[Ovmsdev] OVMS - power drain

Mark Webb-Johnson mark at webb-johnson.net
Thu Jun 5 15:17:43 HKT 2014


My concern is that a 'normal' car battery should be around 1,000Wh. At 2W, that is 500 hours (20 days). Even half that would be 10 days.

The Renault Twizy seemed to last about 3 days with OVMS.

So, either (a) the leaf has a tiny 12V battery, (b) your OVMS module is consuming a lot more than 2W, or (c) Vampire bats.

We can dramatically reduce power usage by powering down the modem (or putting it in a sleep mode), but it appears that only an SMS would wake it up.

Regards, Mark.

On 5 Jun, 2014, at 2:54 pm, Nigel Jones <nigel at cherrybyte.me.uk> wrote:

> 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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