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Proposed DIY solar power station

T

tumbi1

New Member
Joined
Feb 19, 2022
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Hello,

I'm very much a newbie in Australia, but I'm looking to put together my own solar power station using these types of components;

1 of these inverters;
www.ebay.com.au

VEVOR 5KVA 48V MPPT Off-Grid Pure Sine Wave Solar Hybrid Solar Inverter Charger 824889715561 | eBay

Find many great new & used options and get the best deals for VEVOR 5KVA 48V MPPT Off-Grid Pure Sine Wave Solar Hybrid Solar Inverter Charger at the best online prices at eBay!
www.ebay.com.au

4 of these batteries;
www.ebay.com.au

VoltX 12V 100Ah Lithium Battery LiFePO4 Recharge Replace SLA AGM Camping Power | eBay

The 100Ah model can power all your usual devices like LED lighting, charging electronics, radios, fans, small rice cookers and kettles, and also support TVs, small fridges and power tools. Nominal Capacity: 100Ah.
www.ebay.com.au

4 of these panels;
www.ebay.com.au

380W Folding Solar Panel Kit 12V Mono Portable Caravan Camping Controller USB 9355348002591 | eBay

Find many great new & used options and get the best deals for 380W Folding Solar Panel Kit 12V Mono Portable Caravan Camping Controller USB at the best online prices at eBay!
www.ebay.com.au

I was going to mount the inverter and batteries on a trolley.

This will only be to cover powering 1 fridge (150W)/ 1 freezer (125W) for 12 hours a day, 1 water pump (800W, a few times a day for maybe 20 seconds at a time), and some computer gear (300W) for 4 hours a day. I am looking to use it for a potential long term power outage (weeks/months). We already have a petrol generator attached to the house with a lot of fuel storage, so this will compliment it depending on the weather.

Is this system doable, and is it fit for purpose? How long would the batteries take to charge?

Thanks,

Mark.
 
Any reason you're going with 4 SLA's instead of LiFe's? Dollar per Ah the 100Ah are about the same money per unit and provide 2x the draw. Those batteries are only going to give you 50Ah @48v or 2400Wh.

Are you building it way over spec for your load on purpose? The napkin math says a 3Kw should be plenty for your loads. If you did a 3Kw box on a 24v system you could just get 1 of the 24v 200Ah (4800Wh) LiFe's and the AIO which would be less parts to mount and take up less cubic space, plus weigh a LOT less when you go to move that thing around.

I don't know if that water pump is going to play nicely with a HF inverter, you may need a LF inverter to handle its startup draw.

Just for consideration, what about this:
2Kw LF inverter, 24v
1x 24v 200Ah LiFe battery
60a MPPT SCC

You'll have less standby draw, a LF inverter to feed the startup amperage for the water pump, and still quite a bit of headroom if everything tries to kick on at the same time. Plus the benefit of less weight and less pieces to mount up (against 4 AGM's and a physically larger AIO) to your cart.

Just some thoughts.
 
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My personal feeling is that going 48V LFP is a good choice, and using a HF inverter with inductive load that on paper is way to big may work and is lighter than a LF inverter. The waterpump at 800W should be starting on this inverter, I usually think 4x as startpower for a single phase scrirrel motor. And you have 5x available :D
 
Thanks for the feedback everyone, I've come to the right place! Knut, we live in the same region - I am
about 25 minutes west of Kempsey NSW :)

I am starting to think 2 systems now, one LF and the other HF, and split the loads between them. I like the idea of 2 for a certain amount of redundancy. Also I am happy to hear I am actually over reaching capacity wise - I thought with my calculations the size was about right, but I am very inexperienced with this stuff. I will re-check my calculations.

I like the look of the Trinas, thanks for that, will substitute.

I thought the batteries were LiFe's? The subject reads '12V 100Ah Lithium Battery LiFePO4 Cells Recharge Replace SLA AGM 4WD RV Power' and the details say they are LiFe's, but I can easily choose some others as there are plenty available.
 
tumbi1 said:
These batteries look ok;
www.ebay.com.au

ECO-WOTHY 12V 100Ah 130Ah Lithium Iron Battery LiFePO4 Recharge Deep Cycle BMS | eBay

10Ah 30Ah 50Ah 130Ah 12V LiFePO4 Battery. 600W CompleteSolar Panel Kit with 130Ah. 900W Complete Solar Panel Kit with 130Ah. And keep balance between battery cells. Lithium Battery. Lithium Battery & 1000W Inverter.
www.ebay.com.au
Click to expand...
I watched several of Wills battery review videos last night including the battery you link to above. He seemed to like this one more.

 
tumbi1 said:
SLA AGM
Click to expand...
Sealed Lead Acid, Absorbed Glass Mat. Those are 2 of the 3 types of lead acid based batteries (along with Gel). If the ad is saying it's all 3 I'd find another source because they obviously are lying about something. You can't be lead acid AND LiFe at the same time.
 
tumbi1 said:
What about this for a 3kw 24Volt system? How can you tell if it is LF?
www.ebay.com.au

5KW 3KW PWM/MPPT Off-Grid Pure Sine Wave Solar Inverter Charger Hybrid Inverter | eBay

Pune sine wave inverter. inverter can be applied to GEL/AGM lead-acid batteries. Waveform Pure sine wave. Surge Power 2000VA 6000VA 6000VA 10000VA 10000VA. Cold start function. Frequency Range 50Hz/ 60Hz (Auto detection).
www.ebay.com.au
Click to expand...
Just bumping this question, especially the LF part (apologies in advance for a silly question)
 
tumbi1 said:
Just bumping this question, especially the LF part (apologies in advance for a silly question)
Click to expand...
Solar Control Mode: PWM

Is it 3kw or 5kw? Your sellers out there are crazy! It's like trying to get straight answers out of Corporate! :)

You really need to look at sources other than Ebay if you want accurate information.
 
Rednecktek said:
Solar Control Mode: PWM

Is it 3kw or 5kw? Your sellers out there are crazy! It's like trying to get straight answers out of Corporate! :)

You really need to look at sources other than Ebay if you want accurate information.
Click to expand...
Can you direct me to a suitable LF inverter?
 
Those are a little more than inverters, they're AIOs (All In One), they have inverter, solar charge controller and AC battery charger - all in one box.
One can tell they're LF HF because of the weight and of the price.
They're cheapish Chinese knockoffs of... pretty much all AIOs nowadays.I have one. Get one with an MPPT solar charger.

Keep in mind that they usually don't like non-inverter-type generators to charge. They fail to synchronise the phases.
I would say, yes, get a cheapo, they usually last a couple of years - or more, especially if you don't strain them much.
They tend to be noisy. The fans do. Best put outside.
 
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I would say LF inverters are not to common, but they are easy to spot as they are heavy. A 3 to 5 kW under 20 kg is a HF inverter. All LF inverters have the transformer on the output end and feeds the load directly. An HF inverter have its inductance in the voltage bucket Circuit and the waveforming on the high voltage.
 
Gonna have to punt this one to an Aussie, but the dead giveaway on being LF or HF is the weight. A 3Kw LF inverter alone should be weighing about 20Kg, so if the entire unit is 10Kg it's gotta be HF.

That water pump is really what's killing you. If you can get a soft start module/controller for it you could probably swing a regular 3Kw HF AIO unit I would think.

Unfortunately high amp draws have to be tackled 1 (or more) of 3 ways:
1: Low frequency inverters (heavy, expensive, hard to source) that can handle the big current rush that motors require.
2: Massively oversized HF inverters (expensive, lots of wasted standby energy, 48v banks) that have so much extra overhead that the inrush current is still within normal spec
3: Soft start controller and prayer that it's soft enough to not totally overload the AIO
 
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tumbi1 said:
1 of these inverters;
Click to expand...
Looks like a Voltronics clone. 4kW (5kVA) with max 145V solar MPPT.
I have a similar clone unit but mine has lower solar PV input voltage limit (105V) and is PWM, not MPPT.

Hard to know how it would go with your pump. You'd really need to know the characteristics of your pump, or measure it with power meter that can assess surge rating. Perhaps consider a pump soft starter.

Mine runs a pool pump which starts with 900W cycle for 5-min before reverting to all day cycle at ~320W but it has a soft start up and doesn't seem to have a high current surge demand at all.

tumbi1 said:
4 of these batteries;
Click to expand...
Can't connect those batteries in series. 12V systems only.

tumbi1 said:
These batteries look ok;
Click to expand...
That's a better choice - the specs say these can be connected in series. I can't vouch for their quality though, just that the specs say you can connect in series.

I dunno, maybe consider a pre-made 48V battery?

bones1 said:
I would make a substitution for the panels and go with 4 Trinas https://www.ebay.com.au/itm/284461999450?hash=item423b41a55a:g:zOUAAOSw4pVhS83r
Click to expand...
While they are better panels, you need to be careful about panel choice Voc ratings and how that works with your choice of inverter/charge controller. These have a Voc at 25°C of 41.2V, so allowing for a chilly morning west of Kempsey you are looking at a Voc of ~45V.

I think you would be safe to have those panels in a 3S arrangement with that inverter, 2S would also work. But no more or less per string.

Not sure you'd want put all that on a trolley really. Seems more of a wall mount job to me.
 
My cheap (3kW, 24V) Chinese knockoff will take an 800W load for quite some time - like hours - with no apparent strain... except the fans go whoof all the time.
 
wattmatters said:
Looks like a Voltronics clone. 4kW (5kVA) with max 145V solar MPPT.
I have a similar clone unit but mine has lower solar PV input voltage limit (105V) and is PWM, not MPPT.

Hard to know how it would go with your pump. You'd really need to know the characteristics of your pump, or measure it with power meter that can assess surge rating. Perhaps consider a pump soft starter.

Mine runs a pool pump which starts with 900W cycle for 5-min before reverting to all day cycle at ~320W but it has a soft start up and doesn't seem to have a high current surge demand at all.


Can't connect those batteries in series. 12V systems only.


That's a better choice - the specs say these can be connected in series. I can't vouch for their quality though, just that the specs say you can connect in series.

I dunno, maybe consider a pre-made 48V battery?


While they are better panels, you need to be careful about panel choice Voc ratings and how that works with your choice of inverter/charge controller. These have a Voc at 25°C of 41.2V, so allowing for a chilly morning west of Kempsey you are looking at a Voc of ~45V.

I think you would be safe to have those panels in a 3S arrangement with that inverter, 2S would also work. But no more or less per string.

Not sure you'd want put all that on a trolley really. Seems more of a wall mount job to me.
Click to expand...
Many thanks,

I'm learning rapidly - I spotted the limitation with those batteries - there are pitfalls here and there you can easily fall into! I will investigate the pump further to see what I can do.
 
Don B. Cilly said:
My cheap (3kW, 24V) Chinese knockoff will take an 800W load for quite some time - like hours - with no apparent strain... except the fans go whoof all the time.
Click to expand...
An 800W load is no issue. The issue is it's a pump and the wattage rating is only telling us the running power demand, not start up surge power demand.

A pump can draw a start up surge current up to 10 times it's running demand. How high the surge demand is varies by pump. Some pump start up cycles are brutal on electrical supply equipment, while others have a softer start (sometimes with starter electronics to help).

We don't know what the surge demand of tumbi1's pump is. Also, if the pump's normal surge demand cannot be met but the supply is still high enough to start the pump, albeit more slowly, this is not good for the pump's longevity.

There is a fair chance the 5kVA unit will manage but it would be wise to get a better understanding of the actual start up demand of the pump.
 
wattmatters said:
An 800W load is no issue. The issue is it's a pump and the wattage rating is only telling us the running power demand, not start up surge power demand.

A pump can draw a start up surge current up to 10 times it's running demand. How high the surge demand is varies by pump. Some pump start up cycles are brutal on electrical supply equipment, while others have a softer start (sometimes with starter electronics to help).

We don't know what the surge demand of tumbi1's pump is. Also, if the pump's normal surge demand cannot be met but the supply is still high enough to start the pump, albeit more slowly, this is not good for the pump's longevity.

There is a fair chance the 5kVA unit will manage but it would be wise to get a better understanding of the actual start up demand of the pump.
Click to expand...
I've been researching the pump, but there is no extra information in regards the surge demand in the manual unfortunately, and I can't find it for any comparable pumps either. I've also been looking for a module/device to provide a 'soft start' for it, but nothing I can find that the pump can just plug into - they all seem to be wired modules. The pump is under the house, and is plugged into a normal wall type socket. Maybe the safest thing is to invest a bit more and get a higher rated AIO?
 
Just a follow up on this one - I have completed the build and tested it ok. One 'foible' that came up was one I couldn't know from the Vevor description as it wasn't mentioned - it doesn't support using lithium batteries! No problem, I bought 16 second hand Yuasa UXH-125-6FR batteries for $100 each, to give 48V 250Ah. The batteries, although second hand, are barely used and in very good condition. I looked them up online and they are built to last 10 years. I am using Trina solar panels, and 100A copper tinned cables throughout. I have the batteries housed in an old cupboard that was damaged and would have been thrown out, to stop mice etc getting in.

One question; I have a 48V circuit breaker between the batteries and the Vevor, but the batteries add up to 53V, given the extra voltage you get from fully charged batteries. Will that still work? I'm not sure what else to use as breakers only seem to come in a small number of standard sizes like 12V and 48V.
 

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