his is what I'm having issues trying to figure out, and would like some people with a bluetooth scanner to download the Dr.Prius app and help me out to compare data. I'm also posting this to the 3rd gen sub as the system is similar and both generations used NiMH batteries. The Prius is supposed to get better MPG in the city than the highway, as the engine is used more on the highway, but so far this has been completely backwards for me. In fact, in city driving, I'm lucky to get 34mpg. On a flat road, going 50-53, I can get in the mid 50's. That is with the AC on too. The battery itself seems fine, tests fine, so I'm thinking something else is going on. Today it was 86 degrees outside, and the battery was measuring around 113 degrees. But when I floored it from 40 to 60 and held it for 5 seconds, I noticed two things, one right away, and one shortly after. The discharge shot up to 130.85 amps, the pack voltage went down to 192, then the battery temp quickly rose to 117 degrees. When slowing down quickly, the amperage went up to about 80 amps, and the pack rose to 258 volts. Now in any electrical system, resistance means heat, and I'm wondering if perhaps there is something causing the electric motor to draw more amperage than it needs, or perhaps there is a bad connection in the inverter from the hybrid pack or to the electric motor causing higher than normal amp draw. So here is what I need for some comparative data. If you can't give me all data points, that's fine, just pick one. 1. Your current outside temperature (on car or just from a weather app), and then the temperature of the battery pack, car must not have been driven for at least 4 hours, and this temp reading is with the ignition on (KEO), but not in ready mode (don't press brake to power on). 2. Either having a buddy look at your phone or recording the screen, floor the car from either a stop or on a straight road and tell me what it shows for the discharge amperage and pack voltage. 3. Do the same above, but quickly come to a stop from 30-40mph (don't slam on brakes, just quickly slow down) and record the charge amperage and pack voltage. 4. Drive the car for 30 minutes (or just do this after driving your regular commute) and record the outside air temp and the battery pack temps.
Well everybody claims they can get 53 miles to the gallon on 50 55 flat road reg temps say 70 to 85 or so I've seen it once maybe twice and that's on the MFD just showing that when I fill up at a flashing pip and put in the 8.4 to 8.6 gallons on 376 miles as we can see that 50 to 53 MPG showing on the MFD means pretty much nothing. That 50 miles to the gallon was at that point in time during the drive notthevysnl mileage. Cmon if you're getting 53 miles to the gallon at your flashing pip when ya fill up you'd be looking at 475 or so on that same 8 4 gal or at ten gallons added be at 530 miles on trip . So uhhh. All that. My Chevy I think do a lil better computations and the math maths very closely in the volt total miles tank miles elec miles total overall mileage for life of the system to date . Uncannily close
The corresponding thread in the gen 2 forum is this one: Further hybrid system testing and help needed. | PriusChat but so far this one is the one with replies. You may want to start by making sure your concerns aren't just arising from the flaws in your premise. A Prius (that isn't the plug-in or Prime version) only ever gets the energy it uses from the gasoline burned in the engine. It has a small battery where some of that energy can be banked up (at an efficiency cost) for use later (at another efficiency cost), but there is no way of using engine power more efficiently than using it directly, while the engine is running. This is counterintuitive for many first-time owners. Gliding along silently on battery power is nifty. It's cool. It's something conventional cars can't do. But it isn't more efficient than using the engine. (It can look more efficient because the dash MPG display gets pegged when running on energy from the battery. But that's because the dash MPG display doesn't account for the gas that was burned to put that energy into the battery; instead, that shows up in the MPG that you see while the engine runs.) It's fair to say that Prius city MPG sucks less than conventional cars' city MPG, because even the efficiency cost of banking and reusing energy in the battery is better than just throwing it away like other cars do. And it's also fair to say that city driving is typically slower than highway, meaning less of a cost from air resistance. But "as the engine is used more on the highway" is not a reason at all to expect city to be better. Under any driving conditions where the engine can be running in its good-efficiency region, that's as efficient as the car gets.
Wait, what? You're telling me that the average fuel consumption readout isn't accurate? I've been told the old way of figuring mpg won't work because the temperature affects how much gas you can put in, and if the temp has changed between adding gas, your math will be off. I know "process of elimination" isn't everyone's favorite way to diagnose things, but it works sometimes. The engine, having all new components that would affect MPG, spark plugs, PCV, throttle body, oxygen sensors, MAF sensor, fuel injectors, the works should have an effect on "cruising mpg" if something was amiss, but from the lower 50's on the highway, that is not the case. Similarly, I would also expect that figure to be lower if something was causing friction or drag, such as a wheel bearing, brake drag, etc. But the main issue is the engine has to work it's butt off when accelerating, and I don't mean hard, either. If I can get a glimpse into the normal amperage draw of the electric motor, I can compare that with mine to see if mine is somehow using more power than it should be. The readouts on the car itself don't really show electrical usage, but that's what the Dr.Prius app is for. The issue that needs to be fixed mainly, is if I need to floor it a handful of times, like to pass,etc the battery quickly heats up, and I'm thinking this is being caused by higher-than-normal electric amp draw from something. Once this occurs, the battery locks down the capacity to prevent further overheating, which causes the ICE to work even harder, since it no longer has as much "boost" from the battery pack, the MPG falls off a cliff. It's pain to get to the inverter and then take all the 20+ screws holding it down to check the connections there, and taking the connection cover off the hybrid pack to check connections there, and I don't really want to do that if I can get comparative data.
Your battery should fail soon, 113F is beyond the safe temp zone. You’ll be part of the salty crew in no time.
What you say is true, but missing a parameter. Aerodynamic drag increases as the square of speed. so if you are city driving, mostly at slower speeds, you'll get a lot of high efficiency miles, some from the battery and some with the engine on and recharging the battery. Mike
Unfortunately this may be the case, but insofar no one seems to still own a gen2 Prius to get me the data I need.
Two main factors cause low MPG in city use. The first is that a larger fraction of the driving is done when the car has not fully warmed up. The second is all the extra braking and acceleration, and a decreased ability to predict when the braking will be needed. In light or no traffic one can glide to a stop, but in real city driving deceleration is forced by the timing of the lights and actions of the other cars. Our 2007 gets around 25-30 mpg for the first 5 minutes around our house, then it gets in the high 40's. (Factoring out elevation changes, of which there are many.) Conversely, on the highway the car is usually warmed up, and there is greater distance between the cars which allows for fewer acceleration/deceleration events. Of course not in LA rush hour stop and go driving, which is perhaps even worse than city driving, in terms of rapid and unplanned acceleration/deceleration events. V=IR P=IV P=V^2/R P=I^2*R So in most instances the use of more power at a (near) constant voltage is the result of less resistance, not more (3rd equation). That's why toasters and space heaters are low resistance devices. However, if there is circuitry that forces the current to stay at a certain level (by raising the voltage) and resistance increases then power dissipated does go up with resistance (4th equation). When the Prius is accelerating or in regen the situation is more (4) than (3). The currents, voltages, and temperature changes cited don't seem wrong to me. Having the pack only rise 4 degrees after having passed 131 A through it for a few seconds seems reasonable. Although I would expect a slight delay to allow the heat to move out of the modules. Similarly, pushing the voltage to 258V while accepting an 80A current seems reasonable. Most of these tests are going to be full of uncontrolled variables. For instance, (1) will be highly dependent on the amount of sun the vehicle received in the previous 4 hours. I think it would only give a consistent reading for a car which is not in the sun during the test and has not been in the sun at all during the preceding 4 hours. Assuming a pack cools down completely in 4 hours, which might not be true either. I know my car gives high outside air temperature readings at first if it has been sitting in the sun.
The issue that I'm running into after doing some more monitoring, is that the pack is getting hot even cruising along the interstate, I observed temps of 122 degrees when it was only 84-85 outside, and I was not passing anyone, not near any big hills, etc. The cooling system seems to be working well, I know the duct inlet at the rear seat is not sealed to the opening in the vent (so if something covers it, it doesn't burn the motor up), and even then if you put a piece of thick paper, it's sucking damn near like a vacuum cleaner, and flow at the outlet near the 12v battery is good as well. I put my hand around the inlet at the hybrid pack itself, and didn't feel any air leakage. The problem is when setting the hybrid fan to full speed, AC to the highest fan speed and lowest temperature, it takes upwards of 30 minutes for the pack to cool down even a few degrees. When the hybrid pack temp starts going above (IIRC) 113 degrees, the hybrid management computer regulates the capacity of the batteries to prevent further overheating. So my theory is if the cooling system is working normally, something is causing elevated module temperatures, because despite the fan running full speed ahead, and checked for air leakage, the pack is not cooling back down like it should. Either that, or something is causing a faulty temperature reading (computer reading higher than actual temps) causing it to reduce capacity. Once this happens, the ICE has to work harder, dragging down MPG, because it does not have the full capacity in stop and go traffic to help it. I even went as far to put my rear cargo cover back in to keep direct sunlight off that area while driving. I'm going to pick up a wired thermometer like the one below and try to put it as close to a module as possible and see if the temps are being accurately reflected by the computer.
??? Do you leave the windows open for 25 of those minutes??? 125 degrees in my Prius when it sits in the sun for a hour or so. I open the windows half way, turn the ac fan to about 3/4 of full speed, temp set to 72 or so, turn OFF the recirculation, and start driving. About a minute later I close the drivers window, seconds later, passenger front window, maybe a minute later the rear windows. 1 or 2 minutes later, turn on recirculation. Then I set the temp to 75. Total time is less than 5 minutes Even after sitting in the sun in 95+ degrees 8 or 9 hours, my hybrid pack never got to 100 degrees. 88-90 degrees. And it would stay there for a long time, depending on where I was going. If I stayed in city driving, it would rise to 97-100 degrees. If I get stuff in traffic, it got as high as 104, for a short time. But when I got going, it would drop back down to 100 or less. If I got on the interstate, the battery stayed under 100 degrees.... Maybe you should check for blockage in your hybrid cooling system..... Of course, I have the Sodium Hybrid Battery!
