Gen II Prius Individual Battery Module Replacement

I'll try to find time in the next few days to do that. I want to exercise it a bit first, I have no idea how long it sat.


Merged.

Question - when I have force charged in the past, I could take it past green bars - if FCed long enough, the bars top out and then go grey. Would this not be a more valid test? It would absolutely verify that the SOC has hit at least 80%.

I have not logged with TIS yet - can I narrow down to the specific variables I want, or do I have to log and then pick out the streams to graph later?

I'll dig into TIS tonight when I have time and the laptop is charged back up again. And it's cooler. Swapping the packs when it is 90 degrees and crazy humidity really saps my energy. It MIGHT be as low as 70 at midnight in the next few days.

 

It doesn't matter how long it sat. If you're concerned about how long it sat, the last thing you should do is just drive it. You should charge it. It is already sufficiently "exercised" after the first full thermal cycle and dozen accels/decels. A single discharge test per my sig will "exercise" it more than sufficiently as it forces full SoC range of 40-80%.

I've never witnessed the phenomena you describe with gray bars on 8 different cars. When logging with Techstream, it becomes very clear when the car is no longer charging. After a 12V reset per the test, it's not uncommon for it to go a little higher than 80%.

I will revise the test to include a recommended data set for capture.

Lastly, the 70°F is a MINIMUM. Warmer is better because it ensures the compressor runs at max load.

 

Am back on the road now .

My replacements hit Saturday, installed into first position easy ..started the discharge/charge with the Toy charger and it hit my maximum setting 7500 ..so set to 1 more cycle only and let it run. Was putting on cover Sunday morning and just to be sure reran voltages on all 28 ..#17 was at 6.86v so I changed it out with my just purchased spare and ran its discharge/charge with the Toy charger...it topped out at 7500 mAh also, so repeated one cycle only and buttoned it up .

Been driving all week, anti-climatic at this point...but I do have a nice shiny chart of my cobbled together HV pack . The pack is no longer an unknown .. I have a base line of the cells ..still don't know how long this will work again before throwing codes..but was nice to see the last module go out of tolerance (before putting back in car) and referring to my spreadsheet to see that it was one of the older cells.

Kenny

 

Well my 06 has done that as long as I can remember. It goes grey right when the engine shuts down even with the gas floored. I must have a weird one ;-)

I FCed it to all green before running the test drive back to the recycler, so I could verify all the block voltages went up sufficiently. It was purple in the driveway, no great surprise. Ran it back down to bottom blue, so came pretty close as it is.

I'll work on the test soon, to see how it measures up. 55 miles of beating on it, and it's at least still error free ;-)

 

Is the "block" (module pair) number shown in the code? ie- P3010 + block number? I had a P3015 and the bad one was block 5 using Torque. The bad module was the tenth on in from the end opposite the ECU. Some posts seem to confirm this theory, but a few don't correlate. What is your understanding?

 

Gen1 are numbered FROM the ECU.

Gen2 are numbered from end OPPOSITE ECU.

Block 5 would be modules 9 and 10 from the end opposite the ECU.

 

aMhr?

Did he commit a typo here, and actually mean mAhr? He used it in more than 1 post. I can't find a definition for aMhr.

 

Yes, a typo, it should be mAhr.

 

OK, after much reading, and good input from S Keith, Greasemonkey007, and jdenenberg, here's where I'm at.

I've got my workspace all set up.



From left to right, I've go my battery charger (2A, 10A, 50A).



My super manual Samsung Galaxy Tab A data logger/note taker.



Metering with load.



I have a couple of resistors to use as an alternate load. The larger one is 20W 8 Ohm, which will reduce the line current to ~ 850 mA. The smaller one is a 10W 10 Ohm, which cuts the current to about 500-600 mA. Initial reading led me to believe that I'd have to charge at about 700 mA. From further reading, it sounds like that is because the charge/balancers many are using has an upper limit of 1000 mA. I've seen that many are charging at a rate of 5 Amps. I still need to wrap my head around this issue a little better, when the time comes.

The left meter is set to Volts, the right to Amps. The load is in series with the ammeter and a single pole, single throw switch. The bulb is a 70W landscape halogen spot lamp. The two meters are connected to the module in parallel. One lead of the Voltmeter is connected between the switch and module. This allows me to continually watch voltage while switching the Ammeter and load circuit on and off. Consistent with my frugal theme to this project, I downloaded a free schematic app. Here is the circuit schematic:



I actually mounted the switch to the corner mounting hole in the left bottom corner of the battery case to keep bench clutter down.



At the battery, I've bent a couple of 1/2" copper pipe hangers to improve the attachement points at the module. The holes are just a hair small, so I had to open them up by drilling out with a 3/16" bit.



In order to develop a more tactile understanding of the many things I've read and been told on this forum, I've done a little experimenting. First I checked the SOC of each module, and the amps of each one with the 70W load, after 20 seconds using a stop watch (smart phone not pictured).

As I said, I've done some experimenting/testing to get a better feel for how all this fits together. I did two SOC test series, a day apart. Results are on the left, below. I also did a load test of each module using the 8 Ohm resister as the load just to see what would happen (don't ask me why, I just did, LOL). The data from that is on the right. The QA Engineer in me compelled me to do 'as found/as left' open voltages as part of my load test protocol. It is in the center.

I also wanted to play with a few of the modules to see how linear they discharged over a little more time, so I discharged them with the 70W lamp as the load for 15 minutes (using a stopwatch) with spot measurments at 0, 10, and 15 minutes. This is the data on the right, again with 'as found/as left' open Voltages.



As you see, module 19 (Block 10) is suspect. I decided to discharge it and track Volts and Amps every 2 minutes, since I've eventually have to discharge it anyway. I was still operating under the assumption that I had to discharge at or below 700 mA, so I used the 10W 10 Ohm resistor as the load. It crossed the 6 Volt mark early on, but I wanted to see how it behaved under the test, so I continued for a total of 60 minutes. At the end, I waited 10 minutes for the module to recover some, then performed an open circuit voltage measurement, and a 20 second load test using the 70W lamp. Here's that data.



Moving forward, I still plan to repeat the full 20 second load test for all the modules. Then the decision point. Do I purchase a Hitech X4, or do I go 'commando', and just use my charger with a stopwatch and my meters?

I'm inclined jump in with the charges, but I still need to create a protocol. I'd welcome any insights, on what this protol needs to be to prevent hurting the good modules, and be successful.

Thoughts?

 

The hobby charger I used (reaktor 300x2) had a delta V cutoff for charging the nimh's. Also, it calculated total mAH going into, and coming out of each cell. WIth your method, you'd have to take more measurements, and manually interpolate/calculate capacity.

Also, the first cells I received off ebay had good voltage, but held poor capacity : my cells held about 6000mAH average, whereas these held about 1800mAH (they were returned to seller). I didn't pay attention to their discharge amperage, so maybe your method would have detected those as bad cells.

Of course, if you aren't planning to cycle charge/discharge your cells, then maybe you don't need those features. Just swap in a couple replacements and be done with it.

 

I do plan on charging/discharging all of the modules just as other have done. I'm just contemplating doing it manually, and doing manual measurements. I can set up Excel to do calculations of the fly. I believe that the most critical measurements are at the starting point, and as I'm approaching the end. The middle should be uneventful.
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I need to understand better how to identify the endpoint of the charge and discharge cycles, so I know where to increase measurement rate. I also need to know how fast I can charge/discharge the modules, without introducing unreasonable risk of damaging them. It may turn out I already damage module 19 in my set by continuing to discharge even after decay of Amps slowed considerably. (Not sure if I reached some kind of cell plateau, or if the heat in my load was generating more resistance. Can I get away with charging/discharging in pairs to save time? (I found where some one (Britprius, I believe) recommended to someone else to charge them in pairs, and S Keith advised me not to. They both appear to be very knowedgeable.

If I can create a protocol that allows me to use two chargers in series (24V total), like one guy did, I'd consider that.

There's so much to read and learn. There are many conflicting opinions. What I learned about electronics was a long time ago, and there wasn't too much practical application experience. My background is chemistry, inpspection, and test & measurement, not electronics engineering. There's much more that I don't know than there is what I do know. But that doesn't intimidate me. At some point I'll just hold my nose and jump of the high diving board.

Thanks for the comment,

Mike

 

I think you can charge two at a time, or even all 28 at a time, just like the car itself or that $300 hybrid battery hockey puck does. You will no doubt get better information if you do them one at a time.

I'm nowhere near these other guys in knowledge, but I think Steve has previously pointed people to battery university. This is the page on how to charge nimH's: Charging Nickel-Metal-Hydride Batteries – Battery University There arent any detailed instructions or blueprints, but you get the idea that hot batteries are bad, and overcharging too much is bad. At least nimH's dont catch on fire like lithium batteries when they're overcharged.

Good luck

 

OK, It's coming close to crunch time, so I need to check myself here. Though I'm a DIY'er by nature, I'm an Analytical Chemist and a Lean 6 Sigma quality professional, not an EE or even a frequent electronics hobbyist. I've read most of the threads about this process from this forum (some several times), have done a lot of experimenting/testing on a $15 7.2V 1200 mA NiMH RC battery pack, and tried to think this through carefully. I'd feel a lot more confident if some better minds than mine in this forum can offer some critique and analysis.

For a number of reasons I won't go into, I'm going to try to recondition my modules without an RC charger/balancer. Is my set up shown in my post above the proper way to determine Amps when I'm looking for my charging endpoint?

I ask because it seems many use a 50W halogen lamp as the load. Since V=IR, I believe that make current dependent on resistance. I'm doubting myself because 1) it seems at risk for variation. So as voltage drops, resistance changes from the decrease in temperature as the bulb cools. I'm guessing that the dR/dt might be neglible, but don't know.

If I wanted to use a resistor as the load (for measuring), what would be the appropriate Watts and Ohms? Will a higher Watt resistor heat up less than a lower one? I'm thinking a higher wattage than the total nominal power of the module. I'm not sure how to determine Ohms. I'm guessing 10 Ohms because when I experimented with module 19, it discharged at which I believe is which is only slightly below (650 mA @ 5.9 V) the C/10 I see recommended a lot. If this is right, then I'm wondering how much I'd risk damaging the module if I discharged for an hour (or 6.2 V, whichever comes first) with a 2 Ohm resistor (C/2?), then finished the journey to the 6 V target with the 10 Ohm.

Second, I tested the open current out of curiosity without the load in series (though I've read is not the proper way to do it), and got a 15.5 A reading. That would be 70 W at 6 V and 90+ W at 7.5V, which I wouldn't think possible.

Thoughts (or prayers if my approach is hopeless) are appreciated.

Thanks in advance,

Mike

 

I can't imagine a single one that is justifiable.

I haven't commented on your setup or proposal because I don't have the time.

Good luck,

Steve

 

Nice 'tude. Now I know the sound a tree makes in the forest when there's no one there to listen, LOL. Thumper's Daddy used to say "If you can't say anything nice, then don't say nothin'"

 

I think considering Steve is one of the more knowledgeable people on this board regarding the subject you might check the ego at the door and look a bit further into the fact he's suggesting your setup is seriously lacking and I have to agree. I get you don't have alot of cash handy but any smart person looks at risk/reward so doing it right actually saves money in the long run. If this is an experiment on your part then great, let us know how it goes.......if you're actually doing this to rebuild a battery pack then there's alot better setups than what you have decided on so far. There are 2 very well tested methods this thread goes into either using a hobby RC charger or with an HA grid charger and both involve load testing after cycling to see where you stand.

 

It's not an attitude thing. Even a smart person can't create something that doesn't exist. There are those that have done this without the RC charger, and it appears successfully. No one has yet said it can't be done; succsessfully, it at least appears. If he can't help because he can't buy into my motives for needing to do it this way, or he doesn't know the answer, then just don't respond. But to take the time to respond that he doesn't have the time to respond is just a snarky (actually his second) way of expressing disdain, and not necessary. If he really didn't have the time, he wouldn't have responded at all. That's his ego compelling him to respond like that, not mine. When you say 'us', does that mean that the rest of the forum has you speaking for them?

I'm not trying to provoke you or anyone else, and I do understand your point about risk/reward, but isn't the cost/benefit as it relates to my situation my decision to make? If it is a fact that it isn't possible to do it, then say that. That would be helpful to know in itself. Perhaps, to make it work I'd need to buy other materials or equipment that would drive up my cost. Maybe, for instance, a resister won't work to regulate current at an acceptable rate because I'll keep burning them up from the heat so it requires some kind of transistor circuit that controls current (which has it's own cost in time and/or money), it would be constructive to say that as well. If one can't contribute because they don't know the answer, then don't say anything. But if there is a contribution that would improve my chances of success, then why not share them rather than hold the help ransom because of my judgement of my own constraints? At it's best, that 's just complacency, which is actually fine. Everyone has to determine the value of their own time and effort. But at it's worst, that is acually ego.

But apart from the philosophy of how people treat each other, and more to the point: Somewhere, I believe, is a process down this path that has a chance at success; maybe slimmer than the alternatives, but a chance nonetheless. Again, no one has said it isn't possible. Whatever that process is, I don't even have to understand the reason why it will work. Understanding the 'why' will happen as I follow it.

 

Just about anything is possible. Light bulb. Resistor, Hobby charger. Cell phone charger. LED power supply. fuses. Switch. Contacts. Whatever. There is no one right way to do it, especially if you are crafting your own equipment.
No one else will be doing it the exact same way you are.
The main thing is to do all of the modules in a consistent manner.
That way the outliers show up as you analyze the data.
Some variables are things like open voltage, loaded voltage, capacity, internal resistance, charge curve, discharge curve, self discharge rate, etc. You can choose how many of these you want to measure and analyze, and which to skip over.

Charging/Discharging at a high rate in the middle range of SOC is not a big deal.
It's the ends of the SOC range where the problems arise.
As long as you are reasonable, whatever level of charge/discharge you choose, it doesn't make a big difference.
Look at the rates hobby charges are doing and make your decisions from there.
I assume you are not really in a hurry, so do a few modules a day and you'll be done in a couple of weeks tops.

Nimh is pretty resilient when it comes to overcharging/overdischarging. As opposed to lithium which is not.
Make sure to keep everything extremely compressed no matter what rate you choose.

You will likely have to come back and do it all again months from now, so be sure to document your process so that you know what to do the next time you open everything up.

 

Hi .. there's half a dozen reasons why you shouldn't do this for every one reason why you should.

BUT if I desperately "had to" fix car with such limited tools and I was going to DIE later that day if I couldn't get the car running, I would consider.....

-swap out any obviously faulty modules resting under 7v with known good module.
- grid discharge entire pack with globes as per instructions earlier in this thread.
- hit pairs of modules (in series) with the 12v charger (set to 10A) for exactly 5 minutes per pair to elevate all modules just enough to start the ICE.
- install pack in car and force charge to 80%.
- drive with fingers crossed.


but naah .. just don't

 

Dear Mr. Wall of Text,

Don't be so sensitive. I don't have time to stroke your fragile whatever. You mentioned me by name and said you were hoping for input. I chimed in. Thanks for the armchair psychoanalysis BTW. Amazing how much insight you get into someone's character from their posts on an Internet forum. If you had any idea how much time I spend on this forum or in PMs providing assistance, how would that influence your analysis?

Anyway, if you give a crap:

My brain seized up when I saw the 12V charger. Forgive me.

12V chargers are typically limited to 14.4, 14.7 or 15.0V. They can't effectively charge a block pair. They also don't typically operate well at the lower voltages of a single module, but you can try.

Module 19 isn't suspect. It is bad. It must be replaced.
Modules 12 and 13 are suspect because they lie well outside the expected voltage range. They likely need to be replaced, but they might respond to balance charging. Whatever the case, they are very likely to be the next to fail.

The as-removed voltage readings and 70W bulb discharges are the only valuable data collected. The low current stuff is a waste of your time. After populating your chart with the 70W data, continue the discharge to 6.0V and record time.

Good luck,

Steve