HV battery votlages/tests

[EEEE]

Is 100% 100%, is 0% 0%? Why would it matter?

I mentioned in another thread that I would take some readings from the HV battery during a full discharge. The reason for this is that a lot of people are worried about how much of the HV pack is in use, and how much is managed/masked by the indicated SOC readout. The follow on from that is that people are worried about the longevity of the HV pack. I believe one of the main determinants of the life of a cell or battery pack is how low they are discharged (and also it seems how high they are charged to until the voltage cut off is reached). Not that it really matters, because like a mobile phone, you're never getting down to 0% on a regular basis.

This post is just some observations and musings. I charged the vehicle to 100%, reversed it off my drive, took some measurements, drove around over a few days to get the following observations:

SOC% - Cell voltage

98% - 4.13v
91% - 4.03v
81% - 3.94v
68% - 3.83v
54% - 3.79v
49% - 3.69v
39% - 3.62v
28% - 3.58v
19% - 3.55v
14% - 3.53v - Orange fuel symbol kicks in at 15% - only ever seen on the day I picked the car up and performed my longest single journey ever.
8% - 3.5v
0% - 3.47v

At no point did I receive the 'transmission / park issue' that others have observed as recently posted. I even manoeuvred the car at 1% and put back into park/drive but no error. My 12v is in good order.

Whilst trying to drain the last few percent without actually driving off of my drive, I also noticed that putting the heated front and rear windows on actually increased the 12v battery voltage all the way to 14.9v. This was confirmed by both my ODBC scan tool taking voltage reading from the OBD2 port, and via the BM2 at the battery terminals. Seems a little strange, perhaps the DC to DC invertor voltage measurement is not using the 12v battery negative post sensor to measure voltage, so its picking up a big chunk of voltage drop at high currents... ho hum...

So what does the voltage discharge curve tell us? We need to find some data sheets!

I believe the cells in questions are Panasonic UF261591TA NCM622 51Ah. NCM 622 being the specific chemistry composition of the cells. Other details about the cell sizes and weights can be found in the link.
( source https://pushevs.com/2020/07/03/modern-p ... ery-cells/ )

I cannot find data sheets for the cells - I suspect these are only available under NDA.

I also cannot find a generic rule of thumb for cell capacity/life vs DoD (depth of discharge). What I did see is that charging ncm622 to 4.3v /4.4v / 4.5v would decrease the lifespan, so charging to 4.15v seems conservative. Likewise, some discharge tests go well below 3v, but the lifespan is only measured in the 100s of cycles range before significant drop off in capacity.

Make of it what you will, but I suspect that the batteries are not heavily stretched. My scantool did report a 'useable capacity' of 86% , perhaps indicating 14% is reserved (below 0%?) , we'll never know...

[madbiker]

Thanks for the update, interesting reading especially about the 12v battery being charged when the front & rear window heating was on, could this be a good trick to use for the owners with a BM2 connected as it’s so easy to check on the 12v batteries health, like when sitting in the car messing about with controls etc.

[miura88]

well done , How did you measure the cell voltage?

[EEEE]

Bought this to actuate my wifes '17 civic ABS pump but its pretty informative and useful for most cars including the e.

https://www.ukpartsdirect.com/icarsoft- ... utlet.html

I realise it only gives me the first 48cell readings, not the full 96/192. However, for this purpose, just looking at cell 1 gives me all the info I need (they are all identical under no load give or take 0.01v).

[Mathieu]

Can you explain what options (possibilities) there are on the iCarsoft CR MAX in combination with my Honda e?

[EEEE]

It would take an hour to document it all - it can probably do most things except the recoding of modules (I haven't seen anywhere for that). Otherwise, it will let you query all modules on all busses, and then run various actuation tests and read inputs. It will also allow you to perform various service mode items such as retract handbrake/calliper , relearn CVT parameters, things like that. Fairly comprehensive.

In the E I can cycle/test all ABS valves and pumps, I can test the brake light relay, i can test all switch inputs, I can test practically all switchable outputs, I can read many parameters from the various modules including battery/inverter/body control / gearbox / dash etc.

If you have something specific I can check specifically if it does it.

[Mathieu]

Thanks EEEE!!
Still two questions:
- Does the iCarsoft CR PRO+ have the same options as the CR-MAX?
- Can you control the ev battery degradation of the E?

Mathieu

[EEEE]

I am not an expert on scan tools - it would make sense that the more expensive one has more features.

Control the degradation? I'm not sure that question even makes any sense. As mentioned, it doesn't have the facility to recode modules, so I do not believe you can alter the min/max capacity of the cell pack if that is what you are aiming at. The car already has features to stop charging at certain % so I'm not sure I follow the intention.

[Mathieu]

I was wondering if it is possible with the CR-MAX to disable permanently the DD VSP error. When 'off' the HDMI port is enabled when driving even as the car setup menu. See pictures.
Now it automatically installs the limitation (enabled DD VSP error) every time the car is started.