Grounding kit for the Prius - would it make sense?

<div class='quotetop'>QUOTE(jayman\";p=\"89536)</div>

The HV is completely isolated and self contained, including the 3 phases to the motors and the AC compressor.


As for checking for resistance, I would put on all the accessories you can so that you create a substantial current flow. Then measure current through the ground straps, and the voltage across them. Then you can calculate the resistance. Of course, as I mentioned, the voltage drop you see across the ground straps is the voltage not getting to the load.
I really doubt the ICE itself has a substantial load to the 12V system, as the only item is the ignition coils. Then again, I don't know if the coolant pumps are on the powertrain block or bolted to the chassis. I would suspect the latter. The other significant operating load would be the brake hydraulics, which would also be bolted to the chassis. Chassis is fed ground from the DC/DC converter, which is part of the inverter assembly bolted to the powertrain block, and the 12V battery, so both straps would have to be considered.

In a conventional car, the main source of power during operation is the alternator, whose ground is bolted to the engine, but the 'filter' is the battery, so a good ground is needed from the ICE all the way to the negative terminal of the battery. Positive voltage flow should also be considered, especially at the battery where corrosion often occurs. On the Prius, the DC/DC converter should be fairly clean power not requiring the battery to condition it.

 

Dan:

I notice they use a Reactor (An inductor) on the HV side to control transients, and a filter capacitor is used to control ripple.

Just like a Variable Frequency Drive for industrial motor control. Actually, most of the IPM looks like what you would find inside an industrial 3 phase VFD.

I'm still a bit confused by your earlier statement in this thread that the 12 vdc and the HV both share a common ground. That is, both the DC converter and the AC inverter appear to share the same ground.

Jay

 

I never said they share a common ground, I was disputing that you implied it did. You kept insisting on measuring current flow on the HV side, and I kept telling you it has nothing to do with the ground straps, as the HV system doesn't use ground for any of its current flow.

As for the inductor, it is used to generate 500V from 206V as a switching power supply.

 

<div class='quotetop'>QUOTE(ScubaX\";p=\"89697)</div>

It shouldn't. Is it a consumer inverter or an industrial/commercial inverter?

All of my experience is with industrial/commercial equipment and I can tell you that equipment usually does cause interference.

 

I have heard of a device that is supposed to monitor the battery condition and keep it properly charged and conditioned. Maybe that's what the box does. That, or a really big choke.

 

<div class='quotetop'>QUOTE(DanMan32\";p=\"89243)</div>

This is where the confusion entered.

Using the suggested emergency boost point negative, the resistance between the HSD case and the negative is 1 ohm. Unless the case is totally isolated and potted (Typically a silicone solution to isolate electrical leads), you would have to expect a common ground point.

With industrial 3 phase Variable Frequency Drives, the large capacitors are isolated as they function as a filter for the frequent voltage/frequency shifts. Otherwise the IGBT's case are referenced to ground.

I checked again on a 2005 Toyota Echo Hatchback on display at a local Toyota dealer. The battery is on the driver side, the postive post is aft and the negative post is fore. There are two negative cables off the clamp, one goes immediately to the unitbody and the other snakes around underneath to the accessory bracket.

Boy are those dinky battery cables on the Echo!

 

Emergency boost point negative?

It is possible that the inverter cover is strictly an isolated signal shield, otherwise it really shouldn't be one ohm. What is the voltage across those 2 points?

I'll check the cover potential on my car.

But really, the cover shouldn't be an issue. We have 3 different ground 'planes'. One is the engine block, which should include the transaxle. The other is the car chassis, and finally the 12V battery. It is between these 3 points we want to find resistances. We can find the resistances directly, which should be quite low, almost reliably immeasurable through direct means, or indirectly by determining the voltage differental and current flow between the planes.

 

<div class='quotetop'>QUOTE(DanMan32\";p=\"90285)</div>

Dan:

In the owner manual under jump starting procedures, it's that bolt on the firewall you're supposed to attach the negative jumper cable to. The picture on P.241 of my 2004 Owner Manual is a bit small, but it appears to be the bolt on the firewall behind and above the windshield washer tank.

<div class='quotetop'>QUOTE(DanMan32\";p=\"90285)</div>

Yes, that's reasonable. The schematic is very unclear on that. It was in the low mV range, I can't recall and will have to be at home to recall the readings from my Fluke. I didn't take the reading from the actual cover but from one of the bolts that secures the cover to the top of the inverter/converter.

<div class='quotetop'>QUOTE(DanMan32\";p=\"90285)</div>

Due to different resistances of the ground cables and even the metals, I really do think we have to expect minor differences between the unit body, the powertrain, and the auxiliary battery.

<div class='quotetop'>QUOTE(DanMan32\";p=\"90285)</div>

The only practical way to determine direct measurements would be to disconnect ground straps/cables and measure resistance, the same way you'd check resistance in a spark plug wire. Unless I strongly suspected a bad ground, I wouldn't go through all that work just for a science experiment.

At the very least that could create floating grounds during the test, and could be destructive to onboard components, unless the auxiliary battery was first disconnected. A lot of work involved too, as you will probably lose your radio presets and will have to reinitialize the power window anti-pinch function.

As far as measuring current through the ground straps or cables, my ampclamp adapter for my Fluke meters only has 1 mA resolution, so the few times I've tried measuring current through the ground cables I've read 0.0.

However, based on my industrial process control experience, the variances I measured are no cause for concern and indeed appear to be an expected range. You don't shut down an entire process system to chase after variances that low, unless an equipment ground fault monitor happens to indicate more than 40 mA.

The only time you would need far more precision would be with sensors that are sensitive to microvolt variances; eg: temperature RTD or pH ORP.

Jay

 

Did you at least turn on the headlights and the heater before taking current readings? Without a high current accessory, I wouldn't expect much current through the straps, unless the negative side of power was flowing through some other connection.

Minor differences of potential between the ground planes is exactly the whole point of this discussion.
But the differences in potential will be proportional to the current to/from each plane, as it is also a function of resistance between them, which should be a constant.
Again remember, you have 2 power sources, one of which you can turn off: DC/DC converter, and battery. Current flow would be dependent on load AND power source availability and location.

As for ground loops, besides the power carrying ground straps, you also have signal grounds and shields. You don't want amps through those! so I agree, don't remove straps.

 

Dan:

I had time after work to look at my auxillary battery. Actually, I had oatmeal spill all over the rear thanks to a broken bag, so I had an excuse to take everything apart to vacuum the oatmeal out.

I think an extra ground wire and/or a larger one is starting to make sense.

This is the first time I've actually looked in detail at the auxillary battery. There is a tiny wire, maybe 10-12 ga at most, that is around 2.5 inches long. It goes from the negative post of the battery (Negative post faces aft) directly to the unit body.

I expected a larger ground wire than that.

Jay

 

Hmm, that's interesting. However, most of the time, it isn't the battery that will be servicing the load but rather the DC/DC converter.

 

Dan:

I think there was a post last fall or early winter of a member having bizarre electrical problems that were finally traced to a loose negative clamp on the auxiliary battery.

I've learned the hard way that intermittent grounds, poor grounds, and God Help You floating grounds cause no end to your troubles. They usually send you off on a tangent and waste your time too.

I checked the auxiliary battery again and the negative clamp was only snug, not tight. It took only half a turn with a wrench, but next time out at the hobby farm I had better go over the auxiliary battery in more detail.

Jay

 

Someone is grounding their Prius in Japan.

Found this on the Internet, someone has grounded his/her Prius in Japan:

 

[font=Comic Sans MS:38f2cc4e24]That's not a grounding kit! That's a Prius-eating OCTOPUS!!![/font:38f2cc4e24]

 

:mrgreen: It does look like a blood-sucking octopus, thus the reddish color.

 

<div class='quotetop'>QUOTE(Areometer @ Apr 23 2005, 09:51 PM) [snapback]83829[/snapback]</div>

The first diagram on this page is showing arrows traveling from the positive on the battery to the spark plug... Now we should all know that electricity in fact flows from negative to positive...

 

<div class='quotetop'>QUOTE(ilusnforc @ Sep 23 2006, 10:42 AM) [snapback]323944[/snapback]</div>

Benjamin Franklin guessed wrong and we still are stuck with his coin-toss nomenclature to this day.

 

Searching for Prius accessories on Amazon I came across a Toyota Prius Hyper Voltage System. Not sure this is the correct thread under modificiations or not. The link for Amazon ishttp://www.amazon.com/dp/product/B000LPJD9I?tag=priuschatcom-20 Can someone tell if this is the right thread or even worth the money to research a similar mod to the Prius?

 

Total bunkum. Note how the ad copy is written so it could apply
to any car, probably with a simple script to substitute "Prius"
for ${MODEL} and many other types and squirt out tons of these
cowpatties so the search engines pick them up.
.
Save your money. If you really feel a need to wire capacitors
across your 12V system, there are much cheaper places to get them.
.
_H*