Gen II Prius Individual Battery Module Replacement

The cost differential is due to the specialized equipment required to perform sufficient testing, higher labor hours per module required to properly screen them, and higher rejection rate during our pre-sale QC process. This is why we can offer a one year warranty on our modules. We have had scores of Prolong Battery System customers who have bought modules on eBay that were garbage and ended up having to change them twice. This is why we started offering modules - so that our core customers don't have to gamble on eBay or Amazon any more.

If the extra $20 per module isn't worth it to you don't buy them from us, no worries either way. As others here have said you get what you pay for ;-)

 

what are you using?

 

I was using torque pro, an app for android phones(about 5.00) with an elm327 obd2 reader(about 15.00).

 

Hi everyone,
I have been the beneficiary of this chat forum for a long time now and I figured it was time to contribute some of my own:

First and foremost, many thanks to everyone who has contributed here! You are the greatest!

I actually have 3 Prii in my stable: 2017 Prius III, 2007 Gray Prius and 2007 Red Prius. The Red Prius is the topic of this discussion. I bought it two years ago for my #2 son to drive to college. It had 100K miles on it at the time and is in excellent condition both inside and out. About a month after I purchased it the traction battery went out and I experienced my first big red triangle event. I found a company local in Charlotte, NC to replace it for $850 with 2 year warranty. The repair shop mentioned to me that they could tell someone had been in this car before working on the battery so this wasn't the first time it had an issue. After about a year the same thing happened again and the company honored the warranty on the replacement battery minus a $250 labor fee to change it out. 6 months later, another failure and this time instead of going back to the repair shop, I decided to handle it myself. Only thing, I didn't know about this forum at the time but having both electrical and mechanical background, I delved into the car after watching some YouTube videos on how to remove and replace the battery. I knew enough from my skill set to understand how the battery worked and how to troubleshoot it. I found that the #17 module was a volt lower than the others and I surmised that it needed to be changed so I turned to eBay, replaced the bad module and life was good again for about 3 months.

This time, it becoming personal and I was determined to find the smoking gun. That's when I finally started scouring this forum and learning all I could about balancing, load testing, etc, etc. I found a used battery from a nearby junk yard and decided to build the battery from the best of the modules between the two and also swap out the battery ECU. (For reference, I also cleaned and checked the battery cooling fan as well)

I purchased 10 of the iMax B6AC chargers from eBay for about $200. After crafting some longer output leads, I was ready to start separating the bad modules from the good ones. After a week's cycles of discharging and charging I determined I had 6 modules that obviously had a bad cell in them. From the remaining modules I chose 28 that had the highest discharge MAH capacities. I discharged all 28 modules to 7.6 VDC and then began my load test using a trailer rear tail light I had laying around in my garage. I tied both turn signal and brake light filaments together creating about a 2 AMP load for the module. After a minute of load testing (repeated 28 times), using my trusty Fluke meter I recorded my initial voltage along with final voltage and had a delta of .04~.05 VDC on all 28 modules. Since every module measured 7.6X VDC, I decided there was no need to tie all 28 modules together in parallel since they were already fairly equal. I then soaked all of my copper bus bars in a solution of vinegar and salt overnight to eliminate the corrosion and coated each copper bar with a little dielectric grease before reinstalling to keep the corrosion to a minimum.

I felt really confident that I had a pristine battery ready to go back in the car but still one question was nagging at me: Why had so many batteries failed in this car before?

Since the car had been setting for about 3 weeks, I decided I should check the 12V aux battery and give it a charge on my trusty smart car battery charger. The charger I have has a LED bar-graph that displays charge capacity (choice of 2, 4 or 6 AMP charge). Once the battery is fully charged, a green LED comes on and charging automatically halts. Only problem, after hours of charging, I could never get more than 2 bars out of 5. Hmmm... I took the charger off and measured the DC voltage on the battery and found it was 12.5 VDC. Should be OK right? But why didn't it ever finish charging? I could see that the battery had been replaced less than 3 years ago with a Toyota branded battery but I didn't like the fact that it would never reach a fully charged state even after hitting it with 6 AMPS of juice for several hours. I decided to replace the 12 volt battery with a new Optima. Brought the Optima home and put it on the same charger and I get a green light in less than 2 minutes.

I put it all back together and now the car acts like a totally new car. Another tale tale sign was (before) the car could never get better than 42 MPG. Now I'm, easily getting 50 plus MPG. Another sign: The ICE would hardly ever stop running. Now, it stops like it should when setting at a traffic light. Silence is GOLDEN! I think the smoking gun was the aux battery. Reason: the car has a DC-DC converter that is tasked with keeping the aux battery charged which is supplied by the big battery. I think it was constantly struggling to get the aux battery at full charge but never could due to most likely an internal short. Long story short: The little battery was eating the big battery.

 

thanks

 

You need to acknowledge that this result is directly attributable to the job you did. Reading through your post, it is clear that you have done an infinitely better job at rebuilding your battery than those to whom you paid good money. Credit where credit is due.

You, sir, do yourself a disservice, while there is probably a little truth to this, even a battery with a massive internal short would not have that much effect on the HV battery, plus you would have a lot more 12 V battery related issues. It is good that you did test and find that problem with the 12 V battery and replace it, as it would have continued to contributed an unnecessary load, but one you may not have noticed.

You can take comfort in the knowledge that the vast improvement you see, is down to your work in rebuilding your HV battery.

Please come back from time to time and let us know how your HV battery conntinues to perform. Let us know also, if/when you needed to perform more remedial work. It is of interest to the community to have these data points.

All the best.

 

So I got one of these on sale (not 55 lol)

They charge at 6A and discharge at 2A(1.2 realistically). I set to auto mode with 6A charge and 2A discharge to go for 3 cycles with all the other normal settings of 7250 capacity cutoff, discharge to 6.0V, etc. Default nimh sensitivity and it discharged it all fine, but when it tried to charge it keeps saying FULL at random points from 340 mah to 500 mah... some of my other units stop at 1000 mah, or whatever random number.

UPDATE: I tried 2A manual charge mode as well.. same issues persist.. so bizzare. It may just be the chargers at this point.
Going to also try thicker guage cables today to see if that fixes the issue.

 

have you done nominal voltage set to 7.2v?

 

It doesn't allow for me to set nominal voltage.. it'll just display the nominal voltage. At this point it just seems like the chargers themselves are at fault. Doing further tests but most likely the chargers are damaged since at the same setting 2 of the chargers seem to charge the full 7250 during 2nd or 3rd cycles, while the others cut off randomly way before that. regardless of cycle (sometimes with like 500mah it'll say it's done when it's a empty battery.)

 

Alright so I finished cycling most of my modules and finishing up the rest today.. some needed 4-6 cycles to get over the 4500mAH capacity area. So now that they are all fully charged, how do I bring all of them down to normal voltage? Are you guys saying the parallel wiring harness is useless? If so what should I be discharging them down to? A voltage or a capacity? Thanks. Also is it bad if the batteries are all within 4000-5000 maH capacity with half being 4500-5000 and other half being 4000-4500 mah capacity?

Thanks

 

Now as your modules fully charged you need to bleed them to less voltage, aim for 7.4v each using your charger this will make your pack at around 50% SOC this will prevent battery model from flagging DTCs.
I'm using IMAX charger and I can set the target voltage to where I need the charger to stop discharging.

or use what S Keith mentioned before :
"If your modules are all at full charge, discharge @1.2A to some arbitrary voltage well above 7.2V. You only need to bleed off a couple hundred mAh. Start with your lowest capacity module and discharge 200mAh and see where that puts you. Discharge all modules to that voltage at the same current. You're not just balancing based on voltage in this case, but to internal resistance as well."




as long as all your modules above 4AH that will be great.
But what you need to worry about is load testing and internal resistance, all should exhibit approx same voltage drop rate under same heavy load.

 

So after that is all done, do they all have to be the same exact voltage when I put it in? I discharged all to 7.6v, and then came back a day later and some were at 7.96 and 7.8 testing with no load using a multimeter. Or does standing voltage not matter, only what i discharged them too?

 

surface voltage will continue to climb to some point and stops, you have to continue to discharge until it stabilizes to desired voltage or discharge modules to less than desired voltage(in your case 0.20v less) then surface voltage will climb to the voltage that you want(7.4v to 7.6v).


for the differences between voltages I think this is the effect of internal resistance and this why you should do the procedure mentioned above by S Keith.

but after reaching the desired voltage

The maximum allowable difference between module pairs (block) is 0.3v otherwise a DTC will be detected.
so you can do one of two things:
1- applying load to reduce the higher module voltage to match others and wait for surface voltage to stop climbing.
2- matching modules(after surface voltage stop climbing): pair the higher voltage module with the lower one and so on for the rest, this for me is the best practice in which you will match according to internal resistance as well.

after that your battery pack should contain 14 matched blocks with minimal allowable voltage differences.

hope I'm clear and right.

 

Thanks I discharged them all to 7.5V sat on it for 4-5 hours and then put them in the car.. after 200 miles everything is working well!

 

I have a quick question. I was on the process of refurbishing a pack of a low mileage salvaged 2007 prius with 85k. I got the car in auction with a bad pack and found that the pack was a replaced and "refurbished" about 1/4 of the modules are gone so I bought a used pack from a gen3 prius. At what Voltage is it safe to unclamp the modules from the housing to prevent swelling. I'd like to sell the old modules to help offset the cost.

 

As long as the modules not hot after being charged you can unclamp them any time. you can see gap distance between clamped modules plastic bodies if swelling is happening.

 

So are you saying you are selling untested modules? And they are from a pack that previously hacked up.

Hope those modules are dirt cheap.

 

What do you think is a reasonable price? I was thinking about 150-200 dollars for the whole set. Kinda want to keep the battery housing tough.

 

I made a mistake when swapping all of the modules from the gen3 to gen2 pack. I forgot what modules have the bottom sensors, can someone point me what module has the sensor?

 

I dun remember but I know the three sensors only reach so far.
There temperature sensors and honestly it doesn't much matter on which modules there on the bottom as long as there on there.
Sent you a message would like those modules I got the testing equipment and my battery is short of dying and finding a few good modules will give me time to fundraise some more.
terramir