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Li-ion battery pack

Discussion in 'Electronics Homework Help' started by fenner, Nov 18, 2018.

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  1. fenner

    fenner

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    Aug 20, 2018
    I have made up a 3S Li-ion battery pack to convert into my 12V drill If I get an Li-po charger such as the imax B6 would I need any additional circuit boards for protection in my battery pack and would I be better with a 3S or 4S pack. Fenner
     
  2. Audioguru

    Audioguru

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    Sep 24, 2016
    That charger has many functions that you pay for but you will never use. It has a 5A output that might explode your battery. You did not tell us what battery cells you used that the charging current should match. A 4S pack will overpower the drill and might release its magic smoke.
     
  3. fenner

    fenner

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    Aug 20, 2018
    Thank you Audioguru, actually I have not put together the batteries yet but have them in hand, the cells I have got ICR 18650 3.7V 12000mAh the voltage of full charge and cut off discharge is 4.2V and 2.75v. I also bought a protection board 4S PCB BMS Protection Board For 18650 Li-ion Lithium Battery Cell. and wondered if I need both the charger and 4S BMS if I have to use the BMS would I be able to have it as a 3S and not use the last one.
     
  4. dave9

    dave9

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    Mar 5, 2017
    What you are doing makes no sense to me. You're starting with a weak 12V drill, might weaken it further using only 3S cells so nominal voltage is down to 10.8V already, but apparently feel a lot of extra weight (low weight is the only reason to pick a 12V drill over 18V in the first place) is justified to be able to run it many hours continuously, which you wouldn't want to do because it's so heavy now.

    Additionally you wrote 12000mAh? If you mean for each cell, not the additive sum of multiple cells in parallel, then what those really are is fraudulently rated cells that probably aren't good for much over 2400mAh each, if that.

    I could be wrong, might not be understanding what the application is and it's an unusual one, but I don't see the point. Batteries can be swapped when they run low, and modern packs have safety features built in, chargers ready to use, blah blah blah. ;)

    I'd just get a new 18V brushless drill and a couple 6Ah battery packs for it. Besides, redundancy is good. Once this one pack you make, fails, it will be more hassle and expense to fix it.
     
  5. fenner

    fenner

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    Aug 20, 2018
    Thank you Dave. I can see your point and agree with you, I already have modern Dewalt drill, and don't really need another drill, I am a retired engineer, now an hobbyist but hate throwing stuff away and just like tinkering and thought It would be an interesting project modifying the 12v drill. Fenner
     
  6. BobK

    BobK

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    Yes! I have two drills that are 9.6V run from NiCads and have replaced the cells once only to have them go bad again. I have the same idea, to convert to LiIon, but I have not got around to it yet. In my case, a 3S would probably drive it just fine, being about 1V high. They were slow and weak by comparison to modern drills anyway, but, like you, I hate throwing stuff out and buying new ones when they still work (except for the batteries)

    Bob
     
  7. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    We were recently gifted with an ancient Roomba iRobot vacuum cleaner. Unfortunately, it's NiCd battery or NiMH battery (not sure which, but definitely not Li-ion chemistry) will not accept or hold a charge, nor did we receive the wall-wart charger that went with the original unit. Newly manufactured replacement batteries appear to be unobtainable. So, after farkeling around with it for a week or so, I just put it aside. Then a few weeks ago I found a floor display at Home Depot that offered a Shark ION robotic vacuum for an insanely low price. Asked wife if this would be okay to purchase instead of a Roomba. After she did some on-line research her answer was yes.

    We are in the process of building a wood fence on our property, so it was off to Home Depot yesterday for some more wood materials. Wife went off to look for the Shark ION and found one, so we bought it for $250. After charging it for three hours, we were up until 3:00 AM watching it do its thing. When we finally went to bed it was still running, but we woke up this morning to discover it had automagically found its charging dock and was contentedly re-charging. Amazing bit of technology. Our house here in Florida has tile floors throughout and a lot of sand and dust accumulates daily in the grout between tiles. The Shark ION took care of it, so wife was more than pleased. I like it too because now I don't have to run the Swifter dust mop over the floors every day.

    And, yeah, I got plenty of dead power tools that could benefit from the newer rechargeable lithium-ion battery technology... but at my age it is often just easier to replace rather than re-engineer. Still, I have a bunch of those 18650 batteries, from when I was vaping, that have insanely large current capabilities... maybe I can rig a few up to run my Elecraft KX-3 transceiver for Field Day next year. The KX-3 has internal NiMH cells, but I am not happy with the way they perform, although they are easy to charge. You pays your money and you makes your choices. <sigh>
     
  8. dave9

    dave9

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    Mar 5, 2017
    I have nothing against reclaiming old tools, have rebuilt the packs for an old Dewalt 14.4V drill I have, but stuck with NiCd, so the charger was still usable.

    Even so I wouldn't have done it except for that drill coming with a snakelight that's very handy and that I've converted to LED. I use the light a lot but the drill hardly ever. Decided to switch to Ryobi to build a collection because they have 100+ tools that run off the same batteries and you can get most of them as a bare tool without having to buy more batteries and chargers with each.
     
  9. fenner

    fenner

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    Aug 20, 2018
    Please can anybody answer my 1st question as I am not really clued up on electronics.
     
  10. dave9

    dave9

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    Mar 5, 2017
    Yes the pack will need a protection board to keep it from draining too low, and being a drill it will need to be beefier than some, able to handle above the stall current the motor is rated for @ target voltage.

    Typically Li-Ion drill packs have either a PCB with a large copper area and vias to get both sides involved in heatsinking the current conducting 'fets, or a piece of metal to 'sink them. It would be a good idea to have a fuse too, and temperature sensing cutoff.

    Frankly it might be worth the cost (no more expensive when all is said and done, and save a large amount of time) to just buy a drill battery that has battery-side (most do but research it to be sure) protection and just transfer the guts of the pack over to yours.

    However then you may have an issue with whether the protection board will allow charging, if to do that it needs to communicate with a specific charger. You might have to bypass the protection circuit to charge it with a different charger than it was designed for.

    The other option that is gaining popularity, especially these days with people having 3D printers, is to make an adapter so the drill can take a different battery that remains intact, and use the charger meant for that battery.

    It seems like a long road to me to do this safely. I'm getting back to my initial thought that you could just get a new drill with battery and charger included. They aren't very expensive if you need nothing more than to match (or better) the specs of the old 12V drill.

    Then again, The Internet ! You might be able to find someone selling just the bare battery protection board for a drill pack.
     
    Last edited: Nov 19, 2018
  11. fenner

    fenner

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    Aug 20, 2018
    Dave9 once again thank you for your comments but I don't think you are getting my point, I have a DeWalt drill which is brilliant and I do not need another but I did not want to throw the old 12v drill in the bin and decided to make an interesting project in converting it to Li-ion as indeed quite a few more would like to do the same but as I know very little about electronics I decided to ask the forum for advice, Coming back to my question I thought from reading the instructions maybe the Imax charger does the same thing of protecting the charging and discharging safety factors although now I am thinking of installing the small 5A protection circuitboard kit on each battery. Fenner
     
  12. dave9

    dave9

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    Mar 5, 2017
    Is it technically possible to convert it to Li-Ion? Sure, given the time and money.

    AFAIK, "some" newer Dewalt drills have some of the battery management electronics in the tool itself, or maybe I am only thinking of the battery power level indicator. Regardless, yours being NiCd or NiMH, will not have this suitable for Li-Ion packs.

    The Imax charger cannot do anything about protecting against discharge because that happens disconnected, in the tool during use. If you run any cell in the pack down below 2.(n)V during use of the drill, you will likely ruin it. You can measure the current your drill uses, perhaps it's not a lot since it is only 12V, but that it's a good contractor grade brand may work against you.

    My old 14.4V Dewalt, is VERY strong for being only 14.4V, stronger than a typical $100USD Li-Ion drill you'd buy today. Apparently they used high current motors at the time, as it might have been a higher tier product with 18V not very common yet.

    The point is, I'm pretty sure that mine draws more than 10A current, probably 20A is closer. 5A does not seem like enough margin. To put it in perspective, a mid-grade drill may have around a 350W motor. If you have 3S Li-Ion cells so 10.8V nominal, at 5A that's only 54W.

    Converting a drill to Li-Ion is easy to write I want to, but the particulars, especially when it's a lower voltage drill, without the right charger and no protection board (yet) can make it less desirable than just buying new sub-C NiCd or NiMH for it (whichever the original charger supports).

    Consider that there are now Low Self Discharge, sub-C NiMH cells in the market. Whether your charger can do NiMH, I don't known as you never mentioned its model # nor even that of the drill, but since they are LSD cells, it would be less work and less fiddly to use it, with the main downside being that the pack would weigh a little more than if you had stuffed 3 x 18650 Li-Ion cells in it.

    On the other hand the up side to that is you can use 10 sub-C cells and have a 12V drill again instead of a 10.8V drill.

    http://www.farnell.com/datasheets/1655619.pdf
     
    Last edited: Nov 20, 2018
  13. fenner

    fenner

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    Aug 20, 2018
    Thanks Dave you have convinced me that it will be safer and more proficient to abandon the present project and whether or not to work on what you say with the NiCd batteries. However this is why I joined the Electronic Forum. Thanks again for your comments. Best regards Roy.
     
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