Little advice

[mohammedbera2]

Hi guys Mohammed in limpopo (0510)

I'm new to solar looking to go off grid

@the moment

i have 12 x 180ah 12v

4 x12v =48v @180ah

4 x12v =48v @180ah

4 x12v =48v @180ah

Total 540 ah @48v

5kva inverter Mercer

eskom in

solar in

batteries in

220 @ max 4kw out

12 x 255 24v panels

+24-+24-+24-

+24-+24-+24-

+24-+24-+24-

+24-+24-+24-

Wanna Use about max 30kwh/day off grid

Please advise

Need help getting invertor on network also

logging data

and

Was thinking about getting 2v or 4v batteries

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[Guest]

Hi. What help do you need ? You say what you have but I am not sure what you are asking other than to log your data.

[mohammedbera2]

Good morning sorry 4 being unclear
I need help logging data over network
Also
Finding 2v batteries @good price
And
Advice on working out battery bank ah and amount of panels needed to provide +- 30kwh /day

Thanks

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[Guest]

I am not allowed to talk about data logging outside my area. You are welcome to ask questions in that area and I will answer you.

[PaulF007]

9 hours ago, mohammedbera2 said:

Advice on working out battery bank ah and amount of panels needed to provide +- 30kwh /day

Good day Mohammed

Welcome to Powerforum!

To start of just a few questions:

1. It seems like your already have a solar system running , is this the case?
2. If you say that you need provision for 30kwh/day how much of that would you like to draw from batteries?
3. Is there any specific reason why you would like to go off grid? 

Yes there is ample info on data logging of inverters but for a start let's first get the basics info inplace 

Best regards

Paul

[mohammedbera2]

Thanks paul
Firstly i started my solar system as a back up 4 load shedding (2×80w panels 1x105ah deep cycle small pwm charge control and a led stripes in every room )
Voltage drop and wrong wiring got me to up grade to 4x100w+2x80w panels 2000w 24v inverter 1x so called mppt 40a controller 12x 6v golf car batteries "2nd hand " wired in to db with switch over switch mainly used solar 4 lighting

Batteries gave in due to poor maintenance and age im guessing
Found batteries @china mall 180ah 12v i think gel 600mmx300mmx150mm +-50kg
Also bought some @auction
Got total of 14 battries 2 running 12v lighting 12 were connected to 2000w inverter started connection all lights and 80% of plugs no fridge or hi power appliance

Was using more than i was getting of my panels

Bringing me to last upgrade
12 x 24v pv
5kva inverter built in mppt

Now only geyser on eskom when needed solar collector keeps water hot 80%of the time

Solar system
connected
100%lights
50% plugs inc 2xfridge and 2xfreezer inverter shows watts being used around 800w not all the time but i still wanna connect a 3rd fridge and freezer

So i toke 800w x24h =19kwh per day rounder it off to 20kwh +50% for being safe got me to 30kwh

If i can log my data will be able to better understand wat im using and wat I'm charging

Sorry 4 long story

1) i have a system running

2) not sure hopping to be able to get tru the night without killing battries

3) no reason cutting cost using minimum eskom power



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[PaulF007]

3 minutes ago, mohammedbera2 said:

Thanks paul
Firstly i started my solar system as a back up 4 load shedding (2×80w panels 1x105ah deep cycle small pwm charge control and a led stripes in every room )
Voltage drop and wrong wiring got me to up grade to 4x100w+2x80w panels 2000w 24v inverter 1x so called mppt 40a controller 12x 6v golf car batteries "2nd hand " wired in to db with switch over switch mainly used solar 4 lighting
Batteries gave in due to poor maintenance and age im guessing
Found batteries @china mall 180ah 12v i think gel 600mmx300mmx150mm +-50kg
Also bought some @auction
Got total of 14 battries 2 running 12v lighting 12 were connected to 2000w inverter started connection all lights and 80% of plugs no fridge or hi power appliance
Was using more than i was getting of my panels
Bringing me to last upgrade
12 x 24v pv
5kva inverter built in mppt
Now only geyser on eskom when needed solar collector keeps water hot 80%of the time
Solar system
connected
100%lights
50% plugs inc fridge and freezer inverter shows watts being used around 800w not all the time but i still wanna connect a 2nd fridge and freezer
So i toke 800w x24h =19kwh per day rounder it off to 20kwh +50% for being safe got me to 30kwh
If i can log my data will be able to better understand wat im using and wat I'm charging
Sorry 4 long story
1) i have a system running
2) not sure hopping to be able to get tru the night without killing battries
3) no reason cutting cost using minimum eskom power

t from my GT-I9500 using Tapatalk
 

@mohammedbera2 Ok . So atleast you have a good idea as to how not to handle your batteries 

800w on average is "massive" in terms of battery usage and I suspect that you would not like the figures. There is a battery calculator flouting on the forum I think @The Terrible Triplett got one .But here is a "Thumb suck method without all the other factors"  to give you an indication as what size batteries you would need to look at:

Lest assume that you would need to run of batteries for 10 hours a day (Just an easy number to work with)

so 800w x 10 = 8000 wh needed from you batts , now watt = V x A so if you are running a 48v system 8000 / 48v =  166 ah need if you were to discharge 100% but typically you would want to use only 20% of you batts capacity to get optimal usage out of them so  166 ah / 20% = 830 ah battery bank. 

To charge a 830 ah bank you will need , as a rule , 10% of that which will give you a charge controler of 85a , that is well above your Mercer that can only go up to 60a ( I am assuming it is an Axpert) and then you have not made provision for 2 days of bad weather extr.

I am running off grid and the first thing that I did was to get my base load as low as possible especially at night time where my base can be as as low as 150w this results in that I can get away with a much smaller bank and also not having to charge a big bank also help during day time with the loads. So I would suggest that you start there and get your night time base load as low as what your are possibly happy with.

The second option would be to get a reasonable bank for night time use and then setup as that you switch over to grid once you reach 80% SOC ( BTW you will need to get a BMV 700 or 702 - forum shop has them at a good price) . You can do this by either getting software to do it , I have some reservations towards this as you will have to rely on software and a computer of sorts , or have it done via hardware , there is plenty discussion on the forum toward this.

Third Option and the one that I would do if I were in your position is to look at your solar panels for daytime use and going to grid during night , using your old batts as a "backup" . It has been proven many times over that Batteries are the most expensive part of a solar system and that the grid in comparison is a lot cheaper. Since you already have the Mercer I am not going to look at Grid tie but it is also a option.  

So to sum up

1.  Get a massive battery bank and charge controller with inverter and panels to match
2.  Reduce your base load and then design accordingly
3. Get a smaller battery bank and switch over to grid once you reach 80% soc (this might even be at 19h00)
4. Use your current setup in day time and grid at night with your old batts as backup and to maintain the system 

Once you have decided as whitch one of the options will suite you and your pocket best then one can start to look how your current setup can fit into all of this.

As a last thought @The Terrible Triplett also has another "theory" on using multiple devices to drive different things in your house like lights on one inverter , fridges on the other and so on and this could also be a option but you will need to chat to him on that one..

  

[Arandoza]

Hi,

800watts seems very high for a fridge a freezer and some lights.

If the fridge and freezer are old it
May explain the high usage.

I moved to Bosch A++ fridge and seperate upright freezer each consume around 90watts each when running and freezer has a 16 hour period where it can be without power and you won't loose food? I guess provided you don't open it

Got my load down from also around 700w with over/under and a side by side Fridgemasters down to around half of that, with lights.

Fridges last longer than the batteries, so if these are the culprit for high usage, consider A++ or even better A+++ if you can find them at the right price.

Don't consider A+ as the A++ is typically three times more efficient than a A+ based on the info I could find when I changed mine.

Also for interest my axpert 5kva has never generated over 14kwh a day and it has a full complement of panels, but not much storage only 245ah.

On a bad day I can get around 7kwh out of it.

To achieve the 30kwh per day you would need at least two
Of them in ideal conditions, and
Lots of storage if night Time usage is 14 kWh? Which may get worse in winter with the shorter days.

Lower the average load day and night and try To Maximize power
Use during the day

Not an easy task, but enjoy the journey.

[mohammedbera2]

Sorry my mistake[emoji85] ( edited ) im running
2xfridge
2xfreezer
lights (led)
2xtv
Decoders
Chargers
Laptop

thats why 800w

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[Guest]

Mohammed,

Welcome to the forum. We can help.

Without reading all the above, there is really just one question: How long do you want power X watts for?

2nd question: Grid available or off-grid?

From that we can work out exactly what batteries are needed, panels required to recharge them in 5.5 hours peak sunlight etc.

EDIT: And yes, one size does not fit all, as Paul pointed out.

[Guest]

To power 800w for 12 hours, 48v system with 1 days backup, using 180ah 12v batteries:
To 50% DOD, 12 batteries
To 20% DOD, 36 batteries - this is not a good idea.
You will need 18 panels just to recharge them in 5.5 hours, with no load.

If you take Trojan IND 13-6v batteries, 6v 695ah batteries, you will need 16 of them in series / parallel for 20% DOD. And 8 for 50% DOD - this is a very good idea.
IND 13-6v are 2800 cycles @ 50% DOD.

You can also go 2v but then it is a minimum of 24 batteries.

[Guest]

@mohammedbera2 IF you where to consider the above batteries, I would also consider a separate charge controller for the amps you need to charge the batts at, 10% of AH, is going to be quite high and you need a very good piece of equipment to not only handle that, but also treat the batteries with all the care they need, at the volts they need.

The cost of such a bank will be quite high making the investment in a good separate controller worth every sent. Makes I am thinking of are Morningstar or Victron controllers.

[mohammedbera2]

Oki after two weeks of using aicc to monitor whats going on
Set my inverter to only use 20% then switch to grid

Question:
Is it better to switch to grid only running on grid only charge with solar next day
(grid usage average 10 hours )
X kwh

Or switch to grid and charge from grid set @10A utl charging
(Grid usage average 10 hours )
+- 4kwh


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[Guest]

Have a look at peak and off peak time and the rates. We are doing an experiment at this stage to see if it is better to charge from eskom in off peak and use batteries in peak time.

[PaulF007]

I didn't know we had peak and off peak rates in SA . How do they measure it? Very interesting..

[mohammedbera2]

Not sure about peak /off peak rates
But different rates according to usage eg :
0 to 50 kw @ X (R0.87)
51 to 300 kw @ Y (R1.11)
300to 600kw @ Z (R1.78)

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[Guest]

Mohammed here are the 2015/2016 Eskom times.

Here is the tarrif booklet.

http://www.eskom.co.za/CustomerCare/TariffsAndCharges/Documents/tariff booklet proof1.pdf

 

[Guest]

I like that Eskom brochure. All nice pics of solar panels, turbines and transmission towers.

No pics of "smoking hot" power stations? 

[PaulF007]

18 hours ago, JDP said:

Mohammed here are the 2015/2016 Eskom times.

Here is the tarrif booklet.

http://www.eskom.co.za/CustomerCare/TariffsAndCharges/Documents/tariff booklet proof1.pdf

 

Thanks for the booklet. I have looked all over Eskoms site but for the life of me I cannot find the image above. Can you please give the link where peak rates are discussed?

[Guest]

The Eskom booklet also shows cents difference between Peak, Standard and Off-Peak. In large bulk quantities it has an effect. 

So I am also really interested to know more, what are the price differences for home users, can we get a benefit, where in SA is it currently in place, outside commercial usage, and what meters are used?

[Chris Hobson]

Farmers often are off-peak users of electricity for pumps and other high load applications. A farm I hired had a normal domestic meter and the 3 phase was off-peak.

 

[HeinTheTerrible]

I guess you're safe if you have the old disc meter, no way to distinguish between peak and off-peak!