HELP with Gen I 2002 Prius!

I knew I'd seen something on the net about Prius traction battery removal:
Installing a Prius HV Battery

Bob Wilson

 

You can subscribe to https://techinfo.toyota.com.

Hobbit has a copy on his website:

http://techno-fandom.org/~hobbit/cars/TIS/ileaf/toyssc/toysspdf/sscsourc/2004/40g/40gtech.pdf

Pls be extremely careful as you are dealing with high voltages.

 

This TIS document directly addresses the problem that leads to P3009, leak to ground. A systemic problem with the NHW11 modules, pp. 24 shows attachment of an 'absorbent sheet' under the positive terminal of each module. This is to catch the electrolyte leak that can form a conductive path to ground.

Normally, the traction battery is isolated from ground plus there are three relays, one on each external termal lead and one in the middle. Without 12 V power, these relays are open and the traction battery looks like two, independent, ~ 270/2, or ~135 V. packs. Actually, the center is 10 and 9 module pairs so there should be about a 14.4 V differerence but regardless both halves are potentially lethal. This is why the P3009, leak to ground, is so risky.

Although seldom a high current path, the variable resistance of an electrolyte leak to the case means other parts of the buss bar can be 'hot' to the touch. Add a second leak on the same bank and there is a discharge path . . . exactly what is needed to let modules in a bank become unbalanced with one or more having a lower state of charge. Discharge the battery enough and the weakest module gets reverse charged and dies, an unrecoverable error.

So a P3009 is both a safety hazard, it shunts around a safety relay, but also a threat to the battery modules by leading to imbalanced modules. In contrast, the NHW20 modules with superior terminal seals never needed this workaround. This also has implications for battery rebuilders.

That absorbent material will have a finite capacity. If I were rebuilding a traction battery with NHW11 modules, I would want to reapply this TIS to each module. Take each one: strip off the old absorbent tab, wash off any accumulated electrolyte, dry, and put on another absorbent tab. In contrast, NHW20 modules can be tested for capacity, matched modules charged to the same level, and assembled with new buss bars into a solid pack.

Thanks vincent1449p, hobbit's copy of the TIS is spot on to the P3009 code found on this Prius and consistent with one or more modules failing early.

Bob Wilson

 

That surprises me too although the block number matches the P3026 code. Was the car running or just powered up?

Regardless:
16.7 - 15.3 ~= 1.4 V. :: one cell is 1.2 V and there are 6 cells per module, 12 cells per block

Sorry, but this is the signature of a failing traction battery. The modules are numbered 1-19 with #1 being adjacent to the control electronics.

Bob Wilson

 

You are right. My guess is that you have at least a 50% chance of experiencing one of the failures that you noted in your message, over the next 100K miles.

I personally experienced both traction battery and electric steering gear failure on my 2001, however both were warranty repairs. Unless you wish to make the care and maintenance of an old Prius your hobby, you may want to put your money in a newer vehicle.

 

It takes about two hours for two newbies to get the old battery out. Then take a break. And less than two hours to put the replacement battery in. Two people in about 4 hours and it is done.

Bob Wilson

 

No. Although the relays are open, the battery pack is not electrically divided unless the service plug is removed. You can verify this by looking at a wiring diagram.

The system is designed to detect HV leakage to ground well before a safety issue is present.

That's what the code is for.

Yes, but you would be assembling a pack out of two used Gen II packs that are likely to be mismatched. A new, replacement Gen 1 pack also won't have the leakage issue that plagued production packs—and it won't be made of used, mismatched cells.

I'm curious: how would you get the leaked electrolyte back into the module?

 

Not odd at all. In fact, it's quite common. If a failing cell has reduced capacity, it will discharge more rapidly than its neighbors, but it will also charge more quickly than its neighbors.

 

I'll go out on a limb here, and guess that since Bob was talking about re-applying the service campaign 40G procedure, he would do that the same way it was done the first time.

-Chap

 

That service campaign was all about preventing the high-probability, electrolyte leak from throwing a code too soon. As for electrolyte replacement, a better answer is water replacement because amount of KOH lost even in a 6 mol solution is measured in milligrams.

Water replacement is simple in theory but complex in application:

• drill hole(s) (easy)
• add water (easy)
• plastic weld holes closed (not so easy)

Bob Wilson

 

A Google search on

battery campaign 40G technical instructions

finds you the pdf courtesy of hobbit. You want the 56 page document, not the 6 page announcement letter.

It is a pretty good reference for battery R&R and partial disassembly, and you'll probably find it handy for inspection. (But don't be surprised that, despite my earlier tongue-in-cheek comment, it really doesn't contain any instructions for putting leaked electrolyte back in. )

-Chap

 

No. The service campaign was designed to fix the leak.

Again, no. Electrolyte is the best replacement for electrolyte.

However, it appears that you are confusing modules which have dehydrated electrolyte due to heat with modules which have lost electrolyte due to a faulty case design. These are two different kinds of faults. One will need water, the other will need electrolyte. It's just battery basics, really.

At any rate, your proposed method for repairing a leaking Gen I battery pack will not replenish the electrolyte that has been lost. That is something to think about if you want your repair to last.

 

You might join the Yahoo Group, "Prius Technical Stuff." They have an awesome record dating from November 2000.

FYI, here is Hobbit's site.

Bob Wilson

 

Old thread I know but I thought this might be helpful for someone later figuring out how the blocks are numbered on the actual battery pack.

(red lines are module pairs, also called blocks and white numbers show where each block is located)