diy solar

diy solar

Is that all.......

Fraser

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Mar 25, 2021
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Hi everyone. I’m in need of help. I am trying to set up a 48v system. I am looking to get 12 12v 100ah lithium batteries. My question is. Can I really only get 300ah out of this set up? If so is that all I would need to run a home. I have heard about the efficiency of having 48v over 24v. Is it really that much better?
 
Welcome to the forum.

Hi everyone. I’m in need of help. I am trying to set up a 48v system. I am looking to get 12 12v 100ah lithium batteries. My question is. Can I really only get 300ah out of this set up?

Yes.

If so is that all I would need to run a home.

Depends on the size of the home and the power used. This is enough to reliably store 12.3kWh of energy. This is about 41% of the average American household daily consumption.

I have heard about the efficiency of having 48v over 24v. Is it really that much better?

Efficiency is somewhat better. Running at 2X the voltage means 1/2 the current to get the same power. 2X voltage and 1/2 current together also means resistive efficiencies are reduced by 75%, e.g., if a 24V system is losing 4% due to resistance losses, the same system configured for 48V would only suffer 1% resistive losses.

Higher voltage permits fewer solar charge controllers. A 100A solar charge controller can only handle 100A * 24V = 2400W of solar panels, but that same controller on 48V could handle 100A * 48V = 4800W.

Higher voltage also lends itself better to higher outputs. 4000W of power at 12V requires 4000W/12V = 333A - huge, beefy wires. 4000W of power at 48V requires 4000W/48V = 83A, which can be handled easily by lighter gauge wire.

Link #5 in my signature for your available solar.
Link #1 in my signature for an energy audit.

Without the above two, it's just shots in the dark.

If you can't see my signature, turn your phone sideways.
 
12, 12V/100AH would put you out $10,000 USD for Battleborns for example and it is nuts to be perfectly honest.

48V Battery = 16 LFP cells.
16 pcs 280AH cells = 48V/280AH/14.336 kWh is approx $1900 USD Delivered+ BMS, Fuse & Casing.
Two proper 16S 48V/280's in parallel gives 560AH / 28.6kWh for $4000 USD +/-
 
Welcome to the forum.



Yes.



Depends on the size of the home and the power used. This is enough to reliably store 12.3kWh of energy. This is about 41% of the average American household daily consumption.



Efficiency is somewhat better. Running at 2X the voltage means 1/2 the current to get the same power. 2X voltage and 1/2 current together also means resistive efficiencies are reduced by 75%, e.g., if a 24V system is losing 4% due to resistance losses, the same system configured for 48V would only suffer 1% resistive losses.

Higher voltage permits fewer solar charge controllers. A 100A solar charge controller can only handle 100A * 24V = 2400W of solar panels, but that same controller on 48V could handle 100A * 48V = 4800W.

Higher voltage also lends itself better to higher outputs. 4000W of power at 12V requires 4000W/12V = 333A - huge, beefy wires. 4000W of power at 48V requires 4000W/48V = 83A, which can be handled easily by lighter gauge wire.

Link #5 in my signature for your available solar.
Link #1 in my signature for an energy audit.

Without the above two, it's just shots in the dark.

If you can't see my signature, turn
Thank you so much for your help and time spent explaining. Really interesting. I can’t help feeling drawn to 24v for more amp hours. It’s an awful lot of money in the uk to be off grid.
 
12, 12V/100AH would put you out $10,000 USD for Battleborns for example and it is nuts to be perfectly honest.

48V Battery = 16 LFP cells.
16 pcs 280AH cells = 48V/280AH/14.336 kWh is approx $1900 USD Delivered+ BMS, Fuse & Casing.
Two proper 16S 48V/280's in parallel gives 560AH / 28.6kWh for $4000 USD +/-
It’s even worse here. Battle born are renamed here as transport energy and a 100ah battery is £1200. It’s an awful lot of money! I have looked into getting the prismatic cells and it looks risky also. So much Chinese stuff that I have never had luck with. 4000 dollars and really no warranty. Plus I am so green I wouldn’t know which part had gone wrong. Here in the uk the off grid thing is like rocking horse poo. I would be sending out an SOS across the pond every minute. Yeah it’s nuts, I hope they last a long time. Considering 24v to up the ah.
 
It’s an awful lot of money in the uk to be off grid.
That is an aspect to solar/battery systems that is often overlooked, the "real" cost based on local regulations!
Some areas have huge differences in grid cost per kw based on time of day and/or local government "fees" that drive costs thru the roof.

The more power you plan (notice I said "plan", not what you start with) to have, the more it makes sense to increase your battery system voltage. The initial cost to hop to 24v or even 48v makes things much easier later on, but the startup costs can be painful.
Use any of the online solar power planning calculators to get an initial idea of sizing. Startup surges and system efficiency loses are things lots of folks forget about.

You can definitely save a LOT of money with the DIY path, but it does have risks (when things go wrong you can only blame yourself hehe)
buying batteries vs building batteries BIG cost savings, however, avoid "cheap" BMS solutions that is not the place to go cheap.
 
It’s even worse here. Battle born are renamed here as transport energy and a 100ah battery is £1200. It’s an awful lot of money! I have looked into getting the prismatic cells and it looks risky also. So much Chinese stuff that I have never had luck with. 4000 dollars and really no warranty. Plus I am so green I wouldn’t know which part had gone wrong. Here in the uk the off grid thing is like rocking horse poo. I would be sending out an SOS across the pond every minute. Yeah it’s nuts, I hope they last a long time. Considering 24v to up the ah.
There are many who had / have similar feelings yet moved forward and did well. We do have MANY members in the EU & the UK - Literally, from Australia to Zambia, we got people. A lot do DIY their own battery packs and rely on KNown Good Vendors that we have a lot of cumulative experience with.

UK, has a lot of different options & rules depending on location. I, being a Canadian don't know the gritty details and how Bodged up things are. Beaurocracy is an Artform with the British, they really did perfect it after all.

Grid Tied can mean 3 things. + Hybriding
1) Most Common. Generate Solar and send to grid, no storage, and pull from grid as needed.
To grid pays you cents per kWh, from grid costs more cents per kWh.
2) Similar to above BUT with Battery System as a backup IF grid fails - not much difference except you now have a battery system as a backup.
3) Similar BUT, generate, Store in Battery, Use Battery & pull from grid IF battery runs low to charge it, NO PUSH to Grid. Less permits if ANY required, as this is a Charging Device on the grid, no push, only pull.

A Recent Trend has been to reduce the Grid Tariffs being paid out to people, even going retroactively and cancelling agreements / contracts. Utilities are not willing to pay out equitably. There is even a Move in Australia at present to charge folks pushing power to grid rather than pay them, pending on time & usage of the day... Like REALLY, WTF are they thinking ? PUT IN BATTERIES & STORAGE ! geezus Murphy !
 
That is an aspect to solar/battery systems that is often overlooked, the "real" cost based on local regulations!
Some areas have huge differences in grid cost per kw based on time of day and/or local government "fees" that drive costs thru the roof.

The more power you plan (notice I said "plan", not what you start with) to have, the more it makes sense to increase your battery system voltage. The initial cost to hop to 24v or even 48v makes things much easier later on, but the startup costs can be painful.
Use any of the online solar power planning calculators to get an initial idea of sizing. Startup surges and system efficiency loses are things lots of folks forget about.

You can definitely save a LOT of money with the DIY path, but it does have risks (when things go wrong you can only blame yourself hehe)
buying batteries vs building batteries BIG cost savings, however, avoid "cheap" BMS solutions that is not the place to go cheap.
Thanks. Good advice.

What put me off building batteries was the BMS. I couldn’t find anything in this country that looked to be of quality. Ali express Chinese stuff worries me.

It’s pretty rare to live off grid here and unheard of to build your own batteries. I don’t want to be the first here. That should be left to someone far more educated than i.
 
It’s even worse here. Battle born are renamed here as transport energy and a 100ah battery is £1200. It’s an awful lot of money! I have looked into getting the prismatic cells and it looks risky also. So much Chinese stuff that I have never had luck with. 4000 dollars and really no warranty. Plus I am so green I wouldn’t know which part had gone wrong. Here in the uk the off grid thing is like rocking horse poo. I would be sending out an SOS across the pond every minute. Yeah it’s nuts, I hope they last a long time. Considering 24v to up the ah.
Don't get hung up on the Ah. What you really need to look at is the watt hours (Wh). 12 batteries x 12V x 100Ah = 14.4kWh. That's the full capacity. You can use about 80% of it, so you'd have 11.5kWh to use. That capacity is the same if you have the batteries wired in 12V, 24V, or 48V. For a system your size, I strongly recommend 48V.

Why do you want to go off grid? Why not stay on the grid and just have some battery backup for when power goes out? It is hard to save money by going off grid.
 
Thank you for your reply. To start with its 5800 watts off panels.

Example of what I was talking about:

5800W @ 24V: 5800/28V = 207A of charge current required. This would need 2X 100A charge controllers.
5800W @ 48V: 5800/56V = 104A of charge current required. This would need one 100A charge controller.
 
Thanks. Good advice.

What put me off building batteries was the BMS. I couldn’t find anything in this country that looked to be of quality. Ali express Chinese stuff worries me.

It’s pretty rare to live off grid here and unheard of to build your own batteries. I don’t want to be the first here. That should be left to someone far more educated than i.
Hi Fraser.

I am living completely off grid in Worcestershire UK with no opportunity for grid connection, so everything relies on my solar system with a rarely used fall back diesel generator.

After much consideration, I opted for 8 x used L16 AGM batteries giving me just under 20KWH at 24v for £600. I figured it's a reasonable risk and cost, even if I end up changing them every 3 or 4 years until the market for Lithium stabilises or even moves on to a different technology.

These were bought from an eBay seller based mid UK who I have met and found to be completely trust worthy. I can provide details by PM if needed.

Picture attached. I know, the cabling needs some tidying! A few changes and tweaks since I first put it together have made it look a bit messy ?

Hope that helps
 

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Don't get hung up on the Ah. What you really need to look at is the watt hours (Wh). 12 batteries x 12V x 100Ah = 14.4kWh. That's the full capacity. You can use about 80% of it, so you'd have 11.5kWh to use. That capacity is the same if you have the batteries wired in 12V, 24V, or 48V. For a system your size, I strongly recommend 48V.

Why do you want to go off grid? Why not stay on the grid and just have some battery backup for when power goes out? It is hard to save money by going off grid.
Thank you. That makes a lot of sense. I heard about ohms law being used when installing the solar panels it seems like it works for batteries too. I’m going to stick with getting 48v system with the 12 x 12v x 100ah.
We live away from a grid supply. It would cost nearly as much as the solar system. I like self sufficiency and live in a small woodland. We don’t even have mains water. The good life/expensive.
 
Hi Fraser.

I am living completely off grid in Worcestershire UK with no opportunity for grid connection, so everything relies on my solar system with a rarely used fall back diesel generator.

After much consideration, I opted for 8 x used L16 AGM batteries giving me just under 20KWH at 24v for £600. I figured it's a reasonable risk and cost, even if I end up changing them every 3 or 4 years until the market for Lithium stabilises or even moves on to a different technology.

These were bought from an eBay seller based mid UK who I have met and found to be completely trust worthy. I can provide details by PM if needed.

Picture attached. I know, the cabling needs some tidying! A few changes and tweaks since I first put it together have made it look a bit messy ?

Hope that helps
Thanks for your reply.
That’s amazing and well done! We have been struggling for some years with just a generator which we don’t use all the time so we don’t have a fridge or a freezer. But we have a baby now and we need move to something a bit more “normal”.
Thanks but I’m going to bite the bullet and go for the long time return in investment with the lithium. Hope that they last a long time ?.
Your set up looks great!!
 
Example of what I was talking about:

5800W @ 24V: 5800/28V = 207A of charge current required. This would need 2X 100A charge controllers.
5800W @ 48V: 5800/56V = 104A of charge current required. This would need one 100A charge controller.
Yeah going to be the big victron mppt for 48v. People on here have really helped me to make up my mind. Thanks you so much. I’m amazed at how many people have helped today. I don’t get this kind of help when I pay people!
 
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