V11 5A Charging curve

[Halig]

I have been entertaining myself for a while noting every 10 min the % charge and the volts with my 5A charger. If I have time, I will do it with the 2.5A to compare.

It comes out pretty straight.

In the graph below, I have overlaid the graph that comes out with the voltage data and it matches almost exactly.

Below I put the data table.
1h -> 47%
2h -> 73%
3h -> 99%

Edit: last two registers have erroneus hour, is 21:10 and 21:20

I started with a 9% battery (I was already in automatic Go Home mode for 15 minutes and I had said "Please, get out" 8 times).

The final voltage has stayed at 83.0V. Interestingly, in the end it has dropped a little.

For if it helps someone

Edited May 2, 2021 by Halig

[Chriull]

Nice short C(onstant) V(oltage) stage. Seem to be batteries in good condition.

What was your stop criteria? The green charger light?

56 minutes ago, Halig said:

The final voltage has stayed at 83.0V. Interestingly, in the end it has dropped a little.

In the cv/"saturation" stage internal chaege states of the cells equalize. Also by the internal resistance of the charger and the (changing) internal resistance of the cells voltages change with dropping current.

Although such a peak is somehow "strange" (but imho nithing to worry?)

Or, is i just have seen the drop has happened alltogether at 21:00 - do presumably with disconected charger. Then a voltage settling is a very normal li.ion behaviour.

[Halig]

The charger was connected all the time. I didn't notice the green light, I just finished the test when the fan stopped working. My idea was to have a general idea of the times and% of load, to make long routes with intermediate load.

I did not know all that you say about those cargo exchanges. Thanks

[Chriull]

1 hour ago, Halig said:

The charger was connected all the time.

Then this could to be some "not perfect" regulation from the charger side during the change from cc to cv stage? Or whatever...

Theoreticly it could also be a sign that the battery bms cut of prematurely due to single cell group overvoltage (imbalance). If so the charger should have switched to green light at 21:00 and charging current stopped (0A)

https://forum.electricunicycle.org/topic/22351-what-to-do-battery-not-charging-to-100/

Also if you continued logging some more small voltage drop should have occured, if there was the bms cut off - which would hard to distingiush from normal power consumption of the turned on wheel to get battery voltage data But anyhow a sign of charger beeing stopped!

Quote

I didn't notice the green light, I just finished the test when the fan stopped working.

At the cc stage the current is 5A and the fan runs continously. During the CV stage the current drops continously and by this the charger burden decreases so the fan stops.

Li Ion cells should be charged downto some current threshold of about 60mA per cell (specified in the manufacturers datasheet) - so about downto 240mA for 4p cell configurations.

There should be some very roughly additional 5% to 15% to be charged after the change from the CC to the CV stage. (Depending on charge current and cells condition)

1 hour ago, Halig said:

My idea was to have a general idea of the times and% of load, to make long routes with intermediate load.

I did not know all that you say about those cargo exchanges. Thanks

EUCs use battery voltage to calculate charge percent. So everything >=4.1xV is 100% and <=3.3/3.15V is 0%. Everything inbetween is linearly interpolated.

The shortcomming of this method is that it is only valid if the battery rested some time after a charge or burden.

Also the correlation is not strictly linear - the cells hold more charge per voltage difference at higher voltages.

EUC World and Darknesbot have implemented different, optional algorithms to get a better charge % estimation from the wheel data.

[Halig]

37 minutes ago, Chriull said:

EUC World and Darknesbot have implemented different, optional algorithms to get a better charge % estimation from the wheel data.

What you tell me is very interesting, although I am beyond my knowledge.

What we have discussed in the group is that Inmotion now leaves the batteries with a very low voltage. 3V / cell is maybe too much?

EUC World commented that it does not use its own algorithm to calculate% battery but gives the native data that it provides (at least in V11).

In this case of the V11 Inmotion make a perfect algorithm to convert voltage into% battery, according to my test. In the V10F is terrible this algorithm

[null]

Some chargers run the fan based on temperature or amperage, it can stop before the charge is over.
If you can't check Amperage being taken by the EUC, the Voltage stabilising (slowly) should be a fairly good indicator. (correct me if I'm wrong)

[Chriull]

4 minutes ago, Halig said:

What we have discussed in the group is that Inmotion now leaves the batteries with a very low voltage. 3V / cell is maybe too much?

Could be - i'm not in to much of such newer "details". The V11 had some reserve/emergency mode, too? Maybe this was the range from 3.3/3.15V downto 3.0V?

Kingsong had some models discharged downto 3.0V, too (ks18xl?) and then "stepped back" to 3.15V (from ks16x onward?)

4 minutes ago, Halig said:

EUC World commented that it does not use its own algorithm to calculate% battery but gives the native data that it provides (at least in V11).

Afair EUC World now shows the wheels reported charge % as default by now, as there were some confusion with new different percentages shown...

But for every wheel the "optimized" charge % can be selected.

Afaik @Seba optimized the algorithms for V11 personally, as KS and GW wheels.

4 minutes ago, Halig said:

In this case of the V11 Inmotion make a perfect algorithm to convert voltage into% battery, according to my test. In the V10F is terrible this algorithm

In wheellogs open source there is nothing special to be seen in regard to V10F. (https://github.com/palachzzz/WheelLogAndroid/blob/master/app/src/main/java/com/cooper/wheellog/utils/InMotionAdapter.java)

It's just 100% for 82.5V or more, 0% for 68V or less and batt = (volts - 68.0) / 14.5 inbetween.

A bit "special" 0% with 68V/20=3.4V.

[Halig]

22 hours ago, Chriull said:

The V11 had some reserve/emergency mode, too? Maybe this was the range from 3.3/3.15V downto 3.0V?

Yes, it does have a reserve mode "Go Home" (which can be activated automatically and that's as if it didn't, save for a short notice).

In a test I did with the V11, taking it to the end of the reserve (I had to walk back), it reached 61.14V = 3.06 V / cell.

I have read (Wikipedia) that 2.5V is the minimum to avoid deep battery discharge and shortening of battery life so I guess 3.06V is still not a dangerous limit.

Elsewhere I have read that the operating range is between 3.0-4.2 and that the minimum for no damage is 2.75, so 3.06 is not so terrible, as long as it is loaded as soon as possible.

[Aaron P.]

Any chance you gathered that 2.5A Charge data as well?  I was estimating it, based on your chart, but with these batteries it may not be a 1 to 1 comparison just due to half the input current.  Would be cool to see the same wheel tested both ways.