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  1. #1
    Cat 5 field stuffer bbeasley's Avatar
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    Li-ion Battery care

    The manufacturer of my light doesn't go into details on charging. Reading on the web it appears these batteries have no memory and therefore it's better to have multiple short charges rather than one deep charge?

    I'm a daily week day commuter, about a half hour each way, should I just charge it every night, over night 5 days /week? In blink mode it's lasting about 10 days before the charge light goes red indicating it needs charging. As the daylight hours decrease I'll be using it in steady mode and expect that to drain the battery quicker.

  2. #2
    aka Tom Reingold noglider's Avatar
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    One great thing about LiIon batteries is that you can charge them whenever it's convenient for you. So just do you want to, and don't worry, be happy.
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
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  3. #3
    Senior Member a1penguin's Avatar
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    Basic to Advanced Battery Information from Battery University

    This is probably reputable site where you can trust what you read. Personally, I am paranoid about Li-Ion batteries and never recharge my 18650s unless I am near by. The same applies for my laptop, which also has 18650 batteries. Remember the flaming Apple laptops? But I love Li-Ion batts because of the high capacity and longer run times.
    2012 Cannondale Synapse 3, 2012 Trek 7.5 FX Disc, 2003 Trek 2200 WSD, 1997 Specialized Rockhopper Al Comp

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    Senior Member Looigi's Avatar
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    I knew a guy who burnt his house down about 8 years ago charging lithium polymer batteries. I think the built-in batteries and chargers nowadays are much safer with current and over temp protective features built in, except perhaps those in Boeing 787s, though all indications are they have that fixed now. One way to help allay fears is to place the device being charged in a fireproof tray or container away from other flammable items. No guarantee of course but it will reduce the chances of a major conflagration should the battery ignite.

    As for the OP, I try to strike a balance between depth of discharge and number of discharge/charge cycles by running batteries to between 33-66%. I don't overly sweat it though. Most all devices nowadays will shut down before the point at which the battery will get damaged so though not optimal, there's not need to be overly concerned should that happen.
    Last edited by Looigi; 10-05-14 at 07:15 AM.
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  5. #5
    Senior Member Garfield Cat's Avatar
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    This article in the New York Times may not be exactly on target to the discussion but its related and may be useful

    http://www.nytimes.com/2014/02/03/te...tery.html?_r=0

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    Quote Originally Posted by bbeasley View Post
    The manufacturer of my light doesn't go into details on charging. Reading on the web it appears these batteries have no memory and therefore it's better to have multiple short charges rather than one deep charge?

    I'm a daily week day commuter, about a half hour each way, should I just charge it every night, over night 5 days /week? In blink mode it's lasting about 10 days before the charge light goes red indicating it needs charging. As the daylight hours decrease I'll be using it in steady mode and expect that to drain the battery quicker.
    Yeah, with nickel cadmium is was best to fully discharge them, with nimh it was best to charge them regularly but occassionally fully discharge them, with lith-ion it's best to charge them as often as is convenient.

    Lith-ion also degrades as a function of time, and moreso if they get hot. I would never store them in the fridge between rides, but if you're not using them like during the winter it might help their lifespand to store them in the fridge.

  7. #7
    Señior Member ItsJustMe's Avatar
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    The only battery technology with a memory effect is NiCad, and almost nobody uses that anymore. Even NiCad only had a memory effect in extremely specific situations. It was first identified in satellites, where the thing would charge from solar panels exactly a specific number of minutes, then run off batteries for exactly a specific number of minutes, once per orbit repeated thousands of times.

    In general use even NiCad doesn't really have a memory effect.

    What pretty much all batteries do have is a dislike of being dropped to below a specific critical cell voltage. If you take NiCad or NiMH down below a threshold, I think it's around 0.9 volts per cell for NiMH, not sure for NiCad but probably similar, you cause an irreversible crystallization of the electrolyte around the anode, causing the cell to lose much of its capacity.

    People would put a cell on the shelf for 6 months, NiCads have very bad self discharge characteristics, they would self discharge down to below a critical level and people would latch onto something they heard once, that "NiCads have a memory effect, that must be the problem." No, it's not the memory effect, you just trashed the battery by running it too low or storing it too long.

    All that said, the best way to keep LiIon cells happy is to charge them as often as possible. Running them all the way dead has a bigger impact than running them halfway dead twice.

    If you're storing them for an extended period, charge them to 60% and leave them like that.
    Work: the 8 hours that separates bike rides.

  8. #8
    aka Tom Reingold noglider's Avatar
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    Thanks for that, @ItsJustMe. What happens if we charge to 100% and leave them?
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
    Residences: West Village, New York City and High Falls, NY
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    Look at the table about halfway down at BU-702: How to Store Batteries ? Battery University

    For Li-ion batteries, the warmer they are, and the more fully charged they are, the quicker they age. This rule doesn't apply if you freeze the batteries or allow the cell voltage to drop below 3.0 per cell (thus the advice to charge to 60%)

    So if you store at room temperature at 40% charge, you'll lose 4% capacity per year.
    If you store it at room temperature at 100%, you'll lose 20% capacity per year.

    I personally had a bunch of li-ion batteries I had in storage for SEVEN years and just put them back into service, and they're still at about 70% because I charged them to 40 or 50% before I put them away. Had I left them fully charged, they'd probably no longer be useful to me.

  10. #10
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by noglider View Post
    Thanks for that, @ItsJustMe. What happens if we charge to 100% and leave them?
    I've seen it recommended to keep them at 40% capacity for long term storage, to prevent it from losing as much charge capacity. This is the "conventional wisdom", usually claimed that storing them fully charged for oa few months will reduce the capacity to 94% vs 98% if at 40% charge.
    Last edited by wphamilton; 10-06-14 at 12:10 PM.

  11. #11
    Señior Member ItsJustMe's Avatar
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    Quote Originally Posted by noglider View Post
    Thanks for that, @ItsJustMe. What happens if we charge to 100% and leave them?
    I'm not an expert, I just read BatteryUniversity. I think that if you're too close to fully charged for too long, you can cause some chemical reactions to take place that aren't great for the battery.

    Like anything chemical, if you're going to store batteries, it's best to do it at low temps. I actually keep spare batteries in the fridge.
    Work: the 8 hours that separates bike rides.

  12. #12
    Senior Member Looigi's Avatar
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    Check this table from BU:

    Depth of discharge
    Discharge cycles
    Table 2: Cycle life as a function of
    depth of discharge

    A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
    100% DoD
    50% DoD
    25% DoD
    10% DoD
    300 – 500
    1,200 – 1,500
    2,000 – 2,500
    3,750 – 4,70

    Say 100% discharge takes 1 hr. Then 1 hr times 400 cycles is 400 hours of use out of the battery.
    If 50% discharge takes 1/2 hr. Then 1/2 hr times 1350 cycles is 675 hrs of use out of the battery.
    Continuing, 25% discharge is 562 hrs of use and 10% discharge is 420 hrs of use.

    This shows discharging the battery to ~50% before charging will give the greatest total use out of the battery.

    As I mentioned in my previous post I don't sweat it too much but try recharge my batteries when the hit between 33 and 66 % discharged to maximize life.
    Ride more. Fret less.

  13. #13
    Senior Member 01 CAt Man Do's Avatar
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    @ OP.....Since you are commuting the answer is simple, charge the battery when you get home except if you are off the following day. You are correct, it is better to do smaller charges. Since you will be using the lamp the next day it is okay to charge 24 hrs in advance. If you aren't going to use the lamp for some time than best to leave the battery with a partial charge ( 40-60% ).

    I can't tell you how long your battery will last. A lot depends on the quality and the capacity of the cells. Nevertheless if you are truly using the battery almost every day you might get two to three years use without needing a new one ( although it will drop in capacity over time, that is unavoidable ). If you have a cheap Chinese battery you will be lucky to get it to last a year.

    FWIW I have good Li-ion batteries that I've had for at least 5 years. They still work ( 5200mAh 4-cell ) and I trust them to do my typical 2hr night rides. I do have newer batteries though for the longer rides. The old ones are good enough for short commutes though. At some point it will become necessary to test the run time of the battery. I suggest doing this after you have owned the battery at least a couple years. Just keep in mind if the battery typically runs your lamp say, 2.5hrs....subtract 40 minutes when using in cold weather and ...."Never charge a cold battery". Wait till the battery warms before charging.

  14. #14
    Senior Member Looigi's Avatar
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    Quote Originally Posted by 01 CAt Man Do View Post
    ...You are correct, it is better to do smaller charges. ...
    Not necessarily according to chart in my post above. 50% charges are the best in that chart for total use. That might mean charging every day, every other day or every third day depending on the duration of the rides and the total burn time of the light.
    Ride more. Fret less.

  15. #15
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    Quote Originally Posted by Looigi View Post
    Not necessarily according to chart in my post above. 50% charges are the best in that chart for total use. That might mean charging every day, every other day or every third day depending on the duration of the rides and the total burn time of the light.
    I guess I'm not following how you came to that conclusion, based on this chart that you posted?

    Depth of discharge
    Discharge cycles
    Table 2: Cycle life as a function of
    depth of discharge

    A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
    100% DoD
    50% DoD
    25% DoD
    10% DoD
    300 – 500
    1,200 – 1,500
    2,000 – 2,500
    3,750 – 4,700/CENTER]

    Seems like the less the better?

  16. #16
    vol
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    When charging a new Li-ion battery for the first time, should it be charged to 100% (or even slightly overcharging), in order for it to have the maximum capacity during its life? I've seen this recommended for some products.

  17. #17
    Senior Member Looigi's Avatar
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    Quote Originally Posted by PaulRivers View Post
    I guess I'm not following how you came to that conclusion, based on this chart that you posted?...
    Basically, you want to get the most total hours of use out of a battery before it dies. The total hours is proportional to the depth of discharge times the total number of charge cycles before it dies. The table shows how many charge cycles a battery will last based on how deeply is was discharged. So, for example:

    If 100% discharge takes 1 hr: Then 1 hr times 400 cycles to end of life (avg between 300 and 500 in the table) is 400 hours total use out of the battery.
    At the same rate, 50% discharge will take 1/2 hr. So 1/2 hr times 1350 cycles to end of life (avg between 1200 and 1500 on the table) is 675 hrs total use out of the battery.
    At the same rate , 25% discharge takes 1/4 hr. So 1/4 hr times 2250 cycles is 562 hrs total of use.
    Similarly a 10% discharge would yield 420 hrs of total use.

    According to the table you get the most total life out of the battery, 625 hrs, by using it until it's discharged to 50% before recharging it.
    Last edited by Looigi; 10-08-14 at 08:34 AM.
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  18. #18
    aka Tom Reingold noglider's Avatar
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    Hours of run time might be the most important thing. Instead, months of use might be more important, even if it amounts to fewer hours. It depends on how you use it and what the costs of replacing the battery is.
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
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  19. #19
    Senior Member bikemig's Avatar
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    Quote Originally Posted by penguins View Post
    Look at the table about halfway down at BU-702: How to Store Batteries ? Battery University

    For Li-ion batteries, the warmer they are, and the more fully charged they are, the quicker they age. This rule doesn't apply if you freeze the batteries or allow the cell voltage to drop below 3.0 per cell (thus the advice to charge to 60%)

    So if you store at room temperature at 40% charge, you'll lose 4% capacity per year.
    If you store it at room temperature at 100%, you'll lose 20% capacity per year.

    I personally had a bunch of li-ion batteries I had in storage for SEVEN years and just put them back into service, and they're still at about 70% because I charged them to 40 or 50% before I put them away. Had I left them fully charged, they'd probably no longer be useful to me.
    Useful info,

  20. #20
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    As a general rule, Li-Ion is best between 20-80%.

    The main bad things:
    1) Holding/Storing at 100% for long periods of time.
    2) Discharging below 10%
    3) Charging at elevated temperature

    Ideally, you want to charge the battery when it gets to about 20-30% remaining. That leaves some margin for emergency use, without the hassle of daily charging, and no impact on battery life.

  21. #21
    Senior Member Looigi's Avatar
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    IMO, the not storing at 100% is the most annoying aspect. This means it's best not to charge them until just before you're going to use them. To do this you need to know enough ahead of time of when you're going to use them to have enough time to charge them, which kind of rules out spur of the moment use, unless there happens to be enough capacity left for the activity.

    I prefer not to obsess over battery life too much and just do what I find to be practical and reasonable, and accept a somewhat shorter battery life.
    Ride more. Fret less.

  22. #22
    vol
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    How do sellers store their Li-ion battereis or products (lights, etc.) with built-in Li-ion batteries? Wouldn't the batteries die or lost capacity if they don't recharge them from time to time? I don't think they could sell everything within a short period of time.

  23. #23
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    Quote Originally Posted by vol View Post
    How do sellers store their Li-ion battereis or products (lights, etc.) with built-in Li-ion batteries? Wouldn't the batteries die or lost capacity if they don't recharge them from time to time? I don't think they could sell everything within a short period of time.
    If you store initially at ~70% capacity it'll likely have plenty left a year or two later. The main thing for an integrated device is making sure off really is off.

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