On 2023/01/21 at 5:21 PM, Kalahari Meerkat said:

I'd do this after sunset, if I were you, and see tomorrow morning how things look... either way good luck and lets hope it mostly sorts you out...

Thank you.

Strangely, my installer has come around to this idea now - I'm not sure what changed since the previous time we spoke... but it's good news anyway, and he's optimistic about it too.

I'll be watching it today. We changed it about 12:45 yesterday (that's when the installer was able to assist), at which time the batteries were already about 80% SoC. It shot right up to full very quickly after that, but that was really not a good all-day test cycle.

Edited January 23, 20233 yr by Patrick OReilly

On 2023/01/21 at 6:39 PM, YellowTapemeasure said:

just saying 545W isn't good enough, JA Solar makes hundreds of 545W panels 🙂

Good point - I'm learning as I go here - I'll find out more specifically what the panel specs are - for my own interest too. I'm guessing each panel is rated about 45V, since that is what is reported quite consistently, but I'll check.

I'm now seeing just short of 270V from the string of 6 panels. This should put me nicely in the MPPT's sweet spot. Let's see how today goes - it promises to be a clear day...

 

Hi all.

@mzezman @I84RiS @jumper @Kalahari Meerkat @Scorp007 @GreenFields @wolfandy@YellowTapemeasure

Apologies for coming back so late about this.  Long story short - it's fixed !!!!

Thanks to you guys who emphasized that my two strings were marginal on voltage, and for suggesting linking them into one long string instead. Now the system is singing. I've recorded some of the highest days of production in the lifetime of my system, and I've seen the panels peaking at 80%-90% of rated output on several occasions. Fantastic.

So - what did I learn? if the open circuit voltage of the panels is only slightly above the rated "startup" voltage for the MPPT, system performance will be erratic. For best performance, you need long enough strings to get the voltage deep into the operating range of the MPPT. I had two strings producing a measured 132V, on MPPTs that have a minimum rating of 125V. Too close !!!  I now have one string producing 250-260V throughout the day, and the other MPPT is unused, but ready for a fresh string when budget allows.

Just for one example, here's a typical day now - the solar production runs strongly through battery charging phases as well as when load peaks occur, and it only throttles back once there is no place left for power to be used. (This also nicely shows the BMS managing the rate of charge once SoC reaches 90%, then 100%.)

On this day, the peak production reported at 11:40 was 3.03KW, on panels rated at 3.27KW - that's 93% !

Thank you all- I'm now a much happier camper!

7 minutes ago, Patrick OReilly said:

Hi all.

@mzezman @I84RiS @jumper @Kalahari Meerkat @Scorp007 @GreenFields @wolfandy@YellowTapemeasure

Apologies for coming back so late about this.  Long story short - it's fixed !!!!

Thanks to you guys who emphasized that my two strings were marginal on voltage, and for suggesting linking them into one long string instead. Now the system is singing. I've recorded some of the highest days of production in the lifetime of my system, and I've seen the panels peaking at 80%-90% of rated output on several occasions. Fantastic.

So - what did I learn? if the open circuit voltage of the panels is only slightly above the rated "startup" voltage for the MPPT, system performance will be erratic. For best performance, you need long enough strings to get the voltage deep into the operating range of the MPPT. I had two strings producing a measured 132V, on MPPTs that have a minimum rating of 125V. Too close !!!  I now have one string producing 250-260V throughout the day, and the other MPPT is unused, but ready for a fresh string when budget allows.

Just for one example, here's a typical day now - the solar production runs strongly through battery charging phases as well as when load peaks occur, and it only throttles back once there is no place left for power to be used. (This also nicely shows the BMS managing the rate of charge once SoC reaches 90%, then 100%.)

On this day, the peak production reported at 11:40 was 3.03KW, on panels rated at 3.27KW - that's 93% !

Thank you all- I'm now a much happier camper!

We are all glad for your sake. We are all here together and I am sure most of us learn new things about solar every day. 

As we learn we are also here to share when we look at configurations and spot something as in this case thinking it was marginal and all panels in series should do the trick. 

Also a thanks to the forum to provide the platform. 👍👍👍

46 minutes ago, Patrick OReilly said:

Thank you all- I'm now a much happier camper!

Happy to help where we can 🙂

46 minutes ago, Patrick OReilly said:

A side-note on your graph: Is there a way to manage your high consumption during the morning and maybe shift some of it out to later in the day? Your battery is down to 40% at that time - and hence you are drawing from the grid to make up the difference between your load and your PV production. If you'd be able to shift that load out to a bit later in the day when your battery has recovered to a higher SOC (e.g. with smart relays or other timers), you can draw the difference from your battery - and probably still have sufficient time left in the day to get it back to full again. It would allow you achieve even more savings. At the moment, you are using grid in the morning while in the afternoon you have plenty spare PV capacity

59 minutes ago, Scorp007 said:

Also a thanks to the forum to provide the platform. 👍👍👍

Indeed! Thank you Power Forum!

@wolfandy - thanks!  I have noted the same - hours of throttled PV in the afternoon because there's no place for the power to go.

I have couple of plans for future attention:

• The geyser at this site has a 4kw element.  Simply switching that to a 2kw element will shave those peaks notably, and probably allow the combination of Solar plus battery to handle the peak, thus avoiding the need for grid input at the peaks.
• Installing a timer (dumb or smart) on the geyser to limit it to operating between about 10am and 2pm will almost certainly result in plenty hot water and a full battery at 4pm.

And all of this will result in harvesting more of the sun - as you've noted. When this is the case, my next step would be to add a second battery so that we can make it through the night. This would also have the benefit of enabling the system to handle taller peaks on the odd occasion.

Thank you for your input - it confirms that I'm thinking along the right track...

31 minutes ago, Patrick OReilly said:

The geyser at this site has a 4kw element.  Simply switching that to a 2kw element will shave those peaks notably, and probably allow the combination of Solar plus battery to handle the peak, thus avoiding the need for grid input at the peaks.

Agreed. Easy and relatively cheap thing to do. Have done the same with my 2nd geyser (main one is running on heat pump)

32 minutes ago, Patrick OReilly said:

Installing a timer (dumb or smart) on the geyser to limit it to operating between about 10am and 2pm will almost certainly result in plenty hot water and a full battery at 4pm.

If you've changed the element, then you can put something like a Sonoff POW Origin 16A on the geyser and easily manage it via schedules. Cost is just over R300 and works well (I have them both on my heat pump as well as on my 2nd geyser)

36 minutes ago, Patrick OReilly said:

my next step would be to add a second battery so that we can make it through the night. This would also have the benefit of enabling the system to handle taller peaks on the odd occasion.

That will definitely help.

But I have to warn you - it is a dangerous journey 😉 Your bank account will suffer. I also started with 1 Pylon US3000 - and have 5 by now 🙃

39 minutes ago, Patrick OReilly said:

hours of throttled PV in the afternoon because there's no place for the power to go.

One other thought for that (especially for this time of year): I don't know if you have aircons in your house. Use the spare PV to run aircons and cool down the house while it is for free. And especially inverter aircons require very little power to maintain a room temperature once it has been cooled down. My aircons switch on around 15h00 and by the time the sun goes down all rooms are at nice temperature.

Here is my graph from today. You can clearly see when after 09h00 my heat pump went on, then at 12h00 the 2nd geyser. In the afternoon, the aircons switched on

@wolfandy - thanks for all the input!

1 hour ago, wolfandy said:

it is a dangerous journey 😉 Your bank account will suffer. I also started with 1 Pylon US3000 - and have 5 by now 🙃

I have been feeling the urge   I keep telling myself to optimize what I have before adding to it. But it's not easy!

 

1 hour ago, wolfandy said:

I don't know if you have aircons in your house. Use the spare PV to run aircons and cool down the house while it is for free. And especially inverter aircons require very little power to maintain a room temperature once it has been cooled down.

Interesting. I don't have aircons on this site - but I am considering a central aircon installation on another project I'm working for my own future home. What I'm battling to find is meaningful data/guidance on how much power these things actually need - and when. But I suspect I'll be learning by trial and error soon enough.

I'm assuming all those heavy load items (geysers and aircons) are on your non-essential load DB?
With that careful management of load, it looks like you can run on a 5KW inverter - is that correct? or do you have a larger unit?

6 hours ago, Patrick OReilly said:

@wolfandy - thanks for all the input!

I have been feeling the urge   I keep telling myself to optimize what I have before adding to it. But it's not easy!

 

Interesting. I don't have aircons on this site - but I am considering a central aircon installation on another project I'm working for my own future home. What I'm battling to find is meaningful data/guidance on how much power these things actually need - and when. But I suspect I'll be learning by trial and error soon enough.

I'm assuming all those heavy load items (geysers and aircons) are on your non-essential load DB?
With that careful management of load, it looks like you can run on a 5KW inverter - is that correct? or do you have a larger unit?

ha ha. I started with a 5 kw luxpower, 1 Hubble am 2 and 8 panels.I now have 14 panels with another 6 to be added, 2 x Hubble am 2 and swapped my luxpower for an 8kw sunsynk.

I added a geyserwise system and downgraded my element from 4 kw to 2 kw.I did not do an essential/non essential split as i am a small household so I manage it myself which is easy.Its a fun but expensive hobby.

I do think for a lot of guys the extra battery is thought to be a quick solution instead of tweaking the system and loads over a few months and then pull the trigger if it is a need and not a want. 

@wolfandy

Great to see your graph and how well its working. I see you do have a higher than average base load during the night. 

12 hours ago, Patrick OReilly said:

What I'm battling to find is meaningful data/guidance on how much power these things actually need - and when.

I have a couple of 12,000 BTU inverter units around my house. When they have to work hard to cool down a room, they draw around 1.5kW each. During that time they use similar power to a non-inverter unit. Once the room has reached the desired temperature, the inverter benefit kicks in. My older units draw just over 100W during that time (the inside unit's fan runs permanently). On my new unit even the fan on the inside unit switches off, so it draws next to nothing. When the units need to add cooling to maintain the room temp, the power consumption goes up to something like 200-300W. These are some of the ups and downs in my chart during the night.

12 hours ago, Patrick OReilly said:

I'm assuming all those heavy load items (geysers and aircons) are on your non-essential load DB?
With that careful management of load, it looks like you can run on a 5KW inverter - is that correct? or do you have a larger unit?

I am actually running 2x 5.5kW Sunsynks and have everything on the essential side by now. I did at the beginning have heat-pump, geyser, and washing machine / tumble dryer on the non-essential side, but during heavy loadshedding I got annoyed with not being able to laundry whenever I needed. So I eventually moved everything across.

But yes, it also works with the heavy loads on the non-essential side. The smart load management will just help you reduce your Eskom consumption as your Sunsynk will feed your non-essentials from PV

6 hours ago, Scorp007 said:

I see you do have a higher than average base load during the night. 

Yes, last night 2 aircons were running throughout the night 🙃

2 hours ago, wolfandy said:

I have a couple of 12,000 BTU inverter units around my house. When they have to work hard to cool down a room, they draw around 1.5kW each. During that time they use similar power to a non-inverter unit. Once the room has reached the desired temperature, the inverter benefit kicks in. My older units draw just over 100W during that time (the inside unit's fan runs permanently). On my new unit even the fan on the inside unit switches off, so it draws next to nothing. When the units need to add cooling to maintain the room temp, the power consumption goes up to something like 200-300W. These are some of the ups and downs in my chart during the night.

I am actually running 2x 5.5kW Sunsynks and have everything on the essential side by now. I did at the beginning have heat-pump, geyser, and washing machine / tumble dryer on the non-essential side, but during heavy loadshedding I got annoyed with not being able to laundry whenever I needed. So I eventually moved everything across.

But yes, it also works with the heavy loads on the non-essential side. The smart load management will just help you reduce your Eskom consumption as your Sunsynk will feed your non-essentials from PV

Yes, last night 2 aircons were running throughout the night 🙃

I run my 1200 btu in my bedroom off my 2 Hubbles from about 9.30 at night until about 6 am.I precool the room for about 10 min before bed and then set the ac to about 19 deg and low fan.I still have about 38% battery left from my 2 x am2 5.5 kw

@Nicholas Strachan and @wolfandy and @Scorp007:   Thanks for the feedback and info on the aircon loads.

Regarding your experience with your aircons: Thank you! As with so many things, once someone talks you through it, it makes sense.  So, my "concern" would be with the peak loads that occur when the aircon tries to move the room from one temp to another - but if the room is at the desired temp, then maintaining that becomes a much lower load requirement. So, I might just want to do the big temperature moves using grid power, and then do the maintaining off the inverter.

I'm considering a central aircon system, rather than separate units in select rooms. I'm installing new windows with thicker low-e laminate glass (not double glazed), and I will put a decent layer of insulation in the ceiling.  So, I guess I can expect that if I let the house get warm, then it will take a lot of power to cool it down, (or vice-versa in winter) but if I maintain it at the desired temperature, it will (hopefully) smooth the load to a low enough value to be able to manage on the inverter. And this will no doubt give me more reason to increase battery capacity in due course.

FYI: Given my ambitions, you might wonder why I've not chosen to go with the 8KW Sunsynk. It is actually a strategic decision for two reasons: (1) I want to start with a system that will encourage me learn and to fine-tune my needs and behaviors. It may turn out that it is sufficient to my needs. And I'm a bit OCD, so efficiency is just intriguing to me. (2) But - should I prove that I can/need to use more - and that I can make it cost effective in the long term, I can add another 5 KW inverter in parallel, and then I have plenty capacity as well as redundancy. It looks to me like this is the route Andy has gone... 😉

12 hours ago, Patrick OReilly said:

I can add another 5 KW inverter in parallel, and then I have plenty capacity as well as redundancy. It looks to me like this is the route Andy has gone...

I went with 2x 5.5kW rather than 1x 8kW to get the additional 2 MPPT. I am running strings into 3 different directions now

The main point about inverter aircons remain the a inverter type is so much kinder to your battery. A 1.5kW non inverter can hammer a battery to draw over 6kW during starting. The inverter type will not exceed the 1.5kW at any instant in time. 

Such a joy to be able to run my 1.5kW heat pump from 24V lithiums. It starts at 500W and over 2 min ramps up to 1500W. The same inverter/battery combination will never be able to start a non inverter unit.