[Ovmsdev] OVMS - power drain

Nigel Jones nigel at cherrybyte.me.uk
Thu Jun 5 14:54:55 HKT 2014

After leaving the OVMS disconnected for a few days I decided to hook it
back up yesterday evening and leave overnight. Not unsurprisingly I had a
flat 12V this morning (<8V)

My nissan leaf code currently running on the unit is passive only (poll0
indeed just returns 0) - in fact it's only the calculation of the battery
level that was tweaked for msg 0x5b3. I'm using the experimental config
with nothing else change.

I don't have a working meter, but at 2W 2Ah should have been the max
overnight. I'm not sure of the expected capacity of the leaf battery but
I'd imagine it's 30+. The ovms was slightly warm but certainly not hot.

Since I'm not actively polling the bus, and I no longer get this battery
daya when the car is "off" I'm guessing moving the EV-CAN wouldn't change
this behaviour? Yet we know others are using the same framework without
issue. But since ovms works, and the framework is common (no tight loops in
the leaf specific module), and the modem is common it's tricky to figure
out what on earth is the cause unless that 1-3 Ah is really pushing things
over the edge...... Hmmmmmmmmmmmm.

I'll figure out some other test to drain the 12V at a more known rate when
I have a chance though it is surprisingly difficult as pretty much
everything switches itself off.  It is still possible the battery is very
bad given it needs to do so little in the leaf

When connected the ovms seems to work normally, responds properly, replies
to texts on demand - just about 2 in, 3 out during that overnight period
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