2002 Prius Battery working one day...not the next

Start and stop the car three times and report if the error indicators go away.

Consider replacing the 12 VDC auxilary battery.

Bob Wilson

 

The problem is not that you need to put "juice" in the traction battery.

The problem is that you have a high voltage leak, which is indicated by P3009. The problem could be a battery module leaking electrolyte that touches the battery case. Or, the traction battery ECU could be bad. A motor within the transaxle might have a defect in the stator wiring insulation. Or the inverter might be bad.

 

Patrick is right. An electrolyte leak could easily be humidity and temperature sensitive but I always like to know the 12 VDC battery isn't marginal. A weak 12 VDC battery can cause a host of intermittent problems.

Bob Wilson

 

Concerning "parked the car for about 2 weeks and drove something else..when I came back to use it again, the starting battery was dead."
Yes the starting battery is dead and after that long I'm sorry to say the HV battery is also degraded.
The battery pack is not designed to hold a charge that long. In the manual it clearly states not to leave it longer than a week without driving/charging it, and that's assuming a brand new one. In my 03 (6 years old now) it needs to be driven at least every two days or else the hv battery is =<50%. On the 06 I can leave it longer (maybe 5 to 7 days) because it's newer, and always has full charge when parked. If you let the battery pack discharge below about 30% charge, ie:>1week - it will ruin the cells ability to achieve full cell voltage. Also it will draw much more charge current and also get very hot -thus the error codes.
With age the batteries loose their ability to "retain" the charge for as long as they did when new.
Good luck on it and please keep us posted. Thanks

 

Just found this forum. I, too, have a 2002 Prius that is having similar battery and start up problems. Maybe. I also suspect the auxiliary battery. That's the one in the trunk, right? Where can I get one of these? Does it have a particular model name?

Also, would putting a battery charger on the existing auxiliary battery be a good idea, instead, or temporarily? Would any battery charger do this safely? Or at least any charger that works automatically and cuts off? Would a 10 amp charger be OK?

Sorry to be so basic about all this.

Wally

 

The 12V lead acid battery start to show it's age at extreme cold or hot weather. I would check that out first and eliminate it since it is much cheaper than the HV battery.

 

You can get a quick disconnect from Walmart for $10 to disconnect the Auxilary battery when not in use. I use a Mazda Miatta battery for my 2002 battery replacement with a 2x4 block under it to adjuast the hight.

Tracktion battery: When i took the tracktion battery out in 2008 and opened it, all connections were green. All cells read 7.56 DC volts after it was idel for 3 months. Connector cleaners and a tooth brush did wounders. It ran for 2.5 years without any problems. Now I am getting the same codes and cleaning the connectors did not cut it. I am looking for tips on how to diagnose other components such as the ECM.

 

It would help if you post the DTC that you retrieved.

If the DTC point to the traction battery, I suggest that you again measure the voltage of each module. It is likely that you will find that one or more have a voltage reading significantly below the others. That module (or modules) will be the one(s) that need to be replaced.

 

Careful with that.

When my 2002's 12v system battery got weak, the car started throwing codes, and even had runnability problems just after starting. I thought at first it was the MAP sensor. There is a 12v diagnostic available, which helped. It reads 'lower' than the battery at the terminals, losses through the system etc. If the computers etc are reading the 12v system too low, weird things start happening.

If you don't keep-alive the 12v system, and don't have an updated MAP sensor, you'll have problems with that after reconnecting 12v and trying to start the car. It's stops running after a short time. There's a workaround for it, look up the details online. I believe it involved doing 'anything' that would put a load on the drive system. Turn the AC on, put it in drive with the brake on, etc. Run it for a bit after that, letting everything charge up. Then drive around a bit to let the computer relearn the MAP response. It took a few weeks for all of the symptoms to go away (like car threatened to or actually stalled while backing out of a parking space - engine was cold, so it wasn't the normal shutoff; ran rough for 10-20 seconds during the warmup cycle; that sort of stuff).

 

By the way, it turned out my original 12v had a cell go bad. 8 years in MN.

 

w2CO: If one has unknown drains or larger than normal parasitic drains and both the 12V and the HV could be dead after two weeks, especially if the OP was not aware of the batteries condition. It sounds like this was the case, plus perhaps something was left on ( a dome light ) for instance. I am now in Germany and will be leaving my Prius for three months. Of course I took the precaution of charging both battery systems and disconnecting the 12v. AND leaving my trunk hatch ajar :cheer2: