2001 Prius, rebuilt battery but shuts down still

Hi everyone,

I'm new to the forums. I have a 2002 Prius that works well and I love it, but that isn't why I'm writing.

I purchased for a low price a 2001 Prius from someone who had been told by the dealer that it needed a new HV battery. It is a "project" car and I figured it may be fun.

Anyways, I got the car towed to my house. It wouldn't start, but that made sense because the 12v battery was very dead. I took it to the local auto shop to be charged and borrowed the 12 v from my working prius and plopped it into the 2001. It started up with the triangle of death, the check engine light, and the battery icon.

I drove it around some side streets just to see what would happen. It seemed to behave in the textbook "bad battery" manner. It went from 25% to 100% on the battery meter very quickly. When reading low, the car sometimes lagged in acceleration.

I bought a battery from a salvage yard. It came from a prius had been in an accident. I put it into my 2001, and unfortunately the problems continued to just like before. For this test I had put the newly recharged 12 v battery back into the car.

So, I read some threads around here and became inspired. I took apart both batteries, charged them, and picked the modules that held the most mAh. I also discarded several modules from the salvage battery that read an incorrect voltage when charged.

I put the "combined" battery back into the car, and to my great enjoyment it started up without a battery symbol (although there was still the triangle of death and the check engine light). I did find that the 12 v battery was dead again, despite it having been driven very little, so i once again stole the 12 v from my good prius. The triangle and check engine warnings did not necessarily worry me because my 2002 occasionally showed those warnings after the 12 v battery was removed and replaced, but it always "went away" after a day.

I drove the car around some more and the HV battery appeared to behave normally. It stayed within the 50-75 range and there was no lag in accelerating. This is where things get interesting.

After about 15 miles the battery icon came on, but the car continued to behave normally. At around 20 miles I was at a red light with the battery meter in the dash reading 75% when I noticed the dashboard lights/ speedometer were dimming. The car was sitting with the ICE off waiting for the signal to change and everything seemed otherwise ok. Then, suddenly, the dash screen flickered, went totally white, and turned off. The car would not move. I turned the key to off and tried to restart, but it behaved as if the 12 v was low- the dash was dim and the dash screen would not get to the "Toyota" icon but would go white and then shut off.

I got the car towed home (getting the most out of my AAA membership) and pulled the 12 v battery to put it back in my good prius. It was low enough that I had to jump it to start the good car.

So here is my theory and I'd like some feedback: I have read that Priuses don't have an alternator, but instead use the HV battery running through a converter to power the dash, accessories, and recharge the 12 v. I'm wondering if my car's symptoms point to a problem somewhere in that converter system. The dead 12 v batteries, the way the car seemed fine for about 20 minutes of driving... It seems logical to me that if there were a problem with the flow of power from the HV battery to the car's accessories, the car might still run for as long as the 12 v had enough juice to make up the difference. Does this make sense?

Might this also lead to false battery warnings, which would explain why the battery light did not come on immediately as in the past but only after 15 miles, as the 12 v was drained?

I welcome your thoughts. I'm sorry I don't have any codes to report- if anyone knows a way to get a code reader I'd like to hear it! Since this is only a project car I'd like to avoid taking it to a dealer unless absolutely necessary, although when I bought the car the price was good enough that, as a last resort, I could buy a new HV battery and still feel I've gotten a good deal. Right now I'm just wondering whether I should investigate this converter idea further or whether it is more likely that the HV battery is just bad.

Thanks, Brett

 

Hello everyone,

Here is an update on the car.

First, the inverter coolant pump has failed. No bubbles, no pump gurgling noise.

Second, the battery voltage drops about 0.25 volts when the car is on. It continues to go down over time. I let the car run for 10 minutes and the voltage slid down about half a volt.

Third, by some act of god there is a salvage inverter on sale only 10 miles from where I live.

So my plan at this point is to get a replacement inverter assembly and pump. I feel comfortable enough in this diagnosis to make the investment without renting a scanner from Bob. Should I think twice about that?

I'm also trying to think about what to do with my extra battery cells. I'm thinking of putting an electrical assist on my bike. With 3/4ths of a hybrid battery I could really go

Thank you all for the advice so far. I'll wait to see if anyone thinks I should stop and check for anything else before I go pick up the inverter, but notwithstanding any surprises I may go pick it up tomorrow.

Brett

 

Yes, the inverter was cold. I was indeed hoping it would work until hot but no such luck.

Brett

 

Update: ordered a coolant pump. The Toyota dealership said there were only 10 pumps in it's system on a ship from Japan, all of which were spoken for. I ordered one online from ebay (it is new, not used). The person on the other end of the phone said that if the pump had died then the transmission would need to be replaced too. He did not sound particularly knowledgeable, but is there some truth to this?

If I ever get this thing working I'm going to call it the Frankenstein prius- stitched together from parts of the dead.

Brett

 

The 12 volt battery is not the issue because the problem is the same whether I use the battery from either of my two Priuses.

There may be a problem between the inverter and the battery, but the non-functioning coolant pump seems to make a bad inverter very likely? The pump must be replaced either way, and even if this doesn't fix the problem I'll have replaced an inverter that was running who knows how long without a cooling system with a salvage unit with only 64k miles.

If this doesn't work I'll be checking codes. Right now the investment is in line with the risk.

When this doesn't work I look forward to your "told you so."

 

And yes, I am done running the car to drain the 12v. She's charged up and has been running only 20 minutes since then. Right now everything is disconnected; I'm going to take out the inverter and have a look at it. Maybe I'll find a little lump of scortched plastic and metal where the dc dc converter should be? That would be handy.

 

My reasoning is that the pump not pumping nicely explains everything that is happening. It's like I found a body with a man standing over it with a knife. Sure, maybe he was framed, but it seems pretty likely that he did it.

Plus the time and expense of getting the scanner just isn't much lower than an inverter and pump (this may have been different if the inverter wasn't sitting at an LKQ 10 miles from my home). So I'm going to take the inverter out and go from there, at the very least I'm having a bit of fun and learning about these very neat cars.

I fully admit this is guesswork but it is at least reasonably educated guesswork.

Thanks,
Brett

 

Bob, I am happy to ship any and all things to you at the end. If you want some of my leftover battery modules you're welcome to that too.

I'll take pictures as I go.

I probably won't start on any of this until next week, so don't expect updates soon

 

Hello everyone,

I installed a new inverter and a new pump. The voltage on the 12 v battery now reads correctly. So the dc converter seems to have been the problem.

I am having another issue however. The new pump is running (I can feel it and hear it) but i cant get coolant to come out of the right bleed screw. The left bleed screw bubbled and bled coolant after only a few minutes, but the right one just doesn't show anything.

The coolant is reading full but I've only put in slightly less than 2 qts, which is not quite correct either. The right bleed screw seems to come from a hose out of the transaxle area, while the left comes out of the inverter area.

Thus my best theory is that for some reason the transaxle area has a blockage and that if i could get past that I'd have a bleeding screw and be able to add a little more coolant. The pump also cycles between quiet and loud, which I imagine is caused by air bubbles.

Any tricks to get rid of the air? Does it seem that there might be another problem? I think the pump is probably good; it vibrates and is a new toyota part.

A mechanic friend suggested that i may need to drive the car to heat it up and trigger a thermostat that will draw coolant. However, reading about other pump replacements on this forum does not show this to be necessary. He admitted he knows nothing about the prius and that it was just a "general" solution he might try. Does anyone know if heating the car is necessary in the prius? Should I give it a spin around the block and try bleeding it again?