[Ovmsdev] Leaf 2016 30Kwh flapping SOC

Robin O'Leary ovmsdev at caederus.org
Wed May 2 08:48:30 HKT 2018

On Wed, May 02, 2018 at 08:14:24AM +0800, Mark Webb-Johnson wrote:
> This seems to be a hot topic amongst Nissan Leaf owners. Am I correct
> in that the displayed SOC doesn’t show degradation?

Yes, 2nd gen and later models have a numeric 0–100% SOC meter, which
does not account for degradation---there was a separate 12-blob "health"
gauge for that, though that's gone on the 2018 model.

I think a lot of this stems from the fact that the 1st gen didn't have
any numeric SOC display; they had only a 12-blob "fuel" gauge.  Indeed,
it was this lack of precision that sent many of us rummaging on the
CAN bus to find better values.  As there was no documentation and no
standard set by the manufacturer, conventions arose piecemeal as new
nuggests were discovered, which gave us GIDs and the SOC meter relative
to original battery size (which may not have seemed so arbitrary when
there was was only one original battery size).

> In general, OVMS has tried to remotely show exactly what was on the
> car dashboard. We went to some extreme lengths in the original Tesla
> Roadster code to meet that requirement (for example the km/miles
> conversions were not accurate in the car implementation, so we tried
> to mimic the car’s inaccurate algorithm in our approach).
> Absolutely no objection to adding vehicle specific metrics. A GID value
> (for Nissan Leaf) is the obvious example, but also other indications of
> battery health. We have SOC%, SOH%, and CAC currently as global metrics.

I think these are adequate, although I think it might also be useful to
have "battery energy available" in kW·h, for easier range calculations,
(although I see that vehicle modules mostly make their own range
calculations, some quite elaborate).
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