bad battery?

How long have you had the car? I ask because if its new to you, it could be that the battery just isn't living up to your expectations, not necessarily that its bad.

 

how is the 12 volt?

 

sorry, no. but i'm sure someone will. weekends can be slow and people don't pay as much attention. hang in there!

 

So when it's acting like it's got no power, what is the displayed state of charge (number of bars).

It certainly could be that your battery has lost some of it's capacity (amp hours), but as long as there's no actual failed modules the voltage would still measure ok.

 

No it's about 40% at the lowest bar. It's not really the exact amount of charge that's important though, it's the fact that the Prius wont use it (when it's low) that makes it sluggish.

Mine is also really sluggish if the SOC drops to red (2 or less bars) so I think that's pretty normal. The real issue to look into, is what's happening to make it that low in the first place (which certainly could be a low capacity battery).

I find that if let my engine warm up (idle in "P") for about 60 seconds before driving that the battery charge stays a lot higher. Are you noticing these issues predominantly soon after starting, or do they persist even after a long drive?

 

Are you still under warranty? If so, I'd be pushing it hoping it will throw a code that will convince the dealer to replace the HV battery pack for free.

The code is triggered when one of the banks voltage is greatly different from the average (I think 2 volts different). I would guess that is more likely to happen when the battery is charging to full, quickly depleting and then charging again. This is just my speculation though.

 

What warning lights appear?

If there are no warning lights then it is not obvious the traction battery has a fault.

 

As I mentioned on your other thread, this sounds to me more like an overheating issue. Possibly battery fan related.

 

Yep, that's exactly what I was thinking, once we knew it didn't happen until after it had been driven for a while.

Itwrx, take a look at this thread: Fur and dirt causing major battery problems | Page 2 | PriusChat

It would also be a good idea to make sure you inverter coolant system is in good shape.

 

No, that won't have hurt it.

Yes, that's what happens with series batteries. Once one loses capacity the whole pack effectively loses capacity. With the Prius however, it monitors all of the module voltages and will set off an error code if the pack gets too far out of balance like that.

I'm not sure what you can do short of doing a discharge test on every module. If you're really keen you could get hold of some chargers and try re-balancing the whole pack. If you do a search here there are several threads that detail how to re-balance a pack.

 

I think you would notice a bigger difference between the cells if the battery had a low SOC. I wouldn't get it too low, maybe 4 bars and then check it.

 

Yes, you would need to fabricate a suitable load. Since the battery will produce ~200V you need a load that will handle that voltage and also absorb sufficient current.

For example, buy four of the largest incandescent light bulbs (intended for household usage) that you can purchase along with suitable sockets and wire. Suppose you can purchase 250W, 120VAC bulbs. Wire the four bulbs as two pairs. Each pair is wired in series because the bulbs are rated for 120V. Then wire the pairs in parallel.

The four bulbs collectively will absorb 800W or so. The power consumption will be less than 1kW because the battery voltage is lower than 240V.

Then you need to connect the bulb load to the battery by bypassing the system main relays, without causing damage to yourself or the battery.

Once the bulbs are lit, you can measure the voltage across each of the 28 modules and see if one is lower than the others.