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  1. #151
    Newbie
    Join Date
    Jul 2013
    Location
    Southern Illinois
    My Bikes
    two motorized trikes
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    1
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    Hi, I know nothing about electric so please be basic in answering my questions. I have a 48v motor that I am trying to get started. I have put 4 lawn and garden 12v batteries to, but when anyone puts a meter on then I get to much voltage. There are no repair shops for electric bikes and have not found anyone to help me here. Can someone help me?? Or at least tell me where to go for help.

  2. #152
    Senior Member DrkAngel's Avatar
    Join Date
    Oct 2012
    Location
    Upstate NY
    My Bikes
    Various "modded" eZips and multiple econversions
    Posts
    238
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    Lightbulb Care and Feeding of Your Slabatts

    Several years ago, in my "lead sled" youth, I despaired at the lowly SLAs I'd encumbered myself with.
    After rebuilding my oem pack I began researching.

    The care and feeding of the loathsome slabatts.
    1. Never overwork them (never deeply discharge) they become permanently "lazy".
    2. Always feed immediately after working them (recharge immediately) or they digest their own muscle (electrolyte).
    3. They are rated(and designed?) to discharge over 20 hours (1/2 hour discharges do "damage" them more than "rated" use) Don't expect 100's of cycles!
    4. 1/2 hour discharges give less than 50% of "rated capacity" (50% wasted as damaging heat) Especially, excessive heat, during charging or discharging, is damaging.
    5. Don't feed them too fast (manufactures recommend charging at .125C (1.25A charger for 10Ah battery)) a type of permanent "indigestion" can occur (plate corrosion).

    Any wonder that I went Lithium?
    Of course Lithiums are "expensive" so I started recycling used cells .
    See - Homemade Battery Packs

    PS I did purchase and use a BatterMinder Charger-Desulfator.
    I did enjoy a fair degree of success in rejuvenating worn-out batteries!
    A few hours has little affect, weeks of desulfating were required for substantial enhancement.
    Using a desulfating charger constantly has prolonged battery life 200-300%.
    But at $80-$150 for a charger ... is it worth it?
    "Best of all! ... I get to play. ... http://www.bikeforums.net/attachment...&thumb=1&stc=1
    Sorry! ... I'm addicted to improving enhancing.
    With side orders of inspiring enlightening!"

    Acronyms

  3. #153
    Senior Member
    Join Date
    Aug 2007
    My Bikes
    Huffy Wildwood
    Posts
    66
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    Price is dropping on these. Panasonic NCR18650PD

    http://www.fasttech.com/product/1233...ah-rechargeabl

    They are popular for the e cigs so there should be a steady supply.
    Last edited by biker; 08-06-13 at 10:58 AM.

  4. #154
    Member
    Join Date
    Jun 2013
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    Recognizing Battery Capacity as the Missing Link

    Interesting article from Battery University about measuring State of Charge (SoC) or remaining capacity for batteries or packs.

    An excerpt:

    Most users see the battery as an energy storage device resembling a fuel tank dispensing liquid fuel. For simplicity reasons, a battery can indeed be compared as such a vessel; however, measuring stored energy in an electrochemical device is far more complex than drawing fluid from a fixed container

    Full article at http://batteryuniversity.com/learn/a...e_missing_link

  5. #155
    Newbie
    Join Date
    Jul 2014
    Location
    Sydney
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    3
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    Hey all, new guy from Sydney, Australia.

    Ive been reading a hell of a lot about ebikes/batteries over the last 6-8 months and have begun my first project. A 48v 1500w brushless motor and matching controller, and I'm planning on making a 13S8P li-ion battery with BMS, with the cells coming from some 12 cell laptop batteries. I have already bought 1 battery from the seller and tested the cells, they seem to all be 2400 - 2600mAh and charge/discharge quite well (testing on a balance charger from Jaycar).

    Now i am a bit of a noob when it comes to hands on electronics (this being my first project), but don't get me wrong, I've watched countless videos and read article after article about Li-Ion, LiFePO4, LiCo etc. and understand that Li-ions are the most dangerous when not treated or monitored right (hence the BMS), but I am just after a second opinion.

    Anyway, I am just running this by everyone to get their thoughts and to see if I'm on the right track:
    With the 3.7v 2600mAh cells in 13S8P, that would give me a 48.1v 20.8Ah pack. With the 48v motor drawing MAX 40A, is this a well suited battery idea? As i understand you shouldn't draw more than 2C otherwise you get too high of a voltage sag/heat buildup etc. I will also buy a 40A peak / 20A continuous balancing BMS and wire that into the pack <- my insurance policy
    Now when the batteries are at full charge of 4.1-4.2v, is the total 54.6v too high for the motor? or will it simply 'use what it needs'?
    Secondly, am i right in thinking that if i charge each cell to 4.1v rather than 4.2v, and discharge to say 3.2v rather than 3.0v, will that increase the lifetime of the batteries (number of cycles)?
    Finally, with so many cells coming in a 1S4P configuration, what are people's thoughts on using some coin magnets to temporarily connect these cells in series to balance charge? I have heard people say its a HUGE no no, but then others say its ok. Personally I don't understand how it will affect the charging such that the magnetic field is not changing, and with my understanding, shouldn't cause an issue.

    Thanks all, and I am having such a great time tinkering away on all this stuff. Its nice to finally take my mind off uni studies to find a hobby which is also practical by saving me more money in the long run

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