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Inverter and battery choice


TimbaLand

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Hi everyone. First time posting here and I’m with very little understanding of this side of things so please explain like you would do to a novice.

 

I have an option of 2x 5.12v batteries, 12 panels connected to an 8kw inverter or 2x 5kw inverters. I want to use Solar during the day and battery storage at night. Should I go for rhe 8kw or the 2x 5kw inverters? I consume an average of 40kwh per day and can run the big loads during the day. Another option could be to have 3 batteries with the 8kw inverter. 
 

on the 2x 5kw inverters wil they work as independent inverters each running it’s battery or the 2 should be connected to talk to each other and be one bigger system? 
 

I’ll appreciate your guidance. 

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If you get the 1 8kw you will be limited to 2 mppts whereas having 2 5kw inverters you double the mppts to 4. The 2x5kw also give some redundancy / resilience if 1 inverter packs up - all be it at 50%. The 2x5kw will work as 1 systems as the inverters are installed in parallel

Some questions to help you:

  • Do you regularly use more than 8kw of appliances at a time (this helps with 8kw vs 10kw)
  • How much electricity do you use between 4pm and 7am (this will help with battery sizing)
  • How much of that 40kwh usage can be moved to daytime hours?
  • How much roof space do you have (theoretical max number of panels) >> number of mppts

 

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Thanks Mzezman

I have not done an analysis to answer some of your questions  but let me try it this way:

1. I may have short bursts where the kettle is boiling, microwave is on and the oven is on when my wife is doing her thing in the kitchen

2. And he biggest consumer between 4pm and 7am is the geyser and sometimes the oven

3. I can program the geyser to take most of my he load during the day

4. I have ample roof space  north facing I can do 9 panels. East facing I can do 7 and west facing maybe 7 there too 

Edited by TimbaLand
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39 minutes ago, TimbaLand said:

Thanks Mzezman

I have not done an analysis to answer some of your woes tika but let me try it this way:

1. I may have short bursts where the kettle is boiling, microwave is on and the oven is on when my wife is doing her thing in the kitchen

2. And he biggest consumer between 4pm and 7am is the geyser and sometimes the oven

3. I can program the geyser to take most of my he load during the day

4. I have ample roof space  north facing I can do 9 panels. East facing I can do 7 and west facing maybe 7 there too 

If you can shift your geyser to mainly charge during the day using the PV then you'll hopefully reduce or even eliminate the need to have it run overnight

Oven can also be run during the day on PV- the nighttime usage might be an issue with 2 batteries though - remember you always want to have a % in the batteries in the case of a midnight loadshed or fault. There ARE ways you can schedule things and switch them on / off smartly depending on your inverter and general IOT skills. You could also set the time the oven is on to be drawn from ESKOM, e.g. have the house run on Eskom from 5-6pm and use the oven then?

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  • 3 weeks later...
On 2023/03/05 at 3:26 PM, TimbaLand said:

Thanks for the guidance 

Not sure if you have made up your mind, you also did not say which inverter you are considering, but on the Deye and Sunsynk Inverters you will mostly be limited to the 460w panels due to the 13amp limit on the MPPT on the 5kw models.

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13 minutes ago, I84RiS said:

Deye and Sunsynk Inverters you will mostly be limited to the 460w panels due to the 13amp limit on the MPPT on the 5kw models

I have 540 watt ja solar mono panels and they run perfectly fine. 4 in series on one mppt and 6 in series on the second mppt.
No clipping at all and on good days if I have enough load I get over 500 watts per panel continuously.
I have had on some occasions with scattered clouds and diffusion, panels peaking of over 570 watts per panel.
 

Edited by WannabeSolarSparky
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13 minutes ago, WannabeSolarSparky said:

I have 540 watt ja solar mono panels and they run perfectly fine. 4 in series on one mppt and 6 in series on the second mppt.
No clipping at all and on good days if I have enough load I get over 500 watts per panel continuously.
I have had on some occasions with scattered clouds and diffusion, panels peaking of over 570 watts per panel.
 

This is more of an issue with the Canadian panels as they are much more amp heavy than JA panels.. the 550w Canadians will regularly do 13-17A.

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