Hi! New guy, joined because I have a 2010 Camry Hybrid with 220K miles on the odometer. Just recently, the ABS, VSC, Check Engine Lights came on and also a check Chevy Hybrid System error was displayed. Car stayed in driveway for about a month until I had the nerve to tear into it. After removing the battery from the trunk, I checked all cells and they all had a 7.63-7.67 volts reading, so they are good from what I can tell? Next, I removed the copper bus/terminal thingys and cleaned them off as they looked a bit corroded. Wasn't even that bad looking, so after cleaning them up and reinstalling everything, all my check engine lights went away and the Camry lives!!!

Question is, what is the correct behaviour for the battery charging/discharging? I drove it about 60 miles this morning and the the car drove beautifully, and I can see the battery charge and discharge. I did over 70mph up and down some hills. While the battery never fully discharged, I feel like the bars drop down too quickly, but they also charge up just as quick, Is that the normal operation? Thanks.

 

(1) what codes were given?
(2) great way to kill a hybrid battery. Don't do this again.
(3) Incorrect. Resting voltage tells you almost nothing about the health of a module. the only thing you can say is, "it appears that all six cells are holding voltage".
(4) No. This is indicative of severely reduced capacity.


I have seen 4 Camry batteries ranging from 2007-2012 with 124-177K miles on them, and they are all the same.


NONE of the cells actually failed. All modules had "good" resting voltage, but when tested for capacity many were essentially unusable. Each module has a 6.5Ah capacity. 14 of the most recent pack were below 4 with several below 1.5. note that these numbers are AFTER reconditioning, i.e., they won't improve by any means.


Once it deteriorates to about 2.6Ah total capacity, there is very little left for the car to use, and you hit "full" during charge faster and "empty" during discharge faster - thus the fast gauge movement.


When you disconnected the 12V to work on the battery, you cleared the codes.


The car may limp along like this for awhile, but in most cases, codes return in short order. You may also notice reduction in your mpg prior to coding.

 

1. p0a8, and a p0302 i think ( a misfire on cylinder 2, but that was due to bad spark plugs)

2. The car has sat before longer at airport terminals, was never an issue. The nickel-metal-hydride should be fine for up to 3 months from the research I did. Can you post links to where it says otherwise?

3, This is what I was most concerned about, I wasn't able to test the cells with any strain on them. I was hoping to easily identify bad cells by reading a voltage that differed from the "norm" the other cells had. From also reading online, nickel-metal-hydride batteries are easier to diagnose than the lithium by this method, but it is not always 100% reliable. So, can you offer a method to better test them?

4. Well, yeah, the codes were cleared by the battery being disconnected, that is obvious. What isn't obvious is to why the car is running basically like before without any faults showing on the dash. If the batteries were that bad, I think the car would have failed already.

Anyways, can you offer some advice on how to better test the modules? Or should another search on the forum be all I need to do? Thanks.

 

I should mention the MPG has increased. During the last 6 months, I noticed EV mode would take longer to come on and miles to the tank were sub 400, as before it was almost 500. Now, it states 476 miles to empty. Hoping the corroded bus connections were the culprit.

 

That makes sense, is there a guide on how to test the mah on the cells?

 

1) P0A80 is the general battery deterioration code. When cell drops out, one tends to get P30XX "block becomes weak" codes.


2) Most references and recommendations do not consider age and wear. If you want proof, the only thing that I can say is in the last 1.5 years, I have replaced approximately 20 batteries that failed immediately after returning from a sitting period of 1-3 weeks. Toyota's official recommendation to their dealers for maintaining NEW hybrid batteries is to let them sit in ready mode for 30 minutes every 30 days - this is to maintain both the 12V and hybrid batteries.


3) Resting NiMH voltage tells you nothing more than a pass/fail criteron. Low voltage likely means a cell has failed. "Normal" voltage just means all six cells are holding voltage. This is true on any chemistry. Schumacher BT-100 12V load tester ($20-25 from Amazon) will hit a module with 60A. Sandwich two bare bus bars with the terminal nuts on EACH end of the module pointing UP (48 in-lb torque on the nuts). This will allow you to clamp the tester onto the bus bars easily. Attach a separate voltmeter. Note unloaded voltage. Apply load for 15 seconds. Note minimum voltage immediately before terminating load (on separate voltmeter - do not use the tester voltmeter for anything). Allow tester to rest for two minutes under force airflow for 2 minutes between each test. You will have 34 modules with unloaded starting voltages and loaded ending voltages. Any outliers will stick out like a sore thumb. Allow the battery to rest 20+ hours prior to any load testing.


4) Your description made it sound like your work was the cause of the code reset. I wanted to clarify the code reset was due to the 12V disconnect. I suspect that you could have just reset the 12V and you would be hwere you are now. P0A80 without P30XX can take awhile to manifest. You are clearly seeing evidence of deterioration in the gauge behavior. I don't know the specific criteria, but eventually, the car will sense the severe deterioration of the battery, and it will code again. I have seen this in all 4 of the mentioned cars.


At 220K, I'm absolutely certain your battery is completely shot. It will not be a clear cut case of "this module needs to be replaced." It will likely be a case of a pretty wide range of voltages with module readings across the spectrum. The challenge will be where to draw the line in terms of what gets replaced. You should be prepared to replace half the modules in your pack.

 

Everywhere.


it requires a moderate investment in equipment and a big investment in time.

 

Not sure of your climate, but spring and fall are typically the best mileage months due to air charge density and a lack of use of HVAC system.

One cannot definitively say mpg has changed unless detailed records are kept and changes in driving conditions are noted. There are often seasonal changes in fuel blends that can affect mpg noticeably - particularly on the more efficient cars. Actual data often presents a completely different story from a driver's casual monitoring of one or two indicators.

Corroded bus bars almost never contribute to this issue except in extreme cases. Coastal areas where salt spray corrosion is common can have an issue. If you could see a circle of copper where the bus bar was in contact with the module terminal, highly unlikely that bus bar corrosion could contribute even if the rest of the bar was corroded black all over.