2001 prius battery problem and pictures

[statultra]

A couple weeks ago, my 2001 prius would drive normally for about 10 miles then decide to go into limp mode, turtle light triangle brake light, check engine light.

I also noticed that the MFD shows the battery as full, then all of a sudden it would drop to the last "bar" then recharge, that would happen about 5 times then the warning lights come up.

This prius was a salvage car restored, roughly 40-50k miles later this starting happening. the vehicle was not covered under any warranty so the battery seal TSB was not performed on this car.

I have worked on the HV battery before, with my charger, so I understand the dangers associated with high DC voltage.

Today I removed the HV battery from the vehicle and examined the copper plates which were severely corroded.

Here is the imageshack gallery:
ImageShack Gallery




this is the area with worst corossion, i recorded the lowest voltage accross on this module, 7.2 volts vs the rest which were 7.8 volts.




heres some questions, would any experts here suggest removing copper plates, cleaning them with a solution and wipe around the positive and negative terminals, then applying a sealant ?

also can i use muriatic acid to clean the oxidation off the copper?

[john1701a]

There was a TSB which added sealant to prevent corossion.

It's likely your Prius didn't have that work done, but could still benefit. There may be details in the TSB of what to look for and how to deal with it. Sorry, I don't have the number readily available... but someone else may chime in for that.
.

[hobbit]

I'd say that if the battery terminal posts themselves aren't
corroded too badly it's definitely worth cleaning up the copper
bar strips and reassembling. Using de-oxit or some other contact
cleaner/restorer couldn't hurt, as well as a bit of elbow grease
with scotchbrite or something nastier where needed. You're possibly
fortunate that the reseal TSB wasn't done, as that makes the
second go-round on that job much messier -- then you'd have to
soak all the old goo off with acetone or somethibg and then get
back down to bare copper.
.
While the pack is apart into separate modules you can individually
load-test and re-equalize each one and determine which if any
really have gotten weaker over time.
.
Hopefully you've got something else to drive in the meantime,
as all this might take a while!
.
_H*

[statultra]

i checked all the batteries with a volt meter, i got the copper plates off and the orange things surrounding it, the terminals itself look really clean.

I measured 7.8 volts on all the individual modules except for one, which read 6.5 volts. This set that read this low voltage had some real good corrosion.

Luckily i finished rebuilding the accord hybrid in time, so I have that and the 05 prius to drive.

I was planning on repainting the 2001 prius and this ruined my plans


also I was wondering since each module is 7.8 volts wouldn't that make the total voltage 296? which is considerably too high i think.

My guess is the compression was giving the battery ECU a false capacity reading and making the hybrid system charge the battery continuously

[bwilson4web]

Originally Posted by statultra

. . .
I measured 7.8 volts on all the individual modules except for one, which read 6.5 volts. This set that read this low voltage had some real good corrosion. . . .

One NiMH cell has 1.2 V so, 6.5+1.2 = 7.7 :: that module has a failed cell. The corrosion is consistent with the failure of a terminal seal on that module. The electrolyte, KOH, would have leaked out and caused the corrosion.

There are two approaches:

1. isolated module failure - it is possible that one module could be replaced and restore functionality. Seeing corrosion on only one module is a good sign.
2. all modules worn out - the true test is to measure the remaining Ahr capacity of the modules. If at or under 2.2 Ahr, I would call them worn out.

Bob Wilson

[krousdb]

Originally Posted by statultra

also I was wondering since each module is 7.8 volts wouldn't that make the total voltage 296? which is considerably too high i think.

296V is too high for a Gen 2 but it's fine for a Gen 1. Gen 1 is 274V nominal, the Gen 2 is 202V nominal.

[statultra]

ok i made a typo, the one that measured 6.5 is located where there was no visible corossion, Im thinking that maybe the corossion could cause varying voltages between the modules.


i also checked each module to the battery case, one of the modules, specifically the one that had major corrosion read 2.4 volts to the battery case, the rest of them read 0 volts.


the bus bars are removed and i cleaned them and have them sealed until im ready to reinstall, tommorow im probably going to buy some 3m contact adhesive similar to what toyota used for the TSB.


im not sure whether or not to keep going with this battery or to purchase a salvage battery

[Patrick Wong]

Originally Posted by statultra

...I measured 7.8 volts on all the individual modules except for one, which read 6.5 volts. This set that read this low voltage had some real good corrosion...

My guess is the compression was giving the battery ECU a false capacity reading and making the hybrid system charge the battery continuously

The reason the battery is showing wild swings in SOC is because you have a bad module.

Originally Posted by statultra

ok i made a typo, the one that measured 6.5 is located where there was no visible corossion, Im thinking that maybe the corossion could cause varying voltages between the modules.

i also checked each module to the battery case, one of the modules, specifically the one that had major corrosion read 2.4 volts to the battery case, the rest of them read 0 volts.

the bus bars are removed and i cleaned them and have them sealed until im ready to reinstall, tommorow im probably going to buy some 3m contact adhesive similar to what toyota used for the TSB.

im not sure whether or not to keep going with this battery or to purchase a salvage battery

You're wasting your time working on this battery unless you can replace the one module which is at 6.5V. However single module replacement is likely to be a short-term fix only.

Your traction battery ECU may have logged DTC P3009 "high voltage leak" fault code, as well as a DTC related to the failed module pair.

Classic salvage batteries tend to be pretty expensive since the demand seems to be greater than supply; while the expected remaining lifetime of the salvage battery may not be too great since it typically will be at least six years old. If you plan to keep your car you might do better buying two 2G battery assemblies and taking 38 modules out of the 56 available to install in your Classic battery case.

[bwilson4web]

Originally Posted by statultra

ok i made a typo, the one that measured 6.5 is located where there was no visible corossion, Im thinking that maybe the corossion could cause varying voltages between the modules.

i also checked each module to the battery case, one of the modules, specifically the one that had major corrosion read 2.4 volts to the battery case, the rest of them read 0 volts. . . .

Ok, now I am confused. Where is the VOM probe being applied? The center post, nut or bus-bar that links adjacent cells? The terminal post will give the most accurate reading.


The terminals come out of the plastic case and have an O-ring seal. The module on the right, a failed module, had leakage around the O-ring and the photo shows some of gunk used in the sealing TIS.

If you get a chance, it would help to get a reading of all modules number 1-38 where 1 is adjacent to the control electronics. This will give a rough indication of how the modules have aged.

The electrolyte, KOH, is 'slippery' stuff as it combines with the fats on our skin to make soap. Any that leaks will make a conductive path to ground but the stuff is dang near invisible. The Prius system detects very high resistances under 10 MOHM and declares them to be a fault. It may be worth while to try and measure the DC resistance between the terminal of each module and the case. There is no guarantee but any module that shows a detectable resistance would be one I'd schedule for a through cleaning, drying and wipe down.

GOOD LUCK!
Bob Wilson

[Mike Dimmick]

1.2V is actually a very low voltage for a NiMH cell, and approximates to a completely discharged cell. The following chart is for NiCd but NiMH is reportedly similar:



(source)

The chart for Gen 2 State-of-Charge reporting looks like this:



(source)

7.8V per module comes to 1.3V per cell, which would appear as four bars while discharging but only two when charging; 6.6V for that module is pretty much dead. I wouldn't say that 6.6V necessarily indicated a shorted cell in that module, it could be more than one cell with low output, but I don't think it would be recovered by charging.