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

[Anko Hanse]

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}