[Ovmsdev] Battery capacity metrics (for the Leaf, and in general)

[Anko Hanse]

Robin,

Good news: retested after a drive and the xnl.v.b.e.available corrected itself to the expected 30kwh !
Will keep an eye on it over the next weeks to make sure it is not one of these multiplexed thingies that switches in and out of the expected value....

Bad news: the xnl.v.c.duration.range still are at 4095min for me, even though the SOC has now dropped below 80%. This is on a Dec-2015 30kwh model.
I'll add a trace to see what data I receive in the 0x5bc message...
 

xnl.bms.temp_int                         21,23,255,23,21,0°C
xnl.bms.thermistor                       498,480,65535,480
xnl.v.b.e.available                      30kWh
xnl.v.b.e.capacity                       20.8kWh
xnl.v.b.gids                             375
xnl.v.b.hx                               79.17
xnl.v.b.soc.instrument                   64%
xnl.v.b.soc.newcar                       105.337%
xnl.v.b.soh.instrument                   91%
xnl.v.b.soh.newcar                       92.4887%
xnl.v.c.count.l0l1l2                     166
xnl.v.c.count.qc                         255
xnl.v.c.duration.full.l0                 375Min
xnl.v.c.duration.full.l1                 135Min
xnl.v.c.duration.full.l2                 90Min
xnl.v.c.duration.range.l0                4095Min
xnl.v.c.duration.range.l1                4095Min
xnl.v.c.duration.range.l2                4095Min


-----Original Message-----
From: Anko Hanse 
Sent: Monday, 25 February 2019 7:29 PM
To: 'Robin O'Leary' <ovmsdev at caederus.org>; OVMS Developers <ovmsdev at lists.openvehicles.com>
Subject: RE: [Ovmsdev] Battery capacity metrics (for the Leaf, and in general)

Robin, pulled your code and did a quick test:

xnl.v.b.e.available                      21.76kWh
xnl.v.b.e.capacity                       20.8kWh
xnl.v.b.gids                             272
xnl.v.b.hx                               79.59
xnl.v.b.soc.instrument                   82%
xnl.v.b.soc.newcar                       76.4045%
xnl.v.b.soh.instrument                   92%
xnl.v.b.soh.newcar                       92.7%
xnl.v.c.duration.full.l0                 210Min
xnl.v.c.duration.full.l1                 90Min
xnl.v.c.duration.full.l2                 60Min
xnl.v.c.duration.range.l0                4095Min
xnl.v.c.duration.range.l1                4095Min
xnl.v.c.duration.range.l2                4095Min

1. the xnl.v.b.e.capacity=20.8kwh does really not seem right for a 30kwh Leaf on 92% SOH...  I'll give it another go after I have actually driven for a bit (now just tested in Drive-Mode, but parked).

2. Since my SOC.instrument was above 80%, the xnl.v.c.duration.range.l0 - l2 give a strange value that might have the meaning of 'Not Applicable'. You probably need to test on that value and set the time to 0 min instead.

Apart from that I agree with your proposal for the config of xnl.soc.newcar, xnl.soh.newcar, xnl.maxGids and xnl.newCarAh.
I will not pickup implementing that before we have more certainty on the energy capacity metric.


-----Original Message-----
From: Robin O'Leary <ovmsdev at caederus.org>
Sent: Monday, 25 February 2019 2:08 AM
To: OVMS Developers <ovmsdev at lists.openvehicles.com>
Subject: Re: [Ovmsdev] Battery capacity metrics (for the Leaf, and in general)

On Sun, Feb 24, 2019 at 05:34:21AM +0000, Anko Hanse wrote:
> I had been searching for a way to directly get the battery capacity 
> from the can bus, but had not found one. Hence my search for 
> alternatives via the VIN.
> Even if I do a google now on 'leaf can bus 59e' I don't get useful 
> hits. And no finds in the canmsgs google docs either...  Makes me 
> wonder what docs you have access to...

I have no documentation; everything is speculation, based on many forum discussions and my own observations of the car I own (a 2015 UK-built 24kWh Acenta), so it is quite possible that my conclusions are wrong, or don't apply to other models.  I would like others to check whether the value in 0x59e is a useful measure of capacity for them before we adopt it as a standard.

...
> As for the web-interface, we might want to still display the detected 
> battery capacity there, just not as a changeable setting but as 
> readonly info.

Yes, although these are two different things, which may both be useful for different purposes.  Unlike the fixed value of max_gids, the battery energy capacity metric varies over time: as well as a general decrease due to battery age, it also has short-term up and down swings as the BMS recalibrates after charging.  Some people don't like this "randomness", and prefer to see calculations relative to a fixed base-line.  There is something to be said for both approaches.

As for the config page, for now, I would suggest structuring it so that the switches for the preferred SOC and SOH display metrics are paired with conditional settings for the corresponding full-scale value, maybe something like:

	SOC display:				{xnl.soc.newcar}
	.	(*) from dashboard display	{=false}
	.	( ) relative to fixed value:	{=true}
	.	.	[	] (GID=80kWh)	{xnl.maxGids}
	SOH display:				{xnl.soh.newcar}
	.	(*) from dashboard display	{=false}
	.	( ) relative to fixed value:	{=true}
	.	.	[	] (amp.hour)	{xnl.newCarAh}