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Hybrid battery or not?


Ferretkeeper
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My 2009 gen 3 Prius is having problems with the hybrid system. It’s definitely not working and a mechanic friend of my sister, who admits he’s not an expert on hybrids seems to think the hybrid Battery needs replacing. A new Battery for a 2009, 120,000 mile Prius probably isn’t worth it, but a rebuilt one might be. I’m trying to book it into a Toyota dealer to check that the Battery is the problem but they seem a bit busy. I spend some time out of the country and I’m having trouble getting it checked before I leave again. The battery may well need replacing, but there are a few things that make me think that may not necessarily the case.

The car isn’t used that much now but I still have it serviced well within the 10,000 miles, although not necessarily within the 12 months. It was serviced as usual at the main dealer in December 2022 and the battery check was fine. The next service was about 4000 miles later in July last year at a Lexus, Toyota specialist but the battery wasn’t checked but the car was working OK. When the MOT was done, whilst I was away it needed a new 12v battery and when it was driven back it started to go wrong.

Apart from the fact that the hybrid system is clearly not working, four lights come on in the central display. All these are amber, not red. The engine management, traction control/hill start assist, brake warning and master warning triangle. Apart from a slight lack of power at higher speeds, at lower speeds up to 50 or 60 mph, in town or on country roads where it is most of the time you wouldn’t know there was a problem. I’ve tried braking heavily and they seem to be OK, although it’s possible any ABS or other braking assist may not be working. Obviously the Power, Eco and EV modes don’t work, but the cruise control also won’t turn on. That wouldn’t seem to be connected but I have seen it suggested on some forums that the cruise control is affected if there’s a problem with the control system for the hybrid mechanism.

One thing that I’ve noticed is that on the central display there is the  “Check Hybrid System” message, but if you switch to the energy monitor screen the battery shows as fully charged. It doesn’t go down as normal as the battery isn’t being used to power the car but it does lose one bar sometimes, and then it goes back up again. This display doesn’t show any other information regarding the power transfer.

Does any of this suggest that replacing the battery might not solve the issue and instead it may be another problem, possibly with the hybrid control system?

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17 minutes ago, Ferretkeeper said:

....   Does any of this suggest that replacing the battery might not solve the issue and instead it may be another problem, possibly with the hybrid control system?

Quite the contrary, replacing the Battery probably will solve the issue, but that is just a guess.  If you can post the DTC (fault codes) your car has logged, we could say with more certainty whether that's the case.

17 minutes ago, Ferretkeeper said:

...   instead it may be another problem, possibly with the hybrid control system?

If you have a problem with the hybrid control system your car would not be driving at all.

Also, not driving a Hybrid is a recipe for problems, they like to be driven.  If you no longer drive many miles or frequently maybe consider selling the car and replacing it with a non-hybrid.

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9 hours ago, Joseph D said:

Quite the contrary, replacing the battery probably will solve the issue, but that is just a guess.  If you can post the DTC (fault codes) your car has logged, we could say with more certainty whether that's the case.

If you have a problem with the hybrid control system your car would not be driving at all.

Also, not driving a Hybrid is a recipe for problems, they like to be driven.  If you no longer drive many miles or frequently maybe consider selling the car and replacing it with a non-hybrid.

Unfortunately I don't have the equipment to check for fault codes. I was puzzled by the fact that the HV Battery was showing as charged. It obviously wouldn't discharge very much as it isn't being used to power the car but it does lose one bar, probably due to normal discharge over time, but then charges again. I know individual cells can die, and that seems to be what happens over time. In that situation, would the Battery still display as charged. The energy monitor screen shows the charge of the Battery but not any information on the power to or from the engine or the battery. It does show the wheels rotating when the vehicle is moving. Looking at numerous posts on various sites, it seems the engine is started by the HV battery, or, on one site,  "one of the two motors in the transaxle to start the engine." If the latter is the case it might not need the batter, just the power generated by the electric motor.

I was thinking of getting rid of my car as it's getting difficult when I'm away. My sister looks after it and when she had a Fiesta that kept going wrong she used it a lot, but now she's got a more reliable Kuga she doesn't. I just think it will be easier to sell if it works properly.

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It's a strange set of symptoms, if you were anywhere near me I'd be happy to read codes for you (I'm just a DIYer). I'm in the West Midlands 

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On 4/28/2024 at 2:42 PM, Saxmaniac said:

It's a strange set of symptoms, if you were anywhere near me I'd be happy to read codes for you (I'm just a DIYer). I'm in the West Midlands 

I'm in Southampton, so some distance away, although I'd happily drive that distance to try to sort this out. Fortunately I've been able to get it booked in for a Battery check at the dealers on 13th May. If it isn't the Battery then it must be something else, presumably in whatever controls the system. That might be expensive as well, but at least I'd know what needs to be fixed, and have a better idea of whether it's worth it. If it needs a Battery then a new one would be too much but a rebuilt one may be ok. The dealer does supply them, but the last time I asked they didn't have any. There's a company in Milton Keynes, ITS Autos that do them and seem to be ok, although it's difficult to know for sure. I don't know if anyone on here has used thm.

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Rebuilt batteries are a total nightmare, just second hand cells. Think, if you had a torch using 6 D cells, it got a bit dim, would you look for the weakest, replace it with another second hand one that appears to have the same capacity and hope for the best? The next one would fail at any time. That's a gross simplification but the only solution for a knackered Battery is a new one. You really need to know if you need a Battery though. A dealer is probably the worst option for diagnosis and repair of an older car, you need a really good diagnosis by an independent who knows what they are doing! 

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1 hour ago, Saxmaniac said:

Rebuilt batteries are a total nightmare, just second hand cells. Think, if you had a torch using 6 D cells, it got a bit dim, would you look for the weakest, replace it with another second hand one that appears to have the same capacity and hope for the best? The next one would fail at any time. That's a gross simplification but the only solution for a knackered battery is a new one. You really need to know if you need a battery though. A dealer is probably the worst option for diagnosis and repair of an older car, you need a really good diagnosis by an independent who knows what they are doing! 

You maybe right, but I tried an independent and they said I needed to take it to the dealer. If it needs a Battery I don't think a new one would make much sense economically. Once I've found out if it's actually the Battery that's the problem then I can decide what to do. I probably need to get rid of it anyway so it's a choice between a rebuilt Battery or selling it as it is.

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Get the car into a dealer and get it scanned for fault codes. I used to own a 2013 VW Touareg which threw up several warning lights similar to those you are experiencing (ABS/ESP/Lighting/Engine/Cruise Control). It was a faulty ABS sensor and easily enough replaced. It’s pointless just guessing or relying on other people’s opinions when it’s simple enough to have the car scanned for faults 👍

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8 hours ago, CassUK said:

Get the car into a dealer and get it scanned for fault codes. I used to own a 2013 VW Touareg which threw up several warning lights similar to those you are experiencing (ABS/ESP/Lighting/Engine/Cruise Control). It was a faulty ABS sensor and easily enough replaced. It’s pointless just guessing or relying on other people’s opinions when it’s simple enough to have the car scanned for faults 👍

I've managed to find a dealer who can do it on 13 May.

The reason for the OP was to see if anyone else had experienced something like this. Looking at this and other forums, plus YouTube was a bit confusing. Many said you could drive with a failed Battery, but it would be slow and rough. Mine isn't, it fact during normal driving it's no different, apart from the fuel consumption. Others say it's the HV Battery that starts the engine, so if that isn't working, the engine won't start, which would stop me driving it. Then again one said it was the electric motors that start it, and since the HV Battery appears to be being charged that would explain how mine works whilst in motion but wouldn't explain how it starts after first getting in the car.

Hopefully I'll find out. It may be a problem with the control mechanism, which may or may not be less of a problem.

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As stated above, it's no use making random guesses, it could be anything

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It is the hybrid Battery that needs replacement most likely as per the age, mileage and the symptoms plus the warning displayed.
There is nothing unusual or unexpected at this point, hybrid batteries like any other batteries has a lifecycle and this depends on usage, mileage and conditions, temperature, cooling etc. 
Check hybrid system malfunction warning ⚠️ its in most cases a sign of dead hybrids Battery., of course this needs to be confirmed by scanning the car with diagnostic equipment. 

Replace hybrid Battery only with original Toyota battery. 

Anything else as already mentioned it’s only postponed problem that likely will return in very near future.
Only real fix is new original Toyota battery.  If your car is in good shape , has no excess rust, engine doesn’t burn much oil and the car is in general good condition £2000 for a new battery fitted in Toyota dealer is worth any penny. A good Prius will cost well over 5-6000£. If you want to sell it then just sell it with the faulty battery and someone will buy it , fix it and enjoy it or sell it for a profit. It’s down to your personal preference and circumstances. 
Here my personal experience example. 

 

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