Gen II Prius Individual Battery Module Replacement

Sorry for late response. I ended up using a headlight bulb to bring them to similar voltages before assembly.

Thanks to everyone for advises. Here is the result of my rebuild.
I swapped 6 modules:1 initially failed, 4 failed the capacity test, 1 failed internal resistance test.
I got new modules from Eric. (Thanks for quick shipping!)
I was able to restore all other modules to 5200+ mAh.

A year passed, the car is still running good and the battery is holding strong. After rebuild, I noticed it was taking much longer to discharge it while driving.

I don't know if anyone will be interested, but I made a detailed video of the whole process, explaining every step I took. I used info from online and this forum. I showed how to get the battery out, identify bad modules, replace modules, assemble the pack, clean and protect the terminals and install battery back.
Sorry, if my English is annoying at times.

 

FYI.
I see the pic, but no link to the video itself?

 

The picture is the link.

JeffD

Posted via the PriusChat mobile app.

 

Funny. For me, the pic is there as a static photo so nothing happens when I click on it. As if there isn't a link at all.

I got sent the same pic in a private message and the photo is there and works properly as a link when I clicked on it. Weird.

I'm reposting it here just in case.

Good video with a nice amount of detail. Very clear so can see what is going on. Igoryan spent a lot of time doing additional steps that most people skip. It'll be interesting to see how things go over the long term.

Thanks for sharing this video with the community.

 

Nice video Igoryan, really helpful and detailed

This post will be long haha but it's another successful DIY rebuild, so I want to be detailed

ALWAYS wear electric protective gloves when working with the assembled pack connected in series, once you remove the bus bars, there is not so much risk of electric shock.

Finally a couple days ago I finished reassembling everything after cycling all the modules to 4500+ mAH, the best ones required just 2 cycles to show 5000+ mAH, good ones showed 4900+ mAH after 3-4 cycles, the more worn out ones required 5-10 cycles to reach 4500+ mAH, changed 1 module that had a shorted cell, and swapped one with "low" capacity of 4200 mAH after 7 cycles.

Cleaned the busbars and nuts since they had a good amount of corrosion, letting submerged overnight in white vinegar, superb results, cheap and "green" then clean in a solution of water and sodium bicarbonate and dry, after that, just slightly wire brush them to finish the cleanse, cleaned the voltage sensors wires and end connectors with water and sodium bicarbonate since they had corrosion as well.




After all the cycling process completed, I applied a little bit of oxgard to the busbars and hand tightened the bolts, everything working good so far after 45+ miles of driving on slightly hilly roads, great difference in how much time it takes to discharge the pack, nice, now I know how a good working pack operates

My settings are the following if it's any help for any of you reading

Charger: EV-PEAK CQ3 Quad Charger/Balancer, I chose this one because it has an integrated power supply and a decent discharge rate and specs, it's not too expensive under $100 on amazon and I could cycle 4 modules at the same time. Only issue I had with it is it fails to do more than 1 automatic discharge/charge cycle, so had to program one cycle at the time, and it takes a little more time, but that really didn't matter much, keep reading

ALWAYS have a fan blowing cool air over the pack, I used a small USB fan and it seemed enough. If you want to take good care of your charger, ventilate it as well during the discharges, since it will get hot.

I had to build my own custom heavy duty harnesses to connect the charger to the modules, preferably use 12AWG gauge or thicker. I used ring connectors (0.6mm diameter) to attach to the modules with their nuts.

Don't forget, if you are working with a charged pack, configure your charger for DISCHARGE>CHARGE, otherwise you'll end with a discharged module if you are working with a discharged pack, first do a charge, and then set your cycles to DISCHARGE>CHARGE.

DON'T cycle the modules that are next to each other because some might expand quite a bit, I let 2 modules at least in between charging modules, that's XXYXXYXX, where "Y" is a module that is being cycled and "X" is a resting module, that will help with heat dissipation and swelling. 1mm to expansion on each side seems "normal", 1.5mm swelling on each side of the module I found on modules that are a little more worn out. On the more deteriorated, I found 2mm swelling on each side of the modules, I would monitor those modules closely and even use safety goggles. In some of the best modules I wouldn't even notice any significant swelling.

I found the load test with the halogen bulb helpful only if you don't have an obvious bad module, that's only my personal opinion though. In my particular situation I had a module with a shorted cell, so the voltage was 6.X V, pretty easy to find, you will find the best and decent modules in the discharge cycles.

After some tries with the first modules, the best results I got were with the following.

Discharge rate: Set to 2.0A and end voltage of 6.0V, depending on the voltage of the module, this particular charger will discharge the module between 1.2 and 1.5 Amps. I set up the wait time between DISCHARGE and CHARGE to 15 minutes to be gentle on the modules, but I'm a patient man

I used the same discharge rates for the entire cycling.

1st. CHARGE: set to 0.7 A, cut off time disabled, delta peak set to default and capacity cutoff set to 7300 mAH. I was trying to be gentle on the modules and had no hurry in finishing the process since I had a different transportation method, this will increase your cycling time significantly, but I found this helpful particularly with modules that are a little stubborn to take all the charge.

For the REALLY stubborn modules, I used 0.5A charge rate to get all the juice in.

After every charge, if the module didn't swell much or had almost no expansion, I would let rest for at least 20 minutes, on the modules which expanded more, I let them sit until they "shrink" back to normal state, that could take anywhere from 40 to 85 minutes, sometimes a little more. As I stated before, I'm a patient man, and you wanna take care of your pack, trust me

On good and decent modules, I would see increases in discharge capacity between cycles by 700mAH and 900+mAH. For example, first discharge, 3100mAH, second discharge 4100mAH, 3rd discharge 5000+mAH so on and so forth.

2nd. CHARGE: set to 1.1 A, cut off time disabled, delta peak set to default and capacity cutoff set to 7500 mAH if the module handled the first charge well. Some modules will show 5000mAH capacity after the second cycle, I would not do more cycles on those.

If the module is not taking the charge so well, keep using 0.7A or 0.5A until discharge capacity shows significant increase.

3rd. CHARGE: set to 1.5 A, cut off time disabled, delta peak set to default and capacity cutoff set to 7800 mAH if the module handled the second charge well.

If the module is taking all the capacity and not swelling too much I would use the 3rd. Charge setting for the 4th. and 5th. cycle if needed, if it reached 4700+ mAH capacity after the 5th. cycle, I would use that module and consider it "decent". If it's less than 4500mAH after the 5th. cycle, I would consider that module as marginal. Less than 4000mAH after the 5th. cycle I would not recommend to reinstall on the pack as it would be too deteriorated if you have better ones installed as well.

In my first tries, I used 2.0A charge rate but didn't have as good results as with the settings above. Modules would swell quicker and/or not take all the capacity set.

IMPORTANT PART OF THE PROCESS:
Balancing voltages between modules:
I disassembled the pack and rearranged the polarities after cycling the modules, on one side of the pack I would leave only the positive posts, on the other side, the negative posts. This will save you a lot of time since you only have to use one wire along all the posts and tighten with their own nuts to connect them all in parallel. Use 1 wire to connect all the positive terminals among them, and another to connect the negative among them. I left them connected in parallel for at least 7 hours since I had other things to do and worked well. Please if you do this method use the white plastic with the bolts on the cylindrical bars since the pack will be expanded, if you don't use the plastic, any little movement could drop the last module on the edge of the case and cause some electric accident or such. Try to balance to 7.8V or less if possible, so the ECU doesn't read abnormal high voltage.



No particular sequence for the modules on this process, don't mind the numbers on top.

BLOCK REARRANGING:
I rearranged the modules averaging the last discharge capacity amount. Use the weakest with the strongest module you have, always averaging the block (pair of modules), of course, so you get and even capacity among blocks. Similar capacity modules should be together. Also, the blocks where you have a weaker module should be placed as far away from the center of the pack since it will be subject to more struggle due to temperature and what not, and you might want to use the highest capacity module on module #1 and #28, since I see a trend, the ending modules tend to have lower voltage than the rest of the pack.

Make sure your 12V aux battery is properly charged before starting the car again.

Check the HV battery fan and make sure it's not clogged, clean all the vents and area if possible for best results.

This is a time consuming task depending on your equipment, but not difficult at all if you have some experience using even AA or RC rechargeable batteries, you can consider the battery modules on this car just a bigger version of those when not connected in series, don't be afraid of the task but take your precautions

IMO the hardest part of the reconditioning is when you need to fit all the modules between the end white plastics and cylindrical bars after the cycling and balancing process, they are expanded and will be tough to compress. You can see how much did they expand after the process on the image above about connecting the modules in parallel with seeing how much the bolts are tightened on the withe plastic and cylindrical bars, they must be flush in the end. 2 people task IMO.

DON'T forget when you mounted the assembled pack in the car to reconnect the orange service plug, I did and was disappointed for a minute haha, the car won't start if you forget.

After you start the car, the red triangle of death might still be present, start and turn off at least 3 times, if everything is good, triangle will turn off.

You might still have remaining codes if you check with techstream, erase them and check again after driving it at least 3 times.

It seems prii doesn't like to be sitting for long periods of time huh? I never had an issue with the AC, now I think the system is depleted and need refrigerant refill after sitting 2 months haha I will take it tomorrow to the AC technician.

I will update in some months to confirm the longevity of the repair, greetings

 

Sorry I wrote the EV-Peak CQ3 charger was under $100 on amazon, but actually it's under $200 haha, my bad.

 

Thanks for taking the time to write up what you did.

Can you let us know how long this process took?
A few days? A week?

Since you seem like a thorough person, I'll mention something else about corrosion. What most people don't realize, and noone really does anything about, is the big main black negative cable. Often if you have corrosion elsewhwere, there is a fair amount of corrosion on this cable, too. Quite a bit of it can be hidden underneath the sheathing. The only way to see it is to remove the sheathing. Rather than rewrapping it afterwards, I'd say just get a new replacement cable.

 

]Hello, yes, in between work and life, the whole process of cycling and balancing the modules took me about 20 days I think, if I had more spare time maybe it would take me 15 days? that's with the waiting time between cycles and what not Yeah, I know, it was a long time

You're right about the big main cable, I cleaned it just at the end connector part and at the base of the cable, so it might be corroded inside, thing is, I live outside the US, so buying and importing parts gets really expensive here since hybrids are not yet so common, and of course the waiting time of a couple weeks to arrive sometimes. Sometimes you are able to buy things locally for hybrids but they might sell you the worst shape part they have, happened to me with the modules, had to go 3 times to the seller, 2 modules with ultra low capacity, third time's a charm huh. Next time I need to open the pack I will consider cleaning that cable and getting some shrinking tubing to protect it after cleaning

Cheers.

 

Nice video @Igoryan

I think the issue where someone said it looked like a static picture is because they may not have been logged in. It looked that way to me too but once I logged in to my priuschat account it showed up as a video.

Anyway, nice work I'm fixing to rebuild a battery and the video gave me a great perspective of what all to do. Thanks!

 

In your video when you switched your charger from manual to auto will it continue discharging and recharging over and over until you stop it (or allow you to put in a number of cycles like 3 times) or does it only go through one cycle then stop?

 

Can someone explain to me what the magic number I'm looking for is to shut off the charge cycle and discharge back down to 6v on these modules? I just got 5 reaktors in because the imax b6 knockoffs were garbage.

My settings are
Delta peak cutoff set to default
7500 MAH cutoff
Charge set to auto 3A
Discharge 2A 6.0v

I guess what my question is when I am discharging and going through 3 cycles, can I trust the charger to shut itself off when it reaches the module's delta peak? And what is that delta peak? Should I be looking for a certain number like 9v? Can I leave the chargers alone like that and trust they'll work? I'm not super electrical savvy and I've never even used an RC charger before. So I don't really understand what the magic number is and I don't want to overcharge.

 

You cannot really over charge if you keep the current low, say 0.330 amps.

A nice slow soak like that can really help balance things out and really make sure all the cells of the modules are full.

 

So then how do I know when to cut it off? It seems like the reaktors will automatically shut off when the battery gets between 9-9.2v and then it discharges. But the crappy knock off Imax's I've got I don't trust.

 

With NiMH if you charge at a low enough current, the "extra" just goes directly to heat. So as long as the Ic is low enough the heat generated is therefore low enough and it becomes a don't care.

NiMH actual charge profiles include a hump. You're not going to exercise that with a cheap charger.

 

I've got a couple questions hopefully you guys can help me with since there's some very knowledgeable people in here. I have a spare HV that I am going to rebuild following the info in this thread. BUT...I need to store it long term because my current battery is still good. I'm not sure the best way to store it.

I'm thinking that if I wire it up the way the thread shows to balance the cells where you let it sit 24hrs and they level out that this would also be a good way to store it long term but keep it balanced. Can anyone think of a reason that it may be a bad idea?

Also, while wired for balance could I wire in some kind of charger used like a trickle charger that only kicked in when voltage got down to a certain point and shut off when it gets back up to a certain point. Would that be possible while the batteries are wired to stay balanced? And if so, does anyone know of a charger that could do this?

Thanks for any info!

 

I'm sure this is a bad idea to store the battery that way,
even balancing the cells that way is a bad practice as everybody agreed in the previous thread replays.

if you wanna store the battery, just remove all wiring and keep it on a shelf

 

It is not so much a bad idea, as much as it probably will not serve any useful purpose. You also do not seem to understand the process of balancing modules/batteries. What you are referring to above is a process called equalisation, and it has been shown to have very little benefit and is not done anymore as part of a rejuvenation process.

Balancing is two-fold, top balancing and bottom balancing.

Top balancing is where a battery is charged long and slow (~300 mA) so that all cells in the module reach full. Where any cells are at a lesser charge than its peers, it remains charging. As each cell reaches full charge the current injected is wasted off as heat and as long as the current is low the heat is minimal and causes no damage.

Bottom balancing is where the battery is discharged so each cell reaches 0 V and as long this is also done very gently the risk of reversing any cell is lowered. In reality one does not usually go right to zero, but about 0.1 V per cell.

I would not do this. Probably a better idea would be to discharge to 0.1 V per cell and then let it self discharge. Store it in this state and then when ready for use, do a full top balance charge.

 

Years ago I used to store batteries at a low state of charge but much higher than 0.1 V per cell. I found that it was a very good way to kill batteries.

For long term storage charge the modules to full and then leave them alone.

 

I would go by what strawbrad says. I must have been thinking about some other battery chemistry.

 

Sorry for late answer. As far as I understand, on Auto it will decide when to stop automatically, not manually, based on final voltage setting.
It will still cut off at 7500mAh. If the number of cycles was set to 3, it would do this 3 times: discharge, cool off for 5 min, then charge.