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Solar panels, inverters etc


nirvana
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Please point me to a cheap inverter for this panel please ie something on aliexpress would be good

Bluetooth would be funky to monitor stuff on a mobile/computer

I'm a bit confused with the voltages these things pump out. ie this is 34.3v so is that aimed towards a 24v system? or 48v with 2 in series?

 

49aa13d16ebaa652182f27703da0a36c6984cdbd.jpg

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You've mentioned panel and inverter but not what you want to do with it.

Power up a bank of 12 V batteries, i.e. standalone system, or even just a system that works in daylight with no batteries (not very reliable that option).

Feed 240v back to the grid?

 

Voltage output of panels relate to their size and particular construction and is fairly nominal, apart form the 12V and smaller ones they are mainly just designed to  provide a suitable ish voltage for an inverter to work off.

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46 minutes ago, onlyme said:

You've mentioned panel and inverter but not what you want to do with it.

Power up a bank of 12 V batteries, i.e. standalone system, or even just a system that works in daylight with no batteries (not very reliable that option).

Feed 240v back to the grid?

 

good point, fuck the grid, I'm Mr Independent lol

So yes charging batteries......maybe a 48v system for house and if I get around to buying another van, 12v system for camping

thanks!

so let's say I'm after a 40amp inverter...cos 375/12=31.25amps

what's the difference between this one at 20 bucks

https://www.aliexpress.com/item/33059726550.html

and this one at nearly 100 bucks, apart a separate display and/or bluetooth?

https://www.aliexpress.com/item/4000211956813.html

Edited by nirvana
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1 hour ago, nirvana said:

good point, fuck the grid, I'm Mr Independent lol

So yes charging batteries......maybe a 48v system for house and if I get around to buying another van, 12v system for camping

thanks!

so let's say I'm after a 40amp inverter...cos 375/12=31.25amps

what's the difference between this one at 20 bucks

https://www.aliexpress.com/item/33059726550.html

and this one at nearly 100 bucks, apart a separate display and/or bluetooth?

https://www.aliexpress.com/item/4000211956813.html

The 40A seems about right with a little bit of overhead vs rated panel peak power - should check other characteristics as well like peak open circuit voltage.  There seems to be a significant difference in bluetooth enabled devices and one built to a higher specification could have better components all round, no guarantee, but it could have. everything form China is built to a price. Also be aware lots of copies of the same design. A separate display and bluetooth in this instance really nice to have, a lot of faff having to plug something in like a laptop for the usb monitoring for example.

You have multiple uses, so I'd suggest not going the ultra cheap end unless just to play with.  Will have to go up the price range anyway if going 48V, I'd be tempted to stick with 24V so that there are more devices available across the board - you are not going to be powering anything very large with a 375W panel driven setup most likely round a house so cable weight is not necessarily a primary concern - which would d be one reason to go for 48V.

 

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I'd like to build a solar power system and wondered if anyone had any idea what I'd need.

I don't want it to feed into the grid, so I'm thinking solar panels, batteries, a charge controller, an inverter and a bunch of wires. 

Not sure what sort of batteries and panels, and how many, and I wanted to be able to use it to power things all the time (to save money on my electricity bills, and to power my oil fired boiler (and some smaller appliances) if everything went to shit.

Is there a way to hook it up so it can be used all the time and there's a switch which disconnects me from the grid when the grid goes down?

 

@Kurt Barlow

Edited by Carl Fimble
Adding Kurt thing
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3 hours ago, Carl Fimble said:

Is there a way to hook it up so it can be used all the time and there's a switch which disconnects me from the grid when the grid goes down?

if the grid goes down you're disconnected in any case lol

see if you can pick up a few cheap second hand panels locally to have a play

try and find some 'deep cycle batteries' too.....you can pick up a charge controller for not a lot off aliexpress

you really need to decide what you want to power first though!

the camping fans will say 12v is good enough but lots of experts say go for a 24v system or even 48v

Again you can buy cheap inverters (board only) to up the voltage to 240v

but say you wanted to power a computer, both desktop and laptop, you can get away with 24 or 48v

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as an extra, I'd look at something completely stand alone, easier to play with etc

come the zombie apocalypse you'll be v.happy you've got the batteries in any case :)

And I think if you're disconnected from the grid you can just plug your inverter into a plug socket and alakazam you're powering your sockets from the inverter....

BUT I'd check that last point with a sparky first lol

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7 minutes ago, nirvana said:

if the grid goes down you're disconnected in any case lol

see if you can pick up a few cheap second hand panels locally to have a play

try and find some 'deep cycle batteries' too.....you can pick up a charge controller for not a lot off aliexpress

you really need to decide what you want to power first though!

the camping fans will say 12v is good enough but lots of experts say go for a 24v system or even 48v

Again you can buy cheap inverters (board only) to up the voltage to 240v

but say you wanted to power a computer, both desktop and laptop, you can get away with 24 or 48v

Without a power transfer switch that ensures grid is disconnected from local supply at all times then very real risk the power comes up and fries your local supply very short order.  They can be manual or automatic (say firing up a generator automatically on demand).

With boiler to run probably looking at 240V, then as you say need to add up all the loads. and work out total demand.

Bit of a missed requirement, SHTF scenario you want standalone system that can be switched in, to reduce demand form day to day you really want grid tied. I suppose you could use a single panel setup and manage to switich that between grid tied and standalone inverters - or find an inverter that has both functions - if they exist.

 

 

 

 

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6 minutes ago, onlyme said:

Without a power transfer switch that ensures grid is disconnected

aye, couldn't you use the master switch thingy? or put a switch in between the master switch and the wires to your consumer unit? Now in the UK you'll have 3 wires including the earth but in France there is only two cos you supply your own earth, which makes much more sense when you consider earth is all around us lmao

allez les bleus!

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1 hour ago, nirvana said:

aye, couldn't you use the master switch thingy? or put a switch in between the master switch and the wires to your consumer unit? Now in the UK you'll have 3 wires including the earth but in France there is only two cos you supply your own earth, which makes much more sense when you consider earth is all around us lmao

allez les bleus!

Most UK installs the master switch (isolator) is integrated with the consumer unit, so switching that does not help, you could pull the main fuse but those are  wire locked and you are not supposed to pull it yourself.  There is also the issue of knowing when the supply is back on, a modern meter might have an LED but don't think there is any indication on an old meter other than the disc spinning, which obviously if won't if isolated.

France being majorly rural TT (Terre Terre i.e earth at substation earth at house) systems with earth rod are common, but also in the UK whenever the supply is pole fed it is also common to supply own earth with a rod.

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47 minutes ago, onlyme said:

Most UK installs the master switch (isolator) is integrated with the consumer unit, so switching that does not help, you could pull the main fuse but those are  wire locked and you are not supposed to pull it yourself.  There is also the issue of knowing when the supply is back on, a modern meter might have an LED but don't think there is any indication on an old meter other than the disc spinning, which obviously if won't if isolated.

France being majorly rural TT (Terre Terre i.e earth at substation earth at house) systems with earth rod are common, but also in the UK whenever the supply is pole fed it is also common to supply own earth with a rod.

It wouldn't necessarily have to automatically detect anything, I was thinking of power cuts or SHTF situations where I'd know the power was down and could flip a switch to move from grid (and solar/battery) to off grid only. 

Or, would this work (the little triangle things with lines on them are supposed to be things go stop power going backwards towards the grid and to the charge controller/inverter (diodes?)) :

 

Screenshot_20210901-164119.png

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2 hours ago, nirvana said:

@Carl Fimblebuy one of these fukkers, go can parallel them up too

I'm tempted to buy one myself but my plans are a bit up in the air at the mo

https://www.aliexpress.com/item/1005001609525930.html

That looks like it can accept an input from the grid so might well be exactly what I'm looking for. Cheers!

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17 minutes ago, Carl Fimble said:

That looks like it can accept an input from the grid so might well be exactly what I'm looking for. Cheers!

check this vid out, this geezer has got one of those funky inverters and he even talks about sticking a generator on the end of it to charge the batteries

 

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this one seems cheap! and supports up to 75v of panels....so I think you could rig up a couple of decent sized panels to it...

you'd need to check my sums of that one though lol

https://www.aliexpress.com/item/33001361185.html

edit, just realised that's a PWM controller and MPPT are generally better methinks...

so this is the MPPT model https://www.aliexpress.com/item/1005001720604167.html

Edited by nirvana
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9 hours ago, Carl Fimble said:

I'd like to build a solar power system and wondered if anyone had any idea what I'd need.

I don't want it to feed into the grid, so I'm thinking solar panels, batteries, a charge controller, an inverter and a bunch of wires. 

Not sure what sort of batteries and panels, and how many, and I wanted to be able to use it to power things all the time (to save money on my electricity bills, and to power my oil fired boiler (and some smaller appliances) if everything went to shit.

Is there a way to hook it up so it can be used all the time and there's a switch which disconnects me from the grid when the grid goes down?

 

@Kurt Barlow

Solar panels are dirt cheap

You will need a lot of battery capacity which will cost

Plus an inverter - if its for motors you will need an inverter with a peak output approx 3x the rated capacity of the motor to overcome start up inertia

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12 minutes ago, Kurt Barlow said:

Solar panels are dirt cheap

You will need a lot of battery capacity which will cost

Plus an inverter - if its for motors you will need an inverter with a peak output approx 3x the rated capacity of the motor to overcome start up inertia

Yip, I found that out with the air pumps on our inflatable beds when we went camping. For that I have a 400w inverter which has a peak output of 500w, their air pumps are 100w so I thought it would be fine, and it was, but I had to switch it on, then off and on again to get them working.

The motors I'll be wanting to drive will be the fridge compressors and the pump for the oil fired boiler, the big inverter @nirvana posted upthread are rated for 4000w, with a peak of way more, so they should be ok I think. 

What sort of batteries and how many would you imagine would be needed. Aside from the boiler pump (and it's control electronics), fridges and lights around the house (LED) it would just be chargers for phones, tablets and laptops, no kettles, irons or cookers or anything that heats up. 

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2 minutes ago, Carl Fimble said:

Yip, I found that out with the air pumps on our inflatable beds when we went camping. For that I have a 400w inverter which has a peak output of 500w, their air pumps are 100w so I thought it would be fine, and it was, but I had to switch it on, then off and on again to get them working.

The motors I'll be wanting to drive will be the fridge compressors and the pump for the oil fired boiler, the big inverter @nirvana posted upthread are rated for 4000w, with a peak of way more, so they should be ok I think. 

What sort of batteries and how many would you imagine would be needed. Aside from the boiler pump (and it's control electronics), fridges and lights around the house (LED) it would just be chargers for phones, tablets and laptops, no kettles, irons or cookers or anything that heats up. 

The old formula for not killing Lead acid batteries was no more than 10% draw on the capacity. 

So basically for a 100AH 12V that would be 120W. So 10 of them for 1200W

That would be fine for Fridges (80-150w), boiler pump and fan (150W), and lighting (assuming LED) 

TBH - Id go grid tie and have a couple of LA batteries trickle charged for an hour or two each day on the solar with an inverter. If you get a power cut you have enough juice to keep the fridges, boiler and lighting going for several hours. 

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9 hours ago, Kurt Barlow said:

The old formula for not killing Lead acid batteries was no more than 10% draw on the capacity. 

So basically for a 100AH 12V that would be 120W. So 10 of them for 1200W

that's a grands worth of batteries.....also with Lead batteries ain't it no more than 50% decharge?

but with lithium batteries you can drain the crap out of them?

here's an interesting battery that's under 100 bucks with free delivery! https://www.aliexpress.com/item/1005002492752158.html

I know it's meant for a leccy bike but how do you reckon that would cope attached to the hybrid inverter?

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1 hour ago, nirvana said:

that's a grands worth of batteries.....also with Lead batteries ain't it no more than 50% decharge?

but with lithium batteries you can drain the crap out of them?

here's an interesting battery that's under 100 bucks with free delivery! https://www.aliexpress.com/item/1005002492752158.html

I know it's meant for a leccy bike but how do you reckon that would cope attached to the hybrid inverter?

The hope is they get Sodium Ion batteries off the ground in terms of longevity which are only slightly less energy dense than Lithium but about half the price. 

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1 hour ago, nirvana said:

that's a grands worth of batteries.....also with Lead batteries ain't it no more than 50% decharge?

but with lithium batteries you can drain the crap out of them?

here's an interesting battery that's under 100 bucks with free delivery! https://www.aliexpress.com/item/1005002492752158.html

I know it's meant for a leccy bike but how do you reckon that would cope attached to the hybrid inverter?

Hmmmm

Per Kwh thats about 1/3rd the price of a LA battery. 

TBH sounds like the Ebay solar panel my mates wants for his yacht thats 0.25m2 and puts out 300w xD. The rated output for run of the mill solar panels is about 150w /m2 (not that you will get that in the UK) 

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2 hours ago, MrPin said:

A "grid tie" inverter needs a grid to tie to. It's not for charging batteries.

Yes Professor Calculus. I am well aware of that. 

You can still set up your batteries to charge off the mains with a timeswitch set for say 11-1pm. 

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41 minutes ago, Kurt Barlow said:

The hope is they get Sodium Ion batteries off the ground in terms of longevity which are only slightly less energy dense than Lithium but about half the price. 

Dont hold your breath on that one, they wont last anywhere near as long.

Anyway back on topic ;-)

I have the following, 5kw (18 panel) solaredge inverter with the mini inverters for each panel. Separately I have a sofar inverter (connected to mains) with 9.6kwh of pylontech lithium batteries connected. The sofar is charged from solar or can be set up to charge from the mains (which is what you want in winter if it all goes to hell as solar wont help).
Batteries more or less are fully charged from mid/late march to october and I run everything off them (well most of the time).

The sofar has a backup port which you can use to power things if the grid goes down. Currently I have that plugged into the bedroom circuits (although not switched on). I have a manual switchover so if the grid does go down I switch it all off at the incoming to isolate the circuit and then switch the inverter output on to power fridges, freezers etc.

The main solar inverter wont work if the grid is down. I do have two small generators (400w and 1kw) to run and if it does go down they might be enough to mimic the mains and let solar work or at the very least will be enough to power the house (minimally) and charge the batteries. I also have a pure sine wave 600w inverter and a couple of leisure batteries out of the boat/camper which might do the same thing (should really test those ;-))

Lead acid deep cycle batteries are a false economy imho as Ive never had one last more than 3 years... (then Ive bought cheap ones).

I wouldnt buy anything off aliexpress unless its a recognised name, (growatt etc) and you can get those off ebay or elsewhere easy enough.

You need to start with your load and by load I mean startup load, sometimes fridges, freezers etc draw a big load on switchon and you need to be able to cope with that, I tripped an rcb once with four freezers on the same circuit. Odds are they wont all come on at the same time (it was startup) but I now have them on 4 different circuits. Its the peak load you need to look for and to isolate certain circuits so someone doesnt see the lights back on and sticks on the kettle!

I thought about what you are thinking about but after 2 winters of having no output from the solar panels and working out the likelihood of needing the heating circulation pump/lights etc were more a winter thing then the grid tied one was the best option, or at least a backup generator to charge the batteries during winter. Then of course theres the backup to the backup generator ;-) Power outages unless catastrophic (had a substation go here 2 years or so ago, power out for 8 hours until mobile generator arrived) will be cycled through so 4 hours on, 8 off type thing so again grid tied will help out then.

I didnt read all the posts but thats what I have so fire away with any questions.

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17 hours ago, Carl Fimble said:

It wouldn't necessarily have to automatically detect anything, I was thinking of power cuts or SHTF situations where I'd know the power was down and could flip a switch to move from grid (and solar/battery) to off grid only. 

Or, would this work (the little triangle things with lines on them are supposed to be things go stop power going backwards towards the grid and to the charge controller/inverter (diodes?)) :

 

Screenshot_20210901-164119.png

Diodes at the right rating would work for DC, say in between solar panels and generator and charge controller to prevent one power source back feeding another, some panels come with inbuilt diodes.  Won't work properly with AC as above as you have created a half wave rectifier of the supplies.

Instead of the diodes you want a crossover/transfer switch, a manual one would be fine to alternatively select grid or local power course, one being disconnected before connection of the other. 

 

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