elm70
Posts: 1156
Joined: Mon Sep 26, 2016 11:18 pm
Location: Poland
Contact: Website

Re: BMU Cell voltage smoothing

Wed Nov 29, 2017 11:49 am

IR: internal resistance (of the battery)

At 5C load a 'good' Lithium battery should not lose more then 0.15 volt per cell

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: BMU Cell voltage smoothing

Wed Nov 29, 2017 2:34 pm

My car is currently charging. Started at 25.4% and is now at 29.something %. Apparently, it is now doing it's intermittent magic: the charger is still getting 100 - 120 watts from the grid (excluding the power consumed by the eVSE module, so straight from the grid into the OnBoardCharger. But the battery is accepting 0.000 kW. And SOC is hovering around 29.10%. So, it looks like the little grid power taken is used just to perform the magic.

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: BMU Cell voltage smoothing

Wed Nov 29, 2017 3:18 pm

Last one before going to sleep. How's this for "what does it do when it is pausing the charge process?":

Image

Note: The x-axis is not quite lineair, unfortunately.

elm70
Posts: 1156
Joined: Mon Sep 26, 2016 11:18 pm
Location: Poland
Contact: Website

Re: BMU Cell voltage smoothing

Thu Nov 30, 2017 1:50 am

Interesting charging graph

Still you don't share all the info here :evil:

Does this graph start when you start charging the car, or after some seconds/minutes ....
Above you mention "Started at 25.4% and is now at 29.something"

Looking at some screen shot of my EvBatMan (almost 1Ah less time ago) .. I see 3.80v at 28.5% ..and 3.815v at 29.5%

So ... per what you said ... 25.4% is for you 3.82v
And 29% is 3.85v
So .. it is looking SOC and resting volt ... is something "remapped" for each PHEV

Is looking like the charging process stop after 10min .. and has a balancing pause for 15minutes ... which I don't understand the logic ... possibly the pack is seen too unbalanced for continue on normal charging .. and pause until the balancing level is acceptable for continue charging ... just a guess .... hard to know what is the logic here ... it can also be used for measure the IR under a know charging current ....

Also ... it is not visible what happen after 3.98v (with load) .. which apparently you got only after 25min of charging from 3.85 (unloaded) / 3.885 (with load) .... 388v to 3.98v in 25min ... does sound quite fast to me .. but possibly you use 16A charger .. still it is "fast" .. so a sign of a weak battery capacity)

What we also don't know is when and which cell get balanced at any time ... it will be an important information to know what the BMU is doing ... when I charge my hobby Lithium battery ... I know all the time which cell get balanced at any stage

PS: How can you track these info ? ... my OBD2 adapter is not working when the car is "off" or it is connected to the J1772 plug (even if not under charging)

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: BMU Cell voltage smoothing

Thu Nov 30, 2017 3:05 am

For elm70:

I don't hold back any information on purpose, other that it is crappy. In this case, my monitor tools are not 100% stable. There are several gaps and what more. So, I zoomed in on a bit of graph that was pretty much okay. From shortly before arriving home until where I stopped monitoring, I got this:

Image

My OBD Link adapters (I have three running in parallel) wake up as soon as the car starts charing.

Stefunk
Posts: 2
Joined: Mon Jun 29, 2020 7:55 am

Re: BMU Cell voltage smoothing

Thu Aug 20, 2020 10:46 pm

Hello,

I have a question regarding this operation. Should the battery be fully charged to perform this process? I'm getting an error while executing:
You do not have the required permissions to view the files attached to this post.

Fjpod
Posts: 105
Joined: Sat Nov 30, 2013 6:11 pm
Location: NYC

Re: BMU Cell voltage smoothing

Tue Aug 25, 2020 2:31 am

I'm a little confused by this thread. I understand the importance of balancing cell voltage, but doesn't the outlander do that automatically during a full charge?

With my miev it was said, for best battery life, to try to keep the charge between 40 and 80 percent with partial charges, but to run the battery down and fully recharge it for cell balancing once per month.
Previous prius and imiev owner.

dusanhu
Posts: 6
Joined: Mon Jun 29, 2020 3:56 am

Re: BMU Cell voltage smoothing

Thu Aug 27, 2020 2:19 am

Fjpod wrote:
Tue Aug 25, 2020 2:31 am
I'm a little confused by this thread. I understand the importance of balancing cell voltage, but doesn't the outlander do that automatically during a full charge?
Same here, I am quite curous what the smoothing does. Balancing wouldn't make much sense as the cells are balanced pretty much during each full AC charging, so a balancing forced at an intermediate charge state will lose its effect at the next normal AC full charge anyway.

dusanhu
Posts: 6
Joined: Mon Jun 29, 2020 3:56 am

Re: BMU Cell voltage smoothing

Thu Aug 27, 2020 2:21 am

Stefunk wrote:
Thu Aug 20, 2020 10:46 pm
Hello,

I have a question regarding this operation. Should the battery be fully charged to perform this process? I'm getting an error while executing:
I was able to perform smoothing at approx. 80% SoC. Although I am curious what it does in reality and what is the best SoC to start it at.

dusanhu
Posts: 6
Joined: Mon Jun 29, 2020 3:56 am

Re: BMU Cell voltage smoothing

Thu Aug 27, 2020 2:25 am

anko wrote:
Wed Nov 29, 2017 12:51 am
During little over an hour I have retrieved and logged voltages for all 80 cells (628 cycli, so roughly 1 per 6 seconds) and put them in a graph ...

Image

Hard to see, but these are indeed 80 different traces. Highest value: 4.071, lowest value 3.633.
Anko,

Can you pls. share what tools you are using to monitor all 80 cell voltages? This would be really nice to identify the weakest cells. Watchdog only does per cell voltage monitoring during charging.

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