24 vs 48 volt system for beginner

[nexusjosh]

So, I'm just getting into Solar. I was going to go with a 48 volt system, they're cheaper, and from what I've read, generally better, you need double the batteries from a 24 volt system, but that also gives me far more battery life. However, from what I've seen, they appear to be more complicated as far as the solar panels are concerned.

Question is simple for you experienced peeps; Should I continue looking into a 48 volt system as a beginner, or downscale to a 24v system.

 

[croakie321]

I, too, am exploring this option.

 

[iamrich]

Big advantage of 24v is half the battery, which is half the cost, which is substantial... Otherwise everything else is the same really. Technically 48v is not low voltage like 24v, but all this stuff is dangerous.

 

[Supervstech]

Let’s answer this with a question…

what are you going to power with this system, and for how long would you like it to run after dark? How much solar will you have?

 

[rmaddy]

Big advantage of 24v is half the battery, which is half the cost, which is substantial

I wouldn't call that a big advantage of 24V. If you have half the battery then you have half the total power as well, regardless of voltage.

You can easily make a 48V battery that is the same cost as a 24V battery. Both will have the same power. It's just that the 48V will have half the Ah of the 24V version but both have the same Wh. And Wh is the important number when determining how much stuff you can run and for how long.

Let's say you buy 4 12V 100Ah batteries. Whether you wire them in 4P (12V 400Ah), 2S2P (24V 200Ah), or 4S (48V 100Ah), you still have the same amount of total Wh (4800Wh) all for the same cost.

 

[rhino]

However, from what I've seen, they appear to be more complicated as far as the solar panels are concerned.

There is not really any complication regarding this. You simply need to make sure the voltage coming into your charge controller is high enough above your battery voltage for the charge controller to work. With a 12V or 24V battery bank this can be met with a single larger solar panel that may have a Vmpp of 40V... Since that isn't enough to charge a 48V nominal battery bank the "complication" is that you need to connect two of them in series which would double the voltage and then not be an issue charging a 48V bank. You'd have to do same thing with a 12V or 24V bank if the panel voltage was too low.

 

[nexusjosh]

Let’s answer this with a question…

what are you going to power with this system, and for how long would you like it to run after dark? How much solar will you have?

I would like to run it on the batteries for as long as possible. Though I know its scalable. I purchased 2 of These today, they are a bit of a pain, because its "1 per customer." And thinking about it more today, I could start with a 24V system, and later on if I wanted to move to 48V system, I'd just have to do some minor re-wiring, right?

I wanted to use This Solar Charge Converter. It has good specs, and should last a good long time. And I opted with the 70amp version instead of the 60 because there is only a 10$ difference?

That is one thing I am not really clear on however. With this upper end SCC, CAN I power it with 1 or 2 panels, and add more as I build my system, or is there a static requirement for SCC's, On how many panels they need to function?

There is not really any complication regarding this. You simply need to make sure the voltage coming into your charge controller is high enough above your battery voltage for the charge controller to work. With a 12V or 24V battery bank this can be met with a single larger solar panel that may have a Vmpp of 40V... Since that isn't enough to charge a 48V nominal battery bank the "complication" is that you need to connect two of them in series which would double the voltage and then not be an issue charging a 48V bank. You'd have to do same thing with a 12V or 24V bank if the panel voltage was too low.

What I find difficult is the Maaaaaaaaath! Using This video guide. I tried doing the math with These panels. And I came up with needing like 28 of them? I didn't think that was right...

Edit: The SCC has a "Nominal power" Is that what it expects at all times? For example the one I was looking at has a nominal power rating of 4,000Watts, so is that what it expects, or can I build, for example, a 1,000 Watt system first, and slowly add more panels. Page in the Manual

 

[Supervstech]

Depending on the size of the battery bank, and the type of battery, you can start small, and work up within reason.
the math is fairly simple…
Start with the running watts of the intended load. That gives you a number to start with, then you can multiply times the running hours needed to give you Wh. Or you can operate the load for a day or two running through a Wh meter like a kill-o-watt plug in device.
a daily usage number tells you how much energy you need to operate. Take that number and divide by 5 to tell you the minimum solar panel wattage you need.

 

[nexusjosh]

Depending on the size of the battery bank, and the type of battery, you can start small, and work up within reason.
the math is fairly simple…
Start with the running watts of the intended load. That gives you a number to start with, then you can multiply times the running hours needed to give you Wh. Or you can operate the load for a day or two running through a Wh meter like a kill-o-watt plug in device.
a daily usage number tells you how much energy you need to operate. Take that number and divide by 5 to tell you the minimum solar panel wattage you need.

I'm not sure of the load I'll need right at this moment. I'm going to look into a monitoring device and plug it into the sub panel. But right now, one mid-sized refrigerator, with 3 window AC's (Each room will have its own). Along with a TV, Computer, gaming VR setup... And thats all I can think of right at the moment.

There is also a water heater, but for now, I'm going to leave that on grid power. This will all be in Northern California, Shasta Mountan area if you want to look it up. We have brown outs during the day 3 or 4 times a week. This will eliminate that issue. And sometimes, the power goes out for 3 or 4 days. So I would like to build a system that would hopefully be able to run for 2 or 3 days, if not longer. My goal is to slowly build up the system. Likely building a larger, and larger battery array.

Also keep in mind I am going to have a transfer switch wired in from day one. Actually, as the batteries are already in the mail to begin with, I'm thinking about balancing the batteries, and getting the transfer switch plugged in right away? So maybe I can start running off battery during peak hours. Though I need to decide on an inverter before I do that... Which is my next step.

Thanks everyone for the help and feedback so far.

Oh one last question. Is there a Discord server? I would be extremely supprised if there isn't, though I haven't seen a thread around discussing it as of yet.

 

[iamrich]

But right now, one mid-sized refrigerator, with 3 window AC's (Each room will have its own). Along with a TV, Computer, gaming VR setup...

I purchased 2 of These today

I think (hope) the battery link is wrong. The batteries you linked (at least when I click on it) are less than 200wh.

You are already well into 48v territory. 3 AC's running at the same time will be at least a 1500wh draw. I would estimate you need at least 30kwh per day, maybe more to power the house. Figure you get 5 hours of sun? I am thinking 8kw of panels, and at least 60kwh of batteries, or a decent generator to meet your 2-3 day goal assuming you are living life like normal, and not just running essentials. Oh and a big inverter(s), preferably low frequency with lots of copper...

 

[Supervstech]

I think (hope) the battery link is wrong. The batteries you linked (at least when I click on it) are less than 200wh.

You are already well into 48v territory. 3 AC's running at the same time will be at least a 1500wh draw. I would estimate you need at least 30kwh per day, maybe more to power the house. Figure you get 5 hours of sun? I am thinking 8kw of panels, and at least 60kwh of batteries, or a decent generator to meet your 2-3 day goal assuming you are living life like normal, and not just running essentials. Oh and a big inverter(s), preferably low frequency with lots of copper...

200Ah… that’s 2560Wh

 

[nexusjosh]

I think (hope) the battery link is wrong. The batteries you linked (at least when I click on it) are less than 200wh.

You are already well into 48v territory. 3 AC's running at the same time will be at least a 1500wh draw. I would estimate you need at least 30kwh per day, maybe more to power the house. Figure you get 5 hours of sun? I am thinking 8kw of panels, and at least 60kwh of batteries, or a decent generator to meet your 2-3 day goal assuming you are living life like normal, and not just running essentials. Oh and a big inverter(s), preferably low frequency with lots of copper...

Got it. So it would be better to just go for the 48 volt from the get go. Well. Like I said, I want this to be a bit of a longer term project. To slowly build the system up. Adding more panels and batteries.

As for the AC's. One in each room, so they; 1: Won't have to work as hard; and 2: Not all 3 will need to be on 24/7.
HOWEVER. One of the 3 rooms will be turned on 24/7 to act as temp control for the solar gear, and batteries.

So as of now, I'm going to get at least 2 more of those batteries. 2 of them having 2560Wh, so adding 2 more will make it 5,120Wh. Sweet.

Next question is; Are these panels a good idea for my system, or should I look at higher wattage panels? If those panels are good. How many do I need minimum? Again, paired with this Solar Charge Converter.

Thanks for the help!

Edit: I've discovered this! I'm currently researching it, but it appears to be a MPPT, Inverter & Transfer Switch all in one, which is very appealing!

 

[iamrich]

200Ah… that’s 2560Wh

LOL! That makes more sense. For some reason when I click the link it defaults to the other choice. Didn't even see the 200ah version.

 

[iamrich]

Next question is; Are these panels a good idea for my system, or should I look at higher wattage panels? If those panels are good. How many do I need minimum? Again, paired with this Solar Charge Converter.

Thanks for the help!

Edit: I've discovered this! I'm currently researching it, but it appears to be a MPPT, Inverter & Transfer Switch all in one, which is very appealing!

Panel size depends heavily on your amount of real estate. I haven't seen any high wattage panels that can complete with the used 250w panels dollar per watt, but if you can only fit a small amount of panels, then the more expensive, higher wattage panels, make sense.

The panels you linked are good panels, and SanTan is a very reputable company (that's where I got mine). I would figure 80% output into your calculations. They should deliver more, but if you start with 80%, you will not be disappointed. I have the black frame version so I think they are the same. If so they are Trina panels, light scratches, but good quality. The only problem with these panels is that the labels have been stripped off so if you need UL rating for permits or whatnot, these might not work. My setup is completely off grid outside city limits, so it was not an issue.

I don't know anything about the all in one you linked, but there are a bunch of similar products on the market. Watts247.com has similar offerings (MPP Solar and Growatt). I am pretty sure I am going with Schneider when I build my house (soon I hope). Schneider is a little more expense than some, but they have literally everything you need and it all talks together. I am really happy with my LV2424, but I don't know if I would run a house off it. Yesterday I was running AC, charging both 18v and 40V Ryobi batteries, running an attic fan, a box fan and I had no issues, but I don't have any serious amperage draws (well pump, water heater, stove, etc.)

 

[nexusjosh]

Panel size depends heavily on your amount of real estate. I haven't seen any high wattage panels that can complete with the used 250w panels dollar per watt, but if you can only fit a small amount of panels, then the more expensive, higher wattage panels, make sense.

The panels you linked are good panels, and SanTan is a very reputable company (that's where I got mine). I would figure 80% output into your calculations. They should deliver more, but if you start with 80%, you will not be disappointed. I have the black frame version so I think they are the same. If so they are Trina panels, light scratches, but good quality. The only problem with these panels is that the labels have been stripped off so if you need UL rating for permits or whatnot, these might not work. My setup is completely off grid outside city limits, so it was not an issue.

I don't know anything about the all in one you linked, but there are a bunch of similar products on the market. Watts247.com has similar offerings (MPP Solar and Growatt). I am pretty sure I am going with Schneider when I build my house (soon I hope). Schneider is a little more expense than some, but they have literally everything you need and it all talks together. I am really happy with my LV2424, but I don't know if I would run a house off it. Yesterday I was running AC, charging both 18v and 40V Ryobi batteries, running an attic fan, a box fan and I had no issues, but I don't have any serious amperage draws (well pump, water heater, stove, etc.)

Awesome. I'm just getting into this and the more I look into it, the more excited I get. This Phocos one I came across (It actually is sold on the Victron Energy website) but it really doesn't have any youtube reviews anyway.
Edit: HOWEVER, one thing I've notived this Phocos unit is missing is DC output? Which is strange. If I wanted to run, for example, a DC refrigerator. But then I could... connect it straight to the batteries?

Do you have the link to the Schneider system you're going to use?

 

[iamrich]

Edit: HOWEVER, one thing I've notived this Phocos unit is missing is DC output? Which is strange. If I wanted to run, for example, a DC refrigerator. But then I could... connect it straight to the batteries?

I don't have any DC powered items. I run everything off the inverter. I would not hook anything directly to the battery to avoid killing the batteries if for some reason you don't get charging for a while.

Do you have the link to the Schneider system you're going to use?

Probably two of these https://www.invertersupply.com/index.php?main_page=product_info&cPath=1304_258_259&products_id=4488

But I also may just go one of these https://www.invertersupply.com/inde...ct_info&cPath=1304_258_259&products_id=189597

I don't know anything about the supplier linked above, just showing the models I am interested in.

 

[nexusjosh]

I don't have any DC powered items. I run everything off the inverter. I would not hook anything directly to the battery to avoid killing the batteries if for some reason you don't get charging for a while.

Probably two of these https://www.invertersupply.com/index.php?main_page=product_info&cPath=1304_258_259&products_id=4488

But I also may just go one of these https://www.invertersupply.com/inde...ct_info&cPath=1304_258_259&products_id=189597

I don't know anything about the supplier linked above, just showing the models I am interested in.

Cool.

I'm going to research those two. Though right off the bat, the Phocos unit is a smart unit, with an app, web interface, etc, which IT being my trade is important. It looks like with that Schnider gear, you need their Insight Energy Management gear, which... looks to be a significant additional cost. Ugh.

I just filled out the Phocos contact form to see if they're willing to help me with a setup diagram, panels, etc.

In the mean time, does anyone know what my solution would be in regards to powering DC electronics?

 

[nexusjosh]

Thanks to everyone who has helped me so far. I'm moving to the next step of my project, and created a New Thread.

 

[anadiner]

I wouldn't call that a big advantage of 24V. If you have half the battery then you have half the total power as well, regardless of voltage.

You can easily make a 48V battery that is the same cost as a 24V battery. Both will have the same power. It's just that the 48V will have half the Ah of the 24V version but both have the same Wh. And Wh is the important number when determining how much stuff you can run and for how long.

Let's say you buy 4 12V 100Ah batteries. Whether you wire them in 4P (12V 400Ah), 2S2P (24V 200Ah), or 4S (48V 100Ah), you still have the same amount of total Wh (4800Wh) all for the same cost.

I haggled over this also because the 48v does provide more wh. I do everything series parallel which means max wh in 48v sys = 9600wh whereas max in 24v sys = 4800wh.

I still just did not like a 48v sys cuz it gets all electrically... needs combiner box, uses terminal block, etx etc. Yes sounds funny coming from an Elect. Eng but keeping it simple keeps Code off my backside.

Sooo I went with using multiple 24vs designated to items. U know, like lamp, fan, frig off 1... stayed within inverter number of ac output plugs so not running dropcords (remember not doing terminal block).

Ok to answer u: sure sometimes I think about the security of 48v giving me 9600wh BUT keeping it simple outweighs = I like my 24vs

 

[rmaddy]

I haggled over this also because the 48v does provide more wh. I do everything series parallel which means max wh in 48v sys = 9600wh whereas max in 24v sys = 4800wh.

I don't understand how you came up with this statement. To get 9600Wh you need twice as many battery cells as you do to create 4800Wh regardless of the final voltage.

Again, let's say you have a bunch of 12V 100Ah batteries (each battery is 1200Wh). To get a 24V 4800Ah system you need 4 of those batteries in 2S2P. To get a 48V 9600Ah system you need 8 batteries in 4S2P.