OBD2 Bluetooth dongle

I use the Torque app, here's a demo of the torque video overlay:
http://www.youtube.com/watch?v=B7v79M861yk
The dashboard display is very customisable, and has many screens available, Its ideal for a cradle mounted screen.
There is a free trial version but you can't load custom pids.

Torque is Generic (it'll probably do the leaf too with the right Pid's) You'll need a list of custom PiDs for the Volt/Ampera there's a good one here:
https://docs.google.com/spreadsheet/ccc?key=0AvK9F6VeA7dvdFUwSjBzR2FQM1BJTWZoLW43ZFdoTFE#gid=0
You can load this file into torque directly.

There is also a list for OVMS here:
https://github.com/markwj/Open-Vehicle-Monitoring-System/tree/master/vehicle/Car Module/VoltAmpera

ODB2 dongle arrived this morning.

Plugged in and loaded up the Leaf Spy app on my Android phone and it all worked straight out of the box. This is what the app is telling me about my Leaf battery...

Current total capacity: 60.88Ah
Health: 84.09%
Number of rapid charges: 143
Odo: 19668 miles
State of Charge (SOC) when fully charged: 94.8%

The pack voltage difference is 23mV min to max.

The display also shows when a shunt is active on one of the battery cell pairs. A shunt is when a small discharge load is applied to bring down the voltage for that pair. Interestingly I have a shunt indicated as permanently active on one of the cell pairs. Should I be concerned at this?

I am now trying to work out how to load up the Torque App with the PIDs to try it out on the Ampera. I am totally foxxed at the moment as to how to do that :-o

Update:
I have found how to add new PIDs to the Torque app so just need to bash them in and add them to the app display. It works with SOC% YAY!

Got it thx.

I have been chatting to Neil Stratford (@neilstratford) on twitter and he is very skeptical of the figures shown on these apps. He is suggesting that without official confirmation from the manufacturers as to what the numbers mean on theCAN bus then we should not place any reliance at all on the numbers meaning what we think they mean. I am paraphrasing many tweets but I believe that is basically his position (I am hoping he will come over and join the chat here so we can flesh out this discussion further).

I agree with him that the figures involve a lot of guesswork. The manufacturers, especially Nissan, do not publish their CANbus protocols and so it is only by back-engineering and deducing the meanings of each code can these apps be developed. It is not scientific and it is very unofficial. However, I believe that it is possible to back-engineer pretty accurately through observation of the data and comparing it with the real world and that is pretty much what they have done. I accept that it won't stand up to scientific scrutiny but as a driver I don't need that. I just want an indication of what is happening. If the numbers suggest a battery capacity drop of 10.27% and it is actually 10.17% I really don't care. All I need is an indication that it is about 10%. If the figures they use to determine that are not 100% accurate then I really don't care. As long as the end result is a reasonable indication of the truth.

Neil seems to be suggesting that there is no evidence that the battery capacity drops people are seeing with these apps are realistic or at all accurate. Well, everything I have seen to date suggests that the figures are pretty accurate but I am not totally convinced they are 100% accurate. It does depend on the assumptions made by those that back-engineered the code. Having said that, I would imagine that much of the code would be pretty obvious and a sensible deduction could be made as to the meaning based on observation of the real world events.

So, whilst it is fun to play with these apps it is worth remembering that it is just there as a bit of fun and although the figures look sensible to me and I believe the figures to be accurate they could be completely twoddle!

Make up your own minds

I think it would help if there was a list of key OBD values including some details of confidence level and how the value has been verified.

Some items, such as odometer and speed are quite easy to verify, but others can be rather tricky.

As an example, I have done some work on the iMiev OVMS code and one of the key items there is a set of values that appear on 4 PIDs with a number that moves from 1 to 12. This "seems" to give 88 numbers that seem to be about right for battery voltages * 100. There are also 64 values mixed in with these that look very much like cell temperatures in Celsius plus 50 and move up when the battery is charged or used and down when rested. There are 88 cells in the battery pack so the voltages make lots of sense. It also makes sense that there are temperatures sensors throughout the pack, but why 64 and not 88 or 44? Also, the temperature may be offset by 48 rather than 50 or it could be (Fahrenheit / 2) + 20. In fact I have noticed that -55C seems to be a common "low-end" temperature for digital temperature sensors and I often think the temperatures I read are a few degrees higher than I would have expected - so maybe it is Temp + 55.