How to charge bike battery to only 80% ?

PeteCress

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Paoli (near Philadelphia) Pennsylvania USA
I am thinking Li-Ion "Shark" from Luna Cycle: 11.5 ah, 14S 4O Panasonic 18650 cells, 30 amps continuous.

I keep hearing that charging to only 80% maximizes the cycle life of a Li-Ion battery, but do not know how to do that as the supplied charger looks like a plain box with no options.

Can anybody elucidate?
 
There are two or more possible solutions

first option -> smart 14S BMS bluetooth and go to app adjust max charge voltage per cell (if possible @ app)

second option --> but 14S charger with built in adjustable resistor to adjust output voltage.
14S system full charge to 58,8V, but some chargers have this internal adjustable resistor and U can adjust output to 56V. This way each cell gets max 4V maybe arround 80%
 
batteryGOLD said:
...smart 14S BMS bluetooth and go to app adjust max charge voltage per cell (if possible @ app)

That sounds like the ticket to me - especially in light of my other concern about how to monitor the battery's degration in capacity over time.

Do you know if the aforementioned "Shark" supports that?

If not, one that does?
 
I remember there was a charger with a switch to charge to the 3 levels, 100%, 90%, 80%, not sure if its still around.

edit - Wasn't it EM3EV that did those chargers? I dont see any chargers for sale on his website.
I also checked out BMS Battery and didnt see anything right off the bat, maybe you can talk to them and get the switch installed, if not just tell them whatever voltage you want and they will make you a dedicated charger.

Satiator you can program your voltages in.
https://ebikes.ca/shop/electric-bicycle-parts/chargers.html

Meanwell's you can use the pot to dial in your voltages, and even hook them up in series.

CC/CV benchtop power supplies
 
maybe there is also a crazy solution.. but not tested yet..

Diodes have drop of 0,7V
For example 42V charger to charge 80% means 40V charge
use 3 serial diodes at output of charger for voltage drop 2,1V, those 42 will go 39,9V at theory..

I don't know if this work, because diode changes drop voltage at current change.

Anyone to test this?
 
You can DIY yourself a fanless charger that is adjustable for both current and voltage. You are essentially coming up with a DIY Satiator. MTBF on the unit is in the hundreds of thousands of hours and they are weatherproof. I have the 5a model mounted on a couple of my larger ebikes and absent mounting one permanently on the bike I can carry one - with a watt meter for a display - along in a MOLLE water bottle pouch.

Look around and you will see I am far from the only one who has gone and done this. Its an old school DIY thing. But I did do a step by step writeup with sources for parts linked.

https://talesontwowheels.com/2019/09/30/an-ultra-reliable-ebike-battery-charger/

Lab power supplies work great too but they are stationary by nature. They are adjustable to a much finer degree though. This one in my office garage is charging at 0.20a...
pxl_20210223_172616305-e1625440989678.jpg
 
PeteCress said:
I am thinking Li-Ion "Shark" from Luna Cycle: 11.5 ah, 14S 4O Panasonic 18650 cells, 30 amps continuous.

I keep hearing that charging to only 80% maximizes the cycle life of a Li-Ion battery, but do not know how to do that as the supplied charger looks like a plain box with no options.

Can anybody elucidate?
Do you have a defined lifecycle goal and has modeling shown an 80% charge meets that goal?

Commercial (professional) applications generally don't undercharge, but rather increase capacity to decrease depth of discharge and relative discharge rate.

With care, an ebike pack is likely to be upgraded for more capacity and/or current well before it has actually reached EoL.
 
Rather than 80%

just use 4.05Vpc

or 4.10, or 4.15V

The more longevity you want the lower.

But stopping **discharge** is much more impactful

and C-rate most of all.
 
PeteCress said:
I am thinking Li-Ion "Shark" from Luna Cycle: 11.5 ah, 14S 4O Panasonic 18650 cells, 30 amps continuous..
I keep hearing that charging to only 80% maximizes the cycle life of a Li-Ion battery, but do not know how to do that as the supplied charger looks like a plain box with no options.

Can anybody elucidate?
https://lunacycle.com/luna-charger-52v-advanced-300w-ebike-charger/ $99.95 ...
  • 52V (14S) charger charges to maximum 58.8v
    Charge to 80% 90% or 100 percent with simple 3 position rotary knob
    (Read about battery longevity ... https://www.electricbike.com/ebike-battery-longevity/)
    Charge slow or fast (1 - 5 amps) with a flick of a 5 position knob
    (Read about charging speed here ... https://www.electricbike.com/ebike-charging-fast-or-slow/)
    Smaller and lighter than other 5 amp chargers. High quality fan runs quiet and is reliable.
    (Read our online documentation here ... https://electricbike.com/forum/forum/knowledge-base/chargers/58593-luna-advanced-charger-documentation
 
Just buy a Cycle Satiator, you can program it to any percentage of charge/chemistry/voltage/Current level
 
Most of the common chargers can be adjusted (with a screwdriver) via a trim potentiometer inside:
https://www.youtube.com/watch?v=ViORzKrOfHU
 
pwd said:
Most of the common chargers can be adjusted (with a screwdriver) via a trim potentiometer inside:
https://www.youtube.com/watch?v=ViORzKrOfHU
Note that reducing charge voltage accomplishes the objective of reducing max charge level nicely. However, terminating early (i.e. at C/4 instead of C/10 or C/20) does something similar - but also reduces charge time. Both are good options. Early terminate is only available with something programmable like the Satiator.
 
HVC cutoff does the same

no CV stage is needed with LI.

Poorly designed balancing circuits may need a longer finish but that's another matter.
 
Yes when storage voltage is the goal, no precision is needed, ballpark no problem.


But the topic here is a lowered Full charge for longevity

That requires precision in the termination voltage regulation.
 
batteryGOLD said:
14S system full charge to 58,8V, but some chargers have this internal adjustable resistor and U can adjust output to 56V. This way each cell gets max 4V maybe around 80%
Charge percentage is based on controller LVC with 3.2v/cell/p-group in a 18650 pack as an acceptable LVC standard (IMO) ...

10s = 42v to 32v = 10v x 80% = 8v + 32v = 40v (80%) ... OR ... 10v x 90% = 9v + 32v = 41v (90%)
12s = 50.4v to 38.4v = 12v x 80% = 9.6v + 38.4 = 48v (80%) ... OR ... 12v x 90% = 10.8v + 38.4v = 49.2v (90%)
14s = 58.8v to 44.8v = 14v x 80% = 11.2v + 44.8v = 56.0v (80%) ... OR ... 14v x 90% = 12.6v + 44.8v = 57.4v (90%)

During charging connect voltmeter leads to battery output (if possible) to verify percentage. For example 14s at 85% is 56.7v and 12s at 85% is 48.6v and 10s at 85% is 40.5v. My preference is 85% charge ... 85 percent of the time :thumb:
 
john61ct said:
Are you mixing up HVC and LVC?
Is it possible that "I Say, I SAY, I Say" is not aware of the significance between both HVC and LVC ...
https://www.endless-sphere.com/forums/viewtopic.php?t=93908

What is the difference in usable voltage between a Controller LVC of 3.50v versus a Controller LVC of 3.20v when a Grin Cycle Satiator is set at a HVC of 80% when charging a 16s 18650 battery pack ?

  • Hint: 67.20v to 56.00v is a difference of 11.20v x 80% = 08.96v + 56.00v = 64.96v
  • Hint: 67.20v to 51.20v is a difference of 16.00v x 80% = 12.80v + 51.20v = 64.00v
 
eMark said:
Charge percentage is based on controller LVC with 3.2v/cell/p-group in a 18650 pack as an acceptable LVC standard (IMO) ...

10s = 42v to 32v = 10v x 80% = 8v + 32v = 40v (80%) ... OR ... 10v x 90% = 9v + 32v = 41v (90%)
12s = 50.4v to 38.4v = 12v x 80% = 9.6v + 38.4 = 48v (80%) ... OR ... 12v x 90% = 10.8v + 38.4v = 49.2v (90%)
14s = 58.8v to 44.8v = 14v x 80% = 11.2v + 44.8v = 56.0v (80%) ... OR ... 14v x 90% = 12.6v + 44.8v = 57.4v (90%)

During charging connect voltmeter leads to battery output (if possible) to verify percentage. For example 14s at 85% is 56.7v and 12s at 85% is 48.6v and 10s at 85% is 40.5v. My preference is 85% charge ... 85 percent of the time :thumb:
This is not the standard or correct method of calculating or describing SOC utilization, specifically because it is cumbersome and abstracts away the actual SOC window.

SOC window terms refer directly to percentages of the LV and HV limits established in the cell datasheet, such that if the LV limit is 3.0V and the HV limit is 4.2V, then 80% SOC refers to 4.2V - 3.0V = 1.2V * 80% = 0.96V + 3.0V = 3.96V. 0-80% SOC window thus refers to 3.0-3.96V.

Avoiding low SOC with a 20% SOC LV limit would thus be 1.2V * 20% = 0.24V + 3.0V = 3.24V. 20-100% SOC window thus refers to 3.24-4.2V.

As above, you can combine these limits such that 20-80% SOC window refers to 3.24-3.96V.

But abstracting away both is not correct. Just use the SOC windows.
See Extending Battery Lifetime by Avoiding High SOC and Optimized Operating Range for Large-Format LiFePO4/Graphite Batteries

Also, as was previously requested, please stop using dumb font size tags. This is a technical forum and size tags make your posts look like they're written by an incessant, attention-starved adolescent.
 
OP, if you are using a pack with one if the non-programmable BMS's that usually comes with those packs, remember that they usually only balance charge when they are right at 100% (4.2V/cell). So it is important that you have a way to monitor the balance, or at least charge the battery to 100% and let it sit in the charger a few hours regularly, to let the BMS balance if nescessary.

You could get 2 cheap chargers, and trim one of them down with the potmeter. Then you have one for 100% and one for xx%. Or one of the other solitions suggested earlier in the thread.
 
Be aware...when we say "80%, it is not 80% of capacity, it is 80% of max possible voltage.

Look at any discharge graph on the web. When a 4.2V lithium cell begins discharging, there is a fairly sudden drop in voltage to roughly 4V, and then there is a reasonably long a relatively flat voltage output for the fat middle of the cells capacity.

Of course we are seeing compound curves in the graph, but somewhere around 3.0V, there is a pretty steep drop-off.

What I am saying is...if you are only charging to 4.1V-4.0V instead of 4.2V...you are only "losing" about half a minute of range, but you could possibly be doubling the life of your expemsive battery.

Tesla and Chevy have VERY expensive battery packs, and they charge to 4.05V
 
Yes percentage of voltage is virtually useless.

Percentage of Ah/mAh is what should be targeted

whether using theoretical maximum capacity

or SoC% between the 0-100% definitions arbitrarily defined by the user according to their preferences, balancing range vs longevity.

But actually calibrating those percentages to resting isolated voltages through measurement

is required for any accuracy, will differ for every rig.

So, in practice, forget percentages.

Just use voltages, HVC applies to charging, LVC to discharging, e.g. pack at rest an hour after charge termination should be under 4.10Vpc

and pack at rest an hour after use should be above 3.65V

Then work backwards in adjusting your usage and your kit to accomplish those goals.
 
by john61ct » Jul 21 2021 8:39am

Yes percentage of voltage is virtually useless.

Percentage of Ah/mAh is what should be targeted

whether using theoretical maximum capacity

or SoC% between the 0-100% definitions arbitrarily defined by the user according to their preferences, balancing range vs longevity.

But actually calibrating those percentages to resting isolated voltages through measurement

is required for any accuracy, will differ for every rig.

So, in practice, forget percentages.

Just use voltages, HVC applies to charging, LVC to discharging, e.g. pack at rest an hour after charge termination should be under 4.10Vpc

and pack at rest an hour after use should be above 3.65V

Then work backwards in adjusting your usage and your kit to accomplish those goals.

I have my LVC set around 3.30V, never have reached it yet. You think that is two low and prefer not to run a battery that low?
 
The question is, for **your** rig, hitting that LV mark under load

if you stop, isolate it and rest for over an hour,

what is the pack voltage after bouncing back?

Too low for me prioritizing longevity, may be just fine for you.

There is no "damage" to the pack until well below 2.8Vpc or something, see the data sheet

Resting voltage is the only objective measure

Under load is if effect meaningless wrt SoC.
 
spinningmagnets said:
Look at any discharge graph on the web. When a 4.2V lithium cell begins discharging, there is a fairly sudden drop in voltage to roughly 4V, and then there is a reasonably long a relatively flat voltage output for the fat middle of the cells capacity.
Comparing "range" of one lithium cell against PeteCress' 14s LUNA Shark battery pack is misleading ...
spinningmagnets said:
What I am saying is...if you are only charging to 4.1V-4.0V instead of 4.2V...you are only "losing" about half a minute of range, but you could possibly be doubling the life of your expensive battery.
You are comparing one lithium cell (1/2 minute) versus an expensive battery pack. The difference between "4.1v-4.0v (4.05v) instead of 4.20v" even with my meager inexpensive 10s3p 30Q DIY pack gives me an additional range between 1/2 to 1 mile (closer to 1 mile). With a 14s7p battery pack the difference in additional range between a SOC of 4.05v and 4.20v would be far more significant as supported by docware's insightful experiences and experiments as shared in his "Aging" thread ... https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=200 ...
john61ct wrote:
From 4.05 to 4.2V termination point is I understand not significant actual usable mAh capacity, just "surface charge".
Maybe even 4.00?
docware said:
No, no, there is a LOT capacity between 4,0 and 4,1 V. I mean resting voltage. It´s obvious from SOC chart as well from discharge graphs. So optimal charging voltage to exploit capacity may be about 4,12 - 4,15 V (termination point).
docware said:
I continue using LVC 3,4 V for high capacity cells for 21700 also. Frankly, LVC should be determined individually for each cell to draw the same capacity or rather energy,
... and for each battery pack depending on it's usage and desired cycle life longevity.
spinningmagnets said:
Tesla and Chevy have VERY expensive battery packs, and they charge to 4.05V
... 85%? ... but the CAPACITY of the Tesla (and Chevy) battery packs is such that the extra range achieved at full charge (2170 or new 4680 lithium cylindrical cell) instead of say 4.05v would result in a significant enuf loss of cycle life longevity (and bottomline sales).
 
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