CAN View Users (Charge/Discharge Limits)

I've never seen my current limits change based on battery charge at all. Only changes from battery temperature.

And never seen the limits go to 0.

 

Scott, I think the way you are explaining it makes perfect sense. As it approaches the maximum allowable charge, the ECU changes the amperage LIMIT to zero, meaning "no more charge". Then, as the battery becomes discharge, and hits 40%, the ECU removes any limit, and basically says "give me all you've got". Its a LIMIT, no a charge indication.

 

Boy I wish I could help. Soon I am told soon. On the surface the premise appears to be correct. Everyone who uses CanView should help refine the product.

 

This is what I had hoped would happen all along: that individual CAN-view owners would start topics on unusual observations, or on new CAN parameters they think they may be observing, so that I can step back and simply implement changes for public download based on mutual agreement when the dust has settled.

I have been scratching my head on these limits ever since Scott brought it to my attention. On the face of it, it seems quite logical to reduce the charging limit as you approach 80% SOC, in which case I have the charge/discharge limits backwards.

The niggling doubt is that a ) of the few contacted, none have seen any reduction in limits as they approach 80% and b ) if the discharge limit is the lower of the two, i.e 105 amps max instead of 125 amps, then the power the battery can supply into the motor once you take the resistive voltage drop into account is ~105amps x 175 volts which is 17.8kW or 24 BHP which is lower than Toyota claims. Whereas if it were the other limit it would be closer to 125 amps x 170 volts or 21kW or 28BHP which is the figure Toyota claims. So we do need more observations from more CAN-view owners.

But just because 1 version happens to conveniently tie in with specs is no reason to ignore solid observations. Something unusual is happening with Scott's Prius. It may be another manifestation of Toyota's complex battery maintenance modes which we are otherwise unaware of. Or I could be just plain wrong.

One last point to avoid even more confusion. The latest downloads have significantly modified the displayed battery current, but I have not modified the displayed limits from 1st unit shipped to latest download, so comparisons will be valid.

PS the first 5 of those female NAV connectors finally showed up so I will be making a couple of harnesses up tomorrow for a couple of intrepid NAV adventurers.

 

I don't have a CanView (I have NAV) so I can only speculate but it does sound backward to me also. If the battery is 80% SOC then it should want to use it to get back to the normal target SOC of 60%, so the discharge limit should be > 0.

Maybe something else is happening that is causing the Batt ECU to limit discharge, such as high battery temp (from fast charging?). Or perhaps the Batt ECU has detected an imbalance in charge among the cells and is trying to rebalance the cells by repeatedly overcharging (it sets the target SOC to 80%) and overdischarging the battery (with a 40% target SOC). Does it stay at a zero limit or does it eventually go back to normal?

--GaryM

 

Been thinking about this more and maybe I have not seen the limits change like this because my battery tends to stay at 50 to 65 % and though I have seen 80 % I might not have checked the limits that day.

The latest code currents seem to match to the limits very closely now within a few amperes if I push things to the max.

Maybe some can view owner in mountains will see the limits more often.

My limits tend to start out around 50 amps and go up to over 100 when the battery gets reasonably warm.

 

Anybody with a can-view and access to a THHT?

 

what keydiver says makes sense, but i have not noticed the changes either. i also hit a "record" of 82% SOC the other day, but to be honest with ya, charge and discharge are two categories i have not paid much attention to.

i find the format screen is too busy and i had it on the user configured screen (at least while it was still there. updated to latest beta and its gone!!...umm would be nice to bring it back...please) most of the time. might have to check that out. we have a few good hills that always ramps up the charge level, will be a good way to check it out

 

Dave,

I just updated to the latest. Get 3 user spec graphics screens and 2 user spec text screens. All working, along with the new mg1 and 2 rpms!

 

ya i was playing with that this morning. HUGE improvement...

only hope i dont get into an accident, the relationship between MG1, MG2 and the ICE is facinating. anyone make a RPM relationship chart yet? would be interesting to know the conditions that cause the ICE to kick on. i know the general explanation, but the new CANVIEW gives so much more details, it raises that many more questions.

have a pretty substantial hill on I-5 that i will be on later today, interesting to see how high MG1 can get with no RPMs on the ICE... i figure i can now see that -10,000 RPM on MG2!!

 

probably the highest MG1 rpm will occure at almost a stop and when you floor it and have the ICE go to max speed, after that once MG2 starts to rise MG1 starts to fall. Same on the Classic and from what I saw on Thursday when Norm emailed me and posted the code and I reflashed the module and went for a drive. Reflashed it yesterday and went for a drive with the Classic numbers in my head but couldn't duplicate the road speed to compare the results. I guees what I should do is a data dump and a printout from the Classic and then go for a drive with the wife driving and look at the numbers for the 2K4.

 

well what i can see, (yes i admit to looking at the CANVIEW waaay more than where i was going...but to be fair, i had anticipated this and purposely took backroads to my destinations) the relationship of MG1 and MG2 seems to determine if the ICE will run.

when both are positive, ICE will be on. only when MG2 is neg can the ICE RPM be at zero. now how neg MG2 has to be depends on the RPM's of MG1. the lower the RPM's of MG1, the less neg MG2 has to be for ICE RPM to zero...

makes me wonder if knowing the relationship between the two will help predict when the ICE will kick on. ya know what i mean???

take a scenario, cruising in EV...
well below the max speed...
decent SOC readings...
level road...

then

BOOM
ICE kicks in. why? way above the lower charge limit springtime in the middle of the day. no headlights, A/C, nothing.

why doesn't EV stay on until it hits 45% SOC? (i notice this seems to be the lower limit...i guess 40% is only reachable when not moving)

now i guess CANVIEW will not change that, but can observing RPM's let me be able to predict when ICE will come on???

i think it will. it will probably take until spring to get good data on it because defrost and A/C tosses everything out the window...but definitely something to look at.

right now, im busy racking my brains trying to find some excuse to go somewhere

 

Too bad I have projects already going this weekend, Dave. I'd invite you up to Seattle to show off your Can-View and have another geek looking at the numbers while you drive.

The real trick will be figuring out how to modify your driving based on what you want th e ICE to do.

 

when both are positive, ICE will be on. only when MG2 is neg can the ICE RPM be at zero. now how neg MG2 has to be depends on the RPM's of MG1. the lower the RPM's of MG1, the less neg MG2 has to be for ICE RPM to zero...


Dave have you got the MG numbers reversed here?

 

nope.. that is what i said..


Branden: sounds cool, not looking so much to change driving habits, more like maybe knowing ahead of time when the ICE is going to kick on.

ok... i have ulterior motives here. i was wowing a co-worker the other day when sitting at a light on our way back from lunch, i said, watch the ICE is about to kick on. (i used the steering wheel controls to turn on the defrost...didnt publicize that fact ) they were very impressed that i knew my car so well...

 

Dave the only time that MG2 goes (-) is in reverse and we know that the ICE doesn't contribute power other than MG1 output to the motivation of the car in reverse.