Finding a high voltage DC inverter for 110 or 220 output

[aefriot]

I would like to know before designing a system where I can have a replaceable DIY battery in a DIY EV.
I own a Volvo xc70 AWD with a bad engine and the wife wants a AWD electric vehicle. We live off-grid
and will be charging with solar. So, I figure if we are going to try our own EV with high voltages, why not
just have a replaceable battery where we can allow a battery to continue to charge and provide our
household power needs while we still have the ability to go to town with a second battery. We would
never use the vehicle to travel further than 50 miles and most trips are in the 20 mile range. We live in a
cold climate so we would make two battery banks at double the weather distance capacity required to travel
the 50 miles. The vehicle will be kept in a warmed basement garage well above freezing. To aid in cold weather
battery temperatures, I suppose the battery box could be insulated and monitored for temperature to
protect the battery.

Because we are planning on having a high voltage EV with a extra battery, is there an inverter for converting
EV-type DC voltage to household power levels? If so, what might be some pitfalls this plan be?

We do not have the ability to economically connect to the grid. It is far more wallet friendly to add a 20Kw solar array
(DIY) than to connect to the grid.

 

[robby]

The first thing you have to find is an EV that will actually allow you to use Bi-Directional charging.
Then you need to ask the company what Inverters will work with that Vehicle.
As far as I know the only vehicle that has all the pieces in place for this is the Ford F-150 Lightning, it has a system that you can buy called "Ford Charge Station Pro" that works with the Vehicle. I think the 2022 Nissan Leaf and VW EV's can do Bi-Directional charging but I don't think they have released the parts that need to be installed in the house.

So the next problem is crunching the numbers to see if this is worth it versus just getting a Regular Inverter and enough batteries to hold what come in during the day. With that system you are not limited in Vehicle choice. Keeping in mind that you are never going to exceed the power that those 20KW of panels can produce at your location. Powering the house plus charging the batteries is going to be another equation to work out. I highly suggest you use the online pvwatts calculator to see what your location will yield for each month of the year.

Anyway we have some EV enthusiast on the forum that are much better equipped to help you than me.
Hopefully one of them will chime in.

 

[aefriot]

Thank you Robby.

Sorry, I should have said I will be assembling my own batteries from LiFePO4 cells to match requirements of the inverter. I feel they are safer than some of the alternatives, even though a bit bulkier. I do not want to burn our house or car with a silly/stupid error or faulty equipment.
We have been off-grid for 7 years here. I believe I can figure out requirements from our experience here just powering our residence.

 

[Doggydogworld]

I'm unclear - do you plan to convert the XC70 to electric using a kit, or purchased components? Or do you want to buy a AWD EV with a swappable pack?

Do you already have a high voltage MPPT? @FyKnight linked to a HV all-in-one unit in this thread. If you only need an inverter there are industrial ones like this unit from Bel.

Will the car be out and about all day, every day? Or does it sit in the garage 95% of the time? Is it gone during the day, when solar can carry the house loads, or at night when the house relies on battery power? I'm trying to understand why you want full battery swap capability. 50 miles of cold-weather range plus a comfortable reserve in a large-ish AWD SUV will be 30 kWh or so. Figure ~200 kg if air-cooled. Might it work to have 20 kWh permanently in the car plus a couple of 5 kWh "range extenders" that usually stay at home but can be added to the car on those rare 50 mile days?

 

[FyKnight]

Growatt also have some hybrid all-in-one units that support a battery voltage of 360 to 550 V:

Growatt Australia | Global Leading Distributed Energy Solution Provider

Growatt is a global leading distributed energy solution provider, specializing in sustainable energy generation, storage and consumption, as well as energy digitalization for residential and commercial and industrial (“C&I”) end users.

www.ginverter.com.au

It has 2 MPP trackers and is pretty inexpensive (easily found on eBay)
Again, not sure if there will be an issue where it insists on communicating with the battery over some custom protocol, or if it'll just work with any battery of appropriate voltage. The minimum 360 V is suspiciously close to 240 V / sqrt(2), i.e. it can just run an inverter back stage directly from the battery voltage.

 

[aefriot]

I'm unclear - do you plan to convert the XC70 to electric using a kit, or purchased components? Or do you want to buy a AWD EV with a swappable pack?

Do you already have a high voltage MPPT? @FyKnight linked to a HV all-in-one unit in this thread. If you only need an inverter there are industrial ones like this unit from Bel.

Will the car be out and about all day, every day? Or does it sit in the garage 95% of the time? Is it gone during the day, when solar can carry the house loads, or at night when the house relies on battery power? I'm trying to understand why you want full battery swap capability. 50 miles of cold-weather range plus a comfortable reserve in a large-ish AWD SUV will be 30 kWh or so. Figure ~200 kg if air-cooled. Might it work to have 20 kWh permanently in the car plus a couple of 5 kWh "range extenders" that usually stay at home but can be added to the car on those rare 50 mile days?

We are not looking for a speedy car, just reliable, comfortable and AWD. I plan to convert using individual components. Some of which were purchased from The car is mainly just for trips to town 6 miles away and most trips are under 30 miles once per day. I already have two Prestolite DC motors. I am unsure of the model numbers but they weigh approximately 110 lb each. There is also a 96-220V curtis DC controller. I will have to source another CD controller for the second axle. I have 100 ft of new 3/0 welding cable that came with a used welder I purchased at auction. I will make my own cable ends and buss bars from our pile of scrap copper.

The car will be stored inside except for the one trip per day. Or maybe twice if our second vehicle is being repaired and the trip is necessary. It does get very cold here so there will be a heating pad on a thermostat around the battery when out of doors. I am unsure if insulation should be used around the battery as it may get warm in summer. But I don't mind using the ample roof to place solar cells/panels to operate the battery heater pad when out for extended amounts of time so as not to use battery power if there is appropriate light. I do not mind insulating the vehicle and installing a small non-electric heater to maintain cabin and battery temperatures.

The auto's battery will most likely supplement the house battery. We have lived off-grid for seven years on 24V electric motive batteries that were 12 years old when we obtained them. We have not had a difficult time transitioning to this style of living as we both agree that the less we use, the less we have t pay for. We understand that we will not have a 0-60 in 7 seconds car and we, quite frankly, do not care. We look for inexpensive, use it we already have it, clean(er) energy car that we can also share it's battery with the home. It will be parked in the garage where the power equipment will be kept so there will be easy access. It is subterranean on 3 sides so geothermal heat will keep the equipment warm enough to be efficient when not in use.

 

[aefriot]

Growatt also have some hybrid all-in-one units that support a battery voltage of 360 to 550 V:

Growatt Australia | Global Leading Distributed Energy Solution Provider

Growatt is a global leading distributed energy solution provider, specializing in sustainable energy generation, storage and consumption, as well as energy digitalization for residential and commercial and industrial (“C&I”) end users.

www.ginverter.com.au

It has 2 MPP trackers and is pretty inexpensive (easily found on eBay)
Again, not sure if there will be an issue where it insists on communicating with the battery over some custom protocol, or if it'll just work with any battery of appropriate voltage. The minimum 360 V is suspiciously close to 240 V / sqrt(2), i.e. it can just run an inverter back stage directly from the battery voltage.

I checked out the offerings. Looks like everything is acceptable.

Thank you for the input.

 

[Doggydogworld]

I like your "re-use what you already have" approach. Post some pics if you get a chance.

If you stick with the two pack idea you could maybe have a winter pack that's insulated and a summer one that's not. It's probably not that hard in daytime to keep a LiFePO4 pack above the -20 degC discharge temperature you need for the drive back home, but it could take a while after you pull into the garage for a -20C pack to warm up to the 0 degC temperature you need to recharge it. Insulation would help by holding in the heat coming off the cells themselves during the drive home.

I doubt it helps much to add passenger compartment insulation beyond sealing air leaks if any exist. I suspect most heat is lost through the glass. And the trip home isn't long enough to lose much much heat, anyway. Insulation pays off over longer periods. I'd try a seat heater and steering wheel heater to warm the touch surfaces plus a resistance heater to bring the air temp up a little. Rig a way to turn it all on 5 minutes or so before the trip home. That shouldn't drain the battery much, less than 1 kWh. You probably won't even need to preheat on sunny and partly cloudy days.

 

[aefriot]

I like your "re-use what you already have" approach. Post some pics if you get a chance.

If you stick with the two pack idea you could maybe have a winter pack that's insulated and a summer one that's not. It's probably not that hard in daytime to keep a LiFePO4 pack above the -20 degC discharge temperature you need for the drive back home, but it could take a while after you pull into the garage for a -20C pack to warm up to the 0 degC temperature you need to recharge it. Insulation would help by holding in the heat coming off the cells themselves during the drive home.

I doubt it helps much to add passenger compartment insulation beyond sealing air leaks if any exist. I suspect most heat is lost through the glass. And the trip home isn't long enough to lose much much heat, anyway. Insulation pays off over longer periods. I'd try a seat heater and steering wheel heater to warm the touch surfaces plus a resistance heater to bring the air temp up a little. Rig a way to turn it all on 5 minutes or so before the trip home. That shouldn't drain the battery much, less than 1 kWh. You probably won't even need to preheat on sunny and partly cloudy days.

I haven't started the project yet. I need a plan and time to source equipment for the build. That's why I talk to people here. Others people as a whole have vast experience that is useful when do ing a DIY project. Avoid pitfals that others experienced. I buy everything I can used when there is not a need. Batteries, on the other hand, should probably be bought new and cared for. As I think I said previously, I have been using batteries that I obtained 6-7 years ago for my electrical storage for my home. But they were 10-12 years old when I obtained them. Now, nearing 20 years of age, one battery is failing and the other two, while still strong, I cannot faithfully use them for my home. They will most likely go to the workshop for lighting and small electrical tool use. I am in the process of buying LiFePO4 cells to build a couple batteries for the home, but it will give me experience as to how much space the cells may take up in the vehicle and how to arrange them. In a perfect world, I could hide them inside the empty panels of the car as I would lose no compartment space in the back of the wagon. This may not work well as they will cool quite quickly in winter and become less efficient and be prone to freezing. Charging might become an issue as well. Distance to individual cells from the BMS would potentially be pretty great and a larger wire will need to be used. I am not sure that all charging leads need to be the same length to ensure proper charging as it is an individual cell value.
As far as insulated or not, I think removable panels would suffice if the cells were all in one package vs distributed throughout the vehicles empty panels. I still believe we would be best to have an auxiliary heater (LP or fuel oil/diesel) to preheat and keep the passenger compartment warm when it is frigid outside. I suspect that in winter, when the car is in the garage in the basement, it will be 45-55 F when we leave on a trip. To keep it that warm or a bit warmer, will not consume much fuel.
I suspect that I will not start this project until our home is built and the new solar panels and equipment is in place.

 

[Ampster]

I haven't started the projecI t yet.

What is the voltage range of the Curtiss controller? Years ago I did an EV conversion that ran at about 96 volts. I was considering splitting that somehow when I got my first hybrid inverter. In the end I found some inexpensive LFP batteries to power the hybrid inverter. It was going to be a ten minute chore to reconfigure the EV conversion every time I wanted to drive it so I punted.

 

[Doggydogworld]

I can't say how to best wire up controllers or mate the motors to the drivetrain. You can get better info on that from a DIY EV forum. I do know retrofits usually have battery packs in the engine bay, using space freed up by removing the gasoline engines and associated crap (intake, exhaust, radiator, water pump, starter, alternator, etc.). You might have to beef up the front suspension a little, but e-motor plus a short range pack shouldn't weigh much more than the stuff you take out.

The best LifePO4 EVs are made in China. Their packs usually weigh 6-8 kg and take ~5 liters of space per kWh. Based on real-world range for vehicles similar to your XC70, I'd estimate 2 cold-weather miles per kWh. So 50 miles cold weather range means a pack of 150-200 kg and 125-150 liters.

Hiding the pack in a bunch of different body panels sounds cool, but as you note would complicate wiring, temperature monitoring and control, charging and BMS operations like cell balancing. Probably why DIYers usually use the engine bay.

 

[aefriot]

The Curtis controller is good from 96 to 220VDC.

 

[aefriot]

I can't say how to best wire up controllers or mate the motors to the drivetrain. You can get better info on that from a DIY EV forum. I do know retrofits usually have battery packs in the engine bay, using space freed up by removing the gasoline engines and associated crap (intake, exhaust, radiator, water pump, starter, alternator, etc.). You might have to beef up the front suspension a little, but e-motor plus a short range pack shouldn't weigh much more than the stuff you take out.

The best LifePO4 EVs are made in China. Their packs usually weigh 6-8 kg and take ~5 liters of space per kWh. Based on real-world range for vehicles similar to your XC70, I'd estimate 2 cold-weather miles per kWh. So 50 miles cold weather range means a pack of 150-200 kg and 125-150 liters.

Hiding the pack in a bunch of different body panels sounds cool, but as you note would complicate wiring, temperature monitoring and control, charging and BMS operations like cell balancing. Probably why DIYers usually use the engine bay.

For some odd reason, I forget that there will be no engine in the engine bay. So I was trying to figure out how to get the battery in the rear of the wagon. There will be plenty of room.

I feel so dense sometimes. But not for long. I can forgive myself rather quickly.

 

[Doggydogworld]

For some odd reason, I forget that there will be no engine in the engine bay. So I was trying to figure out how to get the battery in the rear of the wagon. There will be plenty of room.

I regularly forget where I put my phone down 5 minutes ago.....

FWIW, I stumbled across this DIY MPPT controller that can directly charge batteries up to 80V. He says the parts cost about $25. I don't know what it would take to bump that to 96V and/or support higher power levels.

 

[curiouscarbon]

this video may be of some insight for layout.

however, due to the weather requirements, undercarriage cell mounting would probably be inadvisable.

wishing good luck to this project!

 

[curiouscarbon]

estimate 2 cold-weather miles per kWh

this lines up with my experience. a model 3 got ~3 miles per kWh in mild weather and as low as 2 miles per kWh in cold weather or otherwise using heating a lot.

50 miles worst case suggests 25 kWh battery

some EV have heat pump which is awesome, but resistive heating always works at COP=1

regarding battery temperature. insulating and ventilating might be of use depending on conditions/use case. air based is the max complexity i am comfortable with. either pulling air out of box or pushing into box.

please feel free to share dimensions and or diagrams of the areas you wish to design into

 

[aefriot]

Very interesting conversion. He has done some things I had not thought of....then, I am not familiar with EV driving and desired helpful equipment, only the basics.

I have the opportunity to buy two complete CODA drivetrains (Controllers, motors and transmissions). One for the front and one for the rear, of course. Anyone have experience with CODA? Any pitfalls? Benefits?

 

[Hedges]

Because we are planning on having a high voltage EV with a extra battery, is there an inverter for converting
EV-type DC voltage to household power levels? If so, what might be some pitfalls this plan be?

Someone took an inverter meant for 48V battery and hundreds of volts PV, and connected HV car battery to PV input. Use a precharge circuit for the capacitors, and a fast fuse. Any hybrid inverter might do that for you, although if it also has LV battery connected to charge (or maybe even powering AC loads in batteryless configuration), it's MPPT algorithm may not work well with the I/V curve of the HV battery.

I'm only in the idle contemplation stage, but Sunny Boy Storage appeals to me for this purpose. It is a bidirectional Powerewall type grid-interactive inverter, can deliver 120V 2000W ("Secure Power"), with external auto-transformer and transfer switch it can deliver 120/240V for off-grid and backup. It's appeal to me is AC coupling to my existing battery inverter and GT PV system.