Revived my 2002 Prius battery.....

Glad to hear you avoided the $3000 dealer cost. There's an outfit in ny called priuskings that services the northeast in the same manner. They'll come to you and fix/balance the battery on the spot. It's great people are offering Prius customers a cheaper alternative.

 

Great news, what did this chap end up charging you for his services? I am sure I will be starring this in the face at some time also and not sure what I would do as I know I will not be buying a new HV battery.
TomK

 

From what I read in the battery postings it takes days to fix a pack right, not hours. How long did he stay with you?

 

Just going by what I have read here on the forum. Even with multiple 4 bank chargers the whole procedure including balancing the whole pack was days. Was he able to do the all the cells at one time?
I hope it works out well for you. Keep us posted.

 

I also want to know how this was done so fast and how well it holds up.
TomK

 

Wouldn't the charge/discharge cycle time be directly tied to the state of the initial charge of the battery as well as it's condition?

 

Seemed to be constant independent of charges. Most I have read run at least three cycles and check numbers. Then a balance of the whole pack is required.

 

The modules are rated at 6.5 Ahr so 1C, the nominal rate, would be 6.5 amps. With four smart chargers that cycle fast enough, and used modules sitting at 2.5 to 3.5 Abr, all 38 could be done in 10 hrs. But Smart Chargers are not cheap.

Often we deal with folks trying to do it 'cheap' and there in is the risk when they do not have charge and discharge limit protection.

Bob

 

And balance the pack?

 

In theory, yes, but there is a big gap between my speculations and the specific steps the reported technician/engineer follows. Be aware, I don't make a living balancing Prius packs.

I've done a couple of hundred hours testing ~80 modules from failed and failing packs and one good pack. My interest was and remains in individual modules and their failure mechanism. So to make a stable, balanced pack, two requirements are needed:

1. similar Ahr capacity - so the voltage change as a function of charge follows the same slope. A too low capacity module will have wider voltage swings than a higher capacity module. If the voltage limits of the low capacity module are exceeded, it will fail. What I don't know (but have a clue) is how large the Ahr capacity can be and still have a functioning pack.
2. identical initial SOC of the 38 modules - so all modules are starting at the same point. Normal pack charge varies around 60% so the key is having all of them start from exactly the same, 60%. But NiMH modules are subject to self-discharge so they all need to be parallel charged to the same point.

Now if I were to 'hang a shingle' rebuilding and balancing packs using the original NHW11 modules, I would:

• Inventory of 3*38 modules, ~120
• Initial survey to group into three, equal number sets: high, medium, and low
• Set a lowest value Ahr capacity from observation and experimentation
• Leave modules in an active, maintenance storage that cycles between 55-65%
• Long warranty as each rebuilt pack is my R&D to further track and improve screening and rebuilding specifications

But I am NOT in this business regardless of how interesting it might be.

Bob Wilson

 

The problem with the 4 bank chargers I have (2 of them) is the discharge rate is very slow so it takes many hours to discharge them. If his chargers had a high enough charge and discharge rate he could do it quickly. Mine have a 10 amp charge rate and a 1 amp discharge rate. Takes 30 minutes to charge and 6 to 10 hours to discharge per cell. My chargers will take 2 modules in series (12 cells) so I can do 16 modules ar a time.

Roy from Canada

 

That would take days to do three cycles then balance pack.

 

I went through his battery, I took initial reading on the state of the individual modules. Marked 3 that I found to be questionable based on initial voltage. Secondly I discharged them all to 1v and brought them back to a charged state aprox. 85% capacity let them cool and took another reading. I did tell him I was taking it to 85% and the ICE management system would not like it. If you take it to 85% the car will run on the gas engine for several minutes with out charging the HV system before it brings it down below what it deems needs g a charge. By discharging them to 1v and recording the time it took to get them to 85% after cooling they dropped to about 79 to 80% it gave me an idea of the state of each set of modules. I had several modules that were discharged/charged individuly due to my charger detecting an issue while they were paired. One of which was an exploded module that we could not visibly see until removed from the pack.

Based on charge taken before my chargers decided to cut off I devised a plan of what modules were in disrepair and should be paired or replaced. We replaced two modules. All modules were within .2v of each other at the end.

I am not a professional, I am a hobbiest. I have a BS in CIS,I am a state certified mechanic, I have my journeymans card in electrical maintance and work in the auto industry keeping the assembly lines moving. I asked him to bring it to my home so I could cycle the battery 3xs and balance it better than what I was able to in the short time I had. I was not able to evaluate the batteries in full.

I did tell him that if I could not get it functioning he owed me nothing but fuel. To date I have rebuilt 6 prius packs and 2 civic packs. I'm currently converting my 03 to second gen modules.

You can criticize my work if you like, I know there was flaws in the method I chose to use based on time. I try to help people in need keep there cars on the road. I also offered if he has any issues with my work I will come back and see what we can do to get it going.

I have followed PChat and many other forums for a long time. I am not an engineer and have no interest in repairing these for a living but if someone needs a hand they can contact me and I will do what I can to help them get back on the road.

 

Thanks for all you help with other prius owners!
This answers some of our questions as to how fast the pack was reconditioned. So it still lacks multiple cycles and a balance then.

 

Correct, I was unable to cycle it multiple times. The time factor was the biggest issue.

If it could have been brought to my residence and had there been more time I would have removed it and done it differently.

I am confident that my work done with the knowledge and experience I do have will last. I don't see any other modules that are failing within the next 6 months. I can't guarantee that cause As we know these modules are approaching 12 years old. If he has any issues I'll help him as I help everyone.

I did enjoy the motorcycle ride out there though.

 

Thanks for the technical details!

Please do not see my following a conservative approach as criticism. There are more than one way to build a pack and I like your 85% pre-charge approach.

I give a high value to those who DO over Gperts and those who stop learning after getting a diploma.

Bob Wilson