Battery confusion.

Discussion in 'Maintenance and Repairs' started by Canny_Scot, Jul 9, 2017.

  1. Canny_Scot

    Canny_Scot New Member

    My wife has just bought an e-bike and I'm confused about the different advice found about battery charging. In the bike's manual it says this - "For the first 3 times, please fully charge and discharge the new battery (please consume all the power after fully charged) and then charge for 24 hours again." I decided to check and consulted Google, where almost all sites warn against ever fully discharging the battery. Help please! The battery is a Li-ion 36v/10ah model.

  2. Please support your local electric bike shop! These guys work hard offering test rides, sharing expertise and performing support.
    EBR strives to be impartial, we don't sell bikes ourselves and keep ads limited and relevant. Donations are greatly appreciated.

  3. J.R.

    J.R. Well-Known Member

    Best practice is not allowing the battery pack drop below 20% charge and if you need to store the battery over winter, maintain the pack at 60% charge. However, if the pack were at 20% and you still have 3 miles to get home, ride the bike and charge when you can. Charge and store at room temperature. I try to charge after the pack has rested a bit after a ride, 1-2 hours. Once charged, I disconnect the charger. It's never a good practice (or safe) to leave on charge indefinitely.

    This is one of the best sources of information for all types of batteries.

    Most important, enjoy your bike!
    Canny_Scot likes this.
  4. Canny_Scot

    Canny_Scot New Member

    Does this apply to her new battery or should we do the 3 full discharges as stipulated in the instructions before charging after each outing?
  5. J.R.

    J.R. Well-Known Member

    If your battery pack is lithium-ion, then no, no full discharge. That advice is for other chemistries and is a holdover for when some Chinese ebikes were using them. We've seen the very same question as yours asked many times and when those manufactures have been nailed down on it, they've admitted that practice is wrong. Lithium-ion does not have a memory like other batteries, so full discharge will not "condition" the pack, or stretch the capacity.
  6. Canny_Scot

    Canny_Scot New Member

    Thanks very much for the clarification. I'll be sure to make sure the correct practices are followed. :)
    J.R. likes this.
  7. Rob Bay

    Rob Bay New Member

    I thought some mfrs put a cutoff voltage so that it won't go below 20 or 30 percent. If not that would be nice. My main issue is getting the largest capacity battery possible so you usually won't push it past that point and it also will result in fewer charge cycles/longer life for the pack. I ride every day about 15-20 miles on a 12.5ah Samsung battery and I rarely go under 3 out of 5 bars and too it off after every ride. Going under 20-30 percent as a habit will certainly lower the life-expectancy of your pack.
  8. jazz

    jazz Active Member

    From Battery University:

    Simple Guidelines for Charging Lithium-based Batteries
    • Turn off the device or disconnect the load on charge to allow the current to drop unhindered during saturation. A parasitic load confuses the charger.
    • Charge at a moderate temperature. Do not charge at freezing temperature. (See BU-410: Charging at High and Low Temperatures)
    • Lithium-ion does not need to be fully charged; a partial charge is better.
    • Not all chargers apply a full topping charge and the battery may not be fully charged when the “ready” signal appears; a 100 percent charge on a fuel gauge may be a lie.
    • Discontinue using charger and/or battery if the battery gets excessively warm.
    • Apply some charge to an empty battery before storing (40–50 percent SoC is ideal). (See BU-702: How to Store Batteries.)
  9. Rob Bay

    Rob Bay New Member

    Simple test I did was I charged my 48v pack with the 54.6v output charter. I put my meter to the battery and got ~54v. Rode the bike for an hour or so then tested again and got ~44.5v. Seems like good numbers.
  10. harryS

    harryS Active Member

    Most 48V ebike controllers will shut off your 48V battery when it gets down to 42-40 volts. You shouldn't hurt the battery if the bike shuts off here, and that's somewhere close to 20% of the battery is left. The battery itself also has a low voltage circuit, usually set lower.

    If you ride your bike right after topping it off, your battery will last longer. What kills capacity is to top it off and not come back for a week or two.
  11. Joef

    Joef New Member

    I also have a 48V battery and on full charge, my cycle analyst shows 54.4 volts, similar to yours. at approx what voltage would the battery be at 80%? I'm asking because I want to limit charging to around 80% or so. thanks.
  12. itsaulgoodman

    itsaulgoodman Member

    Not sure which battery you have, but a good quality one should be doing that itself with it's BMS.
  13. harryS

    harryS Active Member

    You can look at this guy's empirical tests. I take away the following for a single 18650 cell. He's not using these cells for high current, but the numbers are probably close enough.
    40% 3.8 volts
    80% 4.0 volts
    90% 4.1 volts

    Multiply the above by the number of series groups in your battery. A 36V battery has 10. A 48V battery has 13/ A 52V battery has 14.
    So a 48V battery for longer life ought to be charged from 52V (80%) to 53.4V (90%), scaling the above numbers by 13X.

    Means you have to charge with a meter on the output unless you get a charger with 80/90/100 settings.
  14. Joef

    Joef New Member

    Thanks, much appreciated. I've tried reading the articles on BatteryUniveristy but have a hard time understanding them