Should you charge your battery 100%?

[rogerf]

Will charging to 100% damage your battery?
Should u charge to 100% or would u advice charging 20/80.
So when ur at about 20 % u charge, and then u unplug at 80% cirka

 

[dobbyhasfriends]

sounds like you own a tesla with their charging recommendations etc.
no, I always charge to max and then mostly of the time I will empty the battery completely before charging it again.
if not using the bike for a while, I charge to 60% as recommended by specialized and then charge to 100% just before I ride.

 

[Alexbn921]

Lower charging to 80% will significantly increase the life of your battery. If you don't need a full charge then there is not reason to full charge it. If you do then charge to full and ride it.

Storage charge should be 50-60% and it should not be stored at high temperature or at full charge.

 

[Mikerb]

charge to 80% ( ish) unless your next ride needs the full range, and preferably a good few hours before you use the bike. Occasionally charge to 100% to equalise the cells.
The biggest potential for damage to the cells is charging to 100% and discharging below 20%. The more the battery is kept in the 20% to 80% range the longer it will last before degrading.
Store the battery over extended periods of non use at c 60% and preferably at room temperature. Allow a battery plenty of time to cool after charging before using it.
The a bove is the generally accepted best practise for Lithium Ion batteries. Says a lot a bout how long an electric car battery pack is going to stay good doesn't it!!

 

[Aussie78]

charge to 80% ( ish) unless your next ride needs the full range, and preferably a good few hours before you use the bike. Occasionally charge to 100% to equalise the cells.
The biggest potential for damage to the cells is charging to 100% and discharging below 20%. The more the battery is kept in the 20% to 80% range the longer it will last before degrading.
Store the battery over extended periods of non use at c 60% and preferably at room temperature. Allow a battery plenty of time to cool after charging before using it.
The a bove is the generally accepted best practise for Lithium Ion batteries. Says a lot a bout how long an electric car battery pack is going to stay good doesn't it!!

Exactly.


One is a market leader, capitalisation in the billions of USD, offering 8 year warranties on batteries, the others are tiny in comparison, outsourcing r&d to 2nd and 3rd tier suppliers, offering 2 year 300 cycle warranties with primitive tech in comparison, zero cell QC before pack assembly “they all self balance once assembled bro” with practices at best labelled “sheltered workshops”. View attachment 90066

 

[RustyIron]

Will charging to 100% damage your battery?

No.

Should u charge to 100% or would u advice charging 20/80.

Suppose someone on an Internet forum told you it's better to fill the gas tank on your car to 3/4, and to never allow it to get below 1/4 tank.

Would you do it? Even if urban legend suggested that your car "might" last longer--by some amount that no one is able to define?

Would it be worth your time to periodically run out of gas on the highway, just so your car would last longer? It's a question only you can answer.

Personally, I ALWAYS charge my battery to 100%. Maybe I'm just stupid, but I have a hard time predicting how much battery I'll use. Maybe I'll find a new trail I want to explore. Maybe I'll want to shoot for some fast times, and boost it up. There's no way for me to know, so I prepare for the longest ride.

There are a lot of legitimate reasons to cut a ride short, but "I have to go back because I'm trying to save money and only charged my battery half way" is not one of them.

 

[TheRealPoMo]

How do you charge to 80% anyway? I've had Bosch and Shimano chargers that do not appear to have this facility. Do you put them on a timer or check every hour until you have 4/5 bars?

 

[ilostmypassword]

Just charge to 100% and ride the bike

 

[Aussie78]

No.



Suppose someone on an Internet forum told you it's better to fill the gas tank on your car to 3/4, and to never allow it to get below 1/4 tank.

Would you do it? Even if urban legend suggested that your car "might" last longer--by some amount that no one is able to define?

Would it be worth your time to periodically run out of gas on the highway, just so your car would last longer? It's a question only you can answer.

Personally, I ALWAYS charge my battery to 100%. Maybe I'm just stupid, but I have a hard time predicting how much battery I'll use. Maybe I'll find a new trail I want to explore. Maybe I'll want to shoot for some fast times, and boost it up. There's no way for me to know, so I prepare for the longest ride.

There are a lot of legitimate reasons to cut a ride short, but "I have to go back because I'm trying to save money and only charged my battery half way" is not one of them.

RustyIron the issues lie with the manufacturers, not the end users. It’s a very technical topic of discussion. End user is free to do as they please, including purchasing new batteries.


The science behind lithium ion cell charging and discharging is quite a well established science, but is being ignored by many, not just the bicycle manufacturers but many consumer products using lithium ion cells.

Fundamentally many bikes have a battery that is too small. Let’s talk about a hypothetical manufacturer and not single out any one manufacturer. Their battery has a theoretical capacity of 500Wh. It has 10 cell groups, with 4 cells in each group. Aka 10s4p. 40 pieces of a nominal 3Ah (3000mAh) 18650 lithium cell.

The difference between 4.1 and 4.2 is significant for cell longevity, every 0.1 volts reduced from peak charge voltage of 4.2 almost doubles the cells life, while it reduced stored energy by 10-15%. Many are terminating the packs discharge cycle (I.e flat) at 3 or even 3.2volts per cell, when cell manufacturers are saying in their datasheets 2.5 or 2.65 is the bottom end to terminate discharge at. Instead our manufacturer has pushed the voltage window up, using 4.2 down to 3, when it could be 4.1 down to 2.5. Significant ageing occurs in fully charged cell at 4.2v at >30 degrees c.

Tesla et al are charging to 4.1 volts per cell(not 4.2), it’s part of how they can offer 8 year warranties. They also liquid cool the packs. They have custom BMS of course that can activly balance under change, idle and discharge. And they match cells before assembly into batteries.


Problem abound in the real world for bike batteries. The cells commonly are not matched before they are assembled into battery packs for
bikes (or many consumer items, like power tools). All 40 pieces need to be PERFECTLY matched to each other, otherwise a cell group droops when one of the four cells is weaker, that cell group gets down to 3 volts (or whatever threshold the bms has been programmed for) triggering a flat battery condition from the BMS. I’m seeing packs with 50 discharge/charge cycles with cell imbalances so bad, regardless of the BMS bringing all cell groups up to match when fully charged, during discharge the packs effective capacity is degraded by 25%. I.e that 500Wh pack in reality only delivers 380wh before it’s got a cell group at 3volts and cannot be discharged any further.

Maybe this analogy will help understanding the pack balancing issue with regards to miss matched cells. Let’s pretend we have 10 horses pulling a wagon. They have all had a good nights rest, eaten, all have a full stomach. Two horses are suffering from a mild illness. The next day, all 10 start out pulling hard, as a team of 10 they work well. But our two mildly sick horses are the first to tire, and quickly can’t go on from exhaustion. Our team of ten has been brought to a grinding halt by its two weakest members. If all ten had matched, they could have gone all day long.





If the ebike manufacturers actually demonstrated some appreciation and understanding of the science and exhibited professionalism I could accept they have made the design decision to sacrifice longevity for lighter weight packs, but they have just bumbled their way through to where the industry is so far. It is a paradigm shift for the industry, so it will take some time to sort out its blunders.

 

[urastus]

How do you charge to 80% anyway? I've had Bosch and Shimano chargers that do not appear to have this facility. Do you put them on a timer or check every hour until you have 4/5 bars?

I use a timer. Every 1% = 225 sec, that's for up to 80%. I have a shimano slow charger and a 504wh battery. I have a list of about 15 different times now. I set the timer to be finished by 0500, and work back from that. Calculation is pretty simple eg 50% = 50x225 = 11250 secs / 60 = 187.5 mins = 3hrs 8mins. I do a full charge every 4th or 5th time.

 

[Gyre]

I use a timer. Every 1% = 225 sec, that's for up to 80%. I have a shimano slow charger and a 504wh battery. I have a list of about 15 different times now. I set the timer to be finished by 0500, and work back from that. Calculation is pretty simple eg 50% = 50x225 = 11250 secs / 60 = 187.5 mins = 3hrs 8mins. I do a full charge every 4th or 5th time.

Yep, an outlet timer is a good/cheap investment to manage your charging.

 

[urastus]

There are a lot of legitimate reasons to cut a ride short, but "I have to go back because I'm trying to save money and only charged my battery half way" is not one of them.

Do you really think anyone here does that or is suggesting doing that?

 

[TheRealPoMo]

Thanks, I'll use those figures as a baseline and see if I can come up with my own tables.
Begs the question tho, if it's that important, why dont the supplied chargers go to 80%?
If it wasn't so environmentally negligent, you'd think the manufacturers want us to ruin battries early so we buy more.
Yeah I know, crazy talk....of course these guys are all for the environment

 

[urastus]

these guys are all for the environment

Sales and profit - that's business in general. They'll sell more the simpler it is. There's always those of us who are a bit more interested or mechanically sympathetic (chemically sympathetic?) .

 

[Aussie78]

Go look at the price of a new battery, also consider the fact they have locked down the software to prevent 3rd party batteries easily working with the big three.


In bulk, as in buying 200,000 pieces per order, a good 3400-3500mAh cell from the usual suspects is 2-3 usd a pop. 40 pieces in a battery. Let’s call it $120 usd in cells for a pack. Jump up to $4 usd a cell for a 5000mah 21700 in the 700Wh packs


Someone’s getting screwed…..and it ain’t daddy the way he wants it

 

[urastus]

Excuse my ignorance - what chemistry are our batteries? Are they lithium ion phosphate? I assumed they're not, but I don't know.

 

[Alexbn921]

They are not LFP. It doesn't have the energy density for a "performance" application. On a commuter or a work bike it would be a much better solution and the extra weight wouldn't matter as much.
They are a nickel based Li-ion. The exact chemistry will vary based on the supplier.

 

[RustyIron]

It’s a very technical topic of discussion.

is quite a well established science,

Let’s talk about a hypothetical manufacturer

The original question wasn't hypothetical, and was rather specific.
Clearly, you have a vast wealth of knowledge on the subject.
What do you think of the original question?

 

[Planemo]

Begs the question tho, if it's that important, why dont the supplied chargers go to 80%?

Most don't because many would start using the 80% charge too often. It should only be used for long term storage, not on a day to day basis.

We've covered all this before in past threads. You have a far greater chance of ruining your batteries through imbalance (due to not charging to 100%) than any damage they sustain whilst sitting at 100% for a day or so.

Batteries ideally need balancing after every discharge. I would never do a partial charge more than 3 times in a row personally.

Until we have ebike manufacturers that use charge systems which balance throughout the entire charge process (like Tesla), we are stuck with top-end balancing only. Which only starts to activate at around 90%+ charge levels.

Ignore balancing at your peril. It doesn't take long at all for cells to go out of whack and our BMS's can only cope with small differences.

 

[Aussie78]

The original question wasn't hypothetical, and was rather specific.
Clearly, you have a vast wealth of knowledge on the subject.
What do you think of the original question?

Sure.

If riding every day and you need all the capacity you can get, charge to 100%. Don’t charge a battery that’s hot or cold. Hot is >30c. Cold is below zero degrees c.
If you don’t need all the capacity your battery has to offer, charge to 80%.

Yes, charging to 100% does shorten cell life. Definitely don’t ride on Saturday and then charge when you get home to 100% and leave it fully charged till next Saturdays ride. That’s damaging to the cells.


Ideally, charge a few hours before your ride. This gives it enough time to cool before you use it.

Careful planning and usage with an appliance timer for the battery charger works well as a primitive means of control. I absolutely loose my shit when I’m getting ready for a ride, especially when it’s winter, Garmin is flat, Headphones are flat, bike battery is flat and the wife is already upset I’m off for a night ride on a week night and it’s 10pm.

 

[Binhill1]

3 years old two weeks ago the original battery 5600 miles I must be doing something right , three motors though . I don't always charge to 100 percent but most of the time I do.

 

[BeBiker]

Well it's clear the system's technical 0% and 100% is not the battery's physical 0% and 100%.
As there is maybe a potential battery lifetime expectancy optimum at 68,572% of charge at 16,281 degrees Celsius, I'm not here to obsessively trying to reach that.

When I would have the option to improve the range by reducing the safety margins below the system's 0% and above the system's 100%, sacrificing some lifetime expectation of the battery, I would definitely do that. Today.