2005 Prius, 270,000 miles. I'm having some symptoms, sometimes the car loses power and engine revs, and at the same time the battery bars drop very rapidly, like down to 1 bar in 10 seconds. I thought it was the HV battery, but when the info screen said 1 bar, I took the hv battery out of the car and read the individual cells and they were all around 8.1. Then I drove it over to my fathers farm garage to work on it and did the fan test in techstream, and all the cells seemed good. The worst one only went down to 16.58 after a few minutes at 5. When I start the car up, the charging oscilates on and off from the info panel green arrow indicator, and the charging rapidly goes up and down from 6 to 8 bars. That wasn't happening earlier this past fall and winter. I've had bad grounds before. A parking plock problem that went away after I cleaned up a ground under the dash. All the grounds were just tighened down over paint. No star washer from the factory or anything. I've cleaned up all the grounds that I could get to (I have a FSM that shows the ground locations). But those two on the drivers tower I could not get to, and it looks ugly, lots of rust. The head of the bolt isn't even hex anymore, just rust. Anyone think this could be the problem? I'm going to try and strip back the wires where they run above that I can get to and solder them into a wire and ground that new wire. Only thing I can think of, that is almost impossible to get to. Taking off the rain cover doesn't look like it'll help. Thoughts?
As you've already seen in the wiring diagram, there's a really extensive network of ground points. I am very skeptical that a problem with a ground point at the driver's strut tower would be causing any difficulty for the battery ECU or the HV ECU, neither of which is anywhere near there. It sure sounds like your particular area of "usa" must have a pretty corrosive atmosphere. I have a feeling that the more ordinary diagnostic techniques involving watching battery module behavior under load will end up being part of how the answer is found here. Some other posters who do more of that than I do will probably have techniques to suggest.
I would either get the Dr Prius paid app and a compatible OBD2 adapter to run a HV battery capacity test, or get some other prius capable scantool to monitor data from the HV battery ecu. See what the ecu displays for actual State Of Charge, block voltages, and amperage while driving the car. Maybe you have a fault with the battery that is only apparent under load, or maybe there is a problem with the ecu or its wiring. The Dr Prius "life expectancy" (battery capacity) test has you force charge the battery until "full" (near 80% SOC) then has you maintain about 6amps discharge until the battery needs to be recharges (40%). It keeps track of the volts and amps then does the math to figure out approximate total power (ie capacity) of the battery. When I did mine it took over 12 minutes to discharge and claimed capacity over 90% of original. The Hybrid Assistant app also does some kind of capacity test as well- and logs data to a nice looking graph as part of a report. Posted via the PriusChat mobile app.
I neglected to mention I'm also getting communication errors from I think the hv battery. Also a regenerative error and it says replace battery pack. I can't remember the exact codes. I'll post them later today after I retrieve them from the laptop. I thought it was strange the voltages were so high. Many of the blocks were at ~17.00 volts or a little over when the info screen said 1 out of 10 bars for the HV pack. That's 8.5v per cell which is well over 10% of charge that the info screen in the car says. What explains that? When I see other people running the test, their voltages across the board are lower, and a bad module is very apparent by a signicantly lower cell. My lowest was 16.58, which was barely under the other blocks and that was after running the fan at 5 for a few minutes. I also load tested the cells outside of the pack before I put them in after I rehydrated them. Maybe there a bad cell, but I don't see any evidence of it. The strange goings on seem to indicate some other problem IMO. Agree, disagree?
I don't dare do any deep discharging of the battery right now, its cold, -5F (unheated garage). My understanding is NiMH is sensitive to temperature when charging. IMO that's something that ruins these batteries up in these northern climates. I always try and leave the vehicle at 80% so it doesn't have to charge up when the interior of the car (incl battery) is cold.
So what about the cold? If I assume that the car runs, then warm up the engine (and the interior with the heater) . Perform the capacity testing, then force charge again. What does techstream show for battery block voltages and state of charge when you are driving? (assuming that you can keep communicating with the ecu long enough). If you have problems communicating with the HV ecu, are there other codes in other modules that also indicate that? Some people have flakey cables with their techstream (do you have comm problems with any other module on the car?) You want to see if your comm fault is something on the car (actual problem) or your scantool (equipment problem). If you do have an actual comm fault to the battery ecu then you need to (carefully) inspect the connections at the ecu. You need the wiring diagram so that you can "backprobe" (using a small T pin slid into the wire side or back side of the connector, away from the ecu) the low voltage power and ground circuits at the ecu while the car is powered up (be super careful around the HV battery when it's "live".) Measure from the ecu ground circuit to the battery negative- it should show no more than 0.05 volts (drop) when the car is powered up. The battery and ignition power feed circuits should be within 0.25V of battery positive. Ideally you would have male connector terminals that are the EXACT same as the pins on the battery ecu so you can test terminal fit of the female ones on the vehicle harness connector. Loose terminal fit will cause problems. Do not attempt to push anything else into the female terminal (ecu side of the connector). You can test voltages at the ecu for the CAN network circuits, but that is not very useful for intermittant faults. (CAN hi is typically 2.6 to 2.8V while CAN lo is 2.2 to 2.4V) This is where someone with a very good oscilloscope can help, but very few have one. Short form is, if the powers, grounds, and comm lines are "ok" , then the ecu itself is likely the problem. Posted via the PriusChat mobile app.
I checked the grounds I mentioned in the OP with a multimeter and they seem ok, so I think you're right about it being the HV battery having a bad cell or 2. Can you identify a problem based on these screencaps from techstream? The problem seems to be getting worse. The red triangle click on almost immediately after taking off down the road (so I don't dare) and the battery bars drop very rapidly, down to 1 or 2 within 10 seconds. If I turn the car off and wait a while, it seems to become driveable for a short time again. Like you said, it must be a bad cell. Tho which one? Those tools sound great, but unfortunately the mail and package services take weeks to get anything and I have no car right now. I remember a while back when I read codes on techstream, it actually said which block was bad (and I replaced the module). I don't understand why this time it doesn't identify the bad module. With how the voltages plummet, seems like it should be obvious to the ecu I'll try and get some data to post up later today from techstream while driving decoded here are the trouble codes P0A80 – Replace Hybrid Battery Pack C1241 TOYOTA - Low Battery Positive Voltage B1421 TOYOTA - Solar Sensor Circuit Passenger Side B1423 TOYOTA - Pressure Sensor Circuit C2311 TOYOTA - Communication Error From HV ECU I think the pressure sensor circuit is the A/C, which I'm not surprised. AC doesn't work and the system components are very very corroded. The amount of rust on a lot of the stuff under the hood looks like its been down at the bottom of the ocean for 100 years I also think there's a current drain, because it killed a brand new bosch AGM battery in 2 days. I've had to disconnect the 12v battery every time I use it or I come back and its dead. I'm having to a regular car battery for the 12v
There might be something draining your 12V battery, however, your capture shows that you were connected while the car wasn't in "ready" mode- that means that the dc-dc converter wasn't on (and it was not charging the 12V). On a cold day you can run the 12V down fairly quickly that way- might want to use a battery charger if possible. More data while driving will give you a better direction as to what's going on. Looking at your capture- block 3 voltage is 0.5V lower than the highest, that MIGHT be your problem there. When you replaced modules before, did you do anything to balance the whole pack? The low 12V might explain the C2311 in the HV ecu, or you could have a bad ground for that ecu. Posted via the PriusChat mobile app.
Ok so last night I replaced both cells in block 3 with ones I got from Amazon (reseller says he load tested the used cells and they're ok). Plus I noticed that blocks 1 and 4 were also going up quicker than the other blocks, and went down quicker. So I did the best load testing I could with my B6ac charger, picked the best cells out of blocks 1 and 4 (because I don't have enough cells to replace them all). Then I drove it. Didn't go far before it felt like it lost all power, engine revved, and i had to pull over. The 12v battery I had been using was dead after a few minutes of use and luckily I took a 2nd battery, or I couldn't have gotten the car back the 1/2 mile I drove. I didn't run techstream on that trip, but did run it a couple times going back and forth on my driveway. Here's the captures. Do these scans indicate I still have a back cell or 2 and something else going on? Like a bad ground at the ecu as you said? I'll check that. This car spent its life in NH and is quite rusty. I did make some effort to balance the cells, I charged them up to 7.9v before putting them in. Thanks for your help, I really appreciate it!! ok I tried uploading and it says doesn't have allowable extension here, I've uploaded it to this service as this site won't allow it I should note that the data capture below was done after swapping in the used cells I got from Amazon (and the screen caps posted earlier in this thread were from before the Amazon cells) https://mega.nz/file/9uoExBgY#NQiXqNJSxNqaaDJwzleqP0szrYerr_MESV45TVPFsIQ Maybe first thing is to go through and clean up the grounds that I skipped on my ground cleanup that I did last fall? I cleaned up the 12v bat ground, the trunk lid ground, a ground right in front of the driver under the dash, and a ground right in front of the engine on the radiator crossmember
Went through all the grounds in the service manual, I had only missed 1 in my ground cleanup pass this summer, the one by the HV battery blower fan. Undid it, removed the paint with scotch brite roloc and put it back on. Haven't tried the car yet but I don't think this is the issue.
Still doing it. Loses all power, engine revs. If I pull over and turn it off for a few minutes I can get home. No idea what's wrong. I replaced all the cells that were going up and down. Thinking it might be the inverter. Apparently its common for them to overheat.
