Slow acceleration, Battery not charging, Transaxle slipping

All signs point towards the car needing a different high voltage (traction) battery pack. The P0a80 code pertains directly to this.

There are options for pack replacements other than new packs from the dealership service department. Maybe someone will chime in with a business near you that caters to pack replacement with salvage units.

Interestingly, this is the second recent post that mentions transaxle slipping. It's not actually slipping, but this is how the hybrid system behaves when charge state of the HV pack is inadequate.

 

Sounds like a new traction battery is in need

VS980 4G ?

 

you're not too far out of warranty, see if they'll cut you a deal.

 

It is a statistic that has been seen on PC for a while now, where traction batteries from hot climates have a reduced lifetime. Parking in the hot sun after the battery has heated up is particularly hard on it.

 

Another 1 time poster talking about "slipping tranny". There is another one on the same page. Smell fishy to me.

 

I am actually having some similar symptoms on my '05, only just out of warranty (101,000). I'm not sure about the "transaxle slipping", but I have had some of the same traction battery anomalies over the last couple days.

• With no significant changes in our predominantly city driving, the traction battery indicator is staying almost exclusively in the purple zone except for steep descents.
• I've also seen at least one occurrence of the erratic behavior where the meter jumps up several blue bars within 10-20 seconds, and then just as rapidly returns to the single purple bar.
• The ICE runs even when at a stop as the system attempts to charge the traction battery.
• No AC running, didn't leave the car powered on, and the 12V appears okay (>12 according to the onscreen diagnostic)
• No dash warning lights at all, no red exclamation point of doom

Last night I drove the car on the freeway for ~10 miles roundtrip and that managed to get the charge back into the blue/green zones. But more city driving today has brought it back down to the single purple bar. As a result, acceleration is noticeably slower and there is some slight lunging as the car accelerates.

Pretty bummed if this is a traction battery issue given that I am literally only a thousand miles outside of the warranty. Plus I've only owned the (previously single owner) car for the last 20K and was expecting far more mileage out of the battery. Looks like a trip to the dealer is in order, but if anyone else has experience with similar symptoms I'd be curious to hear the outcome.

 

With no lights or warnings, there will be no DTC's set, so the dealer may be of no use. If the car does not say it is having a problem, they won't know where to start. And they won't help with the battery if you don't have specific HV battery codes.

Make sure that the engine is putting out its full power. Check the air filter, spark plugs, throttle body. Anything that makes for reduced power from the engine makes for more reliance on the battery. Let the engine warm up before starting out, as that can reduce stress on the battery as well.

Check the 12V battery at rest, with a load such as the lights on, and with the car in ready mode. It should be >12V with a load, and >13.5V when in ready.

However, if the charge level goes through sudden jumps, up or down, frequently, then that says the battery is getting weak. It does normally jump once in a while, but frequent changes are not good. You might get a hold of a mini VCI and look at all the battery voltages and resistances to see what sort of variation there is.

 

Thanks for your quick reply, much appreciated. And thanks as well for the guidance regarding the dealer, you just saved me some hassle (at least for now).

I recently had the 100K maintenance done at the local Toyota dealer and no red flags were raised (besides some coolant seeping but I'm watching that). I'm technically inclined though not much with cars, but I'll make my way through your suggested check list as best I can and report back. So far, air filter looks fine and the 12V is 12.6 at rest, 12.0 with headlights, and 14.2 at ready. I also recall that the 12V was replaced by the previous owner around 70K or so.

More anecdote, just took the car for short (5 min.) drive around the neighborhood after a brief 1 min. warmup. For the first minute or so of driving, HV battery increased steadily from three blue bars all the way up to green. The HV meter oscillated between blue/green as I drove around for another minute. I then came to a full stop to see if the ICE would switch off (per the usual behavior prior to two days ago). Funny thing happened: ICE kept cutting on and off repeatedly as the HV battery dropped bar by bar to a single purple, at which point ICE stayed on continuously. Any other thoughts on what might be going on? Seems like something more than just reduced power output. This all began quite distinctly over the last couple days; previously, things were all normal (at least as far as I could tell).

Could you share any more info/instructions on how to go about checking voltages/resistances with the mini VCI, presuming I'm able to get ahold of one?

 

When you connect Mini VCI and activate a connection with the traction battery ECU, the unit will display voltages and internal resistances of the 14 module pairs (the traction battery ECU monitors pairs of modules. There are 28 modules installed, hence 14 pairs.)

 

mini VCI is obtainable from Amazon, eBay, others. Here is the sort of info that one can get:
Best software / hardware to recover codes from 2004 Prius? | PriusChat

Your last anecdote does seem to be diagnostic of poor battery performance. The straw poll here on PC shows that the car can have significant driveabilty issues and still not throw codes. Perhaps you will find that one module pair (a "block") has diverged from the rest. If you start to hear the battery cooling fan running in the back seat, you will need to do something sooner rather than later.

Toyota has been absorbing some of the cost for those who also have been getting dealer services, when they are just outside the battery warranty limits, so that is something to keep in mind.

 

Thanks for the added info, I'll keep monitoring things. Is there a way (either for me or the dealer) to definitively test whether it is the battery, without actually pulling the battery and testing individual cells? Would the mini VCI help with this?

More bizarre behavior this morning: after shutting off the car last night with one purple bar, started up the same this morning. But very quickly (within a few blocks of driving) the battery ramped back up to blue/green. My wife is running errands this morning and reports back that the battery remains in the normal blue/green range. Very weird. Any chance that warm air and/or engine temps might be related? Just trying to find some sort of correlation with the timing of onset for these inconsistent battery symptoms.

 

That link above shows an image of exactly that, the monitoring of the battery, in pairs of modules called blocks. It is the same software the dealer uses, but they won't unless you get a DTC (and light on the dash) that says "HV battery failure". Until then, technically you don't have a problem. Your battery symptoms indicate weakness, but not yet a failure.

What is your mpg while going on the straight and level at a constant speed of ~50mph?

 

I'll have to check on the highway speed mpg over the holiday weekend, but it's definitely lower than usual for our city driving (~40 mpg where normally in warm weather it's closer to 46-47). SOC has largely stayed in the 4 to 6 range today, and only rarely in the 1 to 2 range.

To be honest, I've never much paid attention to the SOC meter so I don't know what "normal" behavior looks like. At what frequency would the SOC level be expected to change under city driving? Seems like mine is sometimes fluctuating as often as every 10 seconds or less.

Thanks for the additional clarification on the mini VCI, I'll get one ordered asap.

 

I managed to get the MVCI up and running over the weekend. I'm pasting below a HV Battery data snapshot. Looks to me like the voltages and resistances are okay, but what about the Delta SOC? It stays pretty consistently around the 80% mark which I gather is way above the expected range.

I also tried monitoring the min/max voltage as discussed here (Predictive battery failure analysis for the Prius Hybrid) and they seem to track pretty closely within 0.1–0.3V. I also drove around my neighborhood while recording the HV Battery output. One thing that stood out is that the SOC drops about 0.5% every 1-3 seconds or so, even while parked in "P". See the attached image: the first stair-stepping drop in SOC is while in D but with my foot on the brake, and the second stair-step drop is while in P.

Any advice or suggestions greatly appreciated, thanks again to everyone.

[HV Battery Live] System

[Parameter] [Value] [Unit]
Engine Coolant Temp 127 F
Engine Revolution 0 rpm
Vehicle Spd 0 MPH
Engine Run Time 62 s
+B 14.190 V
DTC Clear Warm Up 255
DTC Clear Run Distance 34821 mile
DTC Clear Min 65535 min
MIL on Engine Run Time 0 min
MIL Status OFF
Mileage after Malfunc 0 mile
Battery State of Charge 49.0 %
Delta SOC 77.5 %
Batt Pack Current Val 1.08 A
Inhaling Air Temp 82.4 F
VMF Fan Motor Voltage 10.0 V
Auxiliary Battery Vol 14.0 V
Charge Control Val -7.0 KW
Discharge Control Val 21.0 KW
Cooling Fan Mode 3
ECU Control Mode 0
Charge Control Signal ON
Equal Charg Out Rly Sig OFF
EQTR Charge Perm Sig OFF
Standby Blower Request OFF
Temp of Batt TB1 109.9 F
Temp of Batt TB2 115.9 F
Temp of Batt TB3 106.9 F
Battery Block Num 14
Batt Block Minimum Vol 16.39 V
Minimum Batt Block No 5
Batt Block Max Vol 16.51 V
Max Battery Block No 14
Battery Block Vol -V01 16.48 V
Battery Block Vol -V14 16.47 V
Battery Block Vol -V02 16.42 V
Battery Block Vol -V03 16.43 V
Battery Block Vol -V04 16.39 V
Battery Block Vol -V05 16.45 V
Battery Block Vol -V06 16.44 V
Battery Block Vol -V07 16.42 V
Battery Block Vol -V08 16.41 V
Battery Block Vol -V09 16.45 V
Battery Block Vol -V10 16.43 V
Battery Block Vol -V11 16.42 V
Battery Block Vol -V12 16.45 V
Battery Block Vol -V13 16.44 V
Internal Resistance R01 0.026 ohm
Internal Resistance R02 0.027 ohm
Internal Resistance R03 0.027 ohm
Internal Resistance R04 0.027 ohm
Internal Resistance R05 0.027 ohm
Internal Resistance R06 0.027 ohm
Internal Resistance R07 0.027 ohm
Internal Resistance R08 0.027 ohm
Internal Resistance R09 0.026 ohm
Internal Resistance R10 0.027 ohm
Internal Resistance R11 0.027 ohm
Internal Resistance R12 0.027 ohm
Internal Resistance R13 0.026 ohm
Internal Resistance R14 0.027 ohm
Battery Low Time 0
DC Inhibit Time 0
Battery too High Time 0
Hot Temperature Time 0
Compliance Regulation OBD2
Emission DTC Num 0
The Stored DTC Num 0
Calculate Load 0.0
Throttle Position 16.0 %
Complete Parts Monitor Avail
Component Monitor CMPL Complete
Component Monitor ENA Enable