Battery confusion.

[Canny_Scot]

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.

 

[J.R.]

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.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Most important, enjoy your bike!

 

[Canny_Scot]

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.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Most important, enjoy your bike!

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?

 

[J.R.]

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?

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.

 

[Canny_Scot]

Thanks very much for the clarification. I'll be sure to make sure the correct practices are followed.

 

[Rob Bay]

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.

 

[jazz]

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.)

 

[Rob Bay]

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.

 

[harryS]

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.

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.

 

[Joef]

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.

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.

 

[itsaulgoodman]

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.

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

 

[harryS]

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.

 

[Joef]

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.

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

 

[john peck]

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.[/QUOTE

just to interject a maintenance tip. Check your cones often as well as your spokes.

 

[rich c]

I'd assume it would help for us to know the brand. Or is it a generic Chinese? I'd trust a minimum shut off on a name brand bike, knowing they have a good BMS in the pack. Now if it is a $500 internet purchase, I wouldn't have the same confidence. Only way you will know for certain is if the display tells you the current voltage level. or you know your way around a volt/ohm meter and measure the voltage at different discharge points.

 

[Sergey Kirienko]

from what i know, Lithium battery are very flexable on their charge capacitance. thats why you have to "teach" the battery the fully charged voltage few times by fully charging it.

 

[john peck]

Mine gets charged about every 4 days. My concern is the effect of cold on the pak. My bike covered
& in a carport, but out in the cold. Anyone know how this might affect my battery?

 

[Sergey Kirienko]

from 0 to +50 (Celsius) there is no dramatic changes. but below zero, there will be bigger capacitance lose.

dont forget when the battery is charging, or discharging (working)
your battery getting hotter and there for the temp increasing to his normal working temperature.

so basically, all you need to know thats when you;
chargign battery, battery getting hotter = good
using your ebike to ride, battery getting hotter = good
battery on idle = not good, but as long you wont forget to charge it once in a while, everything would be good

 

[john peck]

So...looking at the chart, it seems with the average nightly low, I'm still only retaining around 85%. Small
wonder then that with my weight & topography my mileage doesn't begin to reflect the Juiced battery chart.
Will this improve come summer or will it have a lasting effect on my battery?

P.S. Guess I'm gonna start bringing the battery inside at night & see if that helps, bit of
a hassle, but hopefully worthwhile. I've noticed that even when brought inside the pak
remains very cold to touch after charging.

 

[Sergey Kirienko]

a good lithium battery has about 1000 recharge cycles. thats the only thing that you need to concider.

around 500 cycles, you will have 95% maximum from total battery capacitance.
at 1000 cycles 85% or so.

so your best wey to save your battery life, dont charge your battery all the time like we all do with our phones even at 50% battery.
just charge it before you have plans for your next ride.
also keep the track of the kilometers you can do with full charge so you can plan your next ride according to your maximum traveling length.

I've noticed that even when brought inside the pak
remains very cold to touch after charging.

your charger supposed to deliver around 2Amps while charging
it will deliver this much current only when there is a big difference from "current battery voltage" and "charger voltage"
wich means, the more charged your battery will get, the less current will flow to it and keep it cooler and cooler.