10 minutes ago, plonkster said:

At night (after going to bed) my loads are low enough that I can cover all of it from battery.

YES!!!

That is where one starts to factor in, and I have no clue where to even start, the savings software like ESS can add to the big picture because having a battery and not use it, is also a waste.

Having the panels and not using that power, more wastage, as we recently discussed.

So using the right battery with the right loads, having the spare paneling to re-charge it with ease, the ESS software handling that wisely, that is most definitely the finer "cuisine" of solar systems. 🙂 

But that is next level. First we need to deal with the bare bone knuckle busting facts.

Edited May 31, 20197 yr by Guest

13 hours ago, The Terrible Triplett said:

And a few minutes later ... as the clouds move ... 

And you're making less than 500 W from your panels, presumably because your battery is full, and you don't have more load than that. So you're not utilising every potential watt from sunrise to sunset to save utility power (and hence money). Granted, if you were allowed to export power, it would not be wasted. But that seems to not be a realistic option in South Africa for now.

I suspect that Axperts typically work the battery a little harder, so they might be putting the other 1-2 kW you might have available when the cloud passes to put into the battery, to use later and avoid importing grid power then.

I do agree that the AC coupled (grid tied) systems will likely win with panel utilisation overall, but the question is to what degree? With panels fairly cheap, and getting cheaper, does it really matter all that much?

I agree with @plonkster that "split" systems (grid-tied and off-grid) make sense, and indeed I run such a system myself (with the grid tied part lamentably small; I wish I intested more in a larger system back when the incentives were on offer). In 2028 or before if my Feed In Tariff (payment for exported power) expires, I may expand the grid-tied part beyond the present 1.2 kW.

11 hours ago, Coulomb said:

So you're not utilising every potential watt from sunrise to sunset to save utility power (and hence money).

No, I'm not utilising the full potential of the array no, it is a challenge at best if you are not grid tied.

But why must that be the one and only focus?
How much does all the add-ons cost to ensure the full potential is used - if you are off-grid (Axpert)? 
How much more complex is the system going to become?
What is the price tag for that to monitor it all the time for you have to, batteries are expensive.

We say that panels are relatively cheap right? 

So the question I asked myself: How does one save a ton of money, at the lowest possible expenditure, over the longest period of time? 
Answer: You go grid tied - and in SA - without feeding back for it is cheaper to not feed back.
And when we are paid to feed back one day, then the savings can only but increase. But not today.

So my thinking changed. Having been reliant on batteries being off-grid, having to force every single watt out of them panels, sometimes painstakingly so, knowing that I am always going to need Eskom whichever way I look at it, that batteries are more expensive per kw/h than Eskom, that every single load I can make so, must run daytime using off-the -shelf-stock-standard timers to space the loads in order to push the array to is fullest potential whenever possible, with Eskom there to take up the slack = less monitoring, time and costs.

In other words, whatever the house draws, be that 1w - 2400kw (inverter max), that must come from the panels and panels only. Not Eksom (unless there is insufficient solar power) and never batteries. Exactly the same as one would with a grid tied system where one can feed back.

Then I took it one step further and asked: Why do I need batteries? I only need batteries for Eskom failures at night, sometimes when in rains during the day and there is a power failure..
So the questions I had to answer:
If I buy a good solid solar bank, is it worth it? What do I need to do to make it worth it? How much maintenance, reports, settings, software do I need to monitor to ensure a ROI?
Cost of the bank and the replacement against what momentary savings?
Versus I go for a cheaper / smaller battery bank, it is cost I have to incur, one that is kept charged all the time, lasts 5-10 years on standby, that has +- 250 cycles to 50% DOD in the event that Eskom needs to have a burb?
Note: I have not had 250 Eskom outages since Eskom started failing.

So I lose some of the efficiency of the panels by not having a battery bank to put the power into but conversely I have a lot of spare potential to power on demand loads and I can do that BECAUSE panels are relatively cheap and because I cannot feed back.

So why must I focus so hard on optimizing the array's potential when panels are relatively cheap and batteries are THE most expensive part of the entire system, and to get optimal battery utilization, I need more parts making the system even more complex? (This statement excludes DIY'ers, hobbyist and the likes!)

However:
1) We need bats for we do have power issues in SA - but we don't have power drama every single day, year in and year out, so why wasted monies on a expensive or bigger bank?
2) You save the most when the panels power the house being grid tied - smaller inverter + regulations - and with no batteries, even more savings.
3) But a hybrid inverter must have a bank, so keep it charged so you can use a smaller bank.
Solution for me: Make a hybrid system mimic a pure grid tied system as close as possible was my conclusion ... till such time as more batteries become a NEED due to Eskom failing us even more. But then, at that time, we ALL would probably have to go even bigger setups in any event. Till then, I am trying to be wise and sit on my hands. 🙂 

Make sense?

The above logic brought me to the question I asked previously: Which system does really save you the most over 5/10/15 years, Axpert or Victron?
My money is on Victron grid tied for every watt the house needs up to a max of 2.4kw, comes from the array = lower Eskom usage on the spot.

 

11 hours ago, Coulomb said:

agree with @plonkster that "split" systems (grid-tied and off-grid) make sense

Load NEED's and regulations dictates that decision. You can have a hybrid system mimicking it i.e. Keep batteries charge and feed back all surplus power - if you get paid for that power AND if you need batteries - making a Victron Hybrid cheaper than a "split" system.

FWIW. If CoCT did not approve my system I would have gone for a 3.5kw Solis grid tied inverter with the Multigrid as the UPS ... instead of a Axpert. 🤣

Edited June 1, 20197 yr by Guest

tl;dr 🙂

On 2019/06/01 at 4:08 PM, plonkster said:

tl;dr 🙂

That Sir, is your prerogative but I bet it took more time to glance at it, decided on a appropiate response, then open a box to post the above comment than it would have been to fast read it all.

I'm asking a very salient question, with Newbies details included, that could help decisions for newbies into the future. 🙂 

I'm turning into a millenial. Message doesn't fit into a tweet? Move along sir... 🙂

There, I am legal.

 

Edited July 12, 20196 yr by Guest

3 minutes ago, The Terrible Triplett said:

There, I am legal.

 

Well done TTT - may want to block the address boet... We could come for beer and food

 

Now:  NO FIDDLING ALLOWED

3 minutes ago, Mark said:

Well done TTT - may want to block the address boet... We could come for beer and food
Now:  NO FIDDLING ALLOWED 

Too late ... thanks for the heads-up! 

Was quite painless to get it approved I must say. All thanks goes to the sparkies and @Rautenk !!!

Hi everybody,

I am so impressed with this discussion since day one.  I currently have a small 600W off grid system which is made up off 2x 330Watt Canadian Solar panels, a 40 Amp Micro Care MPPT controller, and 2x 12V 120Ah OPR Deep Cycle Rechargeable AGM / GEL Hybrid VRLA Solar Batteries and a 600-Watt inverter.  I also got a Victron 712 Smart BMV wired into the system to watch my SOC. Currently, the system supplies my home office with power during the day.  And then sometimes, when we experience load shedding or a power outage, I divert the Inverter power to the TV, decoder and one or two lights.

I am thinking of upgrading to a Multiplus-II with system specs as described in this thread.  My question is, can I use my existing 40A Micro care with the MTP-II?

Thanks in advance

6 hours ago, Stefan said:

My question is, can I use my existing 40A Micro care with the MTP-II?

You can but with a Victron MPPT, it will be better integrated into the system to use ESS better.

I have had a couple inverters over the years. Each time the time is comes I sell the older one to a newbie who starts out via on his/her solar journey via i.e. Gumtree. I do this by "passing in on" in dropping the price substantially for a quick sale AND so that the next person feels less of a risk getting into solar with a smile on their face. Like my first Cotek inverter. Got it for a steal and that started my journey. Got a few bargains over the years which just worked out perfectly. 

So, your question. With the Micorcare unit the VenusGX / system overall will have no data on what the MPPT is doing. See below, the part in the red block would be missing:
Ps. What a beautiful view, the perfect balancing of charging the batts whilst keeping the house loads covered - no words can describe the relaxation of letting ESS just be. Freaking nice!

 

And if you want to tweak the system, even I now have been shown to do that with a Cron job on the Venus.

Hi TTT, Thanks for the feedback. 

The plan is to eventually move over to all Victron components including a VenusGX. I do have access to the Micro care MTTP via its RS232 port.  I got an ESP8266 connected to it, sending the values to Adafruit.io.  (Will add a screen dump for you).  Going to do the same with the 712 BMV. 

For now I want to start off with 6x  330 watt Solar Panels, a set off 4x Omni power batteries with the Multiplus-II 48/3000VA.  I want to be able to draw an additional 1200 watt on top off my daily 450 watt twice a week.  The question is, will the 40A MPPT be big enough to supply both charging the batteries and provide power to the loads?

Adafruit Dashboard sceen dump(  It is overcast today, hence the low Panel volts:

 

1 hour ago, Stefan said:

... including a VenusGX.

You do know you can start with a Pi and install the VenusGX software for free? 
It is an idea if you are building towards a blue setup, to start that with the Multiplus II, start getting the data to your Victron portal.

And it is a very good idea, as least I think it is, to install a Carlo Gavazzi ASAP into the main DB, just after the main breaker, connected to the Pi with Venus on it. If the main DB data starts coming in with the Multplus II's data, you would get a cleared picture of where to go with the panels.

1 hour ago, Stefan said:

The question is, will the 40A MPPT ...

I would ask the question differently:
Question 1: Is the MPPT big enough to handle all the panels? If you stay within the max VOLTS and max AMPS (Isc) of the panels, then 100%.
Question 2: Are there enough panels on the MPPT to power the load and recharge the batteries?

Here are some calcs for you to guide you a wee bit: Batteries and panels required 

As your budget dictates, the sooner you can sell the Microcare to offset some of the Victron MPPT costs, with the Pi already working, the sooner you will get proper data to estimate the panels.

 

2 hours ago, The Terrible Triplett said:

You do know you can start with a Pi and install the VenusGX software for free?

Interesting ... I actually do have a spare Pi lying around .....  🤦‍♂️

2 hours ago, The Terrible Triplett said:

You do know you can start with a Pi and install the VenusGX software for free? 

 

7 minutes ago, Stefan said:

Interesting ... I actually do have a spare Pi lying around .....  🤦‍♂️

Guys, just keep in mind the positively ancient first gen Pi is not really supported anymore. You really want a Pi-2B or later for this. Pi-3 also well supported. Don't yet know about the Pi-4, have a feeling it is not supported (yet). It will get support at some point...

7 minutes ago, Stefan said:

Interesting ... I actually do have a spare Pi lying around .....  🤦‍♂️

Just note: There is no official support for that so you have to work via the forums for assistance if you sukkel.

So if you are IT literate and like Linux, should be a breeze.

On 2019/08/09 at 9:02 AM, Stefan said:

40 Amp Micro Care MPPT controller

Something you can try. If you set the MPPT to charge 0.4V higher than the Multi is configured for, then surplus PV can be fed to the loads. This is useful when you have the ESS mode set to Keep Batteries Charged, your loads can run from the PV while the batteries remain full.

In optimised mode... of course it already works correctly. You just can't see the data from the solar chargers.

9 minutes ago, plonkster said:

Something you can try. If you set the MPPT to charge 0.4V higher than the Multi is configured for, then surplus PV can be fed to the loads.

Thanks for this ....  and I fortunately do have a Pi-3

Quick noob question. There has been a lot of discussion around the VOC at low temps. Does the temp matter when there is max sun exposure or even at very low exposure.

Hope the question makes sense.

3 hours ago, l3ok said:

Quick noob question. There has been a lot of discussion around the VOC at low temps. Does the temp matter when there is max sun exposure or even at very low exposure.

You're asking if the voltage is proportional to the level of insolation (aka incoming sunlight). Lower exposure does drop the Voc somewhat, but not proportionally to the light level.

This is actually a very cool tool/demonstration. Just move that last slider: https://www.pveducation.org/pvcdrom/solar-cell-operation/effect-of-light-intensity