Are there any high voltage (300-400VDC) mppt controllers?

[ponobill]

I'm going to put a salvaged Tesla model 3 75KWh battery (roughly 350 VDC) in a container with a Sandi 30KW, 300-400VDC input inverter and power my shop, and probably some shop space I'd rent out with it. The simple way to charge that would be long serial strings (say 12S or so of 40V panels to give the MPPT controller 480 V to work with) of PV panels with an MPPT controller that can live with 350V output. I don't have any shading issue, serial strings of perhaps 400-500V would preclude needing massive conductors for lower voltage strings producing a similar amount of power.

I could ditch this idea and do the PV part of the project with microinverters and frequency shift them to shut them off when the battery is fully charged and avoid the issue of buying very fancy contactors to switch off 500V dc at perhaps 50 amps, but that would be a heck of a lot of microinverters. I'm considering something like 60 400 watt panels to start with. Does anyone know of a source for high voltage controllers? It seems industrial and utility solar installations must work this way. Even just looking at the panels in a Costco parking lot I can see that the conductors feeding down from the panel arrays are not thick, and the panels look like they are connected in series for much longer strings than I'm considering.

 

[sunshine_eggo]

Do you know for certain that the Model 3 pack BMS will work in the configuration you propose?

 

[Ampster]

Do you know for certain that the Model 3 pack BMS will work in the configuration you propose?

He has not said at this point. Most configurations that I have seen of Tesla modules just use the BMS and temperature sensor wires to hook up a different BMS because the modules are used in a 24 or 48 volt configuration. In this case, I believe the poster is using the whole pack but communicating with the Tesla BMS could still be an issue.

 

[sunshine_eggo]

He has not said at this point. Most configurations that I have seen of Tesla modules just use the BMS and temperature sensor wires to hook up a different BMS because the modules are used in a 24 or 48 volt configuration. In this case, I believe the poster is using the whole pack but communicating with the Tesla BMS could still be an issue.

That's why I'm asking. To my knowledge, packs disconnected from a car do not have a functional BMS as it relies in part on communication with the managing control module. I would not consider using a whole pack unless I was 100% confident that a functional BMS is in place.

Kinda like an electrodacus triggering HVD or LVD with Victron switches - the BMS sends a "problem" signal, and the attached hardware reacts accordingly (stop charging/stop discharging). I believe EV packs work in this manner with no internal ability to cut off the pack.

 

[Ampster]

I could ditch this idea and do the PV part of the project with microinverters and frequency shift them to shut them off when the battery is fully charged and avoid the issue of buying very fancy contactors to switch off 500V dc at perhaps 50 amps, but that would be a heck of a lot of microinverters.

I assume you are talking about AC coupling them to your Sandi inverter but you would need to check if the Sandi inverter can AC couple with that many kWs of AC coupled solar.

 

[Ampster]

I would not consider using a whole pack unless I was 100% confident that a functional BMS is in place.

There are BMSs with external contactors that can use the existing wires. Orion is one example. I don't know enough about the Electrodacus to say but if the Electrodacus can also be a charge controller that might answer the question in the title?

 

[ponobill]

Sorry, I should have been more clear. I plan to use the controller system from EVTV, the company Jack Rickard started and ran until he died recently. They sell the system with a salvaged pack, preconfigured and tested for just under $20K. I wanted to acquire my own pack and just buy the controller but the only way they sell them is as a package--tested and debugged. The price looks ridiculous until I compare it to a similar capacity in powerwalls or other commercial battery/bms/inverter packages) I've used the EVTV Model S controller before in an incredibly stupid motorhome project I'm doing and it's effective and reliable (so far). The system includes contactors for isolating the battery in an abnormal condition if it somehow approaches an overvoltage or undervoltage condition and a charge enable contactor that controls charging in normal operation. I assume the Model 3 controller is esp32-based as the Model S version is, it has all the usual bells and whistles including the ability to trigger a frequency shift shutdown of microinverters. That's the most compelling reason for me to use microinverters. And even though my shop will likely never experience structural shading there are still clouds in the Northwest, so I might gain some generation benefits.

This is potentially a semi-commercial application, besides powering my shop, which is substantial, I'm contemplating using some of the excess land my shop sits on to create workshop rental space for entrepreneurs looking to build products. My shop is close to the Columbia river, which means power is cheap, so the pure cost calculations don't really pencil out, but having what is essentially uninterruptible power is compelling given wildfire outages and other unpleasant occurrences.

 

[ponobill]

I assume you are talking about AC coupling them to your Sandi inverter but you would need to check if the Sandi inverter can AC couple with that many kWs of AC coupled solar.

Actually, I expect the inverter to just run off the battery and the battery will be charged with a separate charger, there isn't one built into the Sandi inverter--I consider that a good thing. The system will still be grid-connected, if only for three-phase for my rotary compressor and homebuilt power hammer which has a monster 3 phase motor that looks like it came from the turn of the previous century.

This inverter is actually a factory-modified version tweaked to work with the controller. From the specifications sheet: This is a SANDI 30 kiloWatt DC to AC inverter. Perfect for the 300-400vdc input range of our Model 3 battery. This version includes dry contacts for a frequency shift from 60.00 to 62.5 Hz, allowing our Model 3 Controller to shut down microgrid-tied inverters such as the Enphase IQ series or the Solar Edge.

 

[Ampster]

I plan to use the controller system from EVTV, the company Jack Rickard started and ran until he died recently

Jack did some nice work and it is great that some of his team is carrying on his work.

 

[ponobill]

I've been digging a bit to understand what is meant by AC coupling. Most of the explanations I've read so far seem to be simply adding a battery to a grid-tied system and then managing the grid-tied inverters so they don't overcharge the battery. Am I missing something?

In my silly motorhome project (I'm required by a modest level of intellectual honesty to always call this silly or stupid since I don't actually like motorhomes but I put a lot of effort into this 1978 GMC moho restomod) I treated the panels/controller/battery/BMS/inverter as a completely independent system with the single exception that connecting to shore power can charge the battery. I can also disconnect the PV system completely from the distribution system and power everything from shore power. I never attempt to let both sources work in harmony. Here's a picture:

I suspect AC coupling tries to do something more sophisticated, but I'm not sure what it is. Perhaps some hybrid way to charge/discharge from a battery and seamlessly feed the grid or use the grid when battery power gets low?

 

[ponobill]

This is the system I propose to build. I posted about this here in the fall of 2020, but now I'm getting ready to execute. I'm OK with doing this with microinverters if necessary, but the only element I'm missing now is the MPPT controller that will handle the system voltages. It's kind of beautifully simple.

 

[ponobill]

I think the simple fact that a lot of posts on this forum are about complying with increasingly complex utility and state regulations on what you can feed to the grid, how much, and when tells me what I need to know about being grid-tied. There better be some damned big benefits in order for me to care about those complexities, never mind buying equipment to properly manage them.

 

[sunshine_eggo]

I've been digging a bit to understand what is meant by AC coupling. Most of the explanations I've read so far seem to be simply adding a battery to a grid-tied system and then managing the grid-tied inverters so they don't overcharge the battery. Am I missing something?

Not entirely. AC coupled usually refers to a situation where you add an off grid system to a grid tie system, such that when the grid goes down, you can supply your own grid with the off-grid system. In this way, your grid-tie PV array is AC coupled to the output of your off-grid inverter. Inverters capable of AC coupling can use the surplus AC at its output (from the grid-tie system) to charge its batteries thus allowing use of the array.

Some systems can be used for peak shaving and other means of optimizing (minimizing) grid usage to save money.

In my silly motorhome project (I'm required by a modest level of intellectual honesty to always call this silly or stupid since I don't actually like motorhomes but I put a lot of effort into this 1978 GMC moho restomod) I treated the panels/controller/battery/BMS/inverter as a completely independent system with the single exception that connecting to shore power can charge the battery. I can also disconnect the PV system completely from the distribution system and power everything from shore power. I never attempt to let both sources work in harmony. Here's a picture:

Sweet ride.

 

[rmaddy]

Does anyone know of a source for high voltage controllers?

Victron has an MPPT SCC that can handle up to 450V of PV input voltage. It's meant to be used with a 48V battery bank:

SmartSolar MPPT RS - Victron Energy

The SmartSolar MPPT RS solar charge controllers are Victron's solution for systems with large series connected PV arrays charging 48 V DC battery banks.

www.victronenergy.com

 

[time2roll]

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[ponobill]

There are lots of mppt controllers that can handle high voltage inputs, but only low voltage (typically 48V) output. I'm looking for a controller that can handle 380 VDC OUTPUT. I don't care what kind of chemistry it understands, I can turn off the controller with a contactor. It looks like I might have to build my own MPPT controller, adapting one of the open source designs. I REALLY don't want to do that. Using enphase or some other microinverter is probably a better alternative.

I'm kind of surprised that none of the off-grid manufacturers has offered this yet. It seems to me that the most practical source of batteries for off grid is salvaged Tesla Model 3/Y batteries given the rapidly rising production/sales rate. With the long warranty period for the batteries there's really no alternative market for salvaged batteries from wrecks other than perhaps a few hot rodders sticking batteries in old ICE cars. A 75KWh model 3 battery is about 10K or less on eBay. I guess most of the manufacturers would much rather sell their own power walls, and it's probably easier to market what is theoretically a plug 'n play solution, even if it's too small for practical use.

 

[Ampster]

I'm kind of surprised that none of the off-grid manufacturers has offered this yet.

It may be that there is something about DC systems over 60 volts not being approved by building codes. Commercial products are a better source.
I see you have already worked with evtv and they are the only resource that I know of that is doing that.

 

[sunshine_eggo]

MPPT Solar Charger Controllers Archives

MPPT solar charger controller | Battery input: 12V 24V 36V 48V 96V 120V 192V 216V 240V 384V Charge current: 60A, 80A, 100A | Stackable

www.sigineer.com

"Sigineer Power carries MPPT solar charger controller in a wide range with battery voltage at 12V, 24V, 36V, 48V, 96V, 120V 192V 216V 24V and 384V, and charger amperage ranges from 60A to 120A."

 

[ponobill]

It looks like Sandi also makes an MPPT controller that will work well. Now I just need to figure out how to buy one.

 

[SolarPrep]

ponobill could you make a SolarEdge work in this scenario? They purchased Kokam and are bring one of those packs to market, at about $6k for a kw pack, high voltage. I wonder if some clever person here can make another high voltage battery work with the SolarEdge inverters?

Also, just check out Nuvation Energy for some cool projects and high voltage BMS'es.

LOVE your GMC! I've tried to buy one, but my wife hates the look of them. Now I'm looking at a 1960 GMC 4104 bus.