off grid at Gloucester

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Re: off grid at Gloucester

Postby davidg » Fri Oct 26, 2018 7:27 pm

Check this post I did a short while ago.
post53770.html#p53770

A DC coupled system, I installed very recently, good for approx very easy 6kwh's per night from the batteries at night, but can go to about 10kwh's each night draw down from batteries, (inverter is a 7.5KW Selectronic SPMC482-AU). That does not take into account what might be drawn during the day but generally at least the same again with ease and quite likely more is what I designed into it for during the summer (prime use holidays, house can be vacant for long periods of time, had to be an auto restart system without a generator, hence being DC coupled), the PV does suffer some shading at times due to quite large trees however thanks to the 6 strings of panels it's generally limited to only a single string in the morning and single string in the later afternoon.
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Re: off grid at Gloucester

Postby Hastings » Sat Oct 27, 2018 9:15 am

Thank you for your answers once more.
Im learning lots, but having trouble retaining it, so I apologise if I repeat myself as the same parts of the system seem to keep cropping up even though I have asked a different question.

As I said to Gordon, I'm just going to have a crack and start with a small system and of course I will make mistakes.
As long as I don't hurt someone or myself in doing so is the major factor for me.

I recently built a 12 v system in a slide on camper using 1 250w SP, 6v golf batteries in series, 25 amp MPPT charger and it works...... ha ha.

Im really liking the golf cart batteries at present, but I may end up with too many to be cost effective.(24v system)
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Re: off grid at Gloucester

Postby Hastings » Sat Oct 27, 2018 9:26 am

[quote$300 for a 6V 250AH battery does sound rather cheap. What brand and model are they?
Yes, you'd need 4 of them in series, which will give you 250AH @ 24V. For 500AH, you would need another 4 connected in series, all in parallel with the first 4.[quote]
I bought FUSION 6v GOLF CART SOLAR ULTRA HIGH PERFORMANCE AGM BATTERY 320 AMP from the Battery Store.
I found them very helpful over the phone, but others have rated them poorly.
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Re: off grid at Gloucester

Postby Hastings » Sat Oct 27, 2018 9:57 am

Hello again.
Righto.
Ive decided that instead of wasting everyones time, I will start at one end and work through the entire system to see if you all agree with what I'm trying to achieve:
I want to build a system that is expandable and I will start with the following. I will not move onto the next stage until I have nutted out this part first.
Solar panels: 5/ 250 w in series producing 1000 w @ 24v with 41 amps.
Is this correct?
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Re: off grid at Gloucester

Postby jules » Sat Oct 27, 2018 10:14 am

If you connect in series the voltages add together, so 5 X 24V panels in series gives you 120V.
If you were to connect the same set of panels in parallel, you'd get 24 V.

If you are connecting in series the 120V is high enough to be dangerous.

You should probably pick up a decent book on the subject of solar power though any advice you get from some of the qualified [and that excludes me] people here will be excellent.
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: off grid at Gloucester

Postby Gordon-Loomberah » Sat Oct 27, 2018 12:04 pm

jules wrote: so 5 X 24V panels in series gives you 120V.


except that "24V" panels are not 24volts.

Voc is more likely ~38 or 45V, depending on number of cells, so you do not want to connect 5 of them in series, unless you have a charge controller that can accept that voltage. Current will not increase beyond that delivered by one panel if connected in series, only voltage is additive. If connected in parallel, then voltage = the voltage of one panel, and current = current from one panel X number of panels.
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Re: off grid at Gloucester

Postby Hastings » Sat Oct 27, 2018 2:30 pm

Ok
I know I said I wouldn't move on until i nutted out the panels.......but the battery debate came up.

After discussing our needs with my wife, we are thinking about lithium.
However, supposing we will use 6kw/d x 2 days autonomy x dod of 80% (lith)= 14400kw/d Correct?
14400kw/d/48v = 300 amp/h battery Correct?
How many panels and in what configuration would I need for 48v/300 amp/hr system?
Also can the system be upgraded if more kw are required?
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Re: off grid at Gloucester

Postby davidg » Sat Oct 27, 2018 3:32 pm

Hastings wrote:However, supposing we will use 6kw/d x 2 days autonomy x dod of 80% (lith)= 14400kw/d Correct?
14400kw/d/48v = 300 amp/h battery Correct?
How many panels and in what configuration would I need for 48v/300 amp/hr system?


Don't use 80% of the capacity (DOD) with Lithium I strongly suggest use 60% of the capacity.
Note I did not say DOD.

The average house uses a lot more than that per day up round 20kWh's per day with roughly 1/2 of that used overnight.
SPS Standalone Power System/Hybrid specialist - Store the Sun!
SELECTRONIC SPMC482-AU, 8.2kW's of Arrays
Selectronic Certified AC-Coupled Fronius 8.2kW Inverter
1900Ah 48V Bank

An OTT Genset for a house.
PVOutput Stats

Sparkys light up your life :)
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Re: off grid at Gloucester

Postby Gordon-Loomberah » Sat Oct 27, 2018 3:41 pm

When you say kW above, you actually mean kWh = unit of energy. kW is instantaneous power.

If you have a generator and oversized PV array, the whole 'days of autonomy' thing does become a bit less relevant.

Panels are much less expensive than batteries- use your cash on PV instead of storage, and with a generator to charge batteries in overcast weather, or run the house in case of inverter failure, IMO means that you really don't have to think too much about 'days of autonomy' these days. I certainly don't, when using up to 50kWh in a day with a 21kWh battery!
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Re: off grid at Gloucester

Postby Hastings » Sun Oct 28, 2018 10:10 am

Davidg you said only 60% dod for lithium. All the stats and real world reviews I have read, say 80 and even 100%. Is this not right?
Also, my current bill for a household of 4 adults two of which live in flats off the house is 13.81KWh in part due to gas HWS and cooking.
The new place which I will be building, will be very small. Something like 35 sq mtrs as there will only be the 2 of us :P
I'm a retired builder (illness). Ive had the monstrosities and "look at me houses" and have paid the consqencences. Completely over it, so tiny house is it.
I will change threads and discuss my plans there.


Thanks for clearing that up (KW-KWh) Gordon.
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