Battery Vent runs loud, battery never discharges, slow/jerky acceleratio

There are three temperature sensors inside the battery pack, there is also an intake air temperature for that battery pack cooling fan.
if one of those sensors has failed the car could think that the battery is too hot, and run the fan more. Also when the car thinks the battery is too hot or too cold it will limit charging and discharging. So that may be why you don't see the battery level going down. There are several apps you can use. Hybrid assistant is the one I use. Primarily because I live in a very hot climate. And that particular app can override the car and turn on the cooling fan at a set temperature. But it will tell you the temperatures of most of the system's battery inverter engine and mg1 I believe.
Doctor Prius is another one that may give you some information. That gives more detailed information about the battery, and thirdly would be torque, which can also tell you I believe all three individual temperature sensors and the intake air temperature.
All three of those apps have free versions..
and even if you purchase them they're not that expensive. You will need a Bluetooth OBD2 device that talks to the car and sends the data to your phone or tablet.

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Have you cleaned the hv battery fan?

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Ken's guess makes sense to me, but without reading the codes, it's just a guess. The codes will save you untold weeks and thousands of dollars of expensive guesswork.

 

I have seen battery failure similar to this. Module failure causes the engine to run continuously, overcharging the remaining good modules, so overall battery voltage is at a high state, but the battery itself is only as good as it's weakest module. What are the bars showing first thing in the morning after the car has sat overnight? Even better would be one of the many apps available that can display individual block voltages. A significant module failure will show itself after an overnight period.

As Jerry said, the codes will tell the story....................

 

Certainly sounds like a failed/shorted portion of the High Voltage Battery.
Plan on spending around $2,500 if you have someone else install a NEW pack for you.

While they are in there make sure that they clean battery fan as well.

Don't be fooled by ads promoting drastically lower prices (We Fix Hybrid Batteries for $500!!!!)
Those are USED batteries and will never last as long as a NEW battery.

You definitely get what you pay for when it comes to batteries.

If you are a tinkerer you may be able to buy a NEW battery from your local Toyota parts department.
There are some specialized tools you will want to purchase for safety and to properly do the job.
Part will likely cost somewhere around $2,000?

 

p0a80 or some other HV battery-related code is set. Hybrid system is in failsafe, making sure that the pack has enough charge to start the ICE and that's about it. Current from and to the battery is very limited.

You may or may not have a shorted module, but if the code is set, one or more are about to become such anyways (sub-capacity cell in a module, etc).

Prepare for battery work.

If you don't do much stop and go traffic, the MPG shouldn't be affected much - the engine is still running the Atkinson cycle, and the slow throttle response probably makes you drive smoother

 

Another alternative is to find out what modules are bad, take the battery out on stack it and replace it with modules you can purchase on eBay for about 50 bucks. I would get three of them, usually if one module fails the one that is paired with ends up being damaged also. But you can find out this information with some of those apps, doctor Prius will show voltage and resistance on the blocks which is a pair of modules. I believe it also has some built-in tests that you can perform to check battery capacity. But you might not want to do that if the battery is suspect and stress it even further. one of their possibility is that the bus bars have become corroded that connect up the modules to each other. That can cause a high resistance between modules and set a code. you could probably clean the bus bars without taking the battery out of the car. But you want to make damn sure you know what you're doing and how to make the battery safe in order to work on it. It isn't that difficult friend and I have done this procedure a couple of times now on his 2006 Prius. Had a module fail and then a few months later another module failed. but you can certainly continue to repair it I'll hell of a lot cheaper than it would cost you to buy a new battery. I'm not sure that I would invest $2,000 in a car of this age, when you did spend an hour getting the battery out another hour just assembling the battery and repair it for a hundred fifty bucks or so. You can do that several times and still be well worth it financially. And once you have a stable battery Doctor Prius can test the battery for capacity and you can get a pretty good idea if the battery is going to last you a while. It's never a guarantee. there are plenty of videos on YouTube on how to take the battery out and disassemble it and also how to clean the bus bars. They're just brass links that need to be removed cleaned and put back in. If you live in a climate that's very humid or salty this is more of an issue in those areas.

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You swap one "bad" module for another, and the rest will come soon, as has been discussed here a ton of times. Search the forum for whack-a-mole

Long term DIY repair is possible, but requires:
-A source of good modules ("holds charge" is not enough - must be of adequate capacity).
-Hobby chargers and/or a grid charger & discharger.
-Time.

You can read up on rehydrating the pack as well, a few threads here and on greenhybrid (afaik). Even more time-consuming, and you'd better have a hobby charger and a temperature-controlled environment.

If you manage to rehydrate it properly, it >should< outlast a new OEM battery. I say "should" because then you're increasing the likelihood of other Ni-MH failure modes that are usually not experienced - can't give you any info about them, but I'd much rather have a shorted cell due to water evaporation and cell meltdown (electrolyte deposits on plates, less surface area, lalala… read up), than an open cell (resp. circuit since they're linked in sequence) and being stranded. Still, this is speculation on my end.

If you just do the regular "proper" DIY, it still won't be better than a new battery.

If you just swap out the failed modules, you'll have a battery that's only as good as the next weakest module, and only until that module fails as well.

New batteries from 2k1toaster (cylindrical cells) are $1600 without install, read through his threads before you decide that you want to go down that route. New battery from dealership - no clue in the US ($4k?), significantly less in the EU for whatever reason. (EDIT: look below, I stand corrected)

 

In the US, retail price at the counter is like in the $2,100 range.

Yes, if you are willing to invest many hours of time, you can pitter away at replacing individual modules. Heck, I'll sell them to you for $50 of you want.

But this is not a long terms fix.

You are just kicking the problem down the road. And in the meantime you may have an unreliable vehicle.

As others have mentioned, if one fails, others will follow in the coming weeks/months.

And each time you replace module you are adding more variability to your pack. The Prius does not like variability. It likes thing to be the same.

You can combat this variability by purchasing charging/discharging equipment. And spending even more time fussing with the battery pack.

If all this time and effort and unpredictability in your car worth the savings? Only you can decide that.

For a single guy who has a lotlof free time, can walk to work as needed or has another car. Maybe it is worth it.

For a guy with kids that need to be driven to school/childcare, has a job that he needs to be in time, and only one car.. maybe all this fussing is not worth it.

 

I guess I'm way behind on US prices, sorry for posting so much confusion lately. Still wondering why lexus dealers can charge $7k ^_^.

One thing about the charge/discharge - from what I've read if the pack is far gone, it can maintain it... but water has evaporated regardless and crystalline deposits form faster, therefore needing cycling more often, etc. Maintaining a new pack this way sounds like a better idea to me - breaking down deposits to keep temperatures in line.

 

I don't know my friend has a 2006, swapped in a couple of cells, end up having to swap 2 more just as you guys have said. But since then he's put 40 or 50 thousand miles on that pack.
I think it all depends upon how much time you want to spend and how much money you want to spend. I don't know that I would put $2,000 into a 10 year old car. I can buy a lot of $50 modules and spend a 2- 3 hours fixing it. It all depends on what you're using the car for I guess. but with the apps that are available you can get a pretty good idea of how balanced the cells are and if the pack is healthy overall. Doctor Prius will do a battery capacity test, it can tell you what the resistance is across each block and the voltage on that block..
I guess it just depends upon your priorities, how handy you are, and what you're going to use the vehicle for.
I personally drive it 2008, it currently has 273,000 on it still running on the original pack still showing 55% of capacity when I test it. I put 55,000 miles on it last year alone. Obviously I bought it used.. with about 200k on it.
So far my only failure has been the brake accumulator pump. Which I bought at a salvage yard and replace myself.

I think if you're not handy with cars, you're best off to buy a newer one with a warranty. Or quite frankly don't buy a hybrid if you're going to stay with an older model car you're probably better off with a Corolla. Still gets decent mileage and eliminates a lot of the issues that age causes on a hybrid.

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That's one experience.
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So you're putting some sort of cap on repair costs/things worth doing solely based on the age of the car, regardless of what the repair is or what the car is?

Russian roulette, whack-a-mole, however you want to call it. You can probably bring down the work time to an hour or so if you really want to, but you're still blindly changing clearly failed modules with modules of unknown capacity, never mind the condition of the existing modules in the car.

Buy an iMax b6 or whatever ni-mh hobby charger that you can program charge/discharge rates of, and you've got the basic equipment to test all modules and make better guesses... but it takes far longer than 2-3 hours. You're still left with the problem of how good are those $50 modules, unless you decide to rehydrate.​

dr Prius can approximate the per-block capacity. This is 12 cells in sequence. Read up on coulomb counting, and on ni-mh's voltage output depending on its SOC. Combine that with the fact that the car tries to keep the modules between 40 and 80% charge.
So yes, you can approximate capacity, and which blocks are better than the rest (most likey a V-shape). Cell-level balance? Nope.

Speculated 55% capacity. Yes there are many reports of Toyota/lexus hybrids running past 500k miles on original traction batteries. On the other hand, the ones that start to fail usually have quite a few more modules on the way of failing. Failed module usually means melted/internally shorted cell. Dumb (not entirely correct) explanation - you lose capacity due to losing electrolyte and due to crystalline formations in the cell. One happens because of heat and venting of the water component, which might accelerate two (less water to hold the chemistry). Two causes heat due to less surface area for the current to pass through, leading to one. One can be reversed by rehydration, two can (almost completely, apparently) be reversed by a combination of deep charges, deep discharges and temperature. So as a cell loses capacity, it tends to heat up more, accelerating the process. It also heats up the surrounding cells and modules. The modules in the middle of the pack tend to run hotter. Guess what happens

...or just get one with a failed traction battery, spend $2k on it and enjoy the benefits. Mileage is not the only reason to go hybrid. Or get an early 1zz-fe corolla and run it on dyno so that the piston return holes clog (if they haven't already) ​

 

You'll see the code get triggered more often as time progresses. Now is your opportunity to weigh options.

 

It's all fun and games until something catastrophic happens. Like the modules shorting out, bursting and spraying the interior with a nice film coating of electrolyte. IsIthis common? Nope. Have I seen this happen? Yup.

Hopefully you can see the data live and can tell when you are getting to the point of no return.

If you are replacing a module, buy a couple now so that you are prepared. Easier to run out and get parts when you have a (semi) operable vehicle.

Clearing the code does not really fix anything.
Actually leaving the code set may help somewhat protect the battery. As opposed to clearing it and allowing the battery to get pummeled.