Should I buy it? P3006 - Battery Levels are Unusually Different

I learned my lesson about buying "sick" cars. DONT!

 

DTC P3006 is a serious trouble code. The traction battery really has failed. You will have to replace it immediately. The relatively low mpg that you noticed is evidence that the battery is not holding charge from regen braking as it should, assuming that you were not running the air conditioner as max AC where the compressor is continuously running.

When you were driving the car did you notice if the gasoline engine would go off when driving at slow speeds under light load? If the engine kept running that is further evidence that the battery is bad.

When looking at the traction battery SOC indicator in the MFD, did you see the charge level jumping up and down quickly? If so, thats more evidence of a bad battery.

You've come up with a reasonable estimate of $1,800 if you were to use a salvage battery as a replacement (assuming you can find an independent to install for $300; a dealer will not touch salvage parts.) Would a price of $7,300 seem like a good price to you for a 2002 Prius with 138K miles and other possible problems that you haven't noticed yet? If this seems OK then buy the car. If it doesn't seem OK then let it go.

Also note that a salvage battery comes with no guarantee beyond an offer to return if the battery does not work immediately upon delivery. So one year from now or one month from now you could be facing the need to replace the battery again.

Don't forget the other potential service issues that the Classic Prius is known for, such as having to replace the catalytic converter, the engine ECU, the electric steering gear, an occasional transaxle or inverter failure, etc. None of these are inexpensive repairs.

As to your question about why the module pair voltage is reading 17V instead of 14V, this is because the battery pack is normally operating at a voltage of around 320+V when properly charged. 273.6V is the nominal rating for the battery pack with 38 modules, 7.2V each.

 

What catches my eye is that the battery ECU is looking at a charge state of ~ 17.6/block, 334 total, and calling it a 42.5% SoC. And then it's reporting the exact same number, 42.5%, as the Delta SoC. I confess I have no numbers of my own to compare them to, as I am still trying to cobble together some scanning solution (short of having a used Graham scanner fall in my lap) to get numbers on my own car. But do these numbers even make sense? They push my 'weird' button, to the point where if I had a spare battery ECU (which of course I don't) I'd be tempted to swap it in and see if it reported the same numbers, and -then- look at the battery itself.

Somebody who's familiar with normal readings may with complete justice tell me I'm off the track here.

-Chap

 

I'll just chime in and say what I think you've already deduced. This would be a great deal for someone who has the funds available and/or tech skills to go ahead and fix some things up. The car still books for ~$8-10k, so at $4700 theres plenty of margin there for repairs but if your budget is only $5k then that doesn't help you. On top of that you are always taking a risk with a car that needs work, as you never know what other problems could lurking.

Rob

 

$11,810 - Kelly retail price, excellent condition
$9,710 - Kelly private party, excellent
$7,840 - Kelly private party, fair

~$4,600 - Toyota price to replace battery

$7,210 - retail price, broken
$5,110 - private party, broken
$3,240 - private party fair, broken

$5,500 - offered price, broken

Off hand, it looks to be what Kelly Blue Book would consider to be close to a fair price for a battery broken 02 Prius. However, you need an extra $4,600 for Toyota to get it repaired.

In my case, I have the maintenance manuals, tools, spare parts and knowledge to make a battery repair. However, knowing what it would take and the utility of the vehicle, it is only worth ~$2-3,000 to me.

I would have to travel to Denver to inspect the car and make 'field repairs.' Then I would have to drive the car back to Huntsville assuming the car has a tag that would let me drive it back. Then there would be the maintenance when I arrived so the costs would look like:

$1,846 - Delta weekend
$102 - gas for 1277 miles
$80 - two nights room
$50 - meals
----
$2,078 - just to pick it up

$300 - new tires
$30 - transaxle oil
$120 - alignment
$20 - ICE oil change
$10 - wipers
----
$480 - standard repairs
$200 - battery repair
----
$680 - vehicle repairs (assumes no body work)
======
$2,758 - to get and fix-up vehicle

$5,500 - offered price
$2,758 - my expected expense
======
$2,742 - net worth of car to me in HSV

I might be able to get better ticket prices and bring it up to $3,742 but we're getting to the limit. This assumes my labor is free. Is your labor that free?

Now if someone has an extra ~$5k and can get the purchase price down to say ~$4k, they would have Prius whose battery should last another 6 years. Personally, that car doesn't look attractive until the price gets closer to $2k but I've seen salvage cars in terrible states sold for $4k on Ebay. IMHO, you pays your money and takes your chances.

GOOD LUCK!
Bob Wilson

 

I really like this detailed evaluation. I could follow it all until the last step. Are you getting a post-repair net worth by subtracting repair expense from asking price?

Would it be off-base to subtract repair expense from one of the non-broken-condition Kelly values for a post-repair net worth, and then compare that number to the asking price to determine the attractiveness of the deal?

-Chap

 

I was trying to take my expected expense to fetch the car and fix it up to my standards. Even if I cut the air fare down using some of the 'low cost' fares, it still winds up being expensive.

In some accounting systems, my repairs would be treated as an optional, value-added improvement of the base car. I could see someone thinking I've boosted the car value by this expense. However, I see it as my expense to bring the car up to my standards, an additional expense.

If you want, you could take the offered "$5.5k" and add my "$2.5k" and state that the car would cost me "$8k," which only brings it into the lower range of the Kelly value. That makes the car at $5.5k still too expense for my taste. I need some profit.

Bob Wilson

 

Here's my question:
How do you determine which cell block is bad? Normally there will be a much greater difference in cell block voltages (at least 1 volt but more likely >1.2V to account for a bad cell w/in the block). What I see is a good battery and a bad ECU. Like Chap, I would like to swap out the Batt ECU because in reality, there is no error in the cell block voltages.

With that in mind, the wandering SOC and constant ICE run are clear indicators of a bad/weak battery.

Normally I would say try to buy the car for ~$3000 and try to replace the ECU and if that fails, replace one cell with a matched cell from Ebay. These weird symptoms clearly do not allow me to advise this. I've never heard of these particular symptoms.

 

The first thing to do before replacing batteries is to replace the wiring harness, with the control wires. This costs around $110. Mine had corroded several control wires, and rather than attempting to fix, I bought a new one. Take the other side off (without control wires), and clean, very thoroughly, the copper connectors. I mean shiny clean, by sanding with emory cloth or similar. Then reassemble. It took me twice to get it right, since I didn't clean the connectors properly the first time. Torque to the required inch/pounds, meaning tight, but not overly tight, which might break the battery stud. Yes, this happened to me too, and I had to replace a battery cell. I chose to replace two, thinking they needed to be somewhat similar in voltage. I think the "matched cell" hypothesis is a bit of overkill: it is the connections that need to be extremely clean and tight. The P3006 error never came back, well over 1000 miles. Good luck with this, it is a lot cheaper than a new or rebuilt battery.

 

If you sand down copper you must treat it with an anti corrosive. Lots of stuff out there, high quality grease will work fine but sanded raw copper left exposed and especially the sanded connections that have current going through them will quickly corrode around a battery. Current, heat, battery fumes, and a little humidity will make a mess out of your hard work.