Why isn't a 48v to 12v system optimal?

[myersfamilyhome]

I'm trying to understand why configuring a system to take advantage of the optimal output and availability of equipment and power isn't talked about very much. I do understand that finances are a challenge in some cases along with the need for split phase but there is a happy medium that has a benefit to it as well.

Here's an example of what I mean:

Solar Charging:
* 200-500w panel/s
* Charge Controller/s that support multiple battery voltages in one (12/24/48)

Storage:
* Battery bank that can be configured between 12-48v but setup as 48v

Inverting:
* High Amp Buck Converter/s to 12v
* High efficiency 12v inverter/s

Unless I'm missing something, this gives you an optimal setup when the following is the goal:

* Maximum charge power from panel/s
* Quickest charging of storage
* Most flexibility in variable system configuration if/when a battery or cell causes an issue
* Most readily available components on the inverter side that can be more budget friendly

Though I've seen no reviews of high output buck converters, they do exist.

Tian Power DCDC 175A 2500W 48V to 12V Buck Converter and 20A 1000W 12V to 48V Boost Bidirectional Converter with CAN Communication, High Power Automotive Driving Charger for RV, Truck, Forklift https://a.co/d/akRM6UD

 

[rodrick]

You lose efficiency every time you convert voltage why would you use a 12 volt inverter when your at 48 volts run a 48 volt inverter

 

[Shimmy]

You have higher losses inverting from 12V to 120VAC, especially when you are over ~1,200W. The buck converters exist, so supporting 12V loads is easy enough, as is distributing them around a reasonable radius of your home, which is going to give better results than a single large one for small loads.

"Universal" batteries you just have the cost issue.

The PV is trickier for systems under about 1200-1800W though; the MPPT minimum voltages are a little higher than some scenarios I can envision, especially with high-efficiency 60-cell panels.

 

[myersfamilyhome]

You lose efficiency every time you convert voltage why would you use a 12 volt inverter when your at 48 volts run a 48 volt inverter

As mentioned, Most readily available components on the inverter side that can be more budget friendly. 48v is ideal I agree in an ideal world, where everyone has access to 48v inverters down the road to pickup when one goes out, able to order online, or a physical delivery address, but there are some of us that truly live offgrid and investing in a system means designing it optimally to be as flexible in all scenario's with a focus on availability. It's all good and great to have a super efficient system but what value does that have if your 48v inverter fails, a cell goes bad in your 48v bank, or your 48v AIO inverter charger has issues...there's no reconfiguring the system to help you get through below 0° temps in these scenarios if the system does account for it. That's why I'm asking why isn't this considered optimal. I guess it needs to be said that availability of parts and access to resources does define what optimal is. At least in my situation. I have a 48v system with lifepo4. Some do find local availability of replacement parts a deal breaker though.

 

[Tomthumb62]

there's no reconfiguring the system to help you get through below 0° temps in these scenarios

What's the worst thing that could happen if it's below 0F? Pipes freezing or something else? Surely you aren't trying to heat your home with solar electricity? Aren't most off-gridders heating with wood or propane? Cook on them, too or have a propane camp stove for cooking.

99% of electrical needs, during winter, is more related to convenience, not life-threatening. No power to the fridge? Put it all in coolers and stick it outside (it will freeze eventually, so either super-insulate the cooler or move it indoors or to a cold-but-not-freezing mudroom or root cellar.) I suppose if you have necessary medical equipment to be powered, there's that, but if I had such equipment, I would have a dedicated backup system just for that equipment so I didn't have to worry about when the new inverter might show up.

What some people do is a hybrid of what you're speaking of. They have a 48v system - SCC, battery and inverter. Then they have a separate 12v or 24v system as an emergency backup. They might need to disconnect some things and move some cables around (or have the 12v backup system wired into a manual or automatic switch), but they are protected in either case. Or keep a generator-inverter for such emergencies.

 

[Tomthumb62]

Most readily available components on the inverter side that can be more budget friendly. 48v is ideal I agree in an ideal world, where everyone has access to 48v inverters down the road to pickup when one goes out, able to order online, or a physical delivery address, but there are some of us that truly live offgrid

And what do you do when your high-output 48-12v buck converter goes belly up? I mean it sounds like you're just trading a harder-to-get-48v-inverter-than-12v for the buck converter, which isn't something that can be easy to get either without ordering online and not exactly cheap ($90-$100 for my quick search).

As for a physical address, that can be solved pretty easily, too. If it can't be shipped via General Delivery to the Post Office, find a friend who has a physical address and ask if you can have your item shipped there. People in remote areas do it all the time. It's part of the cost of living off-grid and remote, you have to get a bit creative sometimes. If you live hundreds or thousands of miles away from any sort of civilization or "physical addresses", then you'd be wise to simply have replacement parts/devices so you can do the repair right then and there without weeks or months of downtime.

People have lived (and still do) live off-grid and without electricity. Look at some of the Amish, it's 2023 and they still do it. Good skills to have in the back pocket in case of emergencies.

 

[rodrick]

As mentioned, Most readily available components on the inverter side that can be more budget friendly. 48v is ideal I agree in an ideal world, where everyone has access to 48v inverters down the road to pickup when one goes out, able to order online, or a physical delivery address, but there are some of us that truly live offgrid and investing in a system means designing it optimally to be as flexible in all scenario's with a focus on availability. It's all good and great to have a super efficient system but what value does that have if your 48v inverter fails, a cell goes bad in your 48v bank, or your 48v AIO inverter charger has issues...there's no reconfiguring the system to help you get through below 0° temps in these scenarios if the system does account for it. That's why I'm asking why isn't this considered optimal. I guess it needs to be said that availability of parts and access to resources does define what optimal is. At least in my situation. I have a 48v system with lifepo4. Some do find local availability of replacement parts a deal breaker though.

That’s why you have spare parts hopefully you built your own system diy batteries ect and you built in redundancy

 

[CoolWill]

The problem I have with it is reliability and availability. Every step is a critical piece of equipment that can fail. The fewer of those you have the better. Then you have low voltage appliances. There are far more 120/240 volt appliances available than 12/24/48 volt appliances. If you're already running an inverter, might as well use standard appliances that are cheap and plentiful.

 

[Leeds]

As mentioned, Most readily available components on the inverter side that can be more budget friendly. 48v is ideal I agree in an ideal world, where everyone has access to 48v inverters down the road to pickup when one goes out, able to order online, or a physical delivery address, but there are some of us that truly live offgrid and investing in a system means designing it optimally to be as flexible in all scenario's with a focus on availability. It's all good and great to have a super efficient system but what value does that have if your 48v inverter fails, a cell goes bad in your 48v bank, or your 48v AIO inverter charger has issues...there's no reconfiguring the system to help you get through below 0° temps in these scenarios if the system does account for it. That's why I'm asking why isn't this considered optimal. I guess it needs to be said that availability of parts and access to resources does define what optimal is. At least in my situation. I have a 48v system with lifepo4. Some do find local availability of replacement parts a deal breaker though.

If you want the most redundant, hard to kill, no single point of failure setup then you should consider multiple charge controllers (one per string) and multiple inverters, (one per circuit).


I'd still stay with 48v though. Five 2000w 48v inverts would cost you around a grand and any one failure would not set you back much power-wise. You can change the math all you want to spend more or less or have larger or smaller inverters or more or fewer of them but in general parrallelization is the optimal solution for the problem you're presenting.

Here's a 24v system with 3 charge controllers and 6 inverters, each on a dedicated line for a dedicated purpose:

 

[midwestsolarnoob]

I’m actually toying around with an idea like this for my mobile application.

1500w or so if rigid panels
48v EG4 inverter, charger, scc (inverts 48v to 120/240)
20.5 kwh 48v eg4 v2 server rack batteries

Then of course dc to dc inverter for 12v. Which is small loads. E.g. led lights. Vent fans. Fridge

This would be more efficient than running strictly 12v and inverting 12v to 120v ac.

Correct? Or would it be pointless and over complicating a mobile off grid dwelling?

 

[pollenface]

Here's a 24v system with 3 charge controllers and 6 inverters, each on a dedicated line for a dedicated purpose:

View attachment 159081

very tidy