Prius Battery rebalance thread

Hello could I ask, how did you drop the SOC (I assume State of Charge) just by putting it in Neutral. Thanks
I just aquired a Gen2 how long can you except to travel in just ev mode if you have green bars in your battery and your battery is good? (assuming it is flat ground) Trying to get a bench mark

 

What I did didn't last long. Probably worked for a week or two and battery was back to the way it was.

So with this experiment, I'm not sure how the battery rebuilders bring back weak cells long term.

The battery will not charge in neutral, sit stopped in the car in neutral for a while and you'll find out

 

JC91006 Thanks for replying mate!
I've only had the car a few days.

Sorry but I have more questions.
*How long does it take, roughly, to drain the battery?
*Should I leave the lights on to drain quicker?
*How long should the engine run to charge it (and to how many bars does it charge to)?

Also I get to green quite often But one bar before full. (I assume that's seven as I forgot to count).
It is also winter here and evenings/early mornings are below freezing and the wife ALWAYS has the heater going (so I also assume the engine is running a lot for this)

I had 1 bar less than the top and I switched to EV mode and I estimate I drove almost 1 km on flat ground unitil the engine kicked in at 2-3 bars is that good, bad, average?

Thanks very much all!

 

They use the word "weak" vs proper one: "degraded battery module with increased internal resistance and reduced capacity". There is no measurement for “weak” hence they can claim anything.

Whoever claims they “can bring back weak cells to 95% of its original (design) capacity - it is an unjustified claim, or put simply - a lie.
The numbers in claims differ.
What they do is just cycle charge/discharge the pack and claim the difference between couple of non-representative measurements as an improvement.

I have pointed to couple of companies just that - one changed the wording on their web site and claimed that it never existed in the first place :-(

One exception: EV Energy themselves can do battery rebuild professionally by replenishing precisely measured amount of evaporated electrolyte into the vacuumed cells. That is patented technology and not known to be offered to the general public.

Re: Balancing:

Balancing is required only when you are compiling pack from similar modules (e.g. of the same capacity) which have been previously charged at different times, stored long time and lost some charge due to self-discharge . That is easy task and can be done in few minutes with my tools.

With DIY RC tools it will take forever. But I guess it is a good excuse for some to spend that much time in the garage. and escape from other duties....

 

Hello John and MTL hihy,

I have a Gen 1 pack I am trying to fix.

Could you please advise on the ideal setting of the delta peak feature in the Hitec X4 AC Plus ? I have 2 of those chargers.

I do not want to damage the modules y excessive charging , nor to terminate the charging process too early.

What does delta peak exactly do, and what is the ideal setting to it ?

Also another question : Is it better to set the chargers on automatic current with a maximum of 3 Amps for example rather than setting manually o a specific current ?

Last question : sice the battery has bee sitting for a ong time, the modules are all close to zero votage. So, How do I set the cycles i this case? In terms of the seqience of charge and discharge, if I am starting from close to zore voltage ?

Thanks for your help.

Eddy- Toronto.

Hello John and MTL hihy,

I have a Gen 1 pack I am trying to fix.

Could you please advise on the ideal setting of the delta peak feature in the Hitec X4 AC Plus ? I have 2 of those chargers.

I do not want to damage the modules y excessive charging , nor to terminate the charging process too early.

What does delta peak exactly do, and what is the ideal setting to it ?

Also another question : Is it better to set the chargers on automatic current with a maximum of 3 Amps for example rather than setting manually o a specific current ?

Last question : sice the battery has bee sitting for a ong time, the modules are all close to zero votage. So, How do I set the cycles i this case? In terms of the seqience of charge and discharge, if I am starting from close to zore voltage ?

Thanks for your help.

Eddy- Toronto.

 

How would experienced forum members answer Eddy's question?

Some of the literature I've read on NiMH cells suggests that allowing a cell to discharge to 0 volts is very bad for it, and the cell may never recover. I've also read threads here on priuschat that suggest keeping spare modules charged, at least charging them occasionally. Could some of the members who buy/sell used modules chime in and tell us whether they keep their stored cells charged? And have they ever seen a module at 0 volts that could be revived?

-EB

 

A NiMH cell allowed to self discharge down to zero will not be harmed, and they can be stored in this state. Discharging a number of cells in series as with a Prius module (6 cells) other than by self discharge is likely to damage some cells in the module by reverse charging of some cells.

John

 

Thanks Britprius! So there's some hope for Eddy2014's project...

There was one failed module in my 2005 HV battery. One cell in it is a permanent short circuit. This module can be charged and discharged OK on the test bench, but the voltage never gets outside of the "5 cell" range: 6.0 to 7.0 volts.

My conclusion is that my "5 cell" module could never be reconditioned well enough to put it back into an HV battery pack on a Prius. My previous experience with both NiMH and NiCd is that shorted cells can NEVER be recovered.

-EB

 

Hello John,

Could you (or other experienced members) advise me on how to set the cycles to charge up my modules ?

And also, could you advise me on how to set the delta peak feature on my Hitec X4 AC Plus chargers ?

Thanks a lot.

Eddy.

Hello fellow Prius Chat Experts,

Does anyone have an idea on how to set up the delta peak feature on a Hitec X4 AC Plus charger?

Thanks,

Eddy.

 

If you have an owner's manual, look in the first part where it tells about setting up the presets. I think it will show "default" under the NiMh setting. Enter that and you can adjust it I think. The manual tells what the default setting is. I think it's 5. As the setting goes up, it gets less sensitive to the change in voltage. A higher number means less likely to see the delta v. A lower setting would make it more sensitive to the delta v. I raised mine to 7 after having some that had ridiculously low charge/discharge numbers. I'm guessing that the delta v shut it off. If it's working on the default setting, that's what I would use. If not, try raising it up a little and see if that helps. Just be careful not to over do it. You may have to make a few more cycles on some stubborn ones.

 

I am getting packs from wrecks - even completely "dead ones" – e.g for relays.

Just for stats I charge those (initial 0.6A then 2Amps charge) and then do the load test couple of days later @ 6Amps.

Observation - some of those show above 7.2V two days later before I start load test and drop almost immediately to below 5V at the start of discharge. Hopefully you would not be buying something like those on eBay :-(.


Some self-discharge quickly and show whatever < 7V two days later .


From the last 5 packs which were all zero or near zero voltage (all NHW-11): 3 packs - all went to the bin with none standing up.

From the last two packs there were one module in the middle of each which showed ~ 1AH leftover capacity @6 A down to 6 Volts. I keep those for testing my newly built chargers (last night completely re-designed and re-built 2 Amps constant current chargers for 14 and 20 modules in series. Will be testing new scematics for 6Amp charger tonight).


In parallel was running tests on the pile of Li-Ion 18650. Some modules which dropped below 3V threshold after being stored for too long (e.g. 2.4V) were able to take charge and looks OK, all others which dropped to 0 - 1.2V did not take charge.


Although chemistry is different - I see some similarities here: there are design thresholds: 0.8/cell or 4.8V/per 6V module in NiMH (Prius) and 3V in Li-Ion (Laptops / Tesla car) and those thresholds should probably not be abused.


Those tests made me thinking about building low-voltage threshold alarms for the back up battery banks (chemistry does not matter) - i.e. Buzzer and LED when voltage drops below set up threshold. Schematics are all over the net and it is easy to build.

 

Thanks John for your info. I managed without any problems to revive most of my modules, except number 20, which shows a voltage of 5 to 6 volts. Most of the rest of the modules accepted to be fed to a capacity of 7450 mAh, with a current of 2.1 Amps, with a delta peak set at 8mV, ( default is 7 on my 2 Hitec X4 AC Plus chargers).My discharge was set to 0.7 Amps down to 6 Volts, with a cool down time of 3 minutes (My basement in Toronto is cool enough so none of the modules, even the bad one overheated). Also the safety cut off timer was set to off ( no need to use it).
Conclusion: I succeded in reviving my modules and identifying the bad one, even after a long time of storing the dead car). I have a second toyota, non hybrid, so I was not in a hurry to fix my 2001 Prius.
Thanks to all of you fellow Priuschat members for all your valuable info and advice, I will keep you posted on how the car runs as soon as I replace my bad Gen 1 module).

Eddy from Toronto, Ontario.

Thanks for your advice, please see my post below,
Eddy2014.

 

Rebalance procedure for the packs below was quite fast and simple - the pack is discharged all at once to the point first module reaches level of 6V. Then without dismantling - individual modules (some could be about 6.3 - 6.2 - 6.4 V) discharged to 6.0V by applying 6A electronic load (Analyser stops discharge at 6V) - that takes few secs as remaining capacity from 7V down to 6V is very low.
Then the whole pack is charged in 4.5AH @ 2A constant current (Charged capacity is controlled by HV Battery Analyser). Then load tested under 6A load.

Here are couple of screenshots to show battery behavior under load:



Those are modules from Prius 1998 (NHW-10). Battery pack consists of 40 modules.
Common urban legend / myth is that one or two modules fail.
In that pack there were 7 failed modules. In another similar packs the number of failed modules were from 7 to 12 in every pack.

In that 40-module pack - changed 7 donor modules and load tested under 6A load.
Usable Remaining Capacity - 3.7AH (that is at around 6.9V, after that Delta V exceeds 0.3V). Screenshot show individual module capacity captured at 7.0v:



No manipulation to the individual modules. Just aiming at sorting good from bad in the pile of 200 modules and compiling the pack from modules in conformance with each other. Number of failed modules exceed 30%!
Got NHW20 failed pack (28 modules) - the number of failed were 20! Those 20 modules did not take more than 1AH charge - I've captured that during charge mode even without the need for the load test. Remaining 8 modules tested over 3.7AH and will be reused in another pack where 4 modules failed. You'll see..

 

Kiwi,

The "Urban Legend" of 1 or 2 failed modules actually occurs in those HV batteries that are not subjected to extreme temperatures. When an HV battery lives in a hot environment many of the modules will be unusable and all will have a low capacity.

In my case, 195k miles in Connecticut, only one module had failed (shorted cell - 1.2v less than the others) and the 27 other modules recovered to consistent, reasonable capacities when given a 3 cycle discharge/charge "rebalance" protocol.

JeffD

 

Not sure about how "Urban Legend" of one failed module is connected to temperatures ( I would make a bold assumption that it is not), but what is absolutely true is the fact that temperature impacts battery performance.

New Zealand has very mild climate: In Auckland in Winter night temperature drops to +5C (41F) and in Summer day temperature in the shadow is about +25C (77F). Of course in Summer under direct sunlight (we have high UV here) you would literally melt .
Majority of hybrids in New Zealand (we have about 12000 registered since last 10 years) are second hand imports from Japan where temperature range is wider.

Last week load tests I have conducted at temperatures around +10C (50F). Last night it was +16C (60.8F) and the load test on another rebuild 20-module pack has showed URC above 4.9AH. I would assume that in lower temperatures that pack will show little bit less capacity under the same load, please see screenshot below:

In parallel to the load test below another HV Battery Analyser was engaged with NHW20 rebalancing.
Pack is fully assembled with all bus bars attached. In that NHW20 pack which was previously charged - I dropped the pack level to 7.2V (~5 minutes) and then dropped individual module levels (controlled by Analyser) to 7.2V level without dismantling the pack (took few seconds on 24 modules and up to 15 minutes on another 4 modules whihch were charged much more than the rest of the pack). Will top-up charge and load test that pack tonight. You'll see...

 

Just to confirm what Jeff mentioned, I too had a similar issue of just one "bad" module while the rest were fine (heat damage to cells isn't an issue in Canada). All of mine even maintained acceptable capacity (all showed 6000+ mAh) but one showed poor performance under load (voltage dropped 2x faster than the others) thus replacing it I was able to rebuild my battery pack and run it without issue ever since.

 

I have 8 Prius HV modules on my workbench.
​

One module is confirmed faulty: I removed it from my 2005 Prius due to P0A80 DTC codes. I have one other module (also removed from my Prius) due to it consistently having 100 mV lower open-circuit voltage than the other 27 modules. And I have 6 more modules purchased from ebay:

3 modules are "B2" version ( 2008?)
1 module is the "B4" version (2010?)
The other 4 modules have no "B" labels (2005?)​

My new Sky RC charger/tester should arrive today:

I selected this unit because it runs on mains AC power and it also has a USB port which (I assume) permits detailed logging and monitoring of the charge/discharge process.

My rebuilt Prius HV battery pack has been working perfectly for 5 weeks. So I'm in no rush to analyze my 8 spare modules. That's why I decided to get a RC charger/tester that only handles one module at a time.

I plan to conduct enough tests to properly answer several questions:

• What is the usable remaining capacity (URC in Kiwi's posts) of these used modules?
• Is the age of a module a good indicator of its remaining life?
• Is it possible to improve the performance of a module by "rebalancing" it? (e.g, by giving it a very, very, very slow charge all the way up to 100%). Note: This is similar to what "grid chargers" do.
• Is it possible to improve the performance of a module by "deep discharging" it? (This also must be done very, very very slowly). Note: A "grid charger" with "discharge option" can do this.

I'll post my results here on Priuschat

-EB

 

Yesterday another charge test just gave rock solid evidence of why changing more than "one failed" module may not work.
i.e. Pack under test has 4 failed modules and remaining capacity is low ~2.7AH. 4 donor modules with remaining capacity of 3.8AH.
New assembly of 28 (24+4) -> start charge from the same level of discharge (7.2V under 6A load). Then the pack is fed 3.5AH.
Almost all way up DeltaV on pairs is over 0.55V (above threshold) and is becoming near 0.15 when fully charged. If there was just one module - DeltaV could be < 0.3 for more extended range and there will be no error codes. I let that pack idling for 24 Hours and will do the load test of the whole pack tonight and capture Delta V. Although Remaining Capacity (from charged down to 6V under 6A load) of those 24 and 4 modules respectively is not entirely hopeless, they simply do not match - i.e. "Swing" and "Delta V" - those two metrics are out of threshold.

To clarify: URC is only applicable to assembled pack. Please refer to my post from today. Remaining capacity of 24 modules is ~2.7AH each, and 4 modules ~3.8AH each. URC of that assembled pack (24+4) will be captured tonight and it could be in between ZERO and 0.5AH we'll see. Charge graph is enough to say that, but discharge graph will just be a double proof.
Using one channel RC charger even with logging capability will not allow to conduct tests in comparable environment - i.e. to apply the SAME discharge current.

 

well I just got myself a spare HV battery the trip was sort of nutz put a 1000 miles on my prius in the process, going from southern California to the central valley , got to see san fran because construction on the 5 delayed me to where the junk yard was closed. Measured all the cells with a multi-meter before I bought it, one cell is at 6.36V #13 to be exact cell 1 (as in from the left side where the electronics are ) and cell 28 where the blower belongs are 7.5V and 7.46V respectively. The rest of the cells are between 7.59V and 7.62V after I discharge and charge 1, 2, 3 times I will report results but I figure that the cell 13 has a shorted cell not sure yet though could be voltage depression. if I have to buy a cell to replace #13 not a great loss considering I only paid $350 for this HV battery. hoping to swap cells after reconditioning so I can then work on my cells.
terramir
PS: one thing is for sure a royal PITA with the prius filling it up!
today I got a click at 5 gallons 6 gallons and several more till I actually filling manually real slow and ended up over filling as in to the metal. at 10.xx gallons. but here is the kicker even at the slowest setting I would be shy at least 4 to 5 gallons at times, well gas pumps vary.
but this means on the freeway I got about 40 mpg on this trip back (406.7 miles) and that is with me racing at 75 miles an hour at times.
but in the city driving part I'm getting low 30's no battery codes yet though just not much capcity left on mine currently.

 

Post updated: Voting closed. I am in.