120V Inverter Teardown

[Dark-Fx]

I might have missed it: what was the motivation for the teardown? To see if you could retro a 240v inverter?

I was hoping there was something obvious on the board to flip it to 240V. Some inverters will have a dip switch for this. I didn't see anything in my cursory check if the components at all. Since the output connector only has two contacts, it's most likely not possible, or at least not with the ability to use neutral.

Anyone have more detailed specifications for the input DC voltage this part looks for? And what controls it from turn on / turn off (dry contact, relay, CANBUS command, etc? )

Rivian's battery voltage is between 260ish and 460ish, so the inverter likely accepts that input range. The third cable is probably communications. Two pairs makes me think it could be Ethernet. Didn't dig into that at all. I think the actual circuitry to control the on/off state for the HV line is in the battery pack and is digital, but that's mostly speculation. Have no interest in dropping my pack out for that.

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[COdogman]

I might have missed it: what was the motivation for the teardown? To see if you could retro a 240v inverter?

This is another trial run for his upcoming YouTube channel!

 

[fhteagle]

I think the actual circuitry to control the on/off state for the HV line

So as soon as the inverter unit receives HVDC in it immediately starts outputting 120VAC? No switch or config or turn on signal at all? If so, that might just work for what I have in mind then...

 

[Riviot]

In your opinion is it hot to the point where it is unsafe or unhealthy for the electronics nearby?

@Dark-Fx would you consider the passenger seat the Hot Seat? ??

 

[CrazyOne]

I saw a big bad high voltage warning under passenger seat and bought a drop stop to help prevent anything from falling into it. I will never remove the cover, but thanks for sharing. It is good to know what's down there.

 

[Dark-Fx]

So as soon as the inverter unit receives HVDC in it immediately starts outputting 120VAC? No switch or config or turn on signal at all? If so, that might just work for what I have in mind then...

I think it's multi state. HV control and then an activation signal. The HV line was still hot when I went to plug it back in after disassembly. Inverter didn't instantly kick on when being plugged back in.

 

[Dark-Fx]

Some airbag telltales this morning. Putting the truck in gear made it think it was rapidly accelerating backward while on the brake pedal, said something about hold not being strong enough to keep the truck in position due to the angle. Don't think it was actually trying to move on its own. Put it back in park and did a full reset and everything seemed to be good after that.

 

[jwardell]

First off, standard disclaimer here because I discovered it's possible that there is potentially lethal voltages present when the inverter is disconnected, so don't try this at home without the proper equipment.

I wanted to do this to see if there was a way to flip it to 240V. If there is, it wasn't obvious. It could be a software thing and I made no attempt to look into that yet.

The inverter is under the passenger seat. You will have to remove and disconnect the seat to gain access to it. The bolts at all four corners are under these small soft touch plastic pieces. I don't think you actually need to remove them but I did. Should be a T20. One of mine was crossthreaded so a bit more difficult to remove than the others. The bolt was 15mm (actually felt a little loose, could have been an SAE size but I would be surprised).

It might be necessary to move the seat forward and backwards to gain access to the bolts. Probably less chance of damage at removal to have the seat in the most forward position. I scratched up some of my trim because the seat just barely fits through the door cavity.

Once you unbolt the seat, it gives you a lot more room to unplug the connectors. Two of these are for airbags so the secondary disclaimer here about how they could get activated unexpectedly applies. I didn't get a great pictures but they are pretty easy to remove. Seat can just be set on the ground. I didn't disconnect the seat belt.

Once that's out, we gain access to the protective plastic above the inverter. Just the single bolt in the middle to remove it and some normal automotive trim clips to pull against. The seat connectors are also trim clipped to this piece of plastic so also have to be disconnected. The upper connector in the photo is not connected to anything. I'll speculate that it could be a diagnostics port.

The inverter. Mine had been on for several days prior to my investigation here. I was going to hit it with my thermal camera but couldn't find it. It was hot enough to be painful after about two seconds of contact. I flipped off the inverter in the car and waited 15 minutes.

The bottom left connectors here are the input/output of the inverter. After unplugging everything, I metered 0 volts across the leftmost plug.

But then I told the truck to turn the outlets back on. Don't do this without proper equipment. I went and put my PPE on immediately after this. (For those interested, my HV battery was charged to 85% during this)

Then I pulled the inverter apart and took pictures.

After putting everything back into the truck, it seems fine now, but I still wouldn't recommend doing it. The truck acted wonky while the seat was disconnected and there's likely a chance you could end up breaking something.

Wow, thank you for tearing this open for us!

First, this does not look like Rivian's design at all, it is all older tech inside. I couldn't see any branding on the PCB or elsewhere, could you? Do you have any better/closer photos of the PCB?

It also appears to be smaller than the area available on the floor, perhaps a larger unit was planned (maybe when Rivian gets around to designing their own...), would you agree?

Also...glad you didn't get hurt, looks like your finger was a centimeter from bridging HV to chassis! I suggest you pull the fireman's loop in the frunk before disconnecting things...

 

[Dark-Fx]

Also...glad you didn't get hurt, looks like your finger was a centimeter from bridging HV to chassis! I suggest you pull the fireman's loop in the frunk before disconnecting things...

HV is completely isolated from the chassis. Would be safe to touch a lead and the chassis at the same time. Not that I would do that though.

 

[HimuraMOdo]

Probably not hot enough to worry about the electronics. I'd guess it was somewhere in the 130F range. With the amount of heat sinking on the inverter, it's probably pretty evenly heated.

Was that 130F temp on the inverter under no load or full load at the AC outlet?

 

[Dark-Fx]

Was that 130F temp on the inverter under no load or full load at the AC outlet?

Minimal load at the time, just running a fridge in the bed. Inverter is definitely responsible for wasted energy, which is why Rivian forced a timer onto it.

 

[HimuraMOdo]

Minimal load at the time, just running a fridge in the bed. Inverter is definitely responsible for wasted energy, which is why Rivian forced a timer onto it.

Thanks. It seems the whole inverter operates from the HV pack alone. I'm wondering if Rivian will redesign this to make it more efficient.

 

[fhteagle]

More info about the unit and other cars it's used on. Apparently there is a 220V version also...

https://openinverter.org/forum/viewtopic.php?t=2693

 

[chrismc]

To be clear, the spec sheet indicates the alternate version is for Europe/China which is 220V 50Hz and not the same as US-spec 240V 60 Hz. It would also not generate a neutral reference needed for US 120V split-phase output.

 

[Dark-Fx]

To be clear, the spec sheet indicates the alternate version is for Europe/China which is 220V 50Hz and not the same as US-spec 240V 60 Hz. It would also not generate a neutral reference needed for US 120V split-phase output.

Chassis ground on my truck actually seems to be neutral between +hot and -hot, could mean it's possible to pull neutral off if it can be reconfigured to be 240V. I'm also not sure how they'd run in parallel but I suppose it could be natively supported

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