufacturer has to see much $$$$ to design the whole new case and change production. Still I can ask.

  14. #14
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    Quote Originally Posted by C.M.S View Post
    It's for the 880 that uses a different plug , but I assume it could be easily modded with a standard connector ??
    Action LED Lights - Brilliant lighting for all your biking & outdoor sporting activities.

    But yes I'm all in for a simple charger like the 880 one with the standard connector .
    Thing still is, the 2.5A charger for the MJ-880 is specifically designed for 6-cell packs. In MagicShine's own description, it should NOT be used to "fast charge" 2 or 4 cell battery packs. Guess that's why the different, rectangular connector so might not be the best idea trying to mod it? Too bad.

  15. #15
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    Andy, have you read this Charging Lithium-Ion Batteries ? Battery University ? Copied from that source:
    "The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less."

    Tipical good brand cell is 2200mAh or more and 0.5C for it is 1.1A. Two cells in paralell is then safe to charge at 2.2A It can be chaged up to 1C so 4.4A or even more for higher capacity ones. Charging at higher currents would shorten lifetime and decrease capacity over the time. With 2A we are below tipical 0.5C

    Magicshine is using 2200mAh BAK cells so 2.5A should be still just fine to charge 2S2P packs, but not the 2S1P.

  16. #16
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    Maybe you could bump up the current to the maximum safe level for a 6-cell pack. How about a simple switch to select the current.

  17. #17
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    It seems to me that you want to be able to charge at different voltages 8.4v for the pack & 4.2 v for the individual cells, and at different currents depending on the quality and number of parallel cells.

    Maybe I am too skeptical, but to me it seems a hobby charger remains the better solution.

  18. #18
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    Quote Originally Posted by ledoman View Post
    Andy, have you read this Charging Lithium-Ion Batteries ? Battery University ? Copied from that source:
    "The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less."
    Thanks, that article was very clear!

    BTW ledoman did you read this the other day?

    Boffins say they've got Lithium batteries the wrong way around ? The Register
    Last edited by andychrist; 01-11-2015 at 03:41 AM.

  19. #19
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    Quote Originally Posted by ledoman View Post
    Charging at higher currents would shorten lifetime and decrease capacity over the time.
    Hey!

    To be extra safe with capacity preservation I would go down to C/5, one fifth of 1 C, charge rate, that's where the capacity fade seems to level out if this NASA test paper page 11 is anything to go by.

    Smoke free charges!


    JK

  20. #20
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    Now I'm confused -What would the recommended amps be for charging 1S2P? (4.2v) I am assuming 2A is plenty safe.

    How about 2S1P? (8.4v) Is 2A safe for that, or too high, even with Pano cells? If so, A 2.5A charger would be too much.

    BTW, You may want to make your charger safe for 2S1P at least.

    Quote Originally Posted by ledoman View Post
    Andy, have you read this Charging Lithium-Ion Batteries ? Battery University ? Copied from that source:
    "The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less."

    Tipical good brand cell is 2200mAh or more and 0.5C for it is 1.1A. Two cells in paralell is then safe to charge at 2.2A It can be chaged up to 1C so 4.4A or even more for higher capacity ones. Charging at higher currents would shorten lifetime and decrease capacity over the time. With 2A we are below tipical 0.5C

    Magicshine is using 2200mAh BAK cells so 2.5A should be still just fine to charge 2S2P packs, but not the 2S1P.

  21. #21
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    Charging Currents

    Hi!

    Horses for courses. Slower charging is better for the battery health, but it does take its time.

    Quote Originally Posted by Ofroad'bent View Post
    What would the recommended amps be for charging 1S2P? (4.2v) I am assuming 2A is plenty safe.
    A charging current of 2A with two 2000 mAh cells in parallel equals to a 0.5C charge rate and is widely considered safe. One needs to pay attention to the voltage though.

    Quote Originally Posted by Ofroad'bent View Post
    How about 2S1P? (8.4v) Is 2A safe for that, or too high, even with Pano cells? If so, A 2.5A charger would be too much.
    A Panasonic NCR18650B often sold as a 3400 mAh cell is specified with a 1625mA charging current, or a 0.5C charge rate if you like, by the manufacturer. A Panasonic NCR18650 with a typical capacity of 2900 mAh is specified with a 1925 mA charging current, or a 0.7C charging rate, by the manufacturer, but was charged with a 2.9 A current, or a 1C charge rate, in the mentioned NASA test with no issues other than a steady decline in capacity.

    Quote Originally Posted by Ofroad'bent View Post
    You may want to make your charger safe for 2S1P at least.
    A high current charger is not best suited to low capacity packs and should not be used to charge one. Luckily there is an abundance of slow low current chargers available, as every light set comes with one, to use with low capacity packs and the goal here is to get a quick one for the big ones.

    Bright rides!


    JK

  22. #22
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    Quote Originally Posted by Ofroad'bent View Post
    Now I'm confused -What would the recommended amps be for charging 1S2P? (4.2v) I am assuming 2A is plenty safe.

    How about 2S1P? (8.4v) Is 2A safe for that, or too high, even with Pano cells? If so, A 2.5A charger would be too much.
    You can simply calculate it. Recomended is 0.5-1.0C (C stands for Capacity). Take the pack capacity and divide it by 2 (0.5) and you get the bottom recommended current for that pack.

    Quote Originally Posted by Ofroad'bent View Post
    BTW, You may want to make your charger safe for 2S1P at least.
    For those you already have plenty chargers out there charging at 1A (1000mAh) or less. If we take 2S1P into account there is no point to make any effort for faster 2A charger.

  23. #23
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    Quote Originally Posted by ledoman View Post
    You can simply calculate it. Recomended is 0.5-1.0C (C stands for Capacity). Take the pack capacity and divide it by 2 (0.5) and you get the bottom recommended current for that pack.



    For those you already have plenty chargers out there charging at 1A (1000mAh) or less. If we take 2S1P into account there is no point to make any effort for faster 2A charger.
    To be clear here, you are recommending 1.0A-1.6A for a 1S2P ( 2-cell 8.4v pack) depending on the type of cells as a safe charge level, and 2A-2.5A won't destroy them but may shorten their life?

  24. #24
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    Ofroad, charging current has nothing to do with how many cells are in series. Voltage depends on that.
    For the charging current there is important only capacity of the pack (not cells on it's own - theoreticaly they don't need to be and are not the same capacity). Shureley capacity depends on the number of cells in parallel and their capacity. When we doing math we always assume cells has equal capacity (which is not true exactly)

    1. If we take Magicshine BAK cells:
    Nr. cells in parallel Cap C 0.5C 1C
    1 2200 2.2 1.1 2.2
    2 4400 4.4 2.2 4.4
    3 6600 6.6 3.3 6.6

    2. If we take Panasonic 3400:
    Nr. cells in parallel Cap C 0.5C 1C
    1 3400 3.4 1.7 3.4
    2 6800 6.8 3.4 6.8
    3 10200 10.2 5.1 10.2

    Quote Originally Posted by Ofroad'bent View Post
    To be clear here, you are recommending 1.0A-1.6A for a 1S2P ( 2-cell 8.4v pack) depending on the type of cells as a safe charge level, and 2A-2.5A won't destroy them but may shorten their life?
    2-cell 8.4v pack is not 1S2P, but 2S1P, you are doing wrong calculaton.

    To apply values from the tables on two cell 8.4V pack (2S1P):
    1. BAK cells: 0.5C = 1.1A and 1C = 2.2A
    2. Pany cells: 0.5C = 1.7A and 1C = 3.4A

    2A charger is complety safe for BAK and Pany cells It just not recomended for BAK and completly good for Panys with about 0.6C.

    Generaly if you are within 0.5 and 1C limits you are on safe side, it is just lifetime would be shortened with higher. Take anology with engine. If you run it at it's upper limits it will worn out sooner. In fact with quality cells like Panasonic you can even go bit over 1C and you'll still be safe.

  25. #25
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    Quote Originally Posted by ledoman View Post
    Ofroad, charging current has nothing to do with how many cells are in series. Voltage depends on that.
    For the charging current there is important only capacity of the pack (not cells on it's own - theoreticaly they don't need to be and are not the same capacity). Shureley capacity depends on the number of cells in parallel and their capacity. When we doing math we always assume cells has equal capacity (which is not true exactly)

    2-cell 8.4v pack is not 1S2P, but 2S1P, you are doing wrong calculaton.

    To apply values from the tables on two cell 8.4V pack (2S1P):
    1. BAK cells: 0.5C = 1.1A and 1C = 2.2A
    2. Pany cells: 0.5C = 1.7A and 1C = 3.4A

    2A charger is complety safe for BAK and Pany cells It just not recomended for BAK and completly good for Panys with about 0.6C.

    Generaly if you are within 0.5 and 1C limits you are on safe side, it is just lifetime would be shortened with higher. Take anology with engine. If you run it at it's upper limits it will worn out sooner. In fact with quality cells like Panasonic you can even go bit over 1C and you'll still be safe.
    Thanks, I meant 2-cell 2S1P. It's perfectly clear now, +rep given to you for lots of good info!

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