Charging 48V battery to 80%

[wozzlegummich]

I am new to the ebike and Li-ion battery scene.

My question is if I want to charge my battery to 80% in the interests of longer life is this done by charging at a .....

• Lower Voltage?
• Lower Amperage?
• Shorter time?

[Calcifer]

Probably all of the above... but why would you reduce the charge to only 80%? You are really ripping yourself off alot of power and range? I personally charge batteries to their designed capacity, I just choose to charge them with the correct voltage, but less amps... and I wait for the battery to cool (if it has become warm) before charging it and if I am not using the battery soon (the next day or so) this is the only time I would only charge it to 80% (ish) and top it up before the next usage.

To increase potential battery life (they will eventually deteriorate no matter what you do) ... is simply never leave them connected when not in use so they discharge below a safe level, have a good charger, wait for the battery to cool/stabilize after a ride before charging... and if the battery is 'recommended' to be charged at say, 5amps, if you have time, charge it at 1.5 or 2 amps.

I don't see how purposely limiting the charging of a battery will protect it? If the battery is 'healthy' and of good quality, I would charge it to its rated capacity and enjoy the benefits. It is, to me, like saying my petrol car has a 100L fuel tank, but I am only going to fill it to 80 liters to spare the car?

I am sure if battery manufacturers thought only charging a battery to 80% was a good idea, they would all advise to do this...

I wonder what the others think? Maybe I am wrong? Maybe this is an ebike thing I haven't discovered yet? But none of my cordless power tools, RC models or ebike batteries seem to dislike being charged to capacity...

[Steampunk]

My understanding is that a new battery charged to 100% every time will last 400 charging cycles , but a new battery charged to 80% , and not let go below 20% , can last 1000 charging cycles !
All that I have read DOES actually recommend only charging to 80%. It is recommended to charge to 100% maybe monthly , to allow for a full balance of all cells .
I would do more research.

[Calcifer]

Well there ya go then...

Has anyone actually proved this or it is just theory? I am happy to keep charging mine to almost full... I don't want to carry the weight of a battery that can give me 40 miles range and only charge it up to give me 28 miles or so range... especially as batteries lose total capacity as they age anyway....

I guess someone could go up in the voltage then down on capacity (80%) and still have range...

interesting subject... gonna keep an eye on this thread for sure

[73Eldo]

Pretty sure its a real thing.

One thing to note if you do charge to less than 100% that most of the BMS's don't do cell balancing so you do still need to occasionally need to do a couple cycles to 100% to let the balance happen. When I was using mine daily once a month seemed to work well. I could see it took longer and I gained some range afterwards.

Another thing they say helps is slower is easier on things too so if you have a high rate charger but don't need the speed set it for a lower rate when you can.

[Calcifer]

Are there any links to this? When I buy/build a battery, I am trying to get the best range or time of use (RC stuff)... to me, charging a battery lower than it is designed for (to give best range) is counter productive, no matter how long it might make the battery 'last' (in charge cycles)... it is just not giving you the desired range/run time.

Until I see lots of benefits from undercharging, I would rather buy/build a battery with good quality cells and charge it with a quality charger to the voltage the cells are designed for... and enjoy the best range possible with a smile on my face... even if I only get less than a thousand recharge cycles... rather than short charge and have less range, riding with a grimace on my face worrying when it will run out of battery and leave me stranded.

As we know a 10S battery (for example) has a cell capacity of 3.7v per cell, so, in fact, 37v... so a 36v battery showing 36v is essentially flat. A fully charged 36v battery is 42v... so, its useful stored charge is 36-42v which equals a range of 6v of service time/range/time of use. So, if I charge my 36v battery to 80% (80% of 42v) then the battery is only charged to 33.6v which is too flat to even use?

If by charging only to 80% of the 6v between 36v and 42v... then the 36v battery would only be charged to 40.8v which would shorten the range/time usage to not much at all?

If that is the case, then why bother at all... I don't see the point? Hopefully someone can post links to show that the idea is better than I think it sounds? Surely, I must have it wrong?

[Tommycat]

https://www.electricbike.com/ebike-battery-longevity/ and

https://www.electricbike.com/how-to-...-battery-last/


A chart I'd happen to come across in my travels.





I think it comes down to which is more important to the individual, how you ride (distance, frequency, ETC.) and what you expect... maximum capacity/range, or cell longevity?

Regards,
T.C.

[Fred]

Thanks for the chart...very interesting.

[Steampunk]

Thank you for the follow up .
These batteries are quite expensive to replace .
I'm trying to baby mine and get maximum years .

[Tommycat]

"I'm trying to baby mine and get maximum years ."

+1! Two years and counting. ;-)

[Steampunk]

I have 18 mos , maybe 200 charging cycles on a 52v Luna Wolf and have travelled 3300 miles. Still going strong .