Gen II Prius Individual Battery Module Replacement

Roy,
Yo said "Even if all the batteries are weak. but have the same capacity, the computer will not object and call up the triangle of death."
If batteries are weak voltage also weak. Then triangle of death will pop up. Can u please bit ex plane it?

Thusitha

 

If the battery pack has a real low capacity its voltage will drop quickly when under high loads and may drop in voltage enough to trigger the triangle of death from low voltage on the total pack. When you cycle the individual battery modules they may start as low as 1500 Ah and after recycling go up to 3500 AH - if all the modules are around the 3500 Ah your car will have a relatively weak pack but still be stronger then before. the recycling process and maintain its output better then before the recycle process.

. However if the same battery module went from 1500 Ah to 5500 Ah after 3 cycles you would have a strong battery pack and the voltage from the pack would hold up better under high load currents. If you mixed 3500 Ah with 5500 Ah batteries voltage differentials would occur that the computer would pick up even though the capacity of the pack is high.

Hope this helps

Roy

 

If you remove a battery pack from an older car that is working OK you will find each modules discharge capacity to be low, recycling the modules individually will bring their discharge capacity up,
Many people are buying the high voltage chargers to recycle the batteries in the cars - in this case they are bringing all the modules up together at the same time thus increasing the capacity of the pack in a much shorter time frame and with less work.

 

If they charge the battery by high voltage charger how can identify bad module?

Thanks
Thusitha

 

They don't. This is an effort to avoid having early bad modules. You can detect weakening module pairs via the Prius BMS and Prius aware OBD2 testers.

JeffD

 

The high voltage charger is used on batteries that are healthy and working and just need a boost to their capacity and maybe a longer life. To find a bad module you would need a program such as techstream to look at the battery modules in the car as it is on the move under load,
A high voltage charger as sold on priuschat cannot measure the charge and discharge of the battery, it is only used as a boost or maintenance device.

 

I really like the last sentence that contained "respectfully disagree". A respectful discussion of different opinions will move battery reconditioning forward. Opinions backed up with testing and observation are even better. I wanted to know why Kiwi thought paralleling battery modules was a waste of time. As I said before paralleling modules is a good way to bring them to the same state of charge (voltage). Kiwi did answer my question in a round about way. He trusts his charge, discharge, and charge cycle to bring all the modules to the same state of full on the first charge. His one discharge tests the module capacity. The last charge is there to again bring the modules back to the same state of charge. Kiwi uses charging in series and I use paralleling. That does not mean that only one method is right and the other is a waste of time. Kiwi is rightfully proud of his system being able to quickly measure the health of a packs modules. I can and have matched his time with Techstream, parralleling, and RC chargers.

This post is not about beating up on Kiwi. I agree with him that balancing modules does not extend their life and will not bring lost capacity back. Now is the time for everyone else to remember that "respectfully disagree" line. I will use a_triant's tests to back up this opinion. The first discharge cycle was not used because the modules did not start at a full SOC.

#1 D3200 C8000 D4498 C8000 D4742 C9100 D4908 9% increase
#2 D2790 C9100 D4591 C9100 D4939 7.6% increase
#3 D2400 C6866 D3595 C8000 D3719 C9100 D3844 6.9 % increase
#4 D2302 C9100 D3805 C9100 D3704 3% decrease
#5 D2400 C6700 D8000 C8000 D3700 C9100 D3983 7.6% increase (first discharge of 8000mah considered a typo)
#6 D2314 C9100 D3552 C6351 D3513 1.1% decrease
#7 D2000 C7100 D3110 C8000 D3146 C9100 D3277 1.05% increase
#8 D1752 C9100 D3049 C7539 D3045 .0013% decrease
#9 D1--- C9100 D2192 C9100 D2084 5% decrease
#11 D1292 C9100 D1909 C9100 D1939 1.6% increase
#12 D1371
#13 D1158 C9100 D1638 C9100 D1643 .3% increase
#14 D1072
#15 D1101 C9100 D1586 C9100 D1616 1.9% increase
#16 D802

The results show that for a_triant balancing modules did not produce any significant improvement in module capacity.

Respectfully, Brad

 

Roy,
+1 on your first comment.

On your response to Brad: what would be a good range between the high capacity and low capacity modules? Or what would be an acceptable discharge capacity range among all the modules?

Thanks.
Danny

 

-

 

I have put together packs with the strongest module having 50% more capacity than the weakest. They perform fine in a car. With strong modules, 4000mah to 6000mah, I think a 50% spread is no problem. With weak modules, 1366mah to 2000mah, that 50% spread most likley will lead to playing wack a mole. There is just not enough reserve capacity to keep performing well. This is an area where the large rebuilders have an advantage. With thousands of modules available it is far easier to select a tightly matched set. Of course they do not talk about that someone is going to get a 5000mah pack and someone else will get a 3000mah pack.

Brad

 

Brad,

My purpose in rebalancing modules is not to increase capacity, it is to put off the day when a cell will get reversed when the HV battery is drained in use. The capacity increase is indicative of the lower SOC cells catching up to the stronger ones in a module.

JeffD

 

Thanks

 

Brad,
That's very good news for the rebalancing I'm doing now. I'll post my data once I complete all the 28 modules plus the replacement modules for what I would deem bad.
Thanks for the inputs.
Danny

 

My apologies for not being able to contribute or qualify my previous post over the last few days, "due to family illness" but I will endeavor to catch up with this discussion, and contribute where I can.

John (Britprius)

 

I replaced a low cell in a 2005 yesterday. I put it back in the car and now the gas engine won't come on. The triangle comes on and the other lights after a few seconds. I measured voltage at the connection with the car and one time it was 220 v and then it read 8.00 v. I can't find what's causing it to be so low and to vary.

 

It is almost certain you have not installed the safety connector correctly. After fitting and swinging the lever closed it then must slide down.
Service Plug Removal and Install.pdf
John (Britprius)

 

I reset it by disconnecting the 12v. Push start button and after about 4 seconds the triangle pops back on and motor doesn't start. There isn't enough power coming from hybrid battery to start the engine. All the cells are reading over 8.25 V and are all close to the same. The service plug is put in correctly. I checked fuse in connector. The buss bar connected to all cells. I'm stumped. Its probably something simple and obvious I just don't see it.

 

Are you rely sure You installed the safety connector as in the PDF instructions in my post. This is by far the most common mistake, and will give the problem of the HV contactors not pulling in.

John (Britprius)

 

Its true that is the most common problem. I have helped other people with the final push down of service plug. I wish that was the problem. It now reads 12v on the side of the battery before the black relays