battery charging to maximise battery life

[danFan]

Hi All,

I have an ebike with a 36V 10Ah standard size lithium-ion battery which should do a range of 30 miles. The manual for the battery says I shouldn't let the battery discharge to almost empty for care reasons. I do about 7.5 mile to work from home ( some big hills along the way) and back every week day, so my question is would it be good to do a single daily top up charge after my first 7.5 mile journey? Would that type of charging be good or bad?

Cheers,
Dan

 

[Deleted member 25121]

If you do around 7.5 miles a day the battery should be good for 4 days but more likely 3 days or less depending on the gradient and length of the hills and the amount of assistance you use.

I suggest you recharge it up to full when it gets down to 10-25%. It's important not to leave it fully charged or discharged for too long, Bosch for example suggests that the ideal charge status for lengthy periods of storage is approx. 30 to 60%.

https://www.bosch-ebike.com/fileadmin/EBC/Service/Downloads/Akku_Guide/Akku_Guide_August_2019/Bosch-eBike-Battery-Guide-MY2019-EN.pdf?_=1535448290

 

[flecc]

Hi All,

I have an ebike with a 36V 10Ah standard size lithium-ion battery which should do a range of 30 miles. The manual for the battery says I shouldn't let the battery discharge to almost empty for care reasons. I do about 7.5 mile to work from home ( some big hills along the way) and back every week day, so my question is would it be good to do a single daily top up charge after my first 7.5 mile journey? Would that type of charging be good or bad?

Cheers,
Dan

Charge once a day Dan, doing roughly 15 miles and using half or more of the charge each day.

The things that shorten life the most are emptying the battery and the last period of charging that fills the cells to the limit.

The first you can avoid of course, the second you shouldn't because that last part of charging is when the cells are balanced, which is important.

So it's a balancing act, charging well before empty but only when there's enough used to keep the number of charges as low as possible.

That said, the battery quality is what dictates life most. Cheap and cheerful ones last around two years, the best and often most expensive can last five years or more. In fact the most expensive can actually be cheaper over time.
.

 

[danFan]

Hi Thanks for that.

 

[danFan]

Great Info, much appreciated

 

[Deleted member 25121]

Will you do 7.5 miles a day or 15 miles a day, it wasn't too clear in your original post?

 

[danFan]

Hi, sorry it's 15 in total.
The battery showed really low on my way back home. I put on charge as soon as I could which got me thinking about a top up charge while at work each day. It was my first try out of the bike and I had it on the highest assist level all the way there and back There are some big hills along they way which I think is why I'm not getting a 30 mile range.

 

[Nealh]

Another option to not leaving a battery fully charged is to charge it fully allowing balance to take place then ride the bike for 5 or 10mins to bleed or some of the top voltage, this will be good for the battery cells.

 

[danFan]

Another option to not leaving a battery fully charged is to charge it fully allowing balance to take place then ride the bike for 5 or 10mins to bleed or some of the top voltage, this will be good for the battery cells.

Thanks, that sounds like a good tip.

 

[danFan]

I'll probably not keep the bike on full assist in future which should help.

 

[Nealh]

Hi, sorry it's 15 in total.
The battery showed really low on my way back home. I put on charge as soon as I could which got me thinking about a top up charge while at work each day. It was my first try out of the bike and I had it on the highest assist level all the way there and back There are some big hills along they way which I think is why I'm not getting a 30 mile range.

You will only get more mileage /range from the battery with low assist power, high/max assist will demand the battery provide constant current all the time and over time will be detrimental to the cells as well.
Generic batteries contain not the best cells available because they are cheaper, if you continue to use the battery on full assist life expectancy will be about 12 - 18 months then you will notice range/capacity decrease quite markedly.

 

[Deleted member 25121]

Hi, sorry it's 15 in total.
The battery showed really low on my way back home. I put on charge as soon as I could which got me thinking about a top up charge while at work each day. It was my first try out of the bike and I had it on the highest assist level all the way there and back There are some big hills along they way which I think is why I'm not getting a 30 mile range.

Ah, in that case you'll have to charge it each day of course. Try experimenting with the assist level, you'll hopefully find that it will have a big effect on the range.
If it's a quality battery and a quality charger there's nothing wrong in charging it to full, the BMS electronics (Battery Management System) inside the battery pack will ensure that the battery cells aren't damaged. Just don't leave it fully charged for more than a few days.

 

[Nealh]

Save the high assist to get up the hills and use lower assist for the flatter terrain, down hill turn assist to 0 or off.
36 - 40 miles will be the optimum range for flat terrain and low assist.

 

[danFan]

Thank again everyone for the input, really helpful.One last thing I'm wondering: I'm assuming putting the battery on charge but falling short of getting to the balancing phase is bad practice? Maybe not the end of the world if done once or twice but to be generally avoided?

 

[Nealh]

Thank again everyone for the input, really helpful.One last thing I'm wondering: I'm assuming putting the battery on charge but falling short of getting to the balancing phase is bad practice? Maybe not the end of the world if done once or twice but to be generally avoided?

It is dependant on the knowledge & skills of the user.
Generally if the cells are good and matched then short charging with no balance they shouldn't wander but with mass produced batteries you can't always rely o this.
There is no reason to not have a routine and charge to max 40.5 - 41v, and the then carry out a full balance every 6th, 10th or 12th charge etc,etc, (or whatever suits) esp if a battery is in use daily or during the working week.

 

[BadFollow]

Very interesting, but as far as I know, the modern li-on batteries has it's own chip to control the charging cycles and they are way much smarter then we pretend to be, so It doesn't matter how often do you charge your battery

 

[Deleted member 25121]

Very interesting, but as far as I know, the modern li-on batteries has it's own chip to control the charging cycles and they are way much smarter then we pretend to be, so It doesn't matter how often do you charge your battery

That's true of quality battery packs from the likes of Bosch but it sounds as though some to the cheap stuff designed in China may still have some catching up to do.

 

[Nealh]

Batteries as a unit will use a BMS of some sort, either a generic one or like Bosch and others a slightly better type. BMS do go wrong now and then and bleed resistors can and do fail. The likes of Bosch within a closed system monitor charge cycles but your generic battery doesn't.
Cells used in the whole are generic flat top unprotected ones, batteries use/rely a BMS for cell protection.

What we needed is for manufacturers (China) to produce generic BMS with 4.1v top balance to increase the overall cycle life of battery cells so as to stop wasting precious elements that are discarded as scrap.
The usable capacity in the top voltage range 4.1 -4.2v is quite small and often <5% of the batteries actual capacity.