HV battery balancing

Slim if you buy a DC6 or similar make sure you get it with the power supply as some come without one.

John (Britprius)

 

hey john! did you see my pic on the other thread about the dc contactors you were referring to?

 

Hi Slim. My 2000 Insight lasted 149,000 miles on it's first traction battery. (They call it IMA battery). But I read the Prius battery tends to last longer. I should be good for a few years without worrying about the battery, right?

 

The HV battery in your car is an improvement on the gen2 battery so in theory should last even longer, only time will tell.

John (Britprius)

 

i see a lot of people with 2001-2003 priuses that have almost 300k miles on them so i'd like to think you are good to go for quite some time. good luck!

 

My "lower quality" Gen I battery pack is still going strong after 12 yrs and 120,000 miles.

 

235,000 miles on my 2001. I bought it in May and the previous owner said the battery was rebuilt. I don't have information what that meant and by who, but the SOC on the scan gauge stays around 60-64%. When I first bought it, the SOC was 56-60%. It is driving great and I love it. Found the 12v battery was original yet!!!!! Replaced it with a yellow top just to be on the safe side. Loving the high mpg!

 

that's what we like to hear. nice one! i took a trip to cuba and you see everybody (and i mean close to every vehicle in the country) driving cars that are 60 + years old and it makes you wonder.... people here in the USA are afraid of 10 year old cars. haha!

 

Given the voltage data you gave, I never would have connected modules that were so drastically different in state of charge in parallel. I may have been lucky with connecting my modules together in parallel, but I never attempted it with modules that I suspected of having failed. Seriously, this is a really dangerous thing, so don't be cavalier about it.

Having said that, I suggest you disconnect the battery that you have assembled in front of your drum kit, let it sit overnight, and then measure the voltages again. I'm guessing most of those voltages will decay quite quickly. Then group it into several different assemblies, based on the decayed voltages. That is, one group for modules whose voltage is less than 1 volt, another whose voltage is between 1 and 2 volts, between 2 and 3, 3 and 4, etc., and finally a group whose voltage is above 6 volts. This last group, frankly, is the only one I'd hold hope for. I would assume the others are junk.

I'm unfamiliar with the genius g 750 smart charger, but be sure it has the ability to detect the dV/dt drop that will cause a runaway charging condition with nickel metal hydride batteries, which is where the explosions come from. It should say that it has a NiMH charge mode.

 

hello noah! thanks for that. i did disconnect them as i am out of town until next week. my charger doesn't have that feature but i ordered a supermate dc 6 and hope to continue with my experiments after reading up on what all you folks have said regarding the charge/discharge techniques and amp/hrs readings etc. i will keep you posted as i'd like to go about this in the safest way possible. thanks again!

 

does anyone know what is the absolute lowest "total" voltage you can get out of a gen. 1 prius hv battery and still have it function properly and be able to drive the car with no warning signs?

 

The battery ECU is likely to log warnings based on several things it measures, such as overall state of charge, block-to-block voltage variation, per-block internal resistance (the higher that, the bigger the voltage drop you will see between a no-load measurement and when it really matters), and temperature rise. So my thinking is there isn't really an answer to your question as posed. Most battery failures in the wild don't seem to be uniform degradation of all the modules at once; some just go bad first. An exception might be a brand-new or otherwise flawless, well-balanced battery that just gets deep-discharged by running out of gas or something. Is that the scenario you are asking about?

-Chap

 

thanks chapman! well i've been experimenting with charging some modules but i purchased the incorrect style charger. i was wondering if i could just swap out some of the lower reading modules and just replace them with modules i have from another battery pack. i take it from what you stated is that i will most likely have "block-block voltage variation" since my modules are reading as follows:
1. 7.31
2. 7.41
3. 7.34
4. 7.33
5. 7.11
6. 7.23
7. 7.12
8. 6.19
9. 5.01
10. 4.09
11. 5.85
12. 5.56
13. 4.54
14. 6.09
15. 7.21
16. 3.84
17. 7.30
18. 1.38
19. 7.36
20. 7.34
21. 5.61
22. 7.25
23. 3.77
24. 5.07
25. 4.76
26. 6.91
27. 6.07
28. 5.63
29. 7.07
30. 7.12
31. 7.20
32. 7.22
33. 7.23
34. 7.36
35. 7.44
36. 7.41
37. 7.48
38. 7.44

i was wondering if i just switched out my lowest 5-8 modules with other modules reading 6.5 or so plus if this would work without going through all the charge/dis-charge steps etc.?

 

To build a battery that will last a reasonable time i'm afraid there is no shortcut. I do not know the actual value for the gen1 but the gen2 will give out a DTC at <.2volts difference between block pairs (2 modules in series).

The real problem is not so much the difference in voltage, as the difference in capacity. Any low capacity modules, or modules with a low capacity cell are going to be completely discharged in use and then reverse charged destroying them when perhaps they could have saved.

John (Britprius)

 

ok john, i guess there is no shortcut. i should be getting my DC 6 this week and will start the tedious process. the reasoning behind working on one module at a time is to be able to measure the capacity, correct? stringing them up in parallel will allow me to charge them all simultaneously but i won't be able to measure the capacity on each module this way, which is what i need to do to find my "good" modules. as you say by measuring the capacity or "balancing" by charging/discharging 3 times. this can only be done on an individual cell basis. i think i'm finally beginning to understand this.

 

Try not to get the terms module and cell mixed up as this will lead to confusion. A cell is 1/6 of a module a module consisting of six cells.

It is one or more of these cells within a module that can become out of balance (different level of charge) within the module.

The capacity of the module in amp/hrs can only be that of the lowest cell and if discharge continues past this point the lowest cell will be reverse charged, destroying the whole module. The reason for balancing.

Once the module is balanced it can be charged to a given voltage (say 8 volts) and it's capacity recorded on paper and on the module and put on one side for later use.

When you have enough modules of similar capacity, and voltage, you can connect them in parallel to even out the voltages. You do not need to charge them in parallel they will level themselves up. They are then ready to be built into your battery.

John (Britprius)

 

oh yeah, i meant to say "module" not cell. i'm sure you will be hearing from me very soon when my DC6 arrives. they sent me an imax b6 by mistake and i think it was a cheap knock-off as it didn't say authentic or genuine on it. talk soon!

 

hey john! my dc 6 finally arrived and i'm ready to get to work. after doing 3 rebuilds with gen. 2 cells i now have 114 gen. 1 modules to sort through. yikes! i'm gonna start with one module at a time and work safely.

i have some dc 6 set-up questions: (i've been studying the manual but i'm sure my setting will have to be specific to the gen.1 modules i'll be working with)



1. nimh charge current i set to 0.5A (as you suggested earlier)

2. nimh discharge: what Amps and Volts?


3. nimh CHG>DCHG (i should set to 3 cycles correct?)


user set program: (not sure about the settings for these either)


4. nimh sensitivity ?


5. usb/temp select ?
6. waste time ?


7. safety timer ?

8. capacity cut-off ?

9. input power low ?

also, if there are some things i've missed let me know?












thanks much john! -a

 

I have a question. I haven't had any warring lights or messages but think my battery is on the way out. It goes from full to dead and back to full very quickly. Once in a while it feels like your driving a manual in 2nd from the light. No pawer at all and very sluggish. I have 160,000. on it. its a 2006 Prius. Im going to be removing the battery this weekend and checking voltage on the cells. I will post them for your help and advice. How do I balance them. Is there a good source that explains how and what you need?
Thanks
Dave

 

Dave,
I'm amazed you don't have any warning lights yet but, the symptoms you describe are def the battery going dead.

As for how you balance them, that's simple, (connect them all in parallel and wait about eight hours) but, yours will need more than balancing. You will need to find the weak/bad cell(s), replace them, and rebuild the battery pack/restore capacity and then balance. This is done by charging and discharging the modules using an rc type charger like a Supermate DC6 or equivalent. There are so many threads on PC that detail how to do it (mostly in the Gen 1 Forum) and even more info elsewhere (google prius battery rebuilding etc). Search the Gen 1 forum for "Supermate" and that should get you started. There is a wealth of info there.