Was Looking for 2 x 200w panels - Sorted - some good info here for ideas now.

[___]

12 minutes ago, KLEVA said:

Surely if you have a panel that can only handle 4A (rating of the 100W panels) of the 8A(rating of the 200W panels), then the entire array will be limited to that 4A if connected in series?

Correct. I didn't look at the details, I did say they current has to be similar. Quite often the same manufacturer will have a 150W panel and a 300W panel and they are essentially the exact same cell, just twice as many of them in the larger panel. In other words, one makes 8A at 18V , the other one makes 8A at 36V. You can put them in series and get 8A at 54V without losing any power.

Edit: And even if not the same manufacturer, if the Isc/Imax of those panels are close to one another, the same principle applies. String 'em up.

Edited August 26, 2018 by plonkster

[KLEVA]

Ok, understand - Just thought I was losing the plot. We were comparing the ReneSys/Similar (100W) to the existing Tenesol (200W), so missed the current clarification you made in your post.

[Guest]

The 2 x 200w panels in series fits perfectly on a 75/15 (440w on 24v and they cost peanuts), for as I said, to bother with adding more panels on that array with that one panel that met me in person, may or may not hold. If it fails, the other one can continue to add to the mix.

That now leaves the 100/30 open for better specced panels. :-) 

@KLEVA 's idea to get big panels at good prices, could turn out to be cheaper to get a few small controllers with BIG panels to match each one.

2 x 75/15's are cheaper than 1 x 150/30 controller. With grid tie, it is all about the watts in, not the batteries being charge.

Which made me wonder, thinking of @plonkster 's advice not to oversize the array and having large spikes hit the bank, what if one uses a Sonoff relay, that if X Y or Z device are switched on, that a relay is closed to allow a particular controller to add it's watts to the mix? Just a wild idea.

[___]

5 minutes ago, The Terrible Triplett said:

advice not to oversize the array and having large spikes hit the bank,

There's really two sides to that advice. The one is that you should not oversize by more than 50% (20% feels safer to me) relative to the size of the MPPT controller, because overcurrent events are a real thing. The charge controller can deal with them (it switches off and restarts to find a better point on the power curve), but if they are too severe it will pop a fuse in your controller.

The second is that if your solar array is significantly larger than the battery and you use the current limit feature in the ccgx (which is DVCC specific by the way, just so you know), there will be short periods during which the battery may be charged faster than requested. I think it is this second one you worry about.

Caveats around this:

1. Normally a battery accepts as much charge current as it takes to raise the voltage, so for well charged batteries in good health, the current tapers off the moment the voltage reaches the required level. If however the batteries are very flat, or unhealthy in some way, it may charge higher than wanted. So this limit is for safety in these two conditions.

2. If a  large load just switched off and you are within a 30 second window after this event, the charge current may be higher than you want. The current required by loads is passed through a low pass filter that smooths it over approximately a 30 second window, so in short, after that large load turns off the limit will taper down slowly over a 30 second period. After about 30 seconds or so, it will be back around the set limit.

3. This means your battery bank needs to be able to take the situation for 30 seconds, or your PV array needs to be sized like that. This is why I said you can likely size it definitely to C/5 and perhaps as high as C/2: Because it is only for a few seconds, and only in the rare case as mentioned in 1 above.

4. However... the previous comments apply only to the Optimised ESS modes (where the battery is allowed to be discharged to a certain minimum SoC to improve self-consumption). If you use the ESS "keep batteries charged" feature, and you want to feed the excess to your loads, then we turn off the current limit in any case and rely on voltage regulation. That brings you back to sizing the PV array to safe limits, again I'd say no more than C/5.

So think carefully about what you want to do.

[Guest]

2 minutes ago, plonkster said:

I think it is this second one you worry about.

Jip, it is the 30sec part that I am carefully listening to.

Oversizing the controllers, using the Short Circuit Current and Open Circuit Voltage, having seen the Tenesols getting there quite easily, a 100/30 max 1050w. A new 135/30 max 1150w.

 

Starting with a 1330w array, then later push that up to +-2kw array, then even later, with data, go to +-3.3kw.

Will use Optimised ESS on a sliding scale. The bigger the array, the lower the SOC will be set for Optimised ESS.

Over 2kw array on the 225ah 24v bank, I fully expect the T105RE's to be tickled but nowhere near what they can be pushed at seeing as this is not a forklift / Golf cart scenario.

Nor will they last 10 years. :-) 

I need the batts once a week on 100%, SOC on average 80% for the other 6 days, so there is always space for more charge. Will that be a sufficient safety net?

[viper_za]

1 hour ago, The Terrible Triplett said:

2 x 75/15's are cheaper than 1 x 150/30 controller

Is it really cheaper when you add the costs of all the extra cables?
Also does it not need it's own coms cable too?(Can't remember if these also work with the CAT5/CAT6 cables)

[Guest]

19 minutes ago, viper_za said:

Also does it not need it's own coms cable too?(Can't remember if these also work with the CAT5/CAT6 cables)

1 x 150/35 costs about the same as 3 x 75/15's. Obvious, you are tenacious in finding the prices.

So if one was to get 2 x 75/15's, having to get one data cable in any event for 1 x 150/35, the cost for one extra cable is negligible.

I have spare ports for a standard VE.Direct cable, which is even cheaper than the VE.Direct to USB. All cable prices have dropped.

 

19 minutes ago, viper_za said:

Is it really cheaper when you add the costs of all the extra cables?

Good point!!!

The length of the wires needed from the array/s, that can make it break even, or more costly.

In my case, having spare, makes no difference at all.

Not saying that it is a very good idea. Just saying there are more options, depending the requirements, just do the sums carefully, as you rightfully pointed out.

Edited August 27, 2018 by Guest

[___]

Well... I have some trouble this side. The Multigrid trips the earth leakage (Multiplus never did that).  It has  a power-on relay test that checks among others if earth and neutral is properly bonded. On my system, it trips both the RCDs on the input and the output. It only does it if my suitably interlocking changeover switch on the output is on the inverter side, even if the breakers are all off... which means there is an issue with the neutral on that side :-(

[Guest]

51 minutes ago, plonkster said:

... which means there is an issue with the neutral on that side.

Mmmm ... therein my NBEEF saying: "If all checks out, earth, everything, it will be cheap to sign off." It can get very costly, he said.

[___]

Just now, The Terrible Triplett said:

Mmmm ... therein my NBEEF saying: "If all checks out, earth, everything, it will be cheap to sign off." It can get very costly, he said.

I think there are two faults in the system. The one is that there is always a small amount of legitimate/allowable leakage current. In the order of single-digit milliamps, often through surge arrestors. When the Multi imposes its own 10mA on top of that (for a short period to test it), it becomes too much and it trips.

Two possible solutions, one is to set the grid code to None (then no relay test, but technically it doesn't comply). The other is a type-A or type-F RCD that can handle the transients that likely causes this one to trip. I'm going to try the no-relay-test option first.

[Jaco De Jongh]

1 hour ago, plonkster said:

The Multigrid trips the earth leakage (Multiplus never did that). 

Hi Plonk, I think you might have seen this. Posting for if you didn't. Maybe there is an answer in there. 

https://www.victronenergy.com/live/drafts:multigrid_faq

If you have the time, Please disconnect your geyser, even the Neutral and test the MultiGrid again. They tend to have leakage just below trip point. 

[___]

5 minutes ago, Jaco de Jongh said:

Hi Plonk, I think you might have seen this. Posting for if you didn't. Maybe there is an answer in there. 

My buddy Guy Steward wrote that. I know about it, was hoping I would not be affected. I'll contact him and ask about his experiences.

[___]

1 hour ago, plonkster said:

set the grid code to None

Doesn't work, still trips. So I'll have to figure out the problem and fix it. Probably just get better RCDs (not that I thought the Hagers I have are bad...).

[Guest]

8 minutes ago, plonkster said:

Doesn't work, still trips.

Hurry up ... suspense is killing me.

Waiting for that "AAAA here you go ... " moment.

[___]

Suspicion: I need a type-B RCD. Looks like the cheapest kind is type AC (which is technically a bad idea already in most households with non-linear loads), followed by type A and then type B, and if you really want to, type F. Type F seems to start at around R1500. Type AC starts around R250.

[KLEVA]

9 hours ago, The Terrible Triplett said:

I need the batts once a week on 100%, SOC on average 80% for the other 6 days, so there is always space for more charge. Will that be a sufficient safety net?

Not sure if I am misreading your intent or whether that is DOD% instead? Are you only pulling 20% of the power from your batteries 6 days per week? Or are you flatlining your bank one day and nearly flatlining your bank 6 days per week?

[Guest]

3 minutes ago, KLEVA said:

Not sure if I am misreading your intent or whether that is DOD% instead? Are you only pulling 20% of the power from your batteries 6 days per week? Or are you flatlining your bank one day and nearly flatlining your bank 6 days per week?

Being Cape Town in winter, we can have days without good sun.

So if the batts are not fully charge every day, and not drained below a SOC of 80% (DOD of 20%) in 7 days, with at least one day in the 7 day cycle at 100%, it is perfectly acceptable.

Why waste energy on keeping batts every day at 100%, if that energy can be used to power the grid tied system? IF there is spare, go to the batts yes.

However, if we have regularly power issue, then 100% SOC each day is a must.

My current system has gone regularly a week at min of 80% SOC, 20% DOD. Come weekend, it gets back to 100%.

Trojan's can take that. 

 

[Jaco De Jongh]

On 2018/08/27 at 11:53 AM, The Terrible Triplett said:

The 2 x 200w panels in series fits perfectly on a 75/15 (440w on 24v and they cost peanuts)

I liked watching you going backwards and forwards, and glad you found a working solution. 

All of this excitement watching you made me decide to complete my system as well. 6 new panels on the way and my 7th blue component  (another 75/15  MPPT) will follow shortly. 

12 Panels per inverter and maybe somewhere in the future ill add an additional 16 panels to max out the MPPT's

My time to thank you.  

[Guest]

28 minutes ago, Jaco de Jongh said:

I liked watching you going backwards and forwards, and glad you found a working solution. 

All of this excitement watching you ...

Ag dankie Jaco. Dis nou wraggies 'n riem onder die hart.

I hope others also benefited.

 

14 minutes ago, Jaco de Jongh said:

... to max out the MPPT's

That is where I force myself to sit on my hands. I want lots and lots of panels, 15kw inverter, and not look back.

What kills that idea (soos in 'n pletterstop) is when I look at my very very old Effergy meter standing in front of me: When is this house drawing the most power?

That issue about Batteries + panels + inverter vs just Eskom fees at night (that one can switch off), that blerrie fight starts every time it raises its stupid blerrie logical head.

My nirvana is when I reach that point where adding one more panel will not make a damn bit of difference over 12 months. Power generated = power used.
Yes, there are exceptions, but is it worth the extra panel/s, I always ask myself.
Or what if we start working at a office and not at home anymore?

Gotten so damn good at this "fight" that when I present my plan and budget to the wife (after having been here off course), that not even she can burst any bubbles anymore.

And what if the circumstance change after having maxed out the 3kva Victron system, you need more panels daytime?
What if you change your mind and start feeding back to the grid?

For that I can add up to a max of three dedicated Solis grid tied inverters, one at a time.

I'm limited to the DB board breaker, which can be upped I think, and add the max breaker I am allowed to fit, to match the generation capacity.
But then, where is that power going and why?
If it is to feed back, reducing the evening cost to near zero ... dammit, here we go again ... 

... SIT ON YOUR HANDS TTT!!!
Stick to the plan! One step at a time!

[Mike]

5 minutes ago, The Terrible Triplett said:

'm limited to the DB board breaker, which can be upped I think, and add the max breaker I am allowed to fit, to match the generation capacity.

i think you are limited by the breaker in the muni box of 60 / 63A, some muni's will allow a residential home go up to 80A which i did by saying a lift is going in....and at the minute i have a max of 40A pushing thru it from the GTI to the load and export

[Guest]

3 minutes ago, Mike said:

I think you are limited by the breaker in the muni box of 60 / 63A ... 

Thanks Mike.

Without incurring the cost to go 80amp, I'm only allowed to go to 60amps as current, and that is excellent!

It is like the feeding back issue. The R8k+ for fitting a new bi-directional meter plus daily charge payable for being allowed to feed back, those costs has curbed that idea quite nicely for me.

So the breaker size limit = less options to consider.

I like that.

 

[Mike]

6 hours ago, The Terrible Triplett said:

Without incurring the cost to go 80amp, I'm only allowed to go to 60amps

there was no charge to me for the muni to up their breaker to 80A, i had to supply my own for in my property....

[Guest]

1 hour ago, Mike said:

there was no charge to me for the muni to up their breaker to 80A, i had to supply my own for in my property....

And no extra charge per month ... this is very interesting.

That means one can upgrade from 60a to 80a breaker and be legal with a larger wattage inverter as per the specs of CoCT.

[Fuenkli]

10 hours ago, The Terrible Triplett said:

That means one can upgrade from 60a to 80a breaker

in my case it was not possible because the cable from the muni box to my house is only rated for 60A.

[Guest]

28 minutes ago, Fuenkli said:

in my case it was not possible because the cable from the muni box to my house is only rated for 60A.

Aaa, ok, so it can be done, but it depends on the cable in the street.

Thank you.