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  1. #1
    Live Beautifully Jewel's Avatar
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    Batteries --educate me, please

    So I've been researching different e-assist bikes (thanks for the help to my wonderful pals on BF ) & would like to have a "layman's explanation" about how to best recharge a battery.

    Specifically, I would like to know when it's best to recharge the battery on an e-assist bike.

    (off-topic example: I've been told that it's best to recharge a computer or cell phone's battery by letting the computer or phone get to its lowest battery "juice" level, then charge it. someone had said that that's because the battery will "memorize" the last levels and get used to that & only charge to that, so you'll never get the battery to its full battery potential). I don't know if that's a bunch of bologna or if it's true, so I'm asking all you guys who can explain what's the BEST thing to do for recharging a battery.

    For instance, some of the e-bikes that I'm looking at are saying that the bike will go up to 30-40 miles per charge. If I only travel say 20 miles for the day, should I charge it when I get home or try to figure out a place to charge it when out & about. Or am I just making this whole thing too complicated. (I tend to do that )
    "If I ride, I will know the way the trees smell after the rain... My breath will fill the air instead of smoke and car exhaust... Road rage will turn into laughter and I won't be a boy or a girl, I will just be a rider...and the planet will cool down and survive and thank me for riding with flowers & glaciers & fireflies & snow days off from school... I will be strong... I will only use oil in my chains and oil tankers will haul chocolate milk" by People for Bikes http://www.peopleforbikes.org/

  2. #2
    Transportation Cyclist turbo1889's Avatar
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    It depends on the chemistry of the battery.

    ----- Lead-Acid batteries greatly prefer to be charged ASAP and should not be discharged below 50% before being recharged for best battery performance and life.
    ----- NiCd and NiMH chemistry batteries should always be discharged all the way or nearly all the way before being recharged for best battery performance and life. These are the batteries that really have a memory effect, especially the older NiCd chemistry.
    ----- All Lithium (Li) chemistry batteries should not be discharged below 20% before being recharged for best battery performance and life.
    ----- Most Lithium (Li) chemistry batteries should be charged to about 75% of their capacity and not charged up all the way if you intend to put them in long term storage without use for quite a while for them to hold their performance and life best over the storage period (unusual compared to other battery chemistry which usually store best starting with 100% full charge). This is important to know if for example you only your e-bike during the summer months and store it during the 3+ month winter season, if you use any of the more common lithium chemistry batteries the best way to store over the winter is to only recharge the battery to about 75% capacity and pull the charger off short of full charge and then store the battery with nothing hooked up to it to drain power, then give it a good charge to 100% before using it when you pull it back out of storage.
    ----- Most Lithium (Li) chemistry batteries have a minimal memory effect compared to NiCd or NiMH chemistry. I wouldn't recommend continuously only discharging them to say 50% and never taking them down all the way to 20%-25% every once in a while but after a short ride its not a problem to throw on the charger and top them off on charge, just be sure to occasionally take a long ride and pull them all the way down to the 20%-25%.
    ----- There are differences between different lithium battery chemistry types For example Li-Ion batteries have more of a memory effect then LiFePO4 and should be taken all the way down to 20-25% more often.

    On all those % I gave I am referring to how much charge is left in the battery. When I say run a Lithium battery down to 20%-25% every once in a while to prevent memory effect, but don't run it down below that if at all possible, that would be like running a car down to a 1/4 tank of gas left and not going below that before refilling if at all possible. Storing for long periods (months without use) at 75% would be like storing a car with 3/4 a tank left rather then filling it all the way up full.

  3. #3
    Live Beautifully Jewel's Avatar
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    That helps a lot, Turbo. Thanks for the info!
    "If I ride, I will know the way the trees smell after the rain... My breath will fill the air instead of smoke and car exhaust... Road rage will turn into laughter and I won't be a boy or a girl, I will just be a rider...and the planet will cool down and survive and thank me for riding with flowers & glaciers & fireflies & snow days off from school... I will be strong... I will only use oil in my chains and oil tankers will haul chocolate milk" by People for Bikes http://www.peopleforbikes.org/

  4. #4
    Senior Member chas58's Avatar
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    Easy answer:
    What battery type do you have? If it is one of the newer lithium designs:
    Just top it off each time you use it. No real reason not to.

    I think it is good to keep it simple, and it is good to know the basics. Personally, I use about 75-80% of my capacity (range) each day, and charge it to 100% ever day. If you are using 50-65% of your batteries capacity each day, you should do the same.

    The “discharge fully” rule is for older NiCad designs (i.e. the first set of rechargeable AA batteries you ever bought). I don’t think that applies to you right? So, forget that rule.

    Long term storage: ideally keep it around 50% charge, and don’t let it get too low (really, anything between 80% and 35% would be fine). For riding the bike, I wouldn’t worry about running the juice too low, as the system will prevent you from running it too low to do damage. For longevity, you wouldn’t want to run the battery down until it cuts out too often. And, don’t leave it sitting around empty.

    To add more detail:
    Generally, Lithium batteries deteriorate faster at high levels of charge, or high levels of discharge. So, ideally your battery would spend its life at 50% charge. Any off the shelf battery will keep you from going to low on charge just by riding it (unless you drain it as far as it lets you, and then let it sit around for a year).

    If you really, really want to have a battery last a long time, you would charge it up to 85-90% and then not let it get below ~35% power. But, for most people, just charging it up to 100% after each ride is fine.

    The better products will let you charge up to 90% (allowing you to extend battery life by not filling it up to 100%), or to 100% (for when you really need it) or to 50% to keep it in the sweet part for long term storage.

    (P.S. I use wax in my chains).

  5. #5
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    I've read quite a bit from this site, it's an excellent source: Battery University

  6. #6
    Transportation Cyclist turbo1889's Avatar
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    What I really am looking forward too is when they get the new four way chemistry that uses Nickle, Iron, Zinc, and Air-vents to allow Oxygen reaction to make a non-toxic high energy energy battery that has nearly twice the storage density and slightly higher cycle life at way lower costs then current Lithium batteries with similar life spans. They have already developed that technology for large stand-by back-up storage capacity for hospitals and such (batteries the size of 18-wheeler trailers) and are just now starting to experiment with them in electric cars. Can't wait until they get them down to e-bike size especially since their a semi-local product for me (engineering firm that developed the technology is in my state but they have the actual units made else-where).

    Very much looking forward to a non-toxic battery chemistry that packs twice the energy density at a lower price tag then Lithium batteries, but for now lithium based batteries are as good as it gets for e-bike sized batteries.

  7. #7
    Senior Member chas58's Avatar
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    Me too, in about 10 years.

    With all of the work in the automotive industry, we might get lucky...

  8. #8
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    Which is the best battery to buy? In terms of value and bang for the buck!!!
    I want something to ride about 20 miles, some slight hills, probably friction drive, I am 6'6 260 lbs.
    I will probably do it without a kit, just buying up the parts I need and putting it together myself (for value). I have soldering skills, fab skills, but am new to ebikes and motorized bikes in general. There are some cool rides out there, but I dont want to spend a fortune!!
    As far as I know........
    Ah = gas tank
    Watts = size of engine
    Watt Hour is the capacity of the battery.
    36,48,60V is average, 72V is too much and might get shocked.
    Will need a controller, charger, motor, batteries.

  9. #9
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    Typical riding pattern with moderate assist is 15 watt hours per mile, lower if you pedal harder. Times your range - defines watt-hour size of battery (how much energy it has).
    Typical pack is 48V 15 Ahr = around 700 watt hours - divided by 15 will give you a range of maybe fifty miles. A Ping Pack or Headway pack of that size will cost you around six hundred dollars, and will last many years, due to the robust LithiumIronPhosphate chemistry - the safest type - recommended for beginners. I run Pings and Headways, both good solutions. The Headway packs seem to have more reliable BMS systems - I've had several Ping BMS's pack it in and had to replace them. Two packs in parallel will double your range. Lighter packs with different chemistries can be found but are typically less safe (LIPO), or have less longevity (LIMN).

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