Gen II Prius Individual Battery Module Replacement

The criteria is >.3V but, I'd imagine there is a time constant involved as well (it has to stay above .3V for a certain amount of time) I don't claim to know this for a fact but, common sense tells me you need the time measurement as well otherwise, codes would be triggering every minute on a good battery.

 

There is also a time factor in the reported data. I have no idea what the time delay is, but the figures in Techstream seem to hold and jump rather than rising and falling in a continuous manner.

John (Britprius)

 

good point John the voltage is the difference of the highest voltage in the 19 pairs as compared to the lowest. Techstream gives you the highest pair reading and and the lowest reading next to each other - the numbers are constantly changing but usually the same module pair come up repeatedly as the high and low modules in the pack,

Roy

 

DTC could be triggered by lots of things. For example - there is a threshold for pair voltage difference - varies for models of Toyota (according to some sources - 0.3v in NHW-20 and much higher in NHW-11) but also duration of that difference - i.e. if happens momentarily and does not last long enough - DTC will not be triggered. That is common logic in Toyota DTC system – no DTC recorded if event does not happen more than once within the predefined cycle.

I have logged Prius 2009 battery pack behaviour on the car with the HV Analyser attached and observed the following - during 60A current burst - there was an instant drop in voltages to 12V on one pair (6v per module) and voltage difference was above threshold of 0.3V - it was 0.45V but it lasted for just milliseconds and did not cause DTC.

Also what was observed in that live test is: the discharge curve is absolutely not flat and falls abruptly when voltage drops from 7 to 6 volts per module. In that voltage range the amount of energy battery can deliver is insignificant with what it can deliver when discharging from, say 8.4 down to 7 Volts. That is also observed in Department of Energy tests on Prius packs.

Area below 7 Volts is where the difference in remaining capacity of the individual modules plays the part. That is why when capacity is high enough and pack is operated in the shallow range - things are ok, but when remaining capacity is low due to age and mileage - then high loads force modules to drop voltage below 7V - where their discharge curves are not flat - that if last long enough and repetitive – will trigger DTC (that voltage difference is above the threshold).

That is why I emphasize the importance of rebuilding the pack from modules with high enough and equal capacity.

Play safe.

 

Perhaps I should have said discharge curve of the Nimh battery is almost flat compared with many other battery chemistry's. I have recorded a number of time on PC that at the bottom end of it's discharge curve it is like falling off a cliff. The Prius only takes the battery down to the 40% level and this on rare occasions. In fact I have only seen this once in 110,000 miles. This was towing a 2240 lb trailer (caravan) up a 20% gradient for 3 miles.

John (Britprius)

 

The current load on the gen2 batteries is more than the gen1 mainly because of the voltage difference. The voltage for the gen1 battery is over 70 volts more.
Gen1 say 20 KW out at 273.6 volts = 73 amps
Gen2 say 20 KW out at 201.6 volts = 99 amps
Assuming the electric motors run a the same voltage the boost converter has less voltage to step up for the gen1 and becomes more efficient. The figures above are not actual use figures, but demonstrates the difference.
The voltage drop within the battery through internal resistance and therefore the amount of heat energy wasted will also be more in the gen2 because of the higher current.
John (Britprius)

 

Good thinking John - you are probably right - when I install the Gen 2 modules in my Gen prius do you think that will cause more or less codes. My charge and discharge cycles on the gen 2 modules I am going to use in the spare battery are showing a very much stronger battery. My old Gen 1 modules most would not even charge to 6500 ma, the Gen2's go to 7500 ma and up with no trouble and discharge at up to 80 % capacity.

 

The gen2 modules are designed for higher currents so should give less problems as they will live an easier life as you will have almost 33% higher voltage at the same AH capacity. Ten more modules of battery.
This goes for discharging and charging with regen. This is partly why people are now re building gen2 batteries with gen3 modules. Although the battery volts are the same with gen2/3 the gen3 modules have lower internal resistance. This in turn gives them a higher current output and less internal heating losses.

John (Britprius)

 

thanks John - makes sense

Cheers

Roy

 

EV Energy Stipulated that as acheivement when they introduced newer modules for NHW-20. That was done by extra internal connections between cells.
Have not looked into Toyota Tech Docs for that Prius NHW-11 (38 modules) for a long time but 1.2V threshold /pair is for NHW-11 from the top of my head. And it has to be measured bewtween highest and lowest pair.
FYI: Standard Operating Procudure when using TS is called Stall Test - i.e. done when parked. That is the SOP for the dealership to condemn the pack.
The reason you have not seen the pack going down to 6V with your TS tool is because of the limitations of the TS tool. It will not show you that, because TS is slow and will not capture quick changes.
What I observed when HV Analyser was hooked to a car - TS was unable to capture.
Bear in mind I can run tests in parallel: with TS connected via the port and HV Analyser running connected directly to the battery.

 

Correct, if I still remember that manual correctly - 1.2V/pair threshold in 38 Module Pack.
P.S. If your friend in Canada wish to start building HV Analysers locally - let them know - we are happy to assist Canadians. There are quite a lot of chaps who moved to that part of the world whom I grew up with skiing and playing hockey. Would love to go fishing for Canadian Salmon one day...

 

Thanks for the informations, it fits with what I have observed. Will mention to the my friend the battery rebuilder re HV Analysers.

Roy

 

Roy I see you providing tips here but much of what you mention has already been vetted and from experience I'm not sure it is the best way. For instance using a charge capacity that is too low (6500 mAh vs 7000-7250 mAh) will cause issues as will a charge rate that is too high (6A is WAY too high for high SOC charging). Silver plated bus bars sound nice, but silver tarnishes very fast so any benefit there is marginal at best, much better to just use dielectric grease on the bars after cleaning down to bare copper to prevent future corrosion issues. I'm sure you're just trying to help others as we all are but there's definitely better settings for the Hitec X4 chargers (posted several times in this thread) than what is mentioned above.

 

Thanks for your post and I agree with you if the experience of others has proved to do a better job. My post was from my own experience with charging and discharging 2001 prius batteries out of the car as they seemed to work well after the procedure I posted.

The silver plating process came with my background of working with copper bus in high voltage switchgear and re-plating with contacts on AC and DC starter contacts, the silver or nickle process lowers the contact resistance of the joints and will not corrode under the contact surface, however most people would not have or want the silver plating kit and the grease is a good idea. I used a special contact grease on my silvered plates as I use to use it on outside high voltage switchdear contact surfaces (I had it on hand).

The batteries I have done have lasted over a year and seems to have done the job, however I will edit the post and delete the procedure as it may not work for everyone.

Thanks for the information and I will search for better methods of using my chargers for my own use.

Roy from Canada






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Hi this is Roy from Canada - I have deleted my information on my charging process from my previous post and hope others will not follow it as it may not work well for them.


I thank Hihy for pointing out the problems with my process.

 

Roy, no worries, Priuschat is a great community and people want to help each other be successful at whatever they are setting out to do.

Here's a couple of tips that I found useful myself:
Gen II Prius Individual Battery Module Replacement | Page 13 | PriusChat

Here's the best settings I've found for the Hitec/Thunder quad chargers:

Mode: Program Save then use Program Load when cycling other modules
Battery type: NiMH
Nominal voltage: 7.2V
Charge current: 2A (lower is better to prevent excessive heat buildup at high SOC)
Discharge voltage: 6V
Discharge current: 1A (use highest setting available)
Charge capacity: 7000 mAh
DCHG>CHG: 3 (more cycles if modules continue to improve)

Also go into User Set Program and set:
NiMH Sensitivity: D. Peak Default
Capacity Cutoff: on, 7000 mAh
Safety Time: off, (time doesnt matter)
Temp Cutoff: 45C (if you are using temp probes)
Waste Time: 5mins

Don't forget to load test your modules too because they can have good capacity yet still fail a load test.
Gen II Prius Individual Battery Module Replacement | Page 13 | PriusChat

 

Double checked the "stall test" guidelines - there is a set of thresholds mentioned in relation to particular DTC:
1.2V max for VMAX-VMIN
0.3V max for swith-over between CHRG/DSCH
2V max for the "swing"

 

Thanks, will use these new settings on my next battery.

Roy from Canada

Hi kiwi - are these numbers for the 2001 to

Hi Kiwi -- Are these settings for the 2001 to 2003 prius, if so thanks they apply to my cars.

Roy from Canada

 

Those are not settings, those are thresholds you have to observe during the test and if above or below - follow the decision tree of what DTC is related to. That is for yours - 2001 to 2003
P.S. read about your silver plating - you are absolutely right about the electro-chemical mechanism which destroys the contact of different meatls. One re-builder in US uses nickel for that purpose as their parameters are close to copper in that sense.

My personal view on that matter is:
The contact between bas bar and the module is not the weakest point.
Corrosion is travelling up the voltage detective lines and what you perhaps have not seen yet:
I witnessed 5 cases so far on your model - corrosion is going all the way through to the battery comp and kills it
You can't see it unless you disconnect the orange plug and srutinise the contacts on the computer.
When dismantle the comp - corrosion travells onto PCB and to the componentry. Dead beyond repair.

To clean bas bars - you may use phosphoric acid (aka anti rust solution) - no mechanical brushing needed and to keep them in storage and not corrode - just dump them in the motor oil.
If applying the grease - be carefull for the grease to be heat resistant and dielectric.