2005 Prius runs fine, but has warning lights after sitting

Hi all,

I bought a 2005 Prius about two years ago with 124k miles. It now has 142k miles. I have really enjoyed owning it.

I was away over the holidays longer than anticipated, so it ended up sitting in the garage for roughly 1.5 months. I had not initially planned to be gone so long, and I am now learning it is not good for the batteries to go unused.

Last week, I returned and started it up and moved it outside. It started fine first try and acted normally. However, when I went on a longer drive the next morning, the yellow triangle ! came on when returning home. I disconnected the 12v battery to reset the ECU, as I figured it was just unhappy from sitting. The light went away and stayed off for several drives. However, today when returning home, the red triangle appeared, as well as the yellow circle !, and the CEL. I tried using an inexpensive OBDII Bluetooth scan tool to check the codes, but it does not find any. There is also a car with an ! symbol on the info display screen.

I checked the 12v battery voltage via the display screen. It was 13.8v while running, dropping to 11.8v when I shut the car off.

I would appreciate

1. Any insight into what this combination of events and warning lights most likely indicates
2. What type of device I need to read the codes that are causing the warning lights
3. Any helpful troubleshooting guides that indicate what the different combinations of lights mean, and what else I could check on the vehicle

TIA!

 

Thanks for the input guys. I did some more research after making that post, and found out about the Dr. Prius and Hybrid Assistant apps. I ordered a compatible OBDII bluetooth device off amazon (the $13 Veepeak one) as I eventually worked out that the one I already had wasn't able to talk to the Hybrid ECU. I was able to pull codes P3000, P0A80, and P3016. I need to do some more research, but it's looking like I will need to at a minimum replace some cells in my current battery. Any input on how to proceed is appreciated.

 

Thanks for the input @ChapmanF . I was able to read codes P3000, P0A80, and P3016 using Dr. Prius once I found out about that app.

@bisco - in light of the codes that I was able to pull, could this still be 12v battery related? The codes seem to indicate a HV battery issue.

Today I pulled out the interior to expose the HV battery. Not too difficult but kind of annoying with all the clips. I also drove the car a short distance while monitoring battery module voltage using Dr. Prius. Screenshot posted below. Both the battery monitor screenshot I posted and P3016 seem to indicate an issue with block 6. Additionally, I noticed when I was driving that block 6 voltage would be higher while charging and lower while discharging than all of the other blocks.

Questions:

1. Is there any more information on battery/module health that I should get BEFORE pulling the battery? For example, any tests that must be done in the vehicle as opposed to on the bench. I am inclined to pull the battery just so I can take a look at it to better understand how it is constructed, though I recognize there's probably not much I can do to it without some more equipment.
   
2. Is there any way to ascertain overall battery health? If just module 6 is having issues, I would probably attempt to replace just that module. However, if something indicates that overall battery health is poor, I would be more focused on replacement options.

Thanks everyone

 

Update: pulled battery. Some corrosion on terminals. Module 6 voltage about 1.25v lower than average. The other modules are much more consistent with one another.

 

Ah yes, I see. For some reason, up to this point I had thought the two modules composing a block were physically connected to each other, requiring them to be replaced simultaneously. I realize now that was an erroneous assumption.

Either way, it's one (or possibly both) of the two I marked. Thanks for pointing that out!

 

While driving my 12mpg land cruiser has been fun, it's time to get the Prius back on the road for the sake of my wallet.

I already have a small hobby battery charger with an NiMH mode, so I hooked that up to module 11 (the bad module) and am currently charging it at 2 amps. We'll see what the health of that module looks like - I imagine not great since it's the only outlier voltage wise?

Question: when doing a capacity test, what discharge rate is advisable?

Question 2: can a grid charger be used to balance the modules (after I revitalize or replace, if necessary, module 11?), or do I have to individually charge each module to capacity? Ideally I know I would load test each cell individually and then charge all to the same SOC individually before pairing, but I would have to buy a lot more battery chargers to be able to do that in a timely manner. Is it possible to just revitalize or replace my bad module and then build a grid charger to balance the whole pack at low current over several days?

Question 3: when people say load test, what do they mean? Do they mean measure battery capacity (e.g. mAh), or are they talking about instantaneous current delivery ability as a stand in for measuring internal resistance of the battery? I can use the little battery charger I have now to discharge at up to 2 amps to a specified voltage (discharging to 5.4v/module right now), and it will tell me the mAh for that discharge cycle. Is this sufficient to determine capacity or is better to discharge at a higher or lower current?

Thanks guys.

 

So since I last posted, I got a job on the east coast, "fixed" the Prius the day before I moved across the country, drove it 2000 miles without issue, and have had intermittent P0A80/P3000 since.

To summarize briefly what I (remember) doing in the week before I moved:

1. Ran every module through 3 discharge/charge profiles using 4 hobby chargers. Used the last charge/discharge to characterize the capacity of each module
   
2. Purchased 3 used modules from 2nd life battery and replaced the worst modules from my pack. After looking at the state of the pack as a whole, I decided anything below ~4200mAh capacity (memory is a little fuzzy on this one, but I have it in an excel spreadsheet somewhere) was an outlier and would be beneficial to replace.
3. Did 2 minute discharge load test on each module to characterize internal resistance.
4. Reordered the modules to pair high IR module with low IR module in each bank to hopefully normalize voltage drop under load across the pack. Still not sure this was the right move, but this made more sense than pairing based off capacity to me.
5. Grid charged the whole pack using an LED driver for ~36 hours after reassembling it. This did not go quite how I was expecting - the pack never reached the voltages my research indicated it should, though it did get warm.
   
6. Put the pack back in the Prius and drove it to Home Depot to get packing supplies once before it was time to leave.

As we were pulling out, it did give the RToD / CEL. At that there wasn't really anything I could do, so I just ignored it. I knew that if worst came to worst I could swap it out with the Land Cruiser riding on the uHaul car hauler, but I really didn't want to do that for a number of reasons. In the end, the warning lights went away within a few hours and did not come back until a few weeks (I think??) later.. Averaged over 50MPG on some stretches of the trip following behind the uHaul.

For various reasons, I wasn't able to drive it regularly for the first few months - just on the weekends mostly - so it sat during the week a lot more than I would have liked. The P0A80 / P3000 combo would come on seemingly at random and then go away for awhile, but I was never sure if it was a real problem or if it was just because it wasn't being driven enough, as that's what triggered this whole ordeal in the first place. I just kept hoping it would go away However, the last two months it's been driven nearly everyday, and it's still an issue. A number of times it has come on after getting gas, but I don't think this actually has anything to do with putting gas in the car - more likely the driving conditions that preclude me getting gas.

I still haven't been able to figure out what can cause a P0A80 / P3000 code. Before, it gave me P0A80 and also the actual bank that was bad. It's not doing that this time, and the car drives fine. The one noticeable difference is that I've only been getting 39 - 40 MPG, whereas before this whole debacle I was getting 43-45 MPG on average. The other thing I've noticed is that the pack gets quite hot - I don't know if it did this before, as I wasn't monitoring it. I have seem temps up to 127 'F on the center section. If I see this, I will force the fan on with Hybrid Assistant, but I don't monitor it all the time. It's quite possible it's gotten hotter without me knowing.

At this point, it seems like I have 4 options:

1. Figure out if there is some way to fix this issue - perhaps reevaluate my modules pairings?
   
2. Buy all new modules, or maybe the lithium modules
3. Keep driving it like it is. It's been working so far.
   
4. Buy a new(er) car

I actually really like this little car. It's pretty old, it's beat up, it's got ugly fading paint, the rear bumper is cracked and the lower grill fell off 3 months into me owning it. I paid $2900 for it 2.5 years ago, and it had already paid for itself in gas savings before the battery gave out. Additionally, it netted me $1000 in mileage reimbursement when I moved across the country. I've driven this thing up sand dunes. I've ripped through arroyos at 50 MPH. I've had a full size couch in the back with the hatch open. This car owes me absolutely nothing. I'd like to fix it if I can. I like that it's dirt cheap, and that it's still pretty efficient after 18 years of use. I like the efficiency of being able to rebuild the battery pack to get the full lifespan out of all modules.

I'm not sure I really had a point to all this, but I had some time to troubleshoot it tonight (ended up cleaning the battery fan, it was fairly dirty) and I had been wanting to update this thread so as to not leave it without conclusion.