Gen II Prius Individual Battery Module Replacement

That was one of the valuable nuggets that I learned from this site as it stopped me from purchasing a couple of nice, lightly used Prii I was close to purchasing. I was searching for a low mileage Prius, thinking that would extend the life of the traction. It would have been worth paying the premium that the owners were asking- so I thought. Then I learned that sitting around is no good and the battery likes to be driven.

I think in the case of your CT, it would be ok, if the owner lived in an urban area and drove 5-7 miles a day. But the challenge would be how to know for sure if wasn't sitting around. That's why I prefer to purchase from the owner in a private party sale.

 

ok so I went back and took my battery apart ... made sure ALL the copper connectors were looking brand new ... even used some electronics clearer for ALL the connections ... and STILL the battery under load will not either hold the charge or even recharge and I always end up with 1 or 2 purple lines on the display and my regular engine is doing all the work ... now and for the second time im getting an error about the lock mechanism and the transmission "P" ... park the car on a level surface and not sure if these are related ... I also have a new 12v battery brand new and installed maybe 6 weeks ago ... im at a loss now and im about ready to junk this car and the spare hybrid battery I have ... the only thing I can think of now IS .... test all the cells in my spare hybrid battery and replace them all in the hybrid that's in my car now and see if there is a difference???? I don't have any tools to charge and discharge the cells either

 

It's been 10 weeks and 760 miles and the two cell replacement on our red Prius is working great. No issues at all.

Our two Prii have 192000 and 135000 miles on them and are still going strong. The rolling up of big miles has slowed a bit as I have started driving a Model S as my main commuter and it has taken about 450 miles a week off the Prii combo.

Bobby

 

Hello all.

My 2006 Prius has given me the P0A80 error code, along with the symptoms that most users report with a traction battery failure (red triangle, gas engine coming on more often, battery will swing from fully charged to nearly empty etc.). I have read a number of posts on this thread and others regarding replacement, reconditioning, replacing modules (THANKS everyone!). It has been an amazing education in electrical science.

It seems like the BEST practice is to replace the modules and then do the three cycles of charge/discharge and rebalence. Some people even take the modules in the center of the pack and redistribute to the ends (clever!) when they reassemble.

My question is: What if you don't do what is best practice? How successful is it to just swap out an under performing module(s), without rebalencing the modules? In other words, how successful is taking a shortcut and cutting some corners? Based on what I've seen, seems like it is 50/50. I've seen few users and YouTube videos where all they did was swap out a module and then put the battery back in, or maybe wired the modules in parallel for a few hours before reassembling and inserting in the vehicle. Not sure if their interventions lasted a day or two years.

Mind you, I'm not challenging the best practice...but I am just a dude with limited battery experience and time. I can replace a module or two, or I can just bite the bullet and pay for a new Toyota battery and install myself. I already have the traction battery exposed in the vehicle.

Thoughts?

(for reference, my 2006 Prius was located in Phoenix for most of its life).

 

Deadbeat,
Im in the same boat with my '04. Im planning on replacing the bad modules and rebalancing. If you read through a few of the threads with the data of module capacities before and after 3 discharge cycles, there can be a pretty drastic difference in capacity between modules. To my understanding, that is what you are trying to balance out. If you install a different used module that is out of sync (unbalanced) with the rest of the modules, it will be a short term fix and just create the same problem all over again. I plan on balancing all modules after I swap in good used modules to get them all operating in unison.

 

Thanks Will. I agree.

For the record, I have ordered a new Toyota battery. Given the long history of my car in a very hot climate (Phoneix), and the added time investment and uncertainty, I just bit the bullet and will swap the batteries out myself rather than ferreting out the rotten modules and then re-balancing. If I had a bit more time, I'd do exactly what you are doing and it would be awesome and save some money.

For those reading, I live in the Sacramento area. New Toyota battery = $2329 + tax at the Davis dealership. It would be 3600+ tax for the dealer to do parts and labor. So, I'll save a bit of money, but not as much as if I had the time to swap modules and re-balance.

Still, part of me wonders how much time I would have gotten if I just swapped out a couple of modules without re-balancing. Anyone with an opinion? An educated guess? I'm guessing I'd have a 50% chance of getting to one year before I had the same problem.

 

It's more than an educated guess, Deadbeat. There are two issues with elderly modules - low capacity and self discharge. Low capacity is a problem mainly because the battery management system is more likely to report that a block is weak when the voltage drops too much under load. Self discharge is a problem for a Prius with an old pack that has not been driven for several days and/or driven only for very short trips - less than a few miles.

I repaired the pack in my 05 after a cell in one of the modules failed. I bought four used modules of similar vintage from a Priuschat member last year, charged each module with a single channel hobby charger to see how much capacity each could achieve, and load tested each to determine their discharge capacity (they are not the same thing). Unlike other folks in this fantastic thread, I had no luck regaining lost amp-hour capacity in the modules I was unable (actually reluctant) to deep discharge them because I didn't want to buy any more modules. Anyway, after pairing the modules to get roughly equal discharge capacities for each block, my repair was successful and I never had any additional module failures in the next seven months before I sold the car. I made sure to drive it almost every day because self discharge was noticeable - even overnight.

Unless your idea of a great time is removing the interior panels to get to the pack several times a year, you should weed out the weak modules when you do a rebuild. Any module with less than 2800 mAh capacity won't last long. If you can regain lost capacity with a deep discharge you won't have to buy more than one module to replace the failed one.

You're doing the right thing by buying a new pack. Don't be tempted to cancel the order to do a DIY repair unless you have another vehicle. My pack rebuild/repair took me three weeks. Yes you can just swap out the bad module and hope for the best but I would say the odds of success are much less than 50/50 to last a year.

Oh yeah, I forgot, installing a new pack from Toyota isn't a simple swap. You need to move stuff from your old battery to the new one. Not a big deal but you could screw it up if you don't follow the instructions in the service manual.

 

Thanks for pointing that out. I was under the impression the whole unit could be swapped out but I see from a link I found that some hardware does need to be migrated to the new battery, including the housing.

Is there another set of instructions (video, or other) that you've found better at illustrating this point? The best I found was the Dorman Products install video....but that one is about swapping out the battery for a re-manufactured pack.

 

I tried to find the thread where someone took good photos of what needs to be swapped. No luck. Sorry

Basically, Toyota expects you to transfer your battery ECU and some of its wiring to the new pack. You need to connect the harnesses from the ECU to the new modules. Fairly straightforward. The correct torque for each nut is crucial; it is tighter than you'd think they need to be - I thought my torque wrench was certain to snap at least one terminal off of a module but that didn't happen when I did my pack repair. I was using a Harbor Freight torque wrench though LOL! Make sure that you take a lot of photos before disassembling your old pack. It goes back together neatly in only one way. You probably will not remember how to do that. You will also need to inspect the harness connection at the battery ECU. It might have some green corrosion on the pins - you will need to remove it - somehow. I was lucky that my harness connector had no corrosion in it whatsoever.

 

Kiwi. I think this would be cool.
What's the design pack schematics pls?

 

Brits. Nice explanations. You must be a lecturer. Hehehe he! I'm joking though.

 

Hi Brits.

1. Can one achieve the same current measurements using this analogue ammeter in series with a voltmeter to get current on any of the modules?
2. How can I read this meter? The graduations are kinda....for me to read them(that's the first figure by the left).
3. Can I use a 12-24volt battery charge/% monitor to monitor the start of charge of the batteries?
Have any idea of the circuitry connections to the battery modules?


Regards
Dxta

 

Please which manual are you referring to, and do you have any links Sir? Would like to have it too.

 

How do you get to know the equivalent of the voltage, and bring it down to 80%, Sir?
Would appreciate your reply. Ready to learn here.


Regards,
Dxta

 

Have just checked the site for the cellpro charger.
One ????, sir.
How many modules can it charge, and does it have all the necessary features one would need for battery rebuild?

Thanks
Dxta

 

Just to clear up a few things. The battery has 2 main aspects that are important when rebuilding. The first is capacity. This is basically how much work the battery can do when its state of charge goes from 100% to 0% (1.0V per cell or 6.0V per module is effectively this point on a Prius). The second is load testing which has to do with how well the battery can keep up with the demand (load) placed on it (measured as a voltage drop over time using the same load/time on each module).

Think of the first (capacity) like how big the water tank is on a fire truck and the second as how large the hose is to deliver the water. Now lets say you line 30 of these trucks (just like your battery pack) up and they are all trying to put out an absolutely massive fire. I'd much rather have all the the trucks with big fire hoses and varying amounts of water (capacity) in each tank than all trucks with big volumes of water (capacity) while some trucks having fire hoses and others are using garden hoses. At this point the chief (hybrid ECU) is going to tell the truck with the garden hose they have a problem (sends you a CEL). Garden hoses don't put out big fires and this is the same idea that applies to the batteries. This is why load testing is much more important than capacity overall. Ideally capacities and load tests are both matched very closely but when you're looking for new modules which fit in with the rest, voltage drop while load testing is about the best way to ensure the modules will work well together for any period of time afterwards. When people get lucky on the replacement modules and just slap them in and they work, more than likely the voltage drops under load were simply well matched (luck) even though capacity may not.

Hope this helps a few folks understand how this all works.

 

If you haven't return the core to Toyota, and you are curious, and you want to drive to visit Los Angeles area soon, and you have plenty of time, I can give you a core to return to the dealership and run your battery in my car until it dies again.......When it dies again, you'll know

 

Wow. Thank you. That was a very clear explanation and analogy. That does paint a clear picture of those concepts. Next time around I may swap a module now that I'm a bit more familiar with batteries. I'm glad I didn't do it this time, as I don't think I had a clear understanding of the importance of capacity and load testing.

 

Does anyone have any decent gen 1 modules for sale?

 

First used module swap lasted about 6 months in mine. Keep in mind, letting the Prius sit kills it faster. The Prius is a case where "granny only drove it to church on sundays" is BAD compared to a daily commuter driven every day. The Prius loves to be READY. We've replaced our DD HEV vehicles with BEVs as well, and the HEV's can sit for a week or a few weeks before a couple hour drive. Basically the worst possible treatment of a HEV. So be careful with that Model S, it will kill your Prius!

"Decent Gen1 modules" haven't existed for about a decade. But the 2001 through 2015 batteries all use the same battery modules (you just need more of them). Check eBay for modules.