How to choose a good used transaxle. Ideas?

[hobbit]

If you have a ground fault in a winding, that's *not* going to
show up as rotor cogging when you turn it. That would be
symptomatic of a winding shorted to itself or another one, much
more rare as a problem. You will get megger continuity from all
three leads of a given motor to the case in the event of a ground
fault because they're all Y-connected inside so it's essentially
one big hunk of wiring in terms of what the megger sees!
.
Note that several of the codes have to do with rotor demagnetization.
That's always a mild risk for a motor if the windings are ever
subjected to excess currents that build very strong opposing
fields, but I don't think anyone's actually ever turned up a Prius
that had that sort of problem. Those rare-earth PMs are pretty
stable, and I sort of wonder how they get those suckers magnetized
in the first place... probably some games with heating.
.
_H*

[orange4boy]

Just got our Prius home today. Yay.

The motor has serious cogging. wow. It seems kind of random. In neutral It's hard to push the car because of the cogging. It's a bit like bump starting a car but smoother and more random. When I try to start it the car moves a tiny bit and then all the warning lights come up. Confirmation: Transaxle is definitely hooped?

If you have a ground fault in a winding, that's *not* going to
show up as rotor cogging when you turn it. That would be
symptomatic of a winding shorted to itself or another one, much
more rare as a problem. You will get megger continuity from all
three leads of a given motor to the case in the event of a ground
fault because they're all Y-connected inside so it's essentially
one big hunk of wiring in terms of what the megger sees!

The friend who helped me today, an electrical engineer, suggested simply using an ohm meter and if resistance between two leads is different, it's fried.

[bwilson4web]

Originally Posted by orange4boy

Just got our Prius home today. Yay.

The journey begins!

Originally Posted by orange4boy

The motor has serious cogging. wow. It seems kind of random. In neutral It's hard to push the car because of the cogging. It's a bit like bump starting a car but smoother and more random. When I try to start it the car moves a tiny bit and then all the warning lights come up. Confirmation: Transaxle is definitely hooped?

I'm not sure what 'cogging' means ... engine runs but runs rough? Or is there a 'pulsing' when the car moves or is pushed about?

Hard to push in "neutral" means the transaxle has failed ... unless you find the drive shafts and CVTs connecting to the front wheels have a serious problem (very unlikely!) When in "neutral," all power to the transaxle MG1 and MG2 is cut.

To have mechanical resistance pushing the car, there has to be a shorted, loop in MG2 and possibly MG1. Disconnecting the inverter MG1 and MG2 and still having a mechanical resistance turning one or both wheels and you know it is the transaxle.

SAFETY: the traction battery has an orange, safety interlock accessible from the trunk. Please pull that before dealing with any of the power electronics.

Originally Posted by orange4boy

The friend who helped me today, an electrical engineer, suggested simply using an ohm meter and if resistance between two leads is different, it's fried.

Yes as would the inductance.

Bob Wilson

[hobbit]

Cogging in an electric motor is the interaction of the magnets
with the reluctance of the stator poles as you turn it. You've
probably felt it if you've ever played around with a stepper motor.
Which is effectively what the MGs in the Prius are -- big-ass,
computer-controlled steppers with three phases instead of two
or four.
.
_H*

[orange4boy]

Or is there a 'pulsing' when the car moves or is pushed about?

Hard to push in "neutral" means the transaxle has failed ... unless you find the drive shafts and CVTs connecting to the front wheels have a serious problem (very unlikely!) When in "neutral," all power to the transaxle MG1 and MG2 is cut.

To have mechanical resistance pushing the car, there has to be a shorted, loop in MG2 and possibly MG1. Disconnecting the inverter MG1 and MG2 and still having a mechanical resistance turning one or both wheels and you know it is the transaxle.

The ICE does not start at all. It's the mechanical resistance in neutral that is the cogging I referred to. It does feel like a stepper motor but more random. Some of the "cogs" are stronger than others. I was surprised how strong they were.

Is there any cogging on a healthy transaxle? There seems to be a little cogging even on an un-energized PMDC. Is it the severity of the cogging that points to shorting?

Is it possible that the wheels are actually turning the ice or is that impossible in neutral?

I'm going to carefully check the battery for SOC today. What is the SOC voltage range for a gen 1 pack? I know this is harder to read than a lead acid pack but I just want to know if it's dead or alive. I may check individual blocks later but for now I'm just checking the whole pack for leaking, SOC etc.

[bwilson4web]

Originally Posted by orange4boy

The ICE does not start at all. It's the mechanical resistance in neutral that is the cogging I referred to. It does feel like a stepper motor but more random. Some of the "cogs" are stronger than others. I was surprised how strong they were.

That is failed! The short is not a 'designed' loop but involves some carbonized insulation.

Originally Posted by orange4boy

Is there any cogging on a healthy transaxle?

None. But it makes sense to disconnect the inverter and verify the 'cogging' remains. It would be a shame to swap a transaxle only to discover a short, intermittent or otherwise, in the inverter.

Originally Posted by orange4boy

There seems to be a little cogging even on an un-energized PMDC. Is it the severity of the cogging that points to shorting?

Is it possible that the wheels are actually turning the ice or is that impossible in neutral?

Hummm, very, very improbable.

Originally Posted by orange4boy

I'm going to carefully check the battery for SOC today. What is the SOC voltage range for a gen 1 pack? I know this is harder to read than a lead acid pack but I just want to know if it's dead or alive. I may check individual blocks later but for now I'm just checking the whole pack for leaking, SOC etc.

The built-in display has no units. Let's worry the traction battery after getting the transaxle working.

Bob Wilson

[orange4boy]

Thanks for the above info.

Will the system lock you out of staring the car if the transaxle is faulty? I get the ready light but when I turn to start it seems to try to spin up the ice for a split second before it quits and flashes the ps/batt/! It seems to me it's not starting because the traction battery is low. If it is designed to disallow starting with a failed transaxle code why do I get the ready light and a split second of turn over?

I'm not disputing the fact that MG1+2 are toast just trying to understand. If the main battery is low, I should try to find a way to charge it so it does not become completely discharged. It's been sitting for a month and a half already. So either I have to start the car and force charge or use an external charger.

Can the charging/inverter module from the earliest Prius be used or is it a different voltage

[orange4boy]

I have an 18v makita battery charger for MiMH cordless drill batteries. Is that too far off voltage wise to charge individual modules?

[bwilson4web]

Please scan my battery experiment page and let's chat some more. The NiMH batteries are very good but they are not bullet proof. Go carefully into that area!

Bob Wilson

[orange4boy]

For now where can I probe with my multimeter to see the voltage without taking it too far apart. I have linesman's gloves. I have the rear seat out and can access the case. I was thinking about probing through the insulation on the main cables but would rather not if I don't have to. If voltage is fine then I will leave checking on the battery till later.

An "interesting" find when I jacked it up for the first time: No tranny drain plug! Gone. There is a deep gouge on the pan too from an altercation with a curb, no doubt. No perforation. the rest of the underside is undamaged. So much for a sample unless I can get enough out of the pan. I think the dealer didn't bother to replace it with the tranny gone, but why would they bother draining the oil? Hmmm. Could it be someone forgot to replace the plug and hence destroyed the tranny? Inquiring minds want to know.