Gen 2 2004 Prius 200k miles. Bad battery cells. How hard is module replacement?

I have to head out, but I'll reply in detail soon... In the meantime, clear the error codes and force charge the pack (aka: car in drive w/foot on brake, emergency brake on just in case and accelerator pedal floored) And then see how long car goes with regular driving before warning lights come back on and post more screenshots.

 

If you are somewhat mechanical, can write numbers down and operate a stopwatch, you can replace battery modules.

To me it looks like you'll need at least four modules (2 per block). The lazy, but effective way to do this, assuming the rest of your pack is relatively evenly balanced, is to discharge two of them, to get a decent average of how much charge remains. Then discharge and recharge the replacement cells, to the same stage of charge as the average of the two you discharged (this SHOULD be close in voltage, but do NOT use voltage, either under load or at idle to match). You can do this with a hobby charger that costs $50, it may just take a while to do so. Discharging the replacement cells you get can easily be done with a light bulb to speed things along, but don't let them get too low -- let the charger discharge them the rest of the way.

That's the short of it. If you want to be thorough, you do this, but with the entire pack. I'm lazy and this has worked for two cars so far, so I'm going to keep doing it :v

There's a ton of threads you can read for the rest of the info, go search.

The only other thing I'll say is, if you plan to keep the car for 5 years, go buy a full set of new cells from the vendor on here. That's well worth not having to touch the thing again.

 

Great advice from folks so far.

If you have some basic tools and patience you can replace modules. Sockets, screwdriver, trim removal tool , inch-pound torque wrench.

You posted some good questions and thoughts in your "ramblings". I'd be happy to chat on the phone about the ideas you've laid out so far. Call me at 608-729-4082

The real.quesrion is how far down the rabbit hole you want to go.

Sometimes doing an "okay" job is good enough. There's a good chance you can swap the bad modules, closely match voltage using equipment you have around the house, and just keep on truckin'. No need to do do fancy rebalancing of all the modules, quantifying capacity, etc

If you want to go full bore and buy a bunch of equipment, and other goodies, that's fine too. I'd be happy to discuss any of it.

I sell modules to folks on this forum and as part of the sale I offer support along the way. Even if you don't buy them from me O still would be happy to talk.

There are basic videos out there about removing the pack.

Once out it's not much more to open the pack. Go slow. Don't have pets or small kids around. Leave yourself lots of time. Ask lots of questions.

 

Normally I would agree but they are backordered 5 months.

I would recommend buying theProlong reconditioning system and a couple of modules from Hybrid Automotive. They try to match the mileage of your existing pack.

 

Due to Covid, Hybrid Automotive has had some delays. Not too bad. A couple of weeks? But it's an ever-changing situation. Check the web site for latest details.

 

I have recently gone through a similar situation on a 2005 Prius with 220K miles- I knew the battery was somewhat marginal since it did do the up and down charging symptoms when driving it regularly so I ordered a NewPrius Battery - however after it sat for over a week in mid March I got the red triangle regularly repeating and Dr. Prius and Torque apps indicated a bad block 9. unfortunately due to CV19 the new battery was backordered too long for me to wait, as I needed a drive-able car. I found a fairly local (50 miles away) supplier of reconditioned cells for $15 each and picked up 4 of them. I took the battery apart over a weekend, measured the voltages and found one of the cells in block 9 failed with only 6 volts compared to all the rest above 7. I put two of the replacement cells with the highest as received voltages in block 9 and moved the remaining block 9 cell to replace the lowest voltage cell in the other blocks (I think it was one of the block 14 cells). I then hooked up all the negatives and all the positives to balance all the voltages and put it all back together. Initially it seemed to work fine but after a few days the two new cells in block 9 were enough better than the rest so that block voltage approached the delta V amount that came close to tripping the red triangle. It was good enough to drive and the more frequently I drove it got a bit better. But still the NPB backorder was still well out there. I then found a local auto recycler that was selling a complete battery assembly for $200 (given the CV19 they had too many on hand and were discounting them to reduce their stock). I intended to use it as a unit to take my time on to convert to the NPB while still having a car to drive. When I got home and checked it, all the cells looked pretty good so I purchased two Imax B6Ac hobby chargers and went through the discharge/recharge process like the Russian guy on Youtube shows how- it took a while but all of the cells now exceed 6000MA when discharged down to 6.3 volts. So I think I now have a pretty good used battery - and of course just in time for the NPB to be delivered a couple of weeks ago. In any event the quick fix that I did with the two replacement cells is still working even with the reduced driving due to work from home and CV19 limitations. It still does the discharge/ recharge thing but is way more stable than when I first purchased the vehicle in December of last year. I have found working on the batteries to be really easy and a couple of Youtube videos and tidbits on how to set up the chargers from this list to be extremely helpful (including dealing with the buss bar corrosion cleaning) In retrospect given what I need the car for,I probably could have gotten away with using all four reconditioned cells and doing the hobby charger thing on the original battery (with maybe a bit of wack-a-mole down the road as one or more of the old cells went the way of the first one that went bad). I will probably still install the NPB since I already paid for them, to see if my mileage will improve- although I am curious how this reconditioned $200 battery will perform as well. I might just install it and use my original battery to convert to the NPB before reinstalling it - or maybe find a dead battery Prius locally and get some of my money back as I suspect not using the $200 battery will hasten it's demise

 

Nice to hear from you again... You might get more replies if you add some paragraph spacing in above block of text... It was a battle to read through it all without getting lost amid the words. Anyways, sound like you're well learned on all the details of the best way to work on packs. Have you done much deep cycling / reconditioning of other packs yet?

 

I set the hobby chargers for each cell at 7000ma for max charge and charged at 3 amps, discharged to 6.3V at 2 amps repeatedly - one of the chargers was a SKYRC brand, the other was a generic brand - the SkyRC had a "re-peak 2 times menu item that the generic one didn't ( although I don't really know what that did differently). After doing this I would only recommend the SKYRC unit and not try to save a few bucks as it seemed to give more consistent results. Some of the cells only took a couple of charge/discharge cycles to get above the 6000ma discharge rate - one almost made it to 6500 - the better ones were on the outside of the pack as expected - blocks 8,9 and 10 took more, one of those took about 8 cycles to get over 6000

When you ask about deep cycling/recycling, how does that differ from the process that I used? Is that the Prolong charger type of charging?

 

Well... Measuring amount of energy making its way into the battery requires very expensive lab grade electronic gear. The SkyRC chargers are only measuring how much electricity is being sent, not how much is being received... Some of the electricity dissipates as heat and NiMH don't last long if they get too hot! Also the prolong charger is designed to send an oscillating pulse, which is the most efficient way to clear up the poorly conducting crystallization. The NiMH algorithm in SKYRC chargers does this a little bit, but not as well as Prolong device. As for discharging, at first, I too was apprehensive about going much lower than 6v and if you had $30K in gear like my buddy Joe has, there would be no reason to discharge lower than that. But in my experience discharging down to 1volt with light bulbs yields better results if you're using inexpensive DIY gear. Also I charge up from that low voltage in stages with lots of fans blowing to keep the heat away. I also use a thermal camera to search for cells that are running too hot so I know they need to be replaced before they fail.

 

I went through this with my son's 2005 Prius. Fun project to find and replace the bad cells. Easily doable with standard tools. Low risk of shock. A bit tedious as I recall, because the cells are linearly installed (think donuts on a rod), and you might have to take a bunch apart.

He had bought the car used. Seems some cells had already been replaced. After we replaced 2 and reassembled. No reconditioning. The car ran for 3 months before another failure. This time he bought a used battery from a low mileage wrecked 2009 Prius for $300. Been going strong for almost 2 years.

I have 2 other Prius's, 2009 and 2007. If either was worth keeping and I had the battery fail, I'd look out Green Bean Battery | Reconditioned Hybrid Battery Company. $1500 for the lifetime of the car (and is transferable), East Coast of US only! I have no experience or relation to them. Just something I can across while trying to help my son.

Good luck

 

Thanks for the information on how you do it- Sounds like you remove the battery cover when you are using your Prolong charger to measure the charging temps real time. I assume that you have done numerous rebuild/refirbs. How long does it usually take using the light bulb discharge method for each cell to get down to 1 volt or do you do it in blocks (2 cells at a time)? Once down to one volt what would be the best recharge amps setting to recharge at so as to not damage the battery and what stages/steps do you use to bring them back to full volts? in a typical used battery in Gen 2 and 3 cars, what is the amount of cells that get replaced for running too hot?
I originally bought this car to simply use as a temporary driver while I fixed the head gasket on my normal driver. But, being an engineer, the technology in these cars have been fun to research and learn how it all fits together

 

--Prolong Charger is so you don't have to take the battery out of the car and don't have to take the main cover off... The first two rounds of reconditioning can be done this way as long as you don't have any bad modules. The the third round too... But I prefer to build load test and self-discharge test data on a spread sheet and eliminating corrosion so pulling the pack is needed for that

--Light bulb discharge of a module (6 cells) down to 1 volt takes somewhere around 45 mins, sometimes faster, sometimes slower depending on overall health. I sues a 12v 50w and a 12v 20w halogen bulbs on a module and switch to just one bulb when voltage gets low.

--Recharge amps I decided on were based on the 120amp fuse divided by 28 modules or ~4.3amps recharge, though sometimes I push it to 4.4amps. However, these sells because they're lined up in series can handle a hundred amps, so maybe my logic isn't as clear as it need to be. But in all honesty it's probably my impatience making this determination. Lots of cooling fans and not charging up from 1volt all at once was a lesson I had to learn the hard way when water balloons over module vent partially inflated.

--Yes, if you have an engineering backround a Prius will keep your mind way more entertained and engaged in learning way longer than a standard fossil fool vehicle.

 

You said yourself replacing cells only worked for 3 months. That is basically what Green Bean does. Having them replace the pack every few months gets tiring. If they were not backordered you could get a kit of new cells for $1600 basically giving you a new battery. The only recommended cheaper alternative is to get a pack from a low mileage junk Prius.

 

Yes, but GreenBean does way more testing and analysis than DIY builders can do and somtimes their rebuilds last a few years, not just a few months. If I had one of their packs I'd definitely make use of their lifetime warranty for as long as the company survives, which likely won't be much longer...

 

I have a full set of Best hybrid battery cells in stock and ready to ship.
Contact me directly if you are interested in purchasing it. 608-729-4082

 

If this a competitor to newpriusbatteries? I have not heard of them before.

 

LOL. Not a competitor. More like a customer of his.

I work on hybrids for a living.
Been working on hybrids for over 15 years.

I happen to have a set of his here. Among all kinds of other hybrids batteries I install.