Onboard inverter

I haven't been able to find any info on this. I was speaking with someone the other day about the car only charging at 3.3kw vs the 6.6kw. When I go
down a hill (mountain) I can get 20 - 30kw charging from the motor sustained for 10- 15 minutes. If the inverter can handle that, what's stopping someone from
using that inverter to charge the car at the 6.6kw or even higher?

I'm sure there's a simple reason otherwise it would have been done by now. I'd just like to know.

Jeff

There is plenty of prior art here, but the main issue is the lack of galvanic isolation between the AC line and the car's HV system. (Safety)

Then you have the need to install large and expensive contractors between the motor and the inverter, and between the inverter and the AC power line.

Don't forget that the inverter uses the inductance of the motor windings to buck/boost, so you'd then need auxiliary magnetics anyway. (If you want good efficiency).

Since semiconductors are really not all that expensive compared to a bunch of big contractors, why bother?

-Phil

Holly cow! Of course the Capacitance multiplier coupled with the Diode matrix would never be enough to handle the Supply voltage supervisor. LOL
Sounds good though, thanks for the input. I'm glad there are people smarter than me

Seems viable to me but it would have to be part of the design. And then you need three phase power input......

And one reason it's not part of the design is such a system is patented by AC Propulsion.

smkettner said:

Seems viable to me but it would have to be part of the design. And then you need three phase power input......

Click to expand...

Did you see my response? If you avoid the safety implications, it still doesn't make sense in the $ department. It would also make the drivetrain less reliable. Back 15 years ago, this equation was different, but now cheap IPM's have changed this equation.

And you are also wrong about requiring 3-phase. Nothing "requires" 3-phase, it just reduces single phase current in most cases. You don't even need 3-phase for a 3-phase motor anymore, as the LEAF's inverter will happily demonstrate. (DC --> 3-Phase)

-Phil

Yes I read your reponse.

I thought the inverter produced 3 phase power to drive the electric motor. And likewise the motor produces 3 phase power that is used to charge the battery during regenerative braking.

My thought (along with the OP) would be to feed the inverter with 3 phase power from the wall vs from the motor. Yes I assume much would need to be changed. If the inverter could be fed with single phase, I don't know.

Not sure of the galvanic isolation differences between the inverter/charger feeding the battery vs the regular OBC. Need a transfer relay to disconnect the motor. Contacts would not have to switch under load.

Sure it would cost some. But then so does the QC equipment. A 3 phase outlet at the rest stop might be easier to impliment. Might also work across brands vs the current proprietory systems. I like the OP's idea as it could get EVs away from the gas station/gas pump mentality.

Having a large on-board charger is the route Renault took with Leaf's sister; Zoe. In Europe where they use the 3-phase Mennekes standard, even for home charging, this makes a lot of sense. Still, they did not add a bunch of relays and use the same inverter.

The cost of the relays (large contactors) is more than adding another IPM, so there is no point in doing so, and you'd still have the safety implications to deal with.

You cannot feed 3-Phase AC into the inverter without adding inductance. In drive mode, The inverter uses the inductance of the motor windings to achieve buck/boost power conversion. If you fed grid AC into the LEAF's inverter without series inductance, you would likely destroy the IPM in a big fireball. ACP used the motor windings rewired to provide the inductance, which presents significant problems, the least of which is reduced efficiency and yet another set of contactors. So adding external magnetics is the preferred way, then it's all solid-state, and you can preserve galvanic isolation.

If you did have added magnetics and contactors, and did this properly, it would accept single-phase fine, albeit at reduced maximum power levels.

-Phil

everyone here is way smarter than me, but this seemed like the right people to comment on my question. so, without trying to hijack (what appears to be a quieted thread)....here goes:

when it comes the the battery putting out dc voltage somewhere in the range of 350 volts, would it ever be possible to use a "Sunny Boy" sma inverter (the SB8000US accepts a dc voltage b/w 300-600 volts and spits out 240 volts AC) to power items in my home? The leaf inverter would need to be bypassed. For that matter, one could theoretically use the sunny boy to charge the leaf directly via Solar Panels feeding into the inverter -just like a solar battery bank and then when needed, take that power back for home use during the night?

How complex would this be really? I mean, if i could get my hands on a salvaged leaf (or void the warranty on a new leaf couldn't this be accomplished in a rather straightforward manner?

any replies please keep them simple, b/c i am dumber than you are

adeyo said:

would it ever be possible to use a "Sunny Boy" sma inverter (the SB8000US accepts a dc voltage b/w 300-600 volts and spits out 240 volts AC) to power items in my home?

Click to expand...

Yes, that should be possible, with the caveat that it's probably a grid-tied inverter and so would need to be connected to the grid to work - you can't just plug things into it on an "island" (but there are standalone inverters that can do this). I've thought of trying this with an old Leaf battery when they become available, if I can get my hands on one. You'd just have to access the main DC lines to the battery (which I believe you can find connected to the charger - but please don't mess with that if you don't know what you're doing). And I think the car would have to be on.

adeyo said:

For that matter, one could theoretically use the sunny boy to charge the leaf directly via Solar Panels feeding into the inverter -just like a solar battery bank and then when needed, take that power back for home use during the night?

Click to expand...

No, the sunny boy can't charge the Leaf directly. I suppose you could charge the pack directly by taking the DC from the panels through a DC-DC converter, to match the pack voltage, but that seems like a bad idea -you probably want some more sophisticated electronics (like a real charger than can accept DC input) to charge the battery instead of just a "dumb" DC-DC converter, but I'm not sure about this.

If you mean plugging the Leaf charger into the AC output of the sunny boy, again there's the grid-tied issue - since the inverter probably has to be connected to the grid anyway, plugging directly into the sunny boy output is indistinguishable from plugging in to any outlet in your home. And if you're talking about a standalone inverter, I'm guessing the Leaf's charger would not be happy with the wildly fluctuating power that would be produced by your solar panels, but again I'm not sure about that.

Anyway, the next question is why would you want to do this? With a grid-tied solar setup, it makes way more sense to charge your car from the grid when it's cheap overnight and sell power to the utility during the day with it's worth more (you should go on time-of-use metering if you haven't already). With a standalone solar setup, you're probably much better off using the equipment out there that's specifically designed for this purpose instead of "hacking" a Leaf and inverter to do it. Although I suppose you could use a Leaf battery in lieu of standard lead-acid batteries for such a setup, assuming the electronics will work with the pack voltage.

fooljoe said:

adeyo said:

would it ever be possible to use a "Sunny Boy" sma inverter (the SB8000US accepts a dc voltage b/w 300-600 volts and spits out 240 volts AC) to power items in my home?

Click to expand...

Yes, that should be possible, with the caveat that it's probably a grid-tied inverter

You'd just have to access the main DC lines to the battery (which I believe you can find connected to the charger - but please don't mess with that if you don't know what you're doing). And I think the car would have to be on.

adeyo said:

For that matter, one could theoretically use the sunny boy to charge the leaf directly via Solar Panels feeding into the inverter -just like a solar battery bank and then when needed, take that power back for home use during the night?

Click to expand...

...And if you're talking about a standalone inverter, I'm guessing the Leaf's charger would not be happy with the wildly fluctuating power that would be produced by your solar panels, but again I'm not sure about that.

Anyway, the next question is why would you want to do this?

Click to expand...

Thanks for the insight!!! ok, i have some follow up comments/responses to your questions...

1. "i'd have to access the main lines of the DC battery" ....ok, i didn't realize it would be accessible to access the main battery lines. That opens up a few options. (not that i have an approach in mind)

2. "leaf wouldn't be happy with wildly fluctuating power..." that is my presupposition exactly. I'm wondering however, if , using a real charger (some chargers accept DC current) if i could go directly from the DC Solar panels (which might produce 250 Volts (a total of under 6kw -but fluctuating, i understand) and into a charger that accepts DC but that regulates the charge to work with the Leafs BMS (say the quick charge port on the leaf only accepts a constant 230v with 25 amps) ...then i could charge the leaf as long as my charger can put out a minimum constant 230v w/ 25 amps).

3. "why would i want to do this?" I would want to do this because I wouldn't need to buy a separate battery bank for the occasional off grid usage. i.e. power outage etc. Instead, i would charge the leaf during the daytime and use the inverter (12v) battery during the nighttime to power a few essentials: well pump, refrigerator. I am currently grid tied, but this would enable me to "island" in a round about sort of way in emergencies. People have already used their leaf to power such essentials in a storm -the 24kw battery actually recharges the 12v accessory battery and lasts about 2-3 days of use. If i could charge my leaf in an outage, then my runtime for essentials could theoretically go on indefinitely. I could also use a few more items during that time. (also, there are inverters with higher outputs that can be utilized with the leaf.)

adeyo said:

say the quick charge port on the leaf only accepts a constant 230v with 25 amps

Click to expand...

No, that is nowhere close to what the QC port accepts. That port is logically connected directly to the battery terminals, so the DC voltage needs to be in the neighborhood of 400v. Someone correct me if I'm wrong, but it seems obvious to me that the voltage must also be adjusted dynamically by the external charger to yield the current that the car demands. We are talking E = I*R here, where R is (largely) the battery resistance, which varies with charge, and I is a number communicated through the CHAdeMO interface that also varies with charge (and probably battery temperature). The external charger would have to continually monitor the current, and boost or ease E to yield the proper I.

This is way beyond plugging in a solar array output and hoping, or even using an intermediate charger with a constant voltage output.

Ray

planet4ever said:

adeyo said:

say the quick charge port on the leaf only accepts a constant 230v with 25 amps

Click to expand...

No, that is nowhere close to what the QC port accepts.

This is way beyond plugging in a solar array output and hoping, or even using an intermediate charger with a constant voltage output.

Ray

Click to expand...

just made up those numbers for the theory ...so basically the car cannot accept a constant voltage/amperage to its battery and expect to charge at all -quickly or slowly?