12v vs 24v vs 48v, 24v sweet spot?

[iwasforcedtopickausername]

I've been looking into 12V to 5V/USB converters. From what I can see, a great number of them support up to 30V, making them suitable for 24V solar setups. Digging in some more, it seems like there's a lot of support for 24V, even with LED bulbs.

Obviously for a home or larger installation, most are going to benefit from 48V. But for say a cabin or something off grid where you have some DC appliances, 24V may be a special niche.

There is some stuff like USB buck converters that can supposedly handle up to 60V making them suitable for 48V, but they are harder to find and I would be a little more skeptical of the claims.

When using 12V, you may have laptops and other devices that want 19-20V. It's supposed to be more efficient to buck (drop the voltage) than to boost. Whereas with 12V, you may need the odd boost converter.

I did see some LED bulbs that claimed they could handle 48V, but far more that could do 12V or 24V (usually with a 30V max).

Anyway, just thought this was interesting. 12V does have the widest compatibility for radio and definitely makes sense in some cases. 48V, as great as it is, does seem to have less compatibility than 24V, though. Of course you can always use a buck converter to drop from 48V to 24V or 12V. Could maybe wire a cabin with 48V with 12V buck converters for smaller electronics at various "outlets".

Edit: One more advantage to lower voltages is that with some inverters, the standby current is lower. For the Victron Phoenix 1200W inverter, the 12V unit uses 7W, 24V unit uses 8W, and 48V unit uses 10W. If in eco mode, it's more dramatic. 12V uses 1W, 24V uses 1.5W, and 48V uses 3W. It may not be enough to matter, but could also add up. Now the 48V is the most efficient while under power, so it may even out depending on your use.

Edit again: One more advantage, this one is more practical, is that there's a ton of solar charge controllers for 12V or 24V. You have to pay a fair bit more to get 48V most of the time. You may be able to get 2x 24V solar charge controllers for less than the price of one 48V. Obviously, 24V is not the answer for everyone, but if you *know* that you're not going to need more than a certain amount of power and your wire runs are fairly short, 24V may make more sense for you than 48V. But if you want to expand, which may well be the case, 48V is probably worthwhile.

 

[StuartV]

You can find more 24V stuff as trucks run off 24V batteries, so lights and cooking equipment for example (kettle, microwave).

 

[MichaelK]

For me, I consider DC appliances a waste of money. They are really only for the smallest, most marginal systems, where you are counting every single watt. Many have a hefty price premium for being "niche market". I think your money is better spent making a beefier AC system that can handle generic HomeDepot/Lowes appliances.

I went the AC only route for my own cabin, and couldn't be happier. Having a "larger" AC-centric system also means that the more capable system can better handle those odd-ball situations you didn't plan for. The neighbor wants to run his air-compressor to fill a flat tire, no problem.

 

[740GLE]

For modest needs I’d be focused on efficiency rather than voltage. IMO a modest off grid cabin doesn’t need anything above 3k worth of inverter, which is well within 24v. I’d spend more money on an efficient 24v inverter vs extra capacity and higher standby consumption of a 5k or 6k inverter.

 

[MichaelK]

I’d spend more money on an efficient 24v inverter vs extra capacity and higher standby consumption of a 5k or 6k inverter.

Actually, I think that background consumption has more to do with quality of design then sheer size. I have inverters in both 24V and 48V, the Conext 4024, and the big Schneider XW+6848.

The background consumption of both is in the 30W/hr range.

It's the cheapo foreign AllinOne designs that are the worst offenders. They are thrown together with the cheapest quality components available, and their lack of thoughtful design gets reflected in the high backgrounds, in the 100+W/hr range.

 

[740GLE]

Agreed I’d much rather pay for a smaller quality unit than one that checks all the boxes including a larger name plate.

I feel 24v above 3k isn’t worth it due to peak current and conductor sizing needs

 

[Smeeg]

For me, I consider DC appliances a waste of money. They are really only for the smallest, most marginal systems, where you are counting every single watt. Many have a hefty price premium for being "niche market". I think your money is better spent making a beefier AC system that can handle generic HomeDepot/Lowes appliances.

I went the AC only route for my own cabin, and couldn't be happier. Having a "larger" AC-centric system also means that the more capable system can better handle those odd-ball situations you didn't plan for. The neighbor wants to run his air-compressor to fill a flat tire, no problem.

That’s a great point but with DC appliances isn’t the whole system more reliable because we wouldn’t be using an inverter?

 

[MaximusAnonus]

Do the highest voltage you can possibly find stugf for. Even 48V is too low when you start growing your system.

 

[AlanH]

You can still run 12v of the likes of 48v. I have three 12v batteries being charged at 36v but have a 12v inverter running off all 3 at 12V.

 

[MichaelK]

That’s a great point but with DC appliances isn’t the whole system more reliable because we wouldn’t be using an inverter?

In a theoretical sense you may be right, but in a practical sense, I'd say no, because you are talking about low-volume niche market products that don't have the same level of quality control as the big manufacturers.

I've heard that criticism leveled against some of the propane-powered refrigerators. I believe the last post I read about one was the quality was such that it appeared to have been made in someone's garage.

 

[AmpD]

yeah the 48V and up bucks are considerably more expensive. I purchased a 12v to 5v buck for just under $6.

There are some nice ones out there. Some do buck & boost. Others only go one direction. Digital displays or on board screws requiring a multimeter. Some really give you fine tuning for consistent voltage outputs as well.

 

[schmism]

That’s a great point but with DC appliances isn’t the whole system more reliable because we wouldn’t be using an inverter?

The inverter would be a single source of failure yes. However if any of the DC only appliances goes down there is no way your going to get parts/replacements in a a timely manor vs just going and finding a normal everyday 120v ac of the thing.

trying to save 5% was a thing you did when PV was $5/w. now PV is .40/w . put 2 more panels up, get a normal AIO and regular 120v appliances

 

[Checkthisout]

I run 12volts and have a number of devices hooked directly to 12 volts. There is some really nice DC 12 Volt lighting available that merely requires a hole and only 2 wires to be run. No ground, no box etc to install.

For fridge just go 120V.

Even though I run 12 Volts, I am going to change over to 24 volts here in the next year or two. You instantly double the output of your charge controller and running wire becomes cheaper and easier when you don't have to purchase and run 0000 cables.

Lots of things (lights, computers etc) that are nomimally 12 volts DC will usually accept and input of 10-30 volts DC.

As far as things like USB chargers, that stuff is all dirt cheap. It wouldn't even factor into my decision tree in regards to what voltage to use.