Gen II Prius Individual Battery Module Replacement

Im seeing some voltage drop in a couple other modules so am going to swap them out as well. Anyone know at what point a voltage difference in the modules will trip error codes? And does this only happen within the paired modules or across the board?

 

The car cannot not see voltages within pairs. It only compares one pair to the all the others.

 

Ah I see. So would the best thing to do is pair higher voltage mods with lower to yield an average result? My mods range from 7.75 to 7.91 so I think I could do the math and get them all into close pairs. I havnt wired them in parallel yet but ran my last discharge cycle to 7.6 volts on all the mods and they still have this variance in voltage. Figured they are where they want to be and even after the parallel equalization they would likely creep back to where they want to be.

 

Yes, this is a very important aspect of battery rebuilding......you need to match both capacity and load response to keep the codes away.

 

Sounds good ill be doing the load testing later today. Then arrange the mods according to voltages and load response. After this, is is still recommended to do the parallel equalization prior to reassembly and installation?

 

Yes, it is essential to do parallel equalization prior to reassembly and installation.

 

Good to know, thanks! Ive tried to read as much as possible on this whole project but I have often seen conflicting information. Guess everyone has their own method that varies with different generation mods and quality etc... not to mention personal preference based on prior sucess. Heading to home depot again for more wire!

 

There are a lot of people with different ways of doing it but there really is only one "right" way of doing it. The steps to the right way are simple
1) charge and load test the modules
2) measure/restore capacity by charge cycling
3) match pairs by capacity
4) perform parallel equalization

 

Our latest development allows to check the pack WITHOUT the need to install it on the car. We can check the whole pack as is - in assembled mode, check modules, check battery computer and sensors when the pack is OFF the car as well as ON the car. Applicable to 40, 38 and 28 module packs.
Note: it is important to check Battery Computer before assembly and without the modules. From our experience battery computers are faulty sometimes which may result in the error code. If that is the case - then voltage sensing lines could be faulty as well due to corrosion - espcially on the NHW-11 model (38 batteries). Visit our site for details at http://www.hybrids.co.nz

 

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Only thing is I would switch #1 and #2 because load drops may change after cycling and that's really what the hybrid ECU is looking for while the battery is in use.

 

So... further testing has resulted in 4 other modules that load tested bad.. 2 more sheets of paper full of numbers that are gibberish to a non do it your selfer hybrid owner, a messy garage, and a beer when you've made it through the night with some decent progress! I found 4 other decent modules in the junkyard pack, cycled them and voltage drops are in check, sandwiched them while charging in what I could get my hands on with a module for a spacer, then I had a beer or two to monitor voltage drop, now im posting pics of my chaos! Haha. As bad as the pics look, im actually getting some hopeful numbers and should end up with a matched pack, albeit a degraded one. But its all practice to build the right pack with some newer gen mods. This will be a walk in the park with some good modules. Enjoy the pics fellas, this is a grab what you can to get the job done type of set up and no my garage wouldnt be this much of a mess if this project wasnt so involved haha!... and yes that is the prius 12v battery running my charger, while being charged by a another charger.

 

Thanks for the pics. It good to see the effort you are putting into this. Sometimes the verbal descriptions don't adequately quantify the work.

 

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G'day mate, do not waste your time on those 38 modules. I have conducted dozens of tests on them in our Lab. Resisual Capacity is quite low considering the age and you'll find them failing just one after another.
EV Energy analysed their poor performance and no longer manufacture those. The new ones with the silver sides are improved ones with the better interconnectors to reduce resistanse. Those plastic ones are also known to be leaky.
Advice - just change those to the ones from the NHW-20 Prius (28) or Camry (34). They will fit. The only 2 differences are:
- newer modules only use one screw not two from the bottom (not an issue),
- newer modules use different shape fixture for the temperature sensors - not an issue as sensors from NHW-11 and NHW-20 are the same 10 Kohm thermistors - you can use those coming from the newer Prius in your older model. Just make sure you connect them correctly as they use common ground but wiring is not properly color-coded.
As we speak my friend is going to pick up Camry Pack (34 modules) which I soursed for him from the wrecked Camry 2012 to be put in his Estima (30 modules). Although I can give away heaps of those old modules with the known measured capacity of 2.3 - 2.4 Ah I personally think it is just waste of his time to use old ones.

 

I only continued this process for practice and to see if I can get it matched up to pull no codes and to drive it a little bit while I round up newer modules. I had no problem doing it once I realized im "practicing". I already realized these modules are degraded and not worth investing much time but I also realized the knowledge and experience gained was worthwhile. Now that ive got a good grasp on what im doing, the next pack will be a breeze and hopefully this pack will last without pulling codes until the good pack is completed. To be honest I only hope for a month or two, if it doesnt last I dont care, it was still worth the practice. I do appreciate your input though

 

Nice pictures Dana
Not to go off topic but when you connect them all in series is there a danger of high voltage . How do you keep this safe connecting all of these together with 2 wires . This part scares me more than all of the other steps .

 

The only time they're in series is when the buss bars are connected. The voltage equalization is done with a wiring harness in parallel. Once you have the case cover off, you are in a danger zone even with the service plug removed, but you'd have to almost be careless to touch the wrong stuff imho. I've just always been careful and knew how I was in danger, when, and at what voltage etc... once you have the case cover removed, work on one side, remove the buss bars, dont get anywhere near the other side of the pack with your hands, nor near where the computer is at. I used a cordless drill with an 8mm socket and an extension to maintain distance and or possibility of subconsciously grabbing the other side of the pack. Also, leave the black plastic covers on the side your not working on. After this whole project, looking at everything, its not that dangerous if you understand how and when it can be dangerous. I never used class zero gloves because I had a good understanding of when and how I could die or be in serious danger. I must say that although being new to hv hybrid batteries, I am smart enough to know these things. I needed a little help to understand how toyotas computers read the battery's health etc... but if you take the case cover off and understand series wiring and look it over good, you will know where danger is and realize that you'd have to stick your bare fingers in wierd places to hurt or kill yourself. But saftey is still a must so my process was this, (after carpet and bolt removal etc...) :

Heft the pack out of the car, try not to scratch your paint going out the side door. I did this alone, an extra set of hands would have been nice.

Get it to your bench and remove the case cover. Dont touch anything, just look at it and inspect it. Watch some Youtube videos and read alot of priuschat first of course.

Remove the black plastic covers on one side only, then remove all the 8mm nuts on the buss bars. Wearing some gloves and using a thin plastic wedge of some sort, pry the buss bar of the pack. I say plastic because if you used a screwdriver you would really have to know the buss bar pairing and could short out 2 pair at this juncture if your not careful. A bamboo skewer may also be a good tool here.

Once you have one side of the packs buss bar off, take a sigh of relief and know that you just went from nearly 300 volts of danger, to about 16.

Now you cant die. Remove black plastic covers from side 2 and repeat nut removal and buss bar removal. Then get your multimeter out and figure out if you have any bad cells etc...

Im not sure on the dangers of the parallel situation, I acted as though the amperage could kill me even at the low voltage in this stage, so I treated it like it was a buss barred pack at this point again, not at first, but once you have all the positives connected, and begin on the negatives, I treated it carefully and methodically. This part is tedious with many 12" wires requiring stripping at both ends etc...

Anyhow, hope I didnt over explain, or under explain and hope any others can see this and get something from it on knowing the dangers. If it scares you once you have the case cover off, or dont grasp how its wired up, and when your in danger, message me for a number im willing to explain. Im no expert but do know what im doing to some extent. And any guru's that feel my methods are dangerous or anything, no offense taken. I have a good background of electrical and mechanical knowledge, as well as about 8 hours or so of research and you tube videos on prius battery rebuilding to get where im at. Cheers

 

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Just be smart when touching anything hooked up in series (use insulated tools with rubber / plastic handles or materials that don't conduct like wood / plastic) and if you need to touch anything you're not sure about, check it with a volt meter first. General rule of thumb is if it's over 50V DC then you should have a pair of gloves on (even doubled up dish gloves will provide reasonable protection in this case). Battery balancing is done in parallel so no voltage worries there at all either.

 

In you description you missed the step of removing safety plug and testing for the ground fault.
NHW-11 are leaky (year 2001 - 2003 impacted) - meaning that there is a huge chance of voltage between any module and the casing. Meaning that one hand touch with the casing on the concrete flour (conductive) and you standing without the isolation matt - CAN KILL YOU!
I have special section on safety on my page in case you are interested:
Health and Safety » HYBRIDS
Also using wires like you did - unmarked - can lead into trouble - suggest labels
Putting 40Kg pack on the rubbish bin as a bad idea - unstable and unsafe
Putting wood underneath - good idea.

Stay safe

 

Your right, service plug comes out as soon as you pull the carpeting. As far as the wiring... it was speaker wire with one side silver and one copper. I used that as my label so to speak, silver was always negative and copper always positive. I had the packs on a couple stools, the trash bin was about the only I could find to do the equalizing on. Thanks for the info, good call on the service plug. I forgot to mention it but hope anyone attempting this job researches first and will be well aware that it comes out immediately.

 

Yeah the first thing I did was unplug the red safety plug . Now it makes sense when you say parallel when you connect them all together I was just imaging sparks coming from the wire as you hook them up .



Couldn`t find settings for 6 cell I guess this is automatic setting . Set the other parameters such as discharge cool down and max charge .