Gen 1 HV BATTERY REBUILD WITH 2G CELLS

Ok,

You've already started. Let me suggest, as soon as you've gotten at least 5 posts, share some photos?

You know, "hello 1", "hello 2", "hello 3", "Oh photos you want, here they are."
<grins>

Having scored two NHW20 battery packs, you have pretty much 75% of what is needed. Just to fill in any blanks, here is what little I've learned:

Prius Battery Photos

Ok, rebuilding the pack, I would recommend the following:

1. Remove the NHW11 modules, store them for future disposal and/or experiments. Note the + and - orientation before removal.
2. Remove the NHW20 modules and survey each one: (1) static voltage, and; (2) voltage across a 6 V light. Record the serial numbers and the two voltages ... you are making an inventory of the modules.
3. Clean the buss bars. Use distilled water and pH test to make sure they are neutral. KOH is tricky stuff and will find every crevice and crack to hid in. Wicked stuff.
4. Check each sensor wire for corrosion or breaks.
5. Consider gold foil to treat areas that remain 'suspect' as you don't want to go back anytime soon.
6. Select the top 38 modules and use an RC charger, one with dV sense to consider a cycle discharge/charge of the modules. If any look suspect, set aside until you get 38 modules with effectively the same Ahr capacity.
7. Repopulate the NHW11 battery housing putting the strongest pairs in the middle and building out the weakest ones on the ends. Historical data suggests the center modules age first so put the strongest in the center. Don't forget the + and - orientation.

So like a Monty Python policeman, post "hello" "hello" "hello" until you can post photos. <GRINS>

Bob Wilson

 

bwilson4web is probably trying to express open circuit voltage, i.e. voltage with no load.

"Static voltage" would actually be the voltage potential across an electrostatic field.

It's a crude method to test the modules under load.

Some folks have suggested gold foil as part of a busbar replacement scheme. However, new busbars are readily available from Toyota. Assuming that the new modules do not leak electrolyte, new busbars will last the life of the car.

 

Good news about replacement buss bar assemblies being available from Toyota. Check on the price but having a new part instead of trying to deal with corroded metal is a good thing!

So translating a few of my casual terms:

static voltage - open circuit voltage using a high impedance volt-ohm meter.

voltage over 6V light (actually a 12 V light could be used) - just a quick measure of the module under load. Those with a higher ratio are showing greater internal resistance, a bad thing, or a lower state of charge. Regardless, we treat these as 'needing attention' or not a good replacement.

gold foil - some craft shops carry gold foil leaf that can be wrapped around a throughly clean and dry metal to provide a barrier to caustic chemicals and air. But if you can buy a replacement buss bar assembly, you're ahead of the game.

dV test - check the Wiki article on NiMH battery charging as well as some datasheets from the manufacturers. What you'll find is the charging voltage remains fairly flat until the end when there is a quick peak followed by a dV drop. The better RC chargers can detect the dV drop and stop the charge right then. Also, don't forget to clamp the modules as they do generate gas pressure. Also consider that the dV drop is on a per cell basis. The six cells in one module are going to be fairly close. However, module-to-module differences makes bulk charging less likely as their series voltage is additive. The dV hump is likely to occur at different spots causing the individual modules to be at different states of charge ... a bad thing!
​

One last thing, don't be in a hurry as much as pay attention to the technical details. You want to do this job once and right. You're looking at several thousands of dollars of material and a bit of labor. Also, remember safety.

When the modules are in series you are looking at 270+ volts and it is quite lethal. Even half a pack, 135 volts is deadly. As you've no doubt learned, they are heavy too! Take it easy, think twice about what your next steps are going to be and don't be rushed. Safety, insulating gloves should be seriously considered during the initial disassembly and final reassembly. For example:

Remove the buss bar on one side first and make sure it is held away from the module terminals by insulating material. This makes the other side much safer to work on.
​

One of the reasons I keep harping on pictures is they provide a record of what you had before you disassemble the parts. They provide a reference so when you are putting it back together, you have something to compare it to. Your disassembly photos become your reassembly photos. <grins>

Bob Wilson

 

The traction battery modules are normally isolated from the case. You really need to measure the voltage across the terminals of each module.

Metal salts are often colorful but they hide a deadly reality ... the loss of the metal under it.

Assume nothing, measure everything.

Steady, careful and make a careful record. You can post tables here by using "[" the text "table" and "]" with each column header separated by a "|". Each subsequent row has a "|" between the data values. End the table with "[/" and "table" and "]".

Bob Wilson

 

Hello Bob: Just curious, someday I may have to probe this area, but is thier a distinct difference in the reading of separate battery modules, as compared to reading a output of a module while still connected. And how can a bussbar accumulate resistance, that is, this seemingly thick piece of copper, after being mechanically/chemically scoured should read ZERO ohms. True or Not?

 

You'll be putting the VOM probes on the module terminals. Most probes have a pointy tip, just push the pointy part hard and you'll get a good reading.

You should record:

• module serial number
• open circuit voltage
• voltage over a a constant load, say 6V or 12V lamp

Be patient and work carefully.

Bob Wilson

 

Hi UKCLASSICPRIUS,

I had the HV Battery Warning Light about 3 months ago. I'd like to share what I've learned.

The KOH is colorless. When it corrodes the terminals, it formed the blue stuff that you saw. However, even if you don't find any blue stuff, KOH leakage could still be present. The best is to use pH test to confirm.

With the busbars connected, you won't know whether the shortage are from the modules itself, the Battery ECU or both. What I did was to remove the busbars completely and measured the +ve and -ve terminals to chassis. If you don't get 0V, there are leakages.

You have P3030 code which implies there are problems with the voltage sensing wires or the Battery ECU. Measure all the sensing wires for continuity as well as against each other for resistance.

If all are OK, proceed to connect 1 side of the busbar (the one with voltage sensing wires) and measure the +ve and -ve terminals to chassis.

If all are OK, proceed to connect the voltage sensing wires connector to the Battery ECU and measure again.

If there are abnormal voltages, replace the Battery ECU.

 

Hi UKCLASSICPRIUS,

If you can find Boric Acid in your area, use that to neutralize the KOH between the terminals to the chassis. I can't find Boric Acid in my country so I used vinegar and it worked as well.

http://priuschat.com/forums/international-owners/6539-prius-in-singapore.html#post1069605

 

It is the other way round. Those showing 0v to battery case are OK, those showing otherwise have leakage to the battery case.

 

You have non-zero voltages even with the ECU disconnected, that means either the battery modules or the voltage sensing wire connectors have shorts. Therefore, it is necessary to remove the voltage sensing wires to isolate which is causing the shorts.

 

OWCH! I missed this one. Great photos and excellent work!

Bob Wilson