Analyzing, refurbishing/repairing a dead hybrid battery pack (2000 Honda Insight)

[eq1]

My stick-level job restored a lot of lost capacity. But since then I've achieved even better results with a DIY grid charger, but probably more importantly, deeper-than-normal discharge. I'm pretty certain just this last cycle I did, where I let the pack discharge by leaving the car in autostop, put it over the top.

Using autostop I was able to discharge the pack quite a bit more than other in-car means, down to 137V, about 17% SOC, and then I used the grid charger to balance charge ('soak' charge, full charge). Whereas before I was only able to discharge the pack in-car down to about 45% with multiple state of charge resets using the OBDIIC&C gauge/controller (and got my first negative recals at about 52-62%), now I was able to take the pack down to 46% without any problems, still get 40-50 amp assists, and the pack rebounded to 150V (at 46% it was down to 147V, but after sitting it came back up to 150V; normally the pack sits at about 158-162V at about 75%, so the fact that it came back up to 150V is probably a good sign)... I could've gone even lower than 46% under normal driving circumstances...

[Formula413]

I have a question about pack refurbishment, I asked in another thread but I haven't gotten any feedback yet. How long should a subpack be rested after charging before performing a self discharge test?

[retepsnikrep]

I would say a week. You must be consistent to within a few hours or so for all the sticks to get useful/accurate data. Note when they come of the charger then a week later discharge them and note results.

This thread shows a members fairly cheap but effective stick testing setup.

Stick discharge: Carbon pile battery tester? - Insight Central: Honda Insight Forum

[sandt38]

MetroMPG- Thanks for assembling such an in depth, cohesive account of your experience with the Insight battery rebuild!

I am an automotive technician in central NC who has been rebuilding Prius batteries. My shop, and a friend's shop in Raliegh have been active in training, meetings with battery engineers, electric model users, and other professionals across the country who have stepped outside the "toss a pack in it" box and figured out how to do what most shops will not do... dive into the dreaded hybrid battery pack and rebuild it. We have opted to find our own methodology, equipment, and approach to reconditioning batteries outside of the only other option offered by AR&D, at a $90K pricetag with royalty fees of $150 due for every cycle.

While I have done work on several Honda hybrids I was presented with a 2000 Insight with a bad pack this week. My challenge was to ensure that I could properly manage my cycles to compete with an AR&D rebuild that this customer has had done on his 2 othe Insights.

Your detailed information here, and tear down images made me confident that I can achieve the same success that AR&D did with this gentleman's other reconditions. I am grateful that you took the time to research the pertinent info for experienced reconditioners and put them all into a single, well organized place complete with your end results. I was so impressed that I joined the forum to see what else is offered here (and to subscribe to this thread).

Cheers!
sandt

[eq1]

FYI, since my initial work based originally on info in this thread, and similar info at Insight central, I've found that 'blind' cycling isn't a very good strategy to recondition packs. For the most part, the reason is that even very bad sticks can discharge 6500 mAh at a 10 amp rate... You can do 3-5 full charge/discharge cycles and end up balancing the cells to a degree, and will probably be able to spot the really bad sticks if you graph the data. But it takes a long time, and the data aren't very indicative of... much. I wrote up some info at this thread covering my last job/'research'. You can probably skip over a lot of it, there's an outline of a strategy at the bottom of the thread:
stick, IMA battery reconditioning, testing - Insight Central: Honda Insight Forum
These methods take more hands-on, active work, but you can generally break up the project into easier chunks and it doesn't take as long overall. Plus, the data produced are much more informative - you'll know what to expect, which sticks should be replaced, which sticks to pair-up, etc...

[sandt38]

eq1-

Thanks for the info and I will read the thread.

I am using different chargers, that effectively operate the same way that the charger used in this thread work. However, I am not really blind cycling, as I have some very specific battery load testers, to determine effectiveness of the charge. The load testers and chargers are computer based and provide all graphing and analysis information for me, simplifying the analysis of the effectiveness of my charging/cycling.

Sorry, but simply based on the fact that so few people in my industry know how to do what I am doing, and even fewer have really spent the time, money, and effort into figuring out how to do it, I cannot really share the equipment or methods/algorithms I am using... it is simply a matter of making money.

I actually read the entire thread and pulled out certain nuggets I needed to set up my chargers. However, I did notice a few things that I decided to do differently. For example, the charge and discharge rates used are not the rates I elected to use. Not only that, but they are not using what I have found to be the best algorithm to introduce a charge to the chemistry of the batteries in these packs. While the methods described here will work (I am surprised, actually, that the cell/module specifications enclosed within are very, very close to the Gen2 Prius packs, and I have a good amount of experience rebuilding/reconditioning Gen2 Prius packs) I have found that a straight charge is simply not as effective at waking up a weak or dead module as a long term (and well warranted) solution.

So I am not really walking into this blind. However, the specifications enclosed within, the time and effort of the spreadsheet with nicely done results are worthy of tremendous praise as they saved me a lot of time searching for what I needed to establish a baseline for my reconditioning of the packs.

Again, I will check out the thread you linked, as I am always interested in learning how to do what I do even better. So thanks for the link!

[Cobb]

I have to admit as an owner of an IMA powered vehicle and modulator of the forum I tried to follow the comings and goings of this the best I can. As it turned out the more we try to learn it seemed the less we knew.

Last I followed it there was discussion of draining the pack to a very low voltage if not zero and in turn you restored almost full capacity of a weak stick.

Ive decided if I need some hobby power Id just buy a prius pack and if my car or a used hch in my future needs service in the ima departmetn Id just buy a new pack from one of the several vendors out there.

[sandt38]

Originally Posted by Cobb

Last I followed it there was discussion of draining the pack to a very low voltage if not zero and in turn you restored almost full capacity of a weak stick.

I am honestly not a fan of how Honda provides us with such limited information on the goings on in the battery packs of their hybrids via professional level scan tool PIDs. In my experience, Toyota is at the top of the chain in this regard.

After opening up the battery pack of the Insight, and performing my cycles and testing, I found that I wasted a ton of time on the rebuild. I have had to cycle all my sticks to the point where testing was feasible, and I found a lot of dead sticks. I now have 20 sticks on the way from a used pack, and I am forced to test all 20 sticks in the same manner to properly rebuild the battery. All Honda needed to do was provide me with just a little info to make my life easier. Not only that, but this battery has a relatively large amount of cells that are worthless in it compared to all the Toyotas I have done thus far.

Conversely, Toyota provides us with a ton of information on what is going on in the battery packs. I can look at each V-block (or pair of modules) with the pack in the vehicle while in use, and view the blocks' behavior. This facilitates a simplicity of finding bad modules, and performing an effective, efficient repair. As a general rule, what shows bad on a Toyota is what is bad. I have only had one Toyota that had any modules bad outside of the reported failed V-block, and the customer had driven the car until it was no longer drivable, even overheating the MGs and inverter. That car only needed 3 modules, instead of just 1 or 2 as I see in most.

To further complicate matters, you cannot get any new 6.5 modules for Hondas. All that is available is the 8a sticks. You cannot use a mixture of 6.5 and 8a sticks, and relying on used modules is spotty at best.

To summarize, I too will simply be grabbing up packs for the Honda (and Honda inspired designs I have seen in several other Hybrids) and installing assemblies instead of rebuilding them.

[cavalon]

So I've read almost all of this. What I haven't seen and I have a question about is whether solely grid charging would be sufficient to sustain the battery in the cases where there might be a few bad sticks. Or is cycling all of the sticks the only way to sufficiently operate the battery again. I understand the cycling will increase their capacity, but not necessarily balance it. Grid charging will balance it but not increase their capacity. But if a pack is balanced but a few sticks have lower capacity, is all this will mean be that the battery will need balancing more often, since some will discharge/charge at different rates? I don't mind having to grid charge more often if I can avoid taking out the whole battery and going through weeks of testing. And I'm aware of other potential problems that can occur, I am presenting this situaion in the possibility that the only thing potentially wrong in this imagined scenario is bad sticks and/or imbalancing.

Thanks so much for these amazing posts!

[MetroMPG]

"Tavarish" writes some really good articles on Jalopnik about refurbishing/repairing interesting but otherwise flawed vehicles.

He just posted about buying a dead-pack gen. 1 Insight, and linked to us here (calling us "ecomodders.com"):

How To Own The Cheapest And Most Reliable 70+ MPG Hybrid Ever Made