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discharge rate 2c-3c. Is it ok for a drill?

  • makis129 Tuesday, September 20, 2011 7:49 PM Reply
    Hi
    I have a remote drill and i would like to make a battery pack with 18650 batteries.
    My drill needs 18,6v supply so i will use 5 18650 batteries. I will charge them with a hobby charger 4v each.
    I tested the drill already and i found that the amps it needs goes up to 10a!
    The best discharge rate for a 18650 battery is 3c max. So about 7a discharge for each battery
    My questions:
    1)When the drill discharge the batteries with 10a does this mean each battery is pushed to give 10a or each battery gives 2a (5batteriesX2amperes=10)?
    2)What is the risk if i discharge a 18650 battery with 5c rate?
    Sorry for my bad english
    Thank you
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  • myk-au Thursday, October 13, 2011 3:17 PM Reply
    10A @ 18V!? Sounds like a lot. What was the original battery pack? Special high-drain ni-cad?
    Even a good quality 18650 will not do 10A. Too much resistance.
    This is not really the place to ask grade-1 electrics questions. Do not play with li-ion if you do not know series from parallel.
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  • myk-au Thursday, October 13, 2011 4:08 PM Reply
    To clarify,
    drills draw huge current. On second thought your 10A @ 18V is normal.
    You want special high-power cells, not regular ones. I do not think DX sells anything suitable.

    Max for regular cells is around 2A.
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  • myk-au Thursday, October 13, 2011 4:10 PM Reply
    Sorry, 10A sounds right.
    These cells will only do about 2A. So you need 5x5 = 20 of them for 18V 10A.

    You really need special cells for a drill.
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  • myk-au Thursday, October 13, 2011 4:12 PM Reply
    Arrgh! I thought DX ate my 2nd reply. got web-server errors.
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  • myk-au Thursday, October 13, 2011 4:13 PM Reply
    And bad maths. 5 x 4 . I will stop now. :(
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  • makis129 Thursday, October 13, 2011 4:14 PM Reply
    myk-au thank you so much for your reply
    But I don't understand why you said 5X5. Did you mean 5X2?
    1)When the drill discharge the batteries with 10a does this mean each battery is pushed to give 10a or each battery gives 2a (5batteriesX2amperes=10)?
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  • myk-au Thursday, October 13, 2011 4:27 PM Reply
    http://en.wikipedia.org/wiki/Series_and_parallel_circuits

    Add V in series, A in parallel.
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  • Shadowww1 Saturday, January 7, 2012 4:28 PM Reply
    You can use IMR Lithium-Ions instead of ICR ones (like this one). They are capable of 15C discharge, which is 24 amps for 18650 cells (they are ~1600 mAh for best ones, way lower than ICR Li-Ions but safer & more powerful)
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  • makis129 Monday, January 9, 2012 7:41 PM Reply
    Thank you Shadowww1
    I finally bought a18.5v lipo pack which has 20c discharge rate.
    I also bought xt60 connectors and now i use the same battery to
    my drill
    my acer netbook (with a acer car adapter 12-24v. I soldered a xt60 too)
    my 10w led strip from dx sku 80512 with driver SKU 26110 modded to give 900mah
    The main question is still unanswered
    "When the drill(or any other device) discharge the batteries with 10a does this mean each battery is pushed to give 10a or each battery gives 2a (5batteriesX2amperes=10)?"
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