2012 Prius 120k mikes, having issues with HV battery

Also, I really don't think you want to charge batteries in parallel. That is a potential can of whoopass you don't want to open.

 

Agreed...

 

Very much want to know what you mean by that... Never considered it as an option and if you have a chance to explain the whoopass/risks it'd be much appreciated. I suspect what you're saying is that the charge won't be balanced equally among all cells, but was surprised to see the OP's results of a relatively balanced charge among modules.

 

As if...The person working on the pack was competent enough to realize that #11 was the problem if the lower voltage wasn't because of their initial testing and configuring. I look forward to knowing if my assumption was correct...

I will also admit that I participate in so many of these discussions that I lose track of which DIY person I'm talking to and am way less than thorough with "helping" them learn this stuff. I forget to mention all kinds of stuff and am grateful nobody's been electrocuted yet...

Also no matter how much I've learned, I still haven't learned about lots of stuff. Like charging the whole pack in parallel with an 80W IMAX, never spent time thinking of all the details of that. Your reply about the risk of it would helpful and we'd be grateful.

 

Yes, I think I was the person who suggested it wasn't a fair test... But I should have been more inquisitive... As @TMR-JWAP made clear if that module got that way on it's own, then that's the bad one. But if it got that way because you were learning how to do the testing and discharged that one, then it was correct to say it wasn't a fair test. Apologies for not being thorough enough in advising you.

 

Oh, ok... If you look at your first post module 11 was same voltage as all the others.

Hopefully you can drive it around while you order a new module and not do any more damage... Glad you know what needs to be fixed now. in the meantime, use the Hybrid Assistant app to keep your hybrid battery cooling fan running at full speed to keep the pack as cool as possible. Here's the dude I buy used modules from: Toyota Prius Hybrid Battery Cell 8.2v | eBay They usually are such good ones that reconditioning the pack to match 'em is required on Gen2, but maybe it's a good match without that on a Gen3. And again apologies for not being more inquisitive.

 

The 28 modules are in series. They are connected end to end. Every iota of current that passes through the first module also passes through the last module. In a perfect world with perfect chemistry and construction, every module in the series would be at the exact same State Of Charge for the entire life of the battery assembly. It's not a perfect world. Module 11 is showing the classic symptoms of one cell inside the module failing. That's why it has no capacity (you measured as discharge time) at the higher voltage. That bad cell is almost immediately tapped out. The remaining (5) internal cells that are not failing are what is giving you the longer times to get to the lower voltages. The car doesn't care about the lower voltages. It only cares about the higher. One failing cell inside that module causes it to fail as a unit. Don't waste your time screwing around with module 11. Replace it. Don't get yourself stuck. Consider this as having been led to the watering hole....I cannot make you drink from it............

 

We're all clear on that, as well as in agreement on it too... But I still can't figure out what you meant by:

I've asked many a friend who work on Prius and we're still trying to understand what the specific danger/risk that you're referring to?

 

Charging multiple modules in parallel provides NO information about the condition of any individual module. For a basic starting point, look at post 9 in the below thread.

Help with my battery | PriusChat

Multiple module parallel charging like described merely charges all the modules to the same voltage. Voltage means very little in regard to capacity of aged modules with thousands of cycles on them. Some modules may be 9.0 volts with only 200 mAh charged. Some may need 6000mAh. How do you know which ones are which? I probably have a hundred Gen 1 modules that will go from <1 volt to 9 volts with less than 100mAh put through them, because they have practically 0 capacity. If any of those modules are charged in parallel with a bunch of good modules, they would only draw minimal current while the other modules draw significantly more. All the modules will show the same voltage, as they are wired together, but the bad modules will still have minimal capacity. Obviously, this is an extreme example.

Loads in parallel will always drop the same voltage regardless of the current/voltage/power supply. The current is merely distributed unevenly to each branch.

A similar problem exists with the proplong and charging in series. Although the same amount of current is flowing through every module, you still have no idea of what the capacity of each module is. A bad module may only absorb 200mAh before it starts generating heat instead of charging. A good module may need to absorb 6000+. At the end of your cycles, that bad module is still a bad module, but you probably won't know it just from looking at the battery. Individual module charging will provide all the info you need to determine the condition of a battery module. The results CANNOT hide behind a bunch of other modules.

To "recondition" a used module, you need to force current through that module, both charge and discharge. You can't force anything through a specific module if you have a bunch of them in parallel.

 

Thank you very much for explaining your position on all this...

I agree with all your points!

Individual module charging and reconditioning is far superior to doing the whole pack in series via Prolong system because you have way more data to know what will last a while and what's going to fail soon.

Of course, I have found the prolong system can be used in ways that are complimentary... Such as doing a final charge and balance on a reconditioned pack once you're done and the pack is back in the car and you're sure you eliminated all the bad modules.

As for the issue with parallel wiring, I was impressed only because there's lots of DIY people who show up on here who can't afford multiple chargers, as well as other gear to professionally repair a pack and they're simply trying to do the minimum possible to get back on the road. And yes, when it comes to repairing battery packs that's a fools errand, I know, but thought it was clever. Anyways, much appreciate getting back to me on this!

 

Just wanted to say great informative post.