2012 Prius 120k mikes, having issues with HV battery

You have to load test them

 

Just because you get te check hybrid system message, there are many causes.

How’s the hv battery fan cleanliness?

Connections are all good and tight?

 

I have not done it, but you can search battery rebuild threads here. I think they use a lightbulb

 

Do you have a way to read the codes, like access to Techstream?

That’s te true way to figure out why the message is being displayed.

 

Grab you multimeter and pull out one of your headlight bulbs then connect some wires to the bulb, the battery and multimeter... Then use a timer on your phone and write down the voltage drop after two minutes.

You'll find that Each module will behave slightly differently and the worst modules will drop to the lowest voltage or just start giving bad voltage readings. If that still doesn't identify it, next step is to get a smart charger for NiMH radio control car batteries and drain each module down to deeper and deeper levels of discharge with a recharge after each discharge. I use IMAX B6AC V2 chargers... The third and final discharge should go down to 0.6v and doing this with all 28 modules will give you loads of info on each module's health and none of them will be exactly the same.

This process of three successively deeper discharges via the headlight bulbs is also what breaks up all the poorer conducting large crystallization that causes metal batteries to lose capacity over time. The vehicle can still function normally, even with 50% loss of capacity. I recently did reconditioning like this on a 2012 pack with a bank of five chargers and 10 light bulbs and it made a HUGE difference!

And if you'd rather spend money on a less time consuming process, you can buy a charger/discharger system that will do all 28 modules at the same time. Learn more here: FAQ

 

Well... Do you have a way to charge up the modules before load testing? Like a smart charger for NiMH RC batteries?

I mean if you don't have that and just want to be done swap out #11 and put it back in and hope for the best... This guy sells really good used modules: Toyota Prius Hybrid Battery Cell 8.2v Refurbished 04-09 FREE SHIPPING | eBay

But if you want to be more thorough it'd be good to charge up all the modules to a full charge and then load test each module for only 2 mins. In your current situation module #11 is not being given the same test as the others due to unequal voltage.

Or now that you have the hang of the routine you could discharge and recharge each module to lower and lower voltage which will restore battery capacity. And yes, I know that it's super time consuming, but you could always buy multiple chargers and bulbs to speed things up.

It all comes down to how many times you want to take battery pack in and out of the car . The more thorough you are when it's out of the car, the less likely you have to do the whole routine again.

 

each individual module if it's super healthy is going to sit at about 8.2v charge 24 hours after you charged. And because NiMH self discharges alot in the first 24 hours, you'll find the Imax charger at 3.3 amps will go way above 8.2v. Usually I start out cautious and don't charge too high, so 8.4v is a good place to start, but because it's a smart charger and there's 6 cells in each module charging a bit higher at a low amperage rate will ensure all 6 cells in a module are fully charged/balanced. 8.6v is something I've done lots of times. Also have a bad battery pack from a 2004 that has charged modules all the way up to 9.0v, but I think that's because it was really cold out and the cells weren't balanced and it also had super low capacity. Will be interesting to see what happens to 'em when I start reconditioning them!

Most important is that the IMAX has a shutdown function when the battery hits full charge that seems to only work properly when it's hot out in summertime, and doesn't work at all when it's cold out.

 

Wow... Brilliant... Never thought of trying that...

How long did it take to charge up all of them with just one IMAX charger?

Going back to your first post you mentioned that 4 banks were saying 0.0 volts, which after looking at the battery isn't the case in terms of the health of the battery pack, but maybe it's the case with failed voltage sensors, which would definitely get the computers to throw a red triangle and shut off access to the battery to protect the vehicle.

Any sign of corrosion on the voltage sensing wires or bus bars? Any signs of physical damage? Wonder if something else is the problem like a bad hybrid battery ECU is causing this, or something in the voltage sensor circuit?

Perhaps best next step would be to charge the pack way higher so you're certain all 168 cells are well balanced and of equal charge and then voltage test after 24 hours or if you can wait longer that might help point out any weak modules that self-discharge faster than the others...

But at this point I'd say your modules are not the cause of this warning light and it'd be ok to put it all back together and start driving it again, maybe use some di-electric grease to inhibit corrosion and start out fresh soon as the red triangle comes back. Reading the error codes, especially the sub-codes would be the first step if warning light comes back. I don't think that was done when we first started on this one.

Another option if you want to be super thorough you could do three rounds of deeper and deeper discharge and recharge with the final round going down to 0.6v per module via your headlight bulbs, which is super time consuming, but it improves the health of the battery pack to like new condition for a while. The added advantage for you doing this is you might come up with a way to do this work faster than I've been able to. Very impressed with how you charged 'em all at once and that it worked and am eager to know how long it took to charge the pack that way.

 

How were the connections? Any loose?

If you are getting intermittent electrical reporting, I’d bet on a connectivity issue.

 

If you have a bad cell or two you'll need to drive it around for a while to make it worse because it's not yet detectable with load testing... But living in Las Vegas will help because the cells fail once the pack is above 100'.

If I were you I'd go higher than 8.4 in hopes the smart charger senses delta and shut off at a full charge. Just make sure you turn it off before you go to bed because IMAX chargers have a bad habit of not sensing full charge/delta. Maybe even charge it more in morning just to be sure? What's awesome about using one IMAX for the whole pack in parallel is that max amp to each module will only be 0.17amps, which means you can't really screw it up by overcharging or charging too fast.

Lastly, as of last May Torque app is no longer supported, so I'd recommend using hybrid assistant app with it's companion app hybrid reporter, which will give you 10 pages of data on your car even after a short drive. Then you can share that file on here and we can all see what's going on with this mystery. Also the Dr. Prius app is useful for reading error sub codes generated from the hybrid battery ECU.

Key thing to look for from these free apps is real-time data and how the battery modules act under max amp charge and discharge. If you have a fast enough OBD2 reader it will pick up peaks way beyond the battery packs 120amp fuse. One time I saw it catch a 159amp peak load that didn't last more than a 1/10th of a second.

 

So.......I just have to ask.......post #9 shows that module 11 is basically at zero energy compared to the others.......and we're somehow saying there's nothing obvious jumping out at us?

If it were my battery, the only way it could be more obvious would be if it hit me in the face with a hammer.............maybe that just comes from having tested so many..I wouldn't spend my time trying to recover that module. It probably has a serious self discharge issue. Why risk setting yourself up just to have it crap out again a month or two later, most likely at a very inconvenient time..

Post 1 with the last four blocks showing 0 is interesting. Either torque isn't setup right, there's a sensor/harness issue, or an ecu issue.

 

Go back and look at post #9, then look at post #1... The #11 module didn't discharge that low because of what happened in the car, but was given the impression that it was caused by early stages of learning how to do discharge testing.

I'd totally agree with you if #11 module got down to 7.37v on its own, but that's not what I thought was happening... And the fact that #11 didn't drop worse than all the others when all modules started at ~8.0v on follow up load test, I recommended more data gathering via re-conditioning, or putting it back in the car to wait for the bad cell to be more obvious.

 

I was looking at it as if....

November 2nd....got home from a drive....removed battery and checked voltages. Mod 11 was 8.11 v, similar to all the others.

Battery sits overnight while pondering options

November 3rd.. makes a lightbulb rig to do some testing. Checks voltages prior to load testing and now Mod 11 is 7.37 volts while all the others are 7.9+volts. That has "self-discharge problem" written all over it.

If the circumstances leading to the 7.37 are different, then I suppose it's possible that SD isn't an issue.