DIY help on cell replacment/balancing

1. A battery block is composed of two battery modules. The traction battery ECU measures voltages by module pairs instead of individual modules.
2. Hence, if battery block 13 is the problem, either module 25 or 26 would be at fault.
3. Use a voltmeter to measure voltages of each module in your battery. Hopefully you will find one module whose voltage is much lower compared to the others, and that would be the obvious failure.
4. A failing module will overheat and may damage adjacent modules due to this overheating.
5. The 2G and 3G Prius have 28 modules in their traction batteries, while I believe the Camry Hybrid has 34 modules. It is possible that the module type is similar to that used in Prius but I do not know that for a fact.
6. There are many posts from members who have had various degrees of success using a charger to charge/discharge modules. So please look around for those posts.
7. The modules located in the middle of the battery tend to run hotter than the modules on the ends so some members have tried moving modules around the case, thinking that may help.

 

I've rebuilt a few of them. First thing I do is disconnect every module, take a voltage reading of all modules and mark the voltage on the modules. Now you will look for those that have abnormal readings I find that 7.5v to 7.7v is normal to find however I have found modules with 3v before. If you find one with 7.0v or up to 7.4 it doesn't nessasarily mean it's bad it's just out of sync/balance with the rest of the pack. So discharge it to 3v or so and recharge it to about 7.8v let it cool. Never unclamp it from the pack. You'll notice the Voltage will start to drop. It's normal after 45 minutes it should be sitting at 7.5+/- volts. Grab a stop watch or use a smart charger like I do and figure out how many amps the battery is holding. I usually to charge/discharge x3 cycles for the truest readings. Please ignore the 7.2v setting in the picture I was using it for another purpose last.

 

I am not sure whether battery block 1 starts at the traction battery ECU end, or the other end. And the numbering may differ for the Camry Hybrid, anyway.

(Regarding nomenclature: I suggest calling the individual 34 units "modules". A module is composed of six "cells", with regards to Prius modules. Each cell produces 1.2V nominal voltage, thus a Prius module produces 7.2V nominal. Highlander Hybrid is an example where a module contains eight cells. A battery block is composed of two modules.)

 

The battery ECU is the high side and the other side is the low side so here is an example ECU on the Left notice the numbering and the examples of the voltages. Anything more than .2v will cause a problem. Maybe not in the short term but in the long term. You may experience chugging or no start, triangles of death and battery overheating.

 

They are inexpensive, I have 6 of them makes battery charging and discharging fast. It has fault detection as well, it wont let you charge a module with a bad cell. read the instructions for the charger and make sure you select the proper battery type. They are SMART chargers they will not let you over charge a module. You can charge them one at a time or in pairs. In pairs you will need a jumper wire.

 

If you do not already own a Mini VCI cable get one on Ebay or Amazon. The cable will come with Techstream software. You must have a decent scanner to be able to read a P3023 code. As Patrick said your battery has 34 modules each having six cells. The module voltages are monitored in pairs or blocks. So (Battery Block 13 becomes week) means that the 25th or 26th module will be 1.2 to 1.3 volts below the rest. The 1.2 to 1.3 volts is the threshold to cause the code to trip. I can not tell you which end to start the count on your Camry. Most Prius Chat members and the Toyota repair manual will say that on a Gen II Prius that the count starts on the ECU end. I disagree based on dozens of personal observations. So we can not even agree on where to start the count on a Prius. A load test will help identify your bad module. At rest the voltage of a bad module can recover making it hard to identify. For a good description of performing a charge and discharge test using Techstream read this short thread.

Unable to determine the cause of the triangle warning | PriusChat

Brad

 

The B6AC uses the same plugs to charge and discharge, during the discharge the unit will become hot. Its taking the energy and turning it into heat.

 

Look closely at the serial number on your modules. Every 07 Camry hybrid battery that I have rebuilt has "B2" below the serial number. If yours have this also make sure the replacement module has this also as the series resistance could be different with older or newer modules. If you can't find the correct ones PM me and I can help you.

Also... with the supermate DC6 or similar it takes me about 10-14 days (with 6, DC6's) to cycle/balance a Camry pack. With 1 charger it could take a couple months. I suggest getting a grid charger from Hybrid Automotive Restore you Hybrid Battery, Don't Replace it! to speed up the process. You can charge the entire pack at the same time and do 1 cycle per day. You will also be able to use it to maintain the pack down the road.

 

I agree with TampaPrius, I use the hobby chargers because they are easy to work with and I have experience working with HIGH VOLTAGE. I do want to stress that you are working with a lot of energy and I have seen first hand electrical burns that could have been avoided. I usually dont use my hobby chargers to discharge the batteries only to charge. I do use them to monitor Voltage while and signal an alarm when the desired voltage is reached. I have a bunch of DC light bulbs with resisters inline to put an amp draw on the modules. My grandfather was an electrical engineer and has taught me a lot. He was the head electrician at a GM casting plant keeping the melting pots running. Very high voltage.

 

I just had my dash light up with the red triangle check engine vsc and amber circle with a ! in the middle. Also the display has the red car with the ! in the middle. I took the car to the dealer to read the codes and got a P0A80 and a P1121. After getting some great ideas from other prius owners on this site I decided to test the cells on the HV battery myself. After testing each cell 3 times they all are in range ( 8 - 7.8 ). Is there something other than a bad battery causing the P0A80 code to pop up if the individual cells test fine?

 

Maybe that would be a worthwhile preventative maintenance, before issues arise? Coupled with a check of voltage and cleaning all the connector bars and nuts.

 

I assume you are measuring voltage when the traction battery is just sitting there, with no load attached. If my assumption is correct then the voltage test will not find a problem where one module has a higher internal resistance and therefore the voltage will sag when the battery is under load. You would need to apply a load to the battery for a better voltage test.

 

As long as the person doing the job doesn't introduce a fault from sloppy workmanship.

 

If you have this code the battery needs repair/replacement.

Like Patrick said check voltage with a load to find the module/modules with the bad cell.

Your P1121 is the coolant control valve which is a separate issue.

 

I'm working on an 07 Highlander. It is a very different animal than my prius. Does anyone know where I might find a used cell? The battery is a monster 181lbs. Any tips that anyone might have or experiences with a highlander would be greatly appreciated!

 

I find Highlander cells on eBay for the cheapest, I had half a Hybrid battery last year for one. They are not cheap.