SOC-Meter Improvement Suggestions

After spending much like looking for a friction inidcator, I realized I was looking in the wrong place. According to the service manual, such a signal does exist, but on the CarCan NOT the EVCan where I was looking. I guess I'll be out gathering some more braking logs using the CarCan mode today.

I think I'd like to revise my feature request #3 a little. Since it is not really safe to keep looking down at the SOC meter, I think a really killer app for it would be to add a small piezo-electric speaker and have it emit a tone whenever friction brakes are being applied (maybe with frequency proporional to amount of hydraulic pressure). Since most of us avoid friction braking all-together, we will only get the beep whenever we screw up so it shouldn't be too annoying and would allow you to keep your eyes on the road.

Amount of Friction Braking? Great, Good Work!

You might look on the 3-CAN Short Drive Log that is posted.
Get the logs at: http://www.wwwsite.com/puzzles/cando/" onclick="window.open(this.href);return false;

As you find things (Ev-CAN or Car-CAN), let me know
so that I can add them to the CAN-Do Recipes, and
consider them for the next SOC-Meter firmware.

I took a car can log specifically to find something we could use to give better feedback when you start to engage friction brakes. I think I found three signals indicated in the service manual. Target braking force (1CB3<<3+D4>>5), Regen Braking Force (1CB1<<3+D4>>5), and Brake Pressure (1CA1). Here is a graph of a simple test where I pressed the brake pedal three times at the beginning while I was at a standstill, accellerated, then slowly increase brake pressure until I stopped. I repeated again but more gently.

What is interesting is when you start to engage friction braking, regen is turned off. They do not simply add friction on top of regen. I guess they couldn't get the feel smooth enough. So it tells us it is VERY important to avoid friction braking because you waste *everything* once you go there - not just an incremental amount above the regen capability.

Regen Braking Force is D1 and D2 (not D1 and D4)?

These are EV not CAR bus readings?

Scale Friction Brake Pressure by about 3.0 ??

GOOD Find, Good Test!!!

I tried a few tests last night. At about 50-55 mph, I initiated heavy braking. Observing the center display of energy at that point, I was still showing significant regen even though it was clear that I was strongly in to the friction brakes. I would have loved to have a GID meter at that point to see the actual regen power... In any event, it would seem that there is more going on than the logged graph would indicate...

garygid said:

Regen Braking Force is D1 and D2 (not D1 and D4)?

These are EV not CAR bus readings?

Scale Friction Brake Pressure by about 3.0 ??

GOOD Find, Good Test!!!

Click to expand...

Oops. Right D1 and D2 (cut and paste error). These are from the car can.

Not sure of the units and they clearly don't line up on the y axis. It looks the the regen braking signal is not the whole picture. I did some more tests today and I did see current into the battery in some cases when this signal was zero. However, the brake pressure signal does look like a good candidate for a friction braking alert.

TomT said:

I tried a few tests last night. At about 50-55 mph, I initiated heavy braking. Observing the center display of energy at that point, I was still showing significant regen even though it was clear that I was strongly in to the friction brakes. I would have loved to have a GID meter at that point to see the actual regen power... In any event, it would seem that there is more going on than the logged graph would indicate...

Click to expand...

Yes. It does appear that way. However, the amount of regen does drop dramatically when friction is applied. I will post some more detail in the other thread once I have a nice plot but it looks like there is still some current being put into the battery even though the "regen braking" signal has gone to zero.

good work guys, wish i could play.
but, not yet.

I just assembled my SOC-meter. Thanks Gary for putting everything available for the community. The SOC data and the electrical parameters of the battery are very useful.

If possible I think a third set of data on the EV CANBus should be the battery pack temperature, with the average value and the individual 4 sensors (5 values total). For us outside the US and UK, a degrees Celsius version would be perfect.

Yes, the Battery Pack Temperature(s) would be very helpful, but they have not yet been identified.

I am not yet convinced that the 4 internal Pack temps actually occur outside the Pack, at least without an active request.

Probably the 4 individual temperatures may not come out of the BMS, but at least one temperature must be in the EV-CAN for the dash to display the temperature bars. Is it allready identified?

I noticed a "feature" with the SOC-meter firmware that I'm not aware if it is allready addressed. When doing a QC the charge current goes above 99.9A (up to 125A, I guess) but because the display only has 4 digits it stays as -99.9. Is it possible for charging currents above 100A to drop the decimal point so they can be displayed?

Pack Temp:
Not yet identified.

CAN-Do shows 3 values that are candidates for temperatures,
but nothing conclusive yet.

Pack-in current:
Yes, in Ver F1.08 I limited at -99.9 amps, but I will try to
shift to a -100 amp (no decimal) when at 100 or over.

Adding a Friction-Braking Buzzer:

1. We (think) we know the CAR-CAN Message and field for Friction Braking.

2. When switched to the CAR-CAN bus (instead of the "normal" EV-CAN setting) the SOC-Meter can read the Friction-Braking message.

3. A low-power 5v buzzer, activated by the uP on the AVR-CAN board, could be added to the SOC-Meter circuit to "indicate" when Friction Braking is active.

4. Once we have these, new firmware could "buzz" us.

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The only missing link is the selection of an appropriate "buzzer". TickTock might be helping develop and do testing on this new option for us.

Open to suggestions!