24 or 48

[Chief]

Just watched your video "48v Solar Power System for Beginners: Lower Cost and More Power!" from Aug 16, 2019.
You are a savior!

I currently have two small systems but they are going to be broke down and used in other areas in the future.

I am torn between the 24 or 48 volt all-in-one system. This is what I'm doing, so you tell me what I need

I have a small off-grid homestead that the Wife and I will be moving to shortly. It has 4 small buildings (each around 200 sq ft), 2 of them will have air conditioning (small portable units, no window units). We will have one small, apartment size and another under counter refrigerator and a small chest freezer. We will have 3 12 volt pumps for moving water from large tanks to 2 cabins and one to the garden area. Most power tools will be battery powered and I have 2 generators (Honda EU6500 and Predator 2000) for extra power when needed. Two of the building will have ceiling fans, all will have LED lighting, and optional box fan when needed. Two buildings will have kitchen/bathroom exhaust fans.

Exterior lighting is mainly solar powered units and the flashlight you keep in your pocket, so the system will not be needed for that.

So should I go with a 24v or 48v system? My main reason for asking is that the cost between the two is pretty significant and I don't want to build a system that is too large for my needs.

 

[Supervstech]

I'd recommend against the portable ac units for sustained use.
If you already have them, sure, keep em, but I hope they are two pipe units not one pipe.
As for sizing, it all really depends on what loads and duty cycles needed.

There are several online solar estimators online, check out the faqs for newcomers.

 

[Craig]

48 mainly because you can get 2 times as much energy through your SCC than with a 24 also the Inverter will draw half as many amps. I have a 24 volt system and wish I went with 48 and am still contemplating going to 48.

 

[Kep]

I went 48v and I think at this time it is the best option. There are 48v golf cart inverters that produce 30amps of 12v. Wire size isn't as large for 48v so less cost and less weight. I envision that in the future we will be using 700+ volts DC systems. Cummins makes an all electric platform and it is what the future looks like and they use 700v dc. Efficiency of higher voltage systems are the future IMHO.

As for system size I would go larger than needed for battery storage because the more heavily you discharge the system the more quickly it degrades. So effectively you extend the battery life.

 

[krby]

The rule of thumb I was told for DC systems a while ago is "12 volts for every 1000 watts of power". This guide is to keep currents less than about 100A to minimize voltage drop, wire size, and component size. If I'm going to need 2500W of power, I'd go with a 24V system. If the power needs start getting up towards 4000W, I would plan on 48V.

 

[Steve_S]

I'm an off-gridder Cabineer, 2Kw of Panel, Classic 200 Controller, 24V 20kwh of FLA battery being replaced with 24V/400AH pack, and a Samlex 4024 Inverter/charger. Works good BUT because I'm "invested in it, I use it", if I was doing it again, I would just do 48V. Luckily I don't have huge power draws, biggest is well pump 120v/1000w max, then fridge 120v/90w, occasional microwave 1000w. 4Kw Inverter Charge off 24Volts in my option is max, after that should be 48v.

 

[SolarRat]

The bigger the better. I think in the coming years much larger than 48v systems will be the norm. No reason not to.

 

[krby]

The bigger the better. I think in the coming years much larger than 48v systems will be the norm. No reason not to.

The thing keeping me from choosing 48V or recommending to others now for a roughly 24V portable system is there are fewer choices of charger, inverter, drop-in battery. They do exist, but a 48V 1000-2000W inverter is more rare than a 24V or 12V one and the 48V tends to cost more.

 

[Craig]

The thing keeping me from choosing 48V or recommending to others now for a roughly 24V portable system is there are fewer choices of charger, inverter, drop-in battery. They do exist, but a 48V 1000-2000W inverter is more rare than a 24V or 12V one and the 48V tends to cost more.

I concur and once you start getting over 48 volts the power can get dangerous with the amps these things can produce.

 

[Topmaike007]

Go for 48v

 

[SolarRat]

I concur and once you start getting over 48 volts the power can get dangerous with the amps these things can produce.

The higher the voltage the less amps so.... DC is no more dangerous than the AC in our homes (although many myths would say otherwise). I would not be surprised to see 120v battery banks as the norm in the future, it would probably make an inverters job easier. We all live surrounded by high voltages and somehow we are all still alive!

 

[Supervstech]

The higher the voltage the less amps so.... DC is no more dangerous than the AC in our homes (although many myths would say otherwise). I would not be surprised to see 120v battery banks as the norm in the future, it would probably make an inverters job easier. We all live surrounded by high voltages and somehow we are all still alive!

I completely disagree with this notion.

DC voltage above 32v can easily kill you. The higher the voltage, the harder to switch the current off. DC arc effect is very hard on switches above 12v. 48v is safe with good work practices, but certainly not nearly as safe as 12v or 24v to the human body, or the switching controls like breakers.

Ac voltage is certainly dangerous as well. 99% of the world interacts with voltage only with appliances... the rest of us deal with wiring, and working on the mains, be it ac or dc...

 

[Steve_S]

AC or DC – Which One is More Dangerous And Why ?

AC or DC - Which One is More Dangerous And Why ?

Which is More Dangerous - AC or DC? Why AC is More Dangerous than DC? Is DC Voltage really Dangerous than AC Voltage. Which is Harmful, AC Current or DC Current.

www.electricaltechnology.org

Ac OR DC can kill you if the right conditions exist and only a fool ignores such. Friend thought I was overdoing it when I installed a 5'x7' 1" thick Rubber Horse Mat on the floor of my power house (good $45 investment BTW). You can never be too safe.

 

[SolarRat]

I completely disagree with this notion.

That's because the myths got to ya

 

[SolarRat]

The thing keeping me from choosing 48V or recommending to others now for a roughly 24V portable system is there are fewer choices of charger, inverter, drop-in battery. They do exist, but a 48V 1000-2000W inverter is more rare than a 24V or 12V one and the 48V tends to cost more.

A 1000-2000w system doesn't really need a 48v bank, so it's harder to find an inverter in that size at 48v. But once you go to a 5kw+ system 48v inverters and CC's become much more common and comparably priced, and it'll save a lot in wiring and component costs. For a small portable system 12 or 24 is fine for 1k-2kw (1kw per 12v).

 

[Craig]

The higher the voltage the less amps so.... DC is no more dangerous than the AC in our homes (although many myths would say otherwise). I would not be surprised to see 120v battery banks as the norm in the future, it would probably make an inverters job easier. We all live surrounded by high voltages and somehow we are all still alive!

Im not talking about the amps we are using but if you have a 400 amp battery at 48 volts and you cross wires you can do a lot of damage even though you only plan to use 10 amps or whatever. Its not what you use its the potential energy Im worried about. Of course circuit breakers can mitigate this but it still gets woriesome

 

[SolarRat]

Im not talking about the amps we are using but if you have a 400 amp battery at 48 volts and you cross wires you can do a lot of damage even though you only plan to use 10 amps or whatever. Its not what you use its the potential energy Im worried about. Of course circuit breakers can mitigate this but it still gets woriesome

Electricity is dangerous, that's nothing new, and it doesn't matter if it's AC or DC.

20 years in the future I envision most new homes being built with ~30+kwh of PV roofing and 200kwh battery banks. The average Joe wants his 5 ton A/C blasting, a turkey in the oven and veggies in the microwave while charging his electric car in the garage all at the same time. Inverters for a typical 2000sf home will need to be in the 20kw range, drawing a max of 83 amps from a 240v battery bank. You'd need a permit to change batteries or do any work on the system, no different than with today's AC systems.

In the above scenario, a 48v 418 amp system would be far more dangerous, less efficient and more money. There is no good reason for a 48v cap. If safety trumped efficiency our homes would be run on 24v AC and our cars would be limited to 15mph.

 

[svetz]

AC or DC – Which One is More Dangerous And Why ?

AC or DC - Which One is More Dangerous And Why ?

Which is More Dangerous - AC or DC? Why AC is More Dangerous than DC? Is DC Voltage really Dangerous than AC Voltage. Which is Harmful, AC Current or DC Current.

www.electricaltechnology.org

Ac OR DC can kill you if the right conditions exist and only a fool ignores such. Friend thought I was overdoing it when I installed a 5'x7' 1" thick Rubber Horse Mat on the floor of my power house (good $45 investment BTW). You can never be too safe.

When I looked it up I was surprised at how low the hand-to-hand current is to kill you....

More here: http://www.diysolarforum.com/index.php?threads/frequently-asked-questions.70/post-7288

 

[Supervstech]

The higher the voltage the less amps so.... DC is no more dangerous than the AC in our homes (although many myths would say otherwise). I would not be surprised to see 120v battery banks as the norm in the future, it would probably make an inverters job easier. We all live surrounded by high voltages and somehow we are all still alive!

I think your statement needs clarification...

Dangerous exactly how?

Installed... 2,000,000 volts isnt dangerous... ac or dc... I wouldn't want to work with it though. The tools and Personal protection gear is far beyond anything I want to deal with.

A properly installed system left alone and in a secure enclosure isnt dangerous.

A untrained silly individual tinkering with ANY voltage ac or dc can cause serious harm to property, tools, and themselves or others.

So, it all depends on the conditions and precautions. Ac and dc is safe if handled properly. And unsafe if not.

 

[SolarRat]

I think your statement needs clarification...

Dangerous exactly how?

Installed... 2,000,000 volts isnt dangerous... ac or dc... I wouldn't want to work with it though. The tools and Personal protection gear is far beyond anything I want to deal with.

A properly installed system left alone and in a secure enclosure isnt dangerous.

A untrained silly individual tinkering with ANY voltage ac or dc can cause serious harm to property, tools, and themselves or others.

So, it all depends on the conditions and precautions. Ac and dc is safe if handled properly. And unsafe if not.

How does any of that contradict what I wrote? "No more dangerous"...I was pretty clear and vague on purpose at the same time .

We have a bunch of people on this site that I wouldn't trust changing a light switch, let alone building or even tinkering with a high voltage system. But this is an electrical based DIY site, so we shouldn't need to hand-hold and warn about high voltages on every single post. It should be common sense. Electricity is something to respect, not fear like many here seem to do.