Prius Battery Pack Apparent Death

Our gen 2 2005 Prius has 180k and has been awesome.  Until today.  I just got back from a trip and it's been sitting for 6 weeks.  It started right up no prob and I let it idle for a while while I checked tire pressure on a few of the cars.  It idled a bit, then would start and stop after about 3 seconds and wait for another 30 seconds and do it again.  So I figured it was fine and shut it off.  
 

sent my wife out it in an hour later and the red death triangle came right up.   
 

pOA80.   Looks like a hybrid battery pack issue.

I used our amazing search engine to try and find a thread where someone was selling a new pack from their daughter's crashed Prius (iirc). 
 

can anyone point me in that direction??

and anyone have any good writeups on how to fix it short of just buying a whole new pack?  (Testing and replacing cells...)

Uggg. 

Open CL/FB and see if someone local is parting out. 

Or, open car-part.com and see what local JYs are asking. 

I've had a lot of Prius but never had battery trouble so I haven't done any cell swaps myself but the are lots of YouTube on the topic. 

The GRMer with one for sale was in NC and that is likely coat prohibitive to CA. 

My real suspicion is that the 12v battery is weak from the long sit. The car is cycling to charge the 12v.  It couldn't hurt. Put the 12v battery on a charger. 

$50—$200 might get you the cells. $500 might get you a whole plug and play, used unit. $800 might get you a tested, refurb'ed unit. 

Suspicion of weak 12v...

Does your car have a smart key, the kind that senses you've arrived and unlocks the door proactively? 

If so, the system is always "sniffing" for your radio frequency. This constant sniffing is hard on the battery. Right under the steering column is a push button circuit breaker for turning off this feature. Try turning it off. 

Little known fact, if your Prius is equipped with a smart key, it gets a larger battery than the Prius w/o the option. This larger battery is needed because the sniffing runs down battery. 

Try this, take the battery out of your truck, a big 12v battery. Put that battery in the Prius trunk and hook up to the tiny 12v with jumper cables. Drive the Prius this way. See if conditions improve. 

You can even bypass the tiny 12v and just hook jumper cables to car's battery leads and drive this way. 

Good call.   I'll do that.  
i assumed that if the 12v was weak it would have just ran to charge it but it didn't run much and it definitely should have!

If you happen to recall who was selling or could find a link, I wanted to see if They might be interested in shipping.  

I bought a lifetime battery for mine from greenbean in mine

jfryjfry said:

If you happen to recall who was selling or could find a link, I wanted to see if They might be interested in shipping.  

I think this is what you are looking for.

In reply to Slippery :

Yes indeedy.  How'd you find it??

Dusterbd13-michael said:

I bought a lifetime battery for mine from greenbean in mine

Thanks for the heads up - they aren't local to me unfortch but if it looks like the pack is truly bad, I'll call them up. 
 

i am hopeful it's just related to my car sitting for a month. 

jfryjfry said:

In reply to Slippery :

Yes indeedy.  How'd you find it??

Old school way. Going through every page of the for sale forum lol. I had some time :)

I've spoken to one or two battery replacement pros. They recommend against replacing individual cells. Much more time consuming vs replacing the  entire pack, plus the remaining "good" cells are still on borrowed time. Granted, they have a bias in steering me towards a full battery replacement, but I see the logic

That was me selling the battery, I forgot to update the listing, someone bought the whole wrecked car.  The aftermarket batteries get mixed reviews, I went with a new Toyota battery because they had it in stock at the local dealer & let me skip the core charge.

How far are you from Bakersfield?  There is a great Prius specialist there, Reprius, that can do battery packs if needed.

Put a good battery in there and connected it to the 12v via jumpers and drove it around town for a few minutes with no change. 
 

i pulled it off and did some reading that some people have driven theirs in this condition for many many miles and months, and some had it come and go so I figured I'd drive it a bit. 
 

drove it about 1 mile to the store and it had the triangle, check engine, vsc and the brake (drum brake icon) lights illuminated.   The battery pack was only at 2 purple bars when I started. 
 

On the way home the vsc and brake lights were off and the battery ended up at about 75% charged. 
 

Im going to try and get and connect the dr Prius app to see if it can give me specifics on the problem.  

also Checked and it's 14v while idling and the 12v battery is probably 1.5-2 years old.  Plus it fired the car right up when I got home after sitting for 6 weeks so I'm not looking at it as a potential source or cause of the problem  

i can't help but think it's something related to sitting and not on a charger for those 6 weeks and therefore maybe something I can fix. (Corrosion somewhere?  That apparently can cause it and we are near the ocean). 
 

about to drive it on an 11-mile round trip.  Hopefully it doesn't strand me!

Try this...with the big 12v hooked up, do a code scan and clear the code.  I have had situations where with my Torque Pro App, I read codes and it returns no codes but then I clear codes and the situation improves.   I take this to mean that this action does a "refresh" to the ecu.  

I have mentioned before that sometimes these cars seem to get "confused" and I have found that much of this confusion is weak 12v related.  

You said the 12v is only 1-2 years old.  It is then likely fully under warranty.  If so, you might consider trying to get them to warranty the battery.  If you can get a fresh one for zero dollars, there should only be upside to that.  

I still think this is all related to 6 weeks of not driving and the small 12v battery being the culprit. 

I guess I really don't think your 12v is bad but that is just drained down over 6 weeks of smart key sniffing.  Get the 12v battery back to a good level and the car will be fine again.  

If you use Dr. Prius I caution you of its graphing and that it can be a little deceptive.  I just pulled these images of my phone and from my DD 2008 Prius.  This is the same Prius that I drove yesterday  for 5 hours and more than 360 miles, returning an average mpg of 41.9 even though most of my speeds were north of 80 mph (north Michigan driving.)  

Notice that the graphing makes it look like the cells have radical different voltage...its a  scaling problem.  The reality is that as circled in blue, they are all generally the same number.  

Two pictures taken just within minutes of each other:

By way of the graph above, #5 cell looks terrible but upon closer inspection 15.23v is generally the same as #9's 15.26v.  The graph makes them look terribly different.  There is no problem there.  

Minutes later, #11 looks bad...but its not.  

Here's how I have my Torque Pro set up.  I took this screen shot yesterday (just for the heck of it) while I was driving.  Actually, without a regular tach in the car I wondered how many rpms 80 mph represented.  

What the numbers say:

13.7v for 12v battery read at the Control Module (CM)
82 mph at that moment
13.8v for 12v battery read at the OBD2 adapter (ADapter)
62.5% SOC state of charge for Hybrid
2322 rpm at 82 mph
185.0 coolant temp
17.5 to 17.1 individual 14 hybrid cell readings at that moment which are generally all the same number
82.4 degrees outside
76.5 degree temp air coming in to cool the hybrid battery (or the interior temp of the car as the air enters to cool the battery)
97.0, 98.8, 97.8 as the three readings over the battery pack
2.0 is the battery fan has chosen setting/speed #2 of 4 for the fan

Had a great chat with John and we both agreed that the problem is likely related to it sitting for so long and not a new problem.  

he suggested above to clear the codes and I thought it was genius.  
 

just got back from a 1.5 hour total trip after clearing the codes and what do you know???   Apparently that's all you need to do to fix these cars!

back to its normal, pedestrian self.  Doing well what it always does - getting me where I'm going with no fuss and not much gas. 
 

However I am now thinking about having the pack conditioned..... or doing it myself.  Is this (or anything else) an advisable preventative maintenance thing for the hv pack?

Yeah! 

I have never done any hybrid battery reconditioning. My sole recommendation would be that if the Prius ends up out of the regular vehicle rotation then hit the button killing the smart key ability and drain. When the car is back to regular rotation, push again and make smart key work. 

FWIW, last month I had a RAV4 that lost all of its key memory due to a weak battery, and it had to be manually reprogrammed, and our roving programmer guy said "yeah, that is pretty common."

So it seems that Toyota electronics are not the most robust when it comes to being subjected to low voltage.

Great call, John.  I'll do that in the future.   And pete... I'll make sure to stay on top of this better to avoid a scenario like that happening. 

Pete. (l33t FS) 

So it seems that Toyota electronics are not the most robust when it comes to being subjected to low voltage.

this 10000%.  All my Toyotas have had crazy issues with low batteries.  Lots of lights. Steering thst won't work.  It also happens without warning.  One day fine then next day Christmas tree dash lights.   The worst one was when it happened to me int the gas line at costco.  Luckily the gas attendant had some tools and I could walk in and swap the battery out.   
 

long story short. If A Toyota does anything weird electrically and your battery isn't brand new, swap it as a first test.  

Low voltage issue is not a prius thing, it is an IC thing.  Integrated circuits require a specific voltage to operate.  The Jacobs ignition in my 914 30 years ago would not work when the battery was weak.  Starter would draw voltage down, then no spark.  It is a shame the traction battery can't step down to 12V and lend the little battery some electrons.  Off now to put a new inverter coolant pump in.

porschenut said:

Low voltage issue is not a prius thing, it is an IC thing.  Integrated circuits require a specific voltage to operate.  The Jacobs ignition in my 914 30 years ago would not work when the battery was weak.  Starter would draw voltage down, then no spark.  It is a shame the traction battery can't step down to 12V and lend the little battery some electrons.  Off now to put a new inverter coolant pump in.

This has been an issue for BMW and MB for a long time as well. Any electrical issue at all should necessitate a battery test.