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Poll: will it work? Prius as a generator, direct charging of 48V from traction battery

Will it work, or should I expect the magic smoke?

  • Magic smoke release imminent.

    Votes: 0 0.0%

  • Total voters
    9
  • Poll closed .

Consumerbot3418

Fitting square pegs into round holes... for fun?
Joined
Jan 17, 2021
Messages
188
Location
Midwest
I recently picked up an old, used Prius. Planning to use it for transport, and hope to fall back on it as a generator, should the need arise. I've read plenty of threads about using the Prius 12V system to drive an inverter, and the inverter to drive a battery charger, but I'm seriously considering attempting something more direct.

The traction battery is close to a nominal 200V. While monitoring the pack voltage during charging, it reaches about 240V before shutting the engine off again. I happened to pick up some Eltek Flatpack2 HE rectifier modules recently, intending to use them to charge my 48V battery from the grid or a backup generator. But the label on the Flatpack2 says it'll accept up to 250V AC or DC on the input!
signal-2024-03-10-165555.jpeg
Based on that, and the fact that peak-to-peak 250VAC is something like 350V, I'm thinking it may actually be feasible to charge directly from the traction battery. At some point, I'll try to tap the high voltage power cables (using PV wire rated for 600V, maybe?), and then switch through a pre-charge resistor.

This would eliminate the conversion to 12V, and from 12VDC to 120VAC, and from 120VAC to 48VDC. Should be a major efficiency improvement. A single Flatpack2 unit tops out around 35A (2000W), and I've got a means to limit the voltage and current programmatically (better than a Chargeverter!)--another thread about that coming soon!
 
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Why not hook up one of the high voltage inverters directly to the drive battery system?

Aims has one that uses 230v dc. Not sure what the overall range of voltage is for low and high cutouts but it seems like it would be plug and play on a prius.

 
Why not hook up one of the high voltage inverters directly to the drive battery system?
I've already got a pair of XW Pros on the wall, and 48V battery attached to them--and these high-efficiency telecom 48V rectifiers on hand, paid $50 each. If I smoke one, it's not a major loss. Not really sure why I would want to spend another $2000+, unless it's to have some extra redundancy on the inverting side of things?
 
I recently picked up an old, used Prius. Planning to use it for transport, and hope to fall back on it as a generator, should the need arise. I've read plenty of threads about using the Prius 12V system to drive an inverter, and the inverter to drive a battery charger, but I'm seriously considering attempting something more direct.

The traction battery is close to a nominal 200V. While monitoring the pack voltage during charging, it reaches about 240V before shutting the engine off again. I happened to pick up some Eltek Flatpack2 HE rectifier modules recently, intending to use them to charge my 48V battery from the grid or a backup generator. But the label on the Flatpack2 says it'll accept up to 250V AC or DC on the input!
View attachment 201373
Based on that, and the fact that peak-to-peak 250VAC is something like 350V, I'm thinking it may actually be feasible to charge directly from the traction battery. At some point, I'll try to tap the high voltage power cables (using PV wire rated for 600V, maybe?), and then switch through a pre-charge resistor.

This would eliminate the conversion to 12V, and from 12VDC to 120VAC, and from 120VAC to 48VDC. Should be a major efficiency improvement. A single Flatpack2 unit tops out around 35A (2000W), and I've got a means to limit the voltage and current programmatically (better than a Chargeverter!)--another thread about that coming soon!
you obviously know much more about this subject then I do as such i wanted to sub to this thread to see where this leads, best of luck and above all, be careful.
I got zapped by my 500 aH bank last year and it took almost 8 months for the nerves in my left arm to get back to almost normal. (sweaty forearm across several cells while leaning over... it was not even painful, but DC does weird shit to the nervous system.)
 
I got zapped by my 500 aH bank last year and it took almost 8 months for the nerves in my left arm to get back to almost normal
Yikes. Curious to know what voltage that was... @GXMnow shared a similar story in another thread not too long ago, in response to @SeaGal 's assertion that 48V may be safer than 12V, given the lower amps per unit of power (which I tend to agree with, on its face). Seems sweaty arms are something to watch out for! I've experienced it while working on a 12V battery with sweaty arms, and have no desire to find out what 48VDC feels like, let alone 200!

The v4 5kw version has 48v output.
Appreciate you sharing the link. I'm impressed with how they used the under-deck storage! Still think I'd rather see if I can get my little $50 Flatpack2 to do the job, but it's nice to see that tapping the traction battery is a proven approach.
 
for me it was a 48 nominal bank that was probably at about 54 volts. it was 4p16s calb lithium bank and as the space was originally designed for a 3p4s lead acid bank, it was an awkward location. i leaned over the bank, set my (for the most part dry) forearm across several of the cells (so not full 54 volts even) and felt a tingling in my arm and it went numb. I had reduced dexterity and sensation in my pinky finger as well as the next two fingers. so three fingers with less than normal strength and a tingling forearm for about 6-8 months
 
I absolutely adore the idea of stripping the powertrain out of one of these and using it as a standalone generator.

Would take a LOT of skill to make it run like that though.
 
Prius's have a 12 volt battery that is charged directly off the traction battery. I'm not sure how much current it can supply but I used one to run an inverter and it worked fine. The gas engine would start ocassionally to keep the traction battery charged which would keep the 12 volt battery charged.

12 volt to 48 volt boost converters in the 20 amp range can be had for about $200
 
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Should work. Wonder if car will set a DTC due to unexpected power loss from traction battery.

It won't provided you pick up off the hot side of the relays so the car sees the current it's providing by passing through the current sensor. The BCM is pretty flexible with loads. The A/C compressor pulls about 3000W, and it doesn't try to account for it, so it's not going to care about current being pulled elsewhere.

It will jack with the car's SoC computation, but with NiMH, it's a continuous estimate, and it makes all it's logic decisions based on the 14 block voltages.

I absolutely adore the idea of stripping the powertrain out of one of these and using it as a standalone generator.

Would take a LOT of skill to make it run like that though.

Running a 1.5L engine as a 2000W generator isn't particularly efficient, but it works well.

It's relatively hard to get shocked by the traction battery IF you remove the orange safety plug. You literally have to be careless. I've disassembled hundreds, and my PPE is optional nitrile gloves, mostly to protect my skin as I'm prone to dry, cracked skins on my hands. There are certain conditions on failed batteries that do make them potentially dangerous. I'll usually wear nitrile gloves on those... when I remember, and if my hands are dry. :p

Year matters. Connecting to an 04-09 is easier than a 2010+

The concern with the charger is NiMH behavior at cold temps. You may exceed 250V during charging; however, if you keep it under load, you should be okay.

Prius's have a 12 volt battery that is charged directly off the traction battery. I'm not sure how much current it can supply but I used one to run an inverter and it worked fine. The gas engine would start ocassionally to keep the traction battery charged which would keep the 12 volt battery charged.

DC-DC converter is rated for 70A @ 14.0V, and the car consumes about 10A in computers and ignition coil firing. Running more than about 700W continuous off the 12V is impractical.
 
It won't provided you pick up off the hot side of the relays so the car sees the current it's providing by passing through the current sensor. The BCM is pretty flexible with loads. The A/C compressor pulls about 3000W, and it doesn't try to account for it, so it's not going to care about current being pulled elsewhere.

It will jack with the car's SoC computation, but with NiMH, it's a continuous estimate, and it makes all it's logic decisions based on the 14 block voltages.



Running a 1.5L engine as a 2000W generator isn't particularly efficient, but it works well.

It's relatively hard to get shocked by the traction battery IF you remove the orange safety plug. You literally have to be careless. I've disassembled hundreds, and my PPE is optional nitrile gloves, mostly to protect my skin as I'm prone to dry, cracked skins on my hands. There are certain conditions on failed batteries that do make them potentially dangerous. I'll usually wear nitrile gloves on those... when I remember, and if my hands are dry. :p

Year matters. Connecting to an 04-09 is easier than a 2010+

The concern with the charger is NiMH behavior at cold temps. You may exceed 250V during charging; however, if you keep it under load, you should be okay.



DC-DC converter is rated for 70A @ 14.0V, and the car consumes about 10A in computers and ignition coil firing. Running more than about 700W continuous off the 12V is impractical.

Have you brainstormed anyway of making of making both generators work and just use the whole thing (including traction battery) as standalone generator?

That would be a fun little project but getting the engine to run properly would be a serious challenge.
 
Side note...

It's important to remember that these very expensive NiMH batteries have very little usable capacity. The 12V is a 45Ah AGM, 540Wh.

The USABLE capacity of a NEW hybrid battery is:

1.2V * 168 cells * 6.5Ah * 40% = 524Wh... almost the same as the total capacity of the 12V.

The charging will cycle on at 40% and off at around 48-52%.

Used batteries tend to have less than 50% of new rated capacity.

Have you brainstormed anyway of making of making both generators work and just use the whole thing (including traction battery) as standalone generator?

Nope. Only one of the motor-generators, MG1, is attached to the ICE, and IIRC, it's only capable of about 20hp. It's conceivable you could connect MG2 at about 45hp to be driven by the ICE, but you'd have to eliminate the entire transaxle and build a custom housing.

That would be a fun little project but getting the engine to run properly would be a serious challenge.

IMHO, definitely not worth the squeeze. You'd need at least the ECM, BCM, hybrid control unit and the skid control ECU, plus LOTS of spoofing.
 
DC-DC converter is rated for 70A @ 14.0V, and the car consumes about 10A in computers and ignition coil firing. Running more than about 700W continuous off the 12V is impractical.
The gas engine only starts when the battery is low. The gas engines in prius's run very efficiently, probably more so than a standard gas generator.
Is that 10 amps from the traction battery or from the 12 volt battery?
 
It won't provided you pick up off the hot side of the relays
Bummer. I'd prefer if my tap/mod was only hot when the car's ignition is on.

The A/C compressor pulls about 3000W
This gives me confidence that I'm not likely to overburden or wear out any of its components with a few hours at 2000W or less. (y)
 
Bummer. I'd prefer if my tap/mod was only hot when the car's ignition is on.


This gives me confidence that I'm not likely to overburden or wear out any of its components with a few hours at 2000W or less. (y)

How difficult would it be to get a second inverter (oops, voltage converter) off a wrecked prius and run it in paralell?
 
The gas engine only starts when the traction battery is low.

Fixed. At 40% SoC.

The gas engines in prius's run very efficiently,

As a vehicle propulsion system, yes. That doesn't translate to all operating modes.

probbaly more so than a standard gas generator.

Nope. The gallons burned by a 1.5L engine producing 4000W (typical idle charge rate) will be MORE than a 0.5L engine running a 5000W generator at 4000W.

Is that 10 amps from the traction battery or from the 12 volt battery?

10A from the traction battery would be over 2000W.

All numbers were in the context of 12V. The Prius can only charge the battery or power the low voltage DC bus with 70A. Period. It uses a DC to DC converter.

How difficult would it be to get a second inverter off a wrecked prius and run it in paralell?

No idea. Hurts to think about it.
 
Fixed. At 40% SoC.



As a vehicle propulsion system, yes. That doesn't translate to all operating modes.

Nope. The gallons burned by a 1.5L engine producing 4000W (typical idle charge rate) will be MORE than a 0.5L engine running a 5000W generator at 4000W.
What do you mean by "typical idle charge rate"?
Comparing a typical 1.5 L engine to a similarly constructed .5 L engine is an unfair comparison.
The prius engine has a lot of controls (electronic and mechanical), which may produce higher efficiency than a standard gas generator engine. Even at less than max power output.
 
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What do you mean by "typical idle charge rate"?
Comparing a typical 1.5 L engine to a similarly constructed .5 L engine is an unfair comparison.
The prius engine has a lot of controls (electronic and mechanical), which may produce higher efficiency than a standard gas generator engine. Even at less than max power output.

Wouldn't matter. A Honda EU7000i runs fuel injection and is .39 Liters. It will consume less fuel producing 5000 watts than the Prius Motor producing 5000 Watts.

That's basic engine operation.

That's why I asked what it would take to use the voltage coming off the pack directly. You would need to pull around 15Kw in order for the prius gen to start to make sense efficiency-wise.

However, pulling a given wattage out of the battery like say 1500watts and then letting the engine cycle every few hours means the engine is seeing a decent enough load during the recharge that it starts to make more sense from a fuel consumption standpoint.
 
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