Prius as backup generator with midnight classic as voltage converter possible?

[travissand]

!!UPDATE!! 6-10-2020 below you will find the thread and my thought process I went through to make this work. Yes you heard it right it's working and so far been working 8 months 16 hours every night. If you want to know more I suggest you read the whole thread but skipping to February 3rd will give you the gist of it.

ORIGINAL thread starts here:
Is is this possible? I asked Midnites tech support and they said it would likely burn up the fets in the midnight classic charge controller. The 250V model is $300 on eBay with no warranty and they'll charge around $150 to fix it if I burn it up. Tech support also said the classic would have no problem handling over paneling with 25,000 watts of solar with varying voltage from passing clouds so what's the difference?

So my main question is, what do you think? Will the fets blow if I feed power from the Toyota Prius high voltage battery while it's going through its run cycles into the solar input of the midnight classic for it to convert the higher voltage down and feed 48 volts to my house battery and 5kw inverter?

I'd like to turn my Prius into a backup generator for my off grid solar system. I'm tired of running the so-called quiet 2kw Honda inverter generator. It's noisy, it stinks, and it doesn't have a real oil filter. And it overloads when a lot of stuff is on & the fridge tries to start.

I own two of these Priuses. One of them is damaged in the front with a cracked radiator and it's high voltage battery is now missing. The 2005 gen ii Prius is so quiet you can barely tell its running, the exhaust smells like warm steam and it's maintenance is much easier. It's battery can put out 25,000w from its 1.5kwh battery.

When the prius battery gets low the internal combustion engine "ICE" automatically starts at 40% state of charge which is 218V. Then pumps in around 5k watts into the battery and wattage tapers down until it reaches 248 volts at 50% state of charge. Although it's ratings are much higher I've seen the Prius generator put 12,000 watts into it's battery.

The battery control computer in the back with the high-voltage battery has wires going to every cell of its battery pack to keep the cells balanced.

Ultimately I'd like to replace the high-voltage battery with a capacitor Bank and spoof the communication between the battery control computer and the engine computer so that the engine starts and stops as I please instead of on its own program. That way I can better fine tune its cycles with a raspberry pi for the capacitors and it would last longer than a nickel metal hydride battery.

I see people have successfully used they're Prius they normally drive around and temporarily hook to the high voltage system to power inverters designed for that voltage. They leave the car on and it's engine starts and stops on its own and powered their house during hurricanes and such. This hints that the Prius will cooperate. And they reported that it uses one gallon for 8 hours with a 500 watt load which is exactly what my Honda inverter generator consumes with the same load. I believe I can nearly double that by turning the Prius off when its engine is not running. because it has a 400 watt draw on its battery when it is on.

I don't want to do like they did. I want to use my house inverter that I already own and is already working. I don't want to endure the transfer delay between the time it takes to switch from one to the other. Even though my inverter does the transfer pretty quick a lot of the time my electronic devices will reboot during the switch.

I see another supportive thread where a guy rectified the AC output from a small generator and ran it in through a midnight to charge his batteries successfully. http://www.fieldlines.com/index.php/...tml#msg1030639

Oh yeah I just remembered one downside to the cheap eBay deal on the classic that is unlike the regular version. It's missing the ability to differentiate whether it's output current went into the house battery or to the load which is the way most people have it set up anyway.

[Mike90250]

A MPPT charge controller works by shifting the load imposed on the PV array, therefor affecting the PV voltage and being able to manage it from 0 volts (short circuit) to Voc (Open Circuit).
This can be done with a current source like a PV panel. But if you try to pull a 80V battery to 30V to measure it's performance, you will be melting things, batteries are a voltage source and will not respond like a current source.

Before you dismiss outright the Classic 250-CP which is available for a terrific price, read up on it from the mfg, not some Shylock vendor that may not have any idea what they are spewing.
http://midniteftp.com/forum/index.php?topic=4606.0 Classic 250-CP configuration and sales info.

[travissand]

I confirmed with tech support that the discounted midnight has this mode. It shows the most promise for what I'm going to try and do.

Here's what it says in the user manual on page 35 where you can change between modes like hydro wind solar and such...

"U-Set VOC%
This is a fully manual mode based on a percentage of VOC. The Classic will sweep based on the user set
time in minutes and then park at a user set percentage of the VOC the Classic found on that sweep. This
mode is useful for testing or constant voltage sources."

[travissand]

Before you dismiss outright the Classic 250-CP which is available for a terrific price, read up on it from the mfg, not some Shylock vendor that may not have any idea what they are spewing.
http://midniteftp.com/forum/index.php?topic=4606.0 Classic 250-CP configuration and sales info.

Awesome. Thank you for the info it looks like I may not have to buy them from eBay when I could buy them straight from midnight and possibly with a warranty. For some reason I thought they don't have warranties on any of these particular discounted units.

Strange thing though the tech support guy seem to I think that what I'm doing isn't covered under the warranty but the manual that I quoted seems to say that that particular mode is kind of for what I am doing. I think the difference is after it does a sweep and locks on then the Prius internal combustion engine starts up and starts trying to raise the voltage
that's when I think the problem could occur.

so maybe using the hydro setting like the guy with the rectified generator did would be the better choice for me. he created his own custom voltage to amperage curve. I still think there could be problems with that though because his generator had a tiny output compared to the Prius.

[travissand]

Another way I learned to reduce the voltage would be to use one of these. But I read it would have to be modified and there were no instructions. I'm not sure if buying a couple of these would work for me. seller says they'll fit in a flat rate box so he'll ship them to Hawaii for no additional charge.

https://www.ebay.com/itm/Cherokee-International-DPS1450L2-1A-Rev-A-RL0003950-1450W-Power-Supply-TESTED-/200867137833

[Mike90250]

What's the voltage of the reclaimed battery you are looking at ? The classic 250 won't operate above 250V input. It will shutdown and sleep till the voltage comes down.

the hyper-VOC is a sleeping/survival mode where the input can be your 48V battery voltage added to the 250V input limit. but the voltage needs to be lower than 250V for the classic to start up.

I want you to be happy and not buy gear that won't work.

[travissand]

What's the voltage of the reclaimed battery you are looking at ? The classic 250 won't operate above 250V input. It will shutdown and sleep till the voltage comes down.

the hyper-VOC is a sleeping/survival mode where the input can be your 48V battery voltage added to the 250V input limit. but the voltage needs to be lower than 250V for the classic to start up.

I want you to be happy and not buy gear that won't work.

I'm not sure what reclaimed battery you're talking about. I'm not trying to reclaim any batteries. I'm not trying to replace my house batteries with a Prius battery. I'm trying to use the Prius as a backup generator.

[Mike90250]

OK, what's the voltage of that Prius battery? If it's not less than 249V, your classic 250 is not going to be able to use it.

There is a web page dedicated to Prius as A Backup http://www.priups.com/
They seem to use the 12V battery and use a small inverter to power critical loads, letting the HV vehicle battery recharge the 12V battery, and the engine starts as needed to keep the HV battery full.

[travissand]

OK, what's the voltage of that Prius battery? If it's not less than 249V, your classic 250 is not going to be able to use it.

There is a web page dedicated to Prius as A Backup http://www.priups.com/
They seem to use the 12V battery and use a small inverter to power critical loads, letting the HV vehicle battery recharge the 12V battery, and the engine starts as needed to keep the HV battery full.

the answer to your questions in my original post. And yes I've already been to that website that's where I got some of the information in my original post

[travissand]

I just re-read my original post I do have the voltage it charges up to but I left out the lowest voltage it starts from. So I'll tell you here.

The Prius high voltage battery cycles as the internal combustion engine starts up to charge the battery and then shuts off while the battery drains.

During these cycles it goes like this. The engine is off and the prius high voltage battery begins to drain and when it gets down to around 218v the engine starts up and the battery charges at up to 6000 Watts for 1 or 2 minutes until it reaches 248 volts and then the engine stops charging and shuts off. these cycles range the Prius high voltage battery between 40 and 50% state of charge.

The question I'm trying to get answered in this thread is whether or not the fets in the midnight will blow when the internal combustion engine starts and tries to charge the Prius is high voltage battery? Since nobody really seems to know and midnight thinks it will probably blow the fets but They aren't really certain so since nobody knows for sure I'm hoping I can find somebody that actually did it and knows for sure.

[Mike90250]

the answer to your questions in my original post. And yes I've already been to that website that's where I got some of the information in my original post

Well, that's not so good for the Classic 250.

When the prius battery gets low the internal combustion engine "ICE" automatically starts at 40% state of charge which is 218V. Then pumps in around 5k watts into the battery and wattage tapers down until it reaches 248 volts at 50% state of charge.

So it all falls on who's 248V is accurate. 2V is awful tight margin to base this all on.

[travissand]

Yeah that's cutting it pretty close but even if the midnight went into the hyper over-voltage mode and shut down it would only be briefly. The resting voltage of the Prius battery is definitely low enough.

[Mike90250]

Well, I guess you have convinced yourself. Keep us updated on how it works.

[solardreamer]

Yeah that's cutting it pretty close but even if the midnight went into the hyper over-voltage mode and shut down it would only be briefly. The resting voltage of the Prius battery is definitely low enough.

Overvoltage can potentially zap the fets. You might also consider using server class 48VDC PSU's as they are designed to work with input ~100-250VAC (i.e. max 350VDC peak) and they are robust and inexpensive. Typically they can be used in parallel for more power. I have used 2 x 3KW units with 240VAC generator to power 4KW 48V inverter with no issues.

[travissand]

Overvoltage can potentially zap the fets. You might also consider using server class 48VDC PSU's as they are designed to work with input ~100-250VAC (i.e. max 350VDC peak) and they are robust and inexpensive. Typically they can be used in parallel for more power. I have used 2 x 3KW units with 240VAC generator to power 4KW 48V inverter with no issues.

I already spoke of what you're suggesting and explained why I don't want to do that unless you have a way of doing it without the transfer delay and added cost.