Axpert not using the available solar energy

[stuvo]

My SMKSOLAR Axpert MKS 5kVA 4000w 80A Inverter will be humming along at about 2.2kw PV watts in, charging the batteries with 2 or 3 amps float with a 35% load. Then all the sudden my PV watts will drop to about 200 and the BMV 702 shows a discharge of around 30A. This is not in relation to a cloud or anything I have noticed. After a minute or three the PV watts in will slowly start climbing until my full house load is met and I am again putting a charge on the 200ah AGM battery bank. This seems to happen every 10 minutes. Over the course of the afternoon, this reduces my charge percentage from 100% to about 80%. The solar energy is there. Why won't my inverter use it.

PROGRAM:
1      Output source priority               SbU
2      Maximum charging current       40A
3      AC input voltage range              APL
5      Battery type                               AGM
16    Charger source priority              OSO
31    Solar power balance                  SbE

My array is 3.12kw

[Chris Hobson]

A variable load like a iron plays havoc with the MPPT. Sometimes it cannot adjust fast enough causing the MPPT to reset. What sort of load are you powering?

 

[stuvo]

I have a 3/4 hp water pump that is activated by a float switch, maybe that is it. Now that I think about it the wife may have been watering the garden causing the pump to trigger several times this afternoon.  The MPPT resetting causes the PV in to drop?

 

 

[___]

We discussed this before. All MPPTs do this. When you're not operating at the maximum available PV power, the charge controller isn't looking for the maximum power point because it doesn't need to. It sits there just balancing things so the battery voltage remains within bounds.

But if there is a change in loads, it doesn't even have to be a big one it just has to be big enough that the battery voltage dips a little, the MPPT will spring into action  and try to bring the voltage up, and this might cause the CC to go looking for the MPP.

To do that, many MPPTs will simply scan the whole range. They reset and start from zero.

My own particular favourite brand of MPPT does not do this. As the power demand increases it will adjust up to the nearest maximum point, and then it will do three or four quick scans on other voltages to find the best one and settle on that. Even that takes 30 to 40 seconds. See attached video on the CCGX. I increase the maximum discharge current and I send the MPPT hunting. After I enter the SetValue command on the terminal shell, you'll see the PV charger figure make a number of dives...

 

[Chris Hobson]

4 minutes ago, stuvo said:

 The MPPT resetting causes the PV in to drop?

Yes.

I would not expect a ¾ hp motor (0.5kW)  to make a difference but it may have a starting surge that is causing it.

[Guest]

@plonkster I just realised, the guys don't want to know about our particular favourite brand of MPPT, that not only does not have spikes, but can also equalise (manually and automatically) and can be adjusted to all types of batteries. 

We are farting against Axpe...sorry, thunder.

[Sidewinder]

20 minutes ago, The Terrible Triplett said:

We are farting against Axpe...sorry, thunder.

till Inifi (ty) (Solar)

[___]

5 hours ago, The Terrible Triplett said:

the guys don't want to know about our particular favourite brand of MPPT,

Dude, we will ALWAYS be disqualified in this race cause our charge controllers cost as much as their whole inverter/charger!

Also, the BlueSolar does overshoot sometimes. I've seen it overshoot by about 0.3V on my 24V bank. As a software coder there is also something to be said for simpler solutions. Simple is better than complex and complex is better than complicated. Just doing a rescan isn't necessarily a bad idea. Perhaps one ought to be more worried about the battery bank if 60 seconds at a C5 or even a C2 load makes you worry about the MPPT making a quick bathroom trip... :-)

[Guest]

3 hours ago, plonkster said:

... our charge controllers cost as much as their whole inverter/charger!

Jip. Got a dealer price today on a 150/45. Dealer costs is about the same as a 5kva inverter WITH a MPPT build in.

 

So I asked myself for the 100th time: Are one of the manufacturers taking us for a ride ito price / quality, plain highway robbery, or is there something in "you get what you pay for"?

After all this time, and with more and more data and questions being asked like on this thread, based on data we now all have, I am heading to put my head on a block and say: I have an idea that the one controller is messing up the BMV's readings, causing it to not accurately give the right SOC which in turn affects the batteries in that the BMV's SOC is being used to switch loads. Not to even go into the overshooting of said controller,.

I mean, if the BMV must make sure the SOC is calculated properly, and there is a overshoot / no charging (60sec) towards the end of the SOC calc, that must affect the SOC?

 

IF I am wrong, then there are no worries and I promise I will go and sit in the corner, forever holding my peace, and never say a word on this matter again. 

IF I am onto something ... 

 

Now guys, before you take me out and get upset ... ask yourself one question: Why is he doing this over and over? He will never use a Axpert and Victron we ain't gonna buy ... why?

The ONLY concern I truly have is that what if the battery banks are being damaged over time, day after day, ever so slowly costing the owners a lot of tom in the end, damaging the solar industry as a whole.

See, I genuinely care for YOUR batteries for I have sold T105RE's to some of you in the past. I want to KNOW that the monies spent, are safe in the hands ito a controller for if not, I will (I have a few times already) walk away from a deal than sell someone something I know is not a good idea. It always bites you in the arse, for I always say, the client is right until proven wrong. 

One day I will get stats on both MPPT's using the same array, from a person who understands the info the graphs give as well as his setup - before and after - with graphs showing over each other to make comparison easier for all to see and make up their own mind.

[___]

The BMV won't be fooled by the shenanigans of the CC. It counts coulombs, a gap in the line (to use a phrase from the Pixar movie "A bugs life") isn't going to do anything.

I doubt that the lower quality cc can really do damage even with the slow reaction time and the overshoots. I mean, if it overshoots and holds it there like what happened to dockarl then sure, but not the way it's used locally. I suspect the narrow recommended power band (90v to 115v) and the slowness will translate to some lost juice, but probably single digit percentages compared to the high end stuff.

Sent from my GT-I9195 using Tapatalk

[___]

I think for me it's simply this: I ran a 100/15 on a 50% oversized array for three weeks, with cloud edge effect on several days and overcurrent errors, that thing got so hot I could smell it -- though of course some of it is just shedding the new-kit smell -- but the point is I ran it at 100% between 9am and 5pm every day. And not once was I scared that it's going to blow up.

Sent from my GT-I9195 using Tapatalk

[Guest]

1 minute ago, plonkster said:

I doubt ...

So do I. I want to remove the doubt, either way.

Another thing. Have 4 x 12v "Deep Cycle" (what a crock calling them deep cycle) No Maintenance sealed batteries, over 4 years old and I use them off grid every night to 80% DOD.

Auto equalising every 4 weeks as per controller setting.

So I got a Victron balancer - because of this forum - to "feel" how it works on that bank for it must be out of whack.

Never once did the Victron balancer activate to balance them, and it was sitting 1.2m from me in my office so that I could see the LED's, hear it.

After 6 weeks, I traded it for a tablet. Controller does what it is supposed to.

Adding onto your point Plonkster, for me it is as simple as I will not connect my expensive battery bank to a controller that I do not have assistance for, automatic supplier firmware upgrades with recourse if it can be proven that the controller was at fault, i.e. Trojan proves it is charger related, I have the stats over years and can present such to the controller supplier for assistance on the matter, even if they just listen and fix the problem into the future.

 

I want to see the two compared using Emon graphs, by a non-Victron user, who wants to know himself. I am going as far as trying to organize a loan unit, a 150/45.

If you have any pull @plonkster, let me know?

 

[___]

So talking about price. I believe the 150/35 is just over 4k now? That's less than I paid for my 40A Microcare unit back in the day, I believe the MC is quite a bit more now? I admit that isn't exactly an applies-and-applies comparison, the MC has a really neat LCD and two breakers on the unit while the BlueSolar is rather bare-bones, but think about that for a second compared to 4 years ago: These things actually became cheaper in relative terms!

[Guest]

51 minutes ago, plonkster said:

I believe the 150/35 is just over 4k now? That's

Little bit more if you are a reseller. 

[___]

16 minutes ago, The Terrible Triplett said:

Little bit more if you are a reseller. 

300 Euro. Or R4500 to the end user probably about 5k if you include shipping. Sonop has them below 4k on special at the moment (ex VAT). Which is not to say that everything is now awesome and it's affordable, just that we might not have noticed that while a locally made MPPT was about half the price of the imported one 4 years ago... that is no longer the case.

[stuvo]

Just to follow up:

I've been experimenting and I don't believe it was any load turning on that was causing my MPPT to reset. Today was completely sunny, not a cloud in the sky and I had no resets. I think it was intermittent cloud cover that caused the resets.

 

 

[pilotfish]

Ir is possible that your solar array voltage is dropping below the 60v minimum. How many panels do you have, how many panels per string and what type of panel (60 or 72 cell)?

I believe that 2 panel strings voltage is too close to the minimum, and more so when using 60 cell panels, but it would be interesting to know your layout.

[Fritz]

I have the same problem @stuvo. My inverter idle's along until the 'big' 2kW geyser element kicks in. Then the MPPT is not ready and it pulls power out the batteries. 

My 105ah x 8 caravan batteries was recently reduced to 105ah x 4 , now my mppt have plenty power but the inverter wants to charge the batts instead of powering the load!  this makes my very angry as there is more than enough solar power available.(sure of this, clear sun etc)  I aslo have 260 x 12 PV. This have produce more than 3kW on occasions.

Is there a soft start that can make a element draw current in ramp form..

 

 

 

[Coulomb]

39 minutes ago, Fritz said:

My 105ah x 8 caravan batteries was recently reduced to 105ah x 4 , now my mppt have plenty power but the inverter wants to charge the batts instead of powering the load!

105 Ah is much smaller than the smallest recommended battery size for the 4 or 5 kVA Axpert, which is 200 Ah. So I suspect the batteries will sag too much under the load, and cause the SCC to start a new bulk charge cycle.

[___]

1 hour ago, Fritz said:

Is there a soft start that can make a element draw current in ramp form..

Long ago I had thoughts of doing something similar. The simplest way is to use a high-power dimmer switch, chop away part of the waveform to limit the energy and it will lower the average power delivered to the element. It also messes up your power factor something horrible and since the inverter cares about the peak current more than the average, I suspect it will be a bad idea, even if I haven't tried it.

What you want ideally is a way to vary the voltage so you can ramp it up slowly. I can only really think of two ways to do that: A really big buck converter (with peak voltages > 400V, so expect to pay a lot), or a variac with a stepper motor! Old school...

Then I switched to hybrid and now there is just no more motivation to do this.

[stuvo]

@pilotfish I do see a correlation between mppt  resets and pv input voltage sometimes. My pv voltage drops to around 80V or lower with cloud cover.  

My array is 12 x 260 watt in 4 parallel strings of 3 panels.  I don't have the exact figures handy right now but, it's something like 91V nominal. 

 

 

DURAFLEX-SRP-6PB-4BB.pdf

[pilotfish]

Ok if you are using 3 panel strings then that is the best that you can do.

I would be interested to know if @Don experiences similar issues, he also has and Axpert 5kVA inverter and 3 panel strings but utilizing 72 cell panels running closer to 110v peak.

The response from Don wont be of much use to you @stuvo but may help to others in future.

 

[Don]

On 4/27/2017 at 9:34 AM, stuvo said:

I've been experimenting and I don't believe it was any load turning on that was causing my MPPT to reset. Today was completely sunny, not a cloud in the sky and I had no resets. I think it was intermittent cloud cover that caused the resets.

If the MPPT resets, it goes to 0 watt output between 20 - 30 seconds, then goes back to where it should be. If it goes downs to 200 W, it is not resetting, it is just cutting back because of insufficient sun. One of my security cameras is set on my solar tracker. Once my solar output took a dip and I looked at that camera and only saw blue sky. I got out my dark glasses and went outside to see what was wrong with the sun, just to make sure it was not dying on us. I could not believe it, there was only one small little cloud in the sky, right in the path of the sun.

On 4/28/2017 at 3:38 PM, stuvo said:

 

@pilotfish I do see a correlation between mppt  resets and pv input voltage sometimes. My pv voltage drops to around 80V or lower with cloud cover.  

My array is 12 x 260 watt in 4 parallel strings of 3 panels.  I don't have the exact figures handy right now but, it's something like 91V nominal. 

 

That is way above the minimum and should not be a problem.

On 4/28/2017 at 3:55 PM, pilotfish said:

I would be interested to know if @Don experiences similar issues, he also has and Axpert 5kVA inverter and 3 panel strings but utilizing 72 cell panels running closer to 110v peak.

I do have resets once in a while, but not sure what causes them. I have high loads switching on and off on a daily basis, but not sure that it i\s the cause of the reset, otherwise I would have many resets daily, which is not the case. As you can see the before and after output is exactly the same, nothing started up to cause the reset. For some reason the MPPT gets confused, perhaps too many if's and but's in the code. Then it goes all the way down to 0, recalculates everything and goes back to where it should be.

 This is what a reset looks like. I had to go back a few days to find it.:

 

[stuvo]

I have some more info which may be relevant. The resets only seem to happen when I am operating at nearly full PV capacity. 

Since I can't sell my excess back, I bought an air conditioner. My battery bank gets to full charge around 1100 to 1200. Then on hot days I turn on the AC. The input watts go from around 900w to 2200w or greater (3.12kw max array). I'm still getting a 2amp trickle charge to the batts, and everything is fine on a full sunny day, but if it's partly cloudy, that's when the MPPT reset occurs. 

 

edit: Did mouse wheel scrolling stop working on only this site, or is it just me? 

[ibiza]

it is you