Off-grid Solar system advice

[Spikeuk]

Hi Guys,

With the rising costs of electricity here in the UK i'm looking to get a solar setup.
I'm a complete newb so please reply with comments/advice etc - any would be greatly appreciated!!!

We use a lot of power approx £600 per month as I have some computer servers running from home. approx 3600w per hr in total
I realise I would need a lot of panels to fully run this setup from solar, however we don't have the space or budget...

With this in mind, I just want to save some money - I was hoping to setup a 4 panel array (340W each) linked to some batteries and also a ATS - which will switch mains power/solar as and when batteries reach a certain % until they recharge. I was hoping to run a portion of my servers approx 1200w p/h

As I don't have much roof space (I think I could fit 8 or 9 max)- I have been looking for panels at high wattage & reasonable price.
I found these panels which look reasonable :

I would be looking to get max of 4 panels (maybe just 2 initially) , for a total of 1360w.
I would like the option to be able to add more same panels in future without having to buy new battery charger.

I had a look at the calculator to try and work out which mppt controller would work.

(I think I filled out the boxes correctly) - looks like I would need a controller with max operating 200v. - however wouldnt be able to add more panels.


I have some newb questions as follows:

- Can you use cheap mppt controllers rated a lot lower and just connect e.g. two panels to each one, linked to the same batteries? - I can still have a single invertor linked to both controllers?

-I understand I need some deep cycle batteries, and to chain 2 x 12v together to get required 24v, im not sure how to work out the AH requirement.. With the ATS I will switch seamlessly to mains power when the batteries are flat and so charge time is not an issue - bigger the battery the better.

I'm not sure if any of this can be achieved for my budget - Ideally id like to buy 2 small cheap controllers rather than an expensive £500+ one, i'm not sure how much the batteries would cost or spec. I guess a 2000w invertor would happy supply the 1200W required.... any advice or comments greatly appreciated..




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[GLC]

What is your budget and hopeful backup power usage?
As a baseline, I have a solar array of 4-used 305 watt panels, 1-40 amp solar controller, 4000 watt inverter, tied to 6-100 ah LPO4 batteries. This is 7200 backup storage watts. So if I would use 300 wats per hour continuously, this stored energy would be depleted in 24 hours. I have appx $7000 invested in this setup. You could go cheaper with marine batteries but then you are only going to be able to pull 50 percent from them without hurting them at a time. Also the lifetime on a marine battery maybe 1+ years. LPO4 has a life cycle of 3000 to 5000 cycles of 100% to 0% which for my usage is 10 to 17 years plus.

And to answer a couple of your questions.
Yes, you can use multiple solar controllers to feed a battery bank, I have this.

Yes you can link 1 or more inverters to a battery bank, I do. Bear in mind the more energy you are pulling out of the batteries the faster they will drain.

I use a manual transfer switch to supply different circuits in the house as I need them.

 

[Spikeuk]

Thanks GLC - budget as little a possible - power usage as much as possible (im using upto 3600w p/h 24/7)- when batteries are drained I will switch to mains, its just to bring power costs down. It's about 25p kwh at the moment during day, comes down to 5p over night so if I can bring down day costs a bit that would be great.

Sounds like I will have to re-think and scrape second hand bits together over time, start small and expand as my initial budget I want to spend is just over £1.5k.

I looked at grid tied but get paid pennies 5p kwh - compared to paying 25p kwh when im drawing from grid

I don't think running without batteries is an option as my equipment would go offline if any shade etc?, I can only see to use batteries monitoring them with ATS to seamlessly switch to grid power when low?.


Whats the advantage of having a single large expensive battery controller? as opposed to a number of really cheap smaller ones and just break the system up ?

 

[GLC]

Your biggest expense will be battery storage. The more batteries the more energy you will have when the sun is not shining. Start looking for used lead acid deep cycle batteries like golf cart batteries. Also are there any used solar panels in your area? I paid $80 each for 305 watt panels. Lets say that you use my setup as an example and purchase used solar panels and used batteries, smaller 2000 watt inverter. smaller controller. You can easily put together a smaller system for $1500. It will be limited of course but it will get you started. Think about a cheap smaller controller like a PWM. It may do what you need starting out but, it is inefficient and will need to be replaced quickly. Start out with a decent mid priced MPPT controller and it will grow with your needs.

 

[Spikeuk]

Thanks for reply, I found these batteries recommended online :

8Pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell NEW CALB CA100 Plastic 12v200AH 24V100AH​

1280.0US $ |8pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell New Calb Ca100 Plastic 12v200ah 24v100ah For Solar Rv Pack - Rechargeable Batteries - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I watched some vids online and most recommented Lifepo4 batteries, I found some on Aliexpress direct from china
£712 with delivery for 8 batteries at 100ah each ~ 24v 800ah - which should run 1200w for approx 4 hours when fully charged?

From looking at other prices this doesn't seem to bad? - I don't there there is any issues on 24v over 48v if i'm drawing 1200w ? I think I can fit at least 4 300w panels onto this system?

Does this battery offer look reasonable to you?

 

[Wellbuilt]

There is nothing cheep about it , you would probably be better off just paying the blood money

 

[houseofancients]

Thanks for reply, I found these batteries recommended online :

8Pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell NEW CALB CA100 Plastic 12v200AH 24V100AH​

1280.0US $ |8pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell New Calb Ca100 Plastic 12v200ah 24v100ah For Solar Rv Pack - Rechargeable Batteries - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I watched some vids online and most recommented Lifepo4 batteries, I found some on Aliexpress direct from china
£712 with delivery for 8 batteries at 100ah each ~ 24v 800ah - which should run 1200w for approx 4 hours when fully charged?

From looking at other prices this doesn't seem to bad? - I don't there there is any issues on 24v over 48v if i'm drawing 1200w ? I think I can fit at least 4 300w panels onto this system?

Does this battery offer look reasonable to you?

please stay away from aliexpress for cells...
they are 99% scams and used, degraded cells...
do a search here for aliexpress, and thank me later...

there are a few good sellers here on the forum like @Jenny Wu .
Cells are a bit more expensive, but are what they should be and will last you a long time

 

[GLC]

Thanks for reply, I found these batteries recommended online :

8Pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell NEW CALB CA100 Plastic 12v200AH 24V100AH​

1280.0US $ |8pcs 3.2v 100ah Lifepo4 Battery Garde A Lithium Iron Phosphate Cell New Calb Ca100 Plastic 12v200ah 24v100ah For Solar Rv Pack - Rechargeable Batteries - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I watched some vids online and most recommented Lifepo4 batteries, I found some on Aliexpress direct from china
£712 with delivery for 8 batteries at 100ah each ~ 24v 800ah - which should run 1200w for approx 4 hours when fully charged?

From looking at other prices this doesn't seem to bad? - I don't there there is any issues on 24v over 48v if i'm drawing 1200w ? I think I can fit at least 4 300w panels onto this system?

Does this battery offer look reasonable to you?

Lpo4 are the best batteries that i know of that work great with solar applications. Good quality batteries are pricy. Either you or me are mis reading that add. Does it show 8 cells to produce 100 ah at $883 at 24 volts or 200 ah at 12 volt? If so that is very cheap but that the makings for 1 battery not 8. You will also have to assemble and purchase a bms. Still a good buy for 1 but if something seems too good to be true it probably is.