1 hour ago, jdp said:

The power does not go via the battery bank

Well.... I kinda suspect that on a wiring level it does, but because the MPPT and Inverter are tightly integrated and can balance these things between them it's probably accurate to say that it's not like the "old inverters". :-)

I may be wrong though... I suppose it is possible that the Axpert takes your solar and steps it up directly to 325VDC (or more) for making AC... like a GTI would... but I kinda got the idea all they did was bundle an existing MPPT with an existing inverter and added some Serial comms. I think coulomb explained how the two units sync up and even recalibrate each other so they agree on voltage... something which is a little odd unless they are or once were separate pieces of hardware.

Edit: to my Victron-invested brain it comes across as a hub-1 system, just without the true hybrid functionality. The first Hub-1 versions needed a canbus cable so the inverter could sync up with the mppt... it wasn't a popular setup due to the cost of that canbus cable. So put them both in the same box... and you get an Axpert. Sort of.

Haha that pic on Facebook was from yesterday. The sun is out today ;-)

solar is SBU and grid is bypass mode. 

Plonky if you look at the BMV 702 it will only show a current of up the the max charge current set on the Axpert As it is a shunt that sits in line it will show everything that pases through it. I asked the product manager of the Victron BMV if it only shows the differance and he state it shows everything. Thus if the power to the loads go via the bank why is the BMV not showing it? It only shows the charge current up to max charge current as set on the Axpert. Are you telling me the inverter is only pulling the correct amount of current out of the bank to leave the charge current at max?

11 minutes ago, jdp said:

Are you telling me the inverter is only pulling the correct amount of current out of the bank to leave the charge current at max?

I suspect that is what it does. It maintains an internal DC bus. The MPPT dumps the energy onto the DC-bus, and the inverter grabs energy from there and turns it into AC. If the MPPT dumps more on the bus than the inverter consumes, that will turn into battery charge current... but since you have a piece of clever software in charge (pun intended), you can dial back the MPPT so it balances with what the inverter consumes, thereby carefully controlling the remainder that goes to the battery. So perhaps I'm just being confusing here. No, the solar charge doesn't go "through" the bank, but I suspect it does go through the DC bus that is connected to the bank.
 

If you think about it, if you have a separate CC and inverter, perfectly balanced... the solar power also doesn't go "through the bank". It goes via the one cable right up to the terminal of the battery, and then leaves via the other cable without ever passing through the battery.

If you had a BMV in circuit, it would flow right to the shunt, and then leave and go off to the inverter without going through the shunt.

So we have a more "exposed" DC bus, but it's sort of the same thing.

At least, I THINK that's how they did it.

OK but it still does not effect the battery bank as the amps are not pushed into the bank. It only passes the bank on the bus to the inverter. If the bank is at max charge current and there is no load the mppt backs off and makes less power. Older charge controllers would push max on the bus and not know what the inverter needs. Thus working the bank hard all the time. 

6 minutes ago, plonkster said:

I suspect that is what it does. It maintains an internal DC bus. The MPPT dumps the energy onto the DC-bus, and the inverter grabs energy from there and turns it into AC. If the MPPT dumps more on the bus than the inverter consumes, that will turn into battery charge current... but since you have a piece of clever software in charge (pun intended), you can dial back the MPPT so it balances with what the inverter consumes, thereby carefully controlling the remainder that goes to the battery. So perhaps I'm just being confusing here. No, the solar charge doesn't go "through" the bank, but I suspect it does go through the DC bus that is connected to the bank.
 

If you think about it, if you have a separate CC and inverter, perfectly balanced... the solar power also doesn't go "through the bank". It goes via the one cable right up to the terminal of the battery, and then leaves via the other cable without ever passing through the battery.

If you had a BMV in circuit, it would flow right to the shunt, and then leave and go off to the inverter without going through the shunt.

So we have a more "exposed" DC bus, but it's sort of the same thing.

At least, I THINK that's how they did it.

I think you are correct, you can see this happening when you turn off a load. It will "boost" charge the batts for that 1s it takes for the MPPT to adjust

Ok..Sooo..

Although i know my battery bank is not ideal (at all) This should not affect my available power to my house from PV during the day(Sun permitting of coarse)

So my problem is most likely the voltage that is too low which causes the MPPT controller to disconnect itself when dropping below 60V? Which i can fix by adding two more panels and changing the string set-up.

Other MPPTs I've worked with generally wants about 5V above battery voltage. So for a fully charged 48V bank at almost 59V, you might need at least 64V. So in operation I would expect it will start charging when Voc reaches about that voltage, and it will only gain full power once Vmp is also above 64V. That is to say, size the array so that Vmp is above 64V and Voc is below 145V.

48 minutes ago, jdp said:

OK but it still does not effect the battery bank as the amps are not pushed into the bank. It only passes the bank on the bus to the inverter. If the bank is at max charge current and there is no load the mppt backs off and makes less power. Older charge controllers would push max on the bus and not know what the inverter needs. Thus working the bank hard all the time. 

I have a older charge controller. Nogal 'n PWM to boot.

It uses say 756w of the 930w panels (27v x 28amps). BMV shows maybe 2-3 amps going into batts, perfect day zero going in.

Rest is just missing ...   ... no used by inverter. 

Switch off the inverter under that load, then as stated above CC drops down to +-2 amps, or zero, after a minute or so.

So I would hazard and say if older charge controllers pushes max onto the bus and not back down, that it is faulty.

On 3/22/2016 at 9:18 PM, plonkster said:

I suppose it is possible that the Axpert takes your solar and steps it up directly to 325VDC (or more) for making AC... like a GTI would... but I kinda got the idea all they did was bundle an existing MPPT with an existing inverter and added some Serial comms.

There is a ~ 400 VDC bus, but that's internal to the inverter. You can see "bus voltage" as one of the parameters of the QPIGS command (Query general status). If the solar (SCC) is charging the battery, there is no need to go to 400 V and back down again.

The Axperts actually go to a lot of trouble to make the inverter more or less reversible. There are two full bridges, at 48 V and ~ 450 V, for the battery and mains ends respectively. Then there is a buck converter, so that if the battery is a bit full, the fixed transformer ratio doesn't make too high a bus voltage. That's three power conversion processes when inverting from battery or solar to power loads.

I believe, but am yet to confirm, that they use the TI trick for charging from the mains. They leave off the upper two transistors of the full bridge, and PWM the lower pair together to adjust the charge current. The buck stage is bypassed (leave the buck transistor on), and they juggle the mains side PWM ratio and 48 V side PWM ratio to charge the battery at the required current, while keeping the bus voltage within safe limits. Quite clever software, really.

[ Edit: I've just (November 2016) reread a manual (the "Axpert MKS-4000/KS-5000 Service manual") which says that the buck stage is *only* active when line charging the battery. The above may be right, but then I don't see why they need the buck stage. ]

Hi Mike. Am I then correct to assume the Axpert will only send to the battery what it needs. It does not send to the bank what the loads needs?

6 hours ago, Coulomb said:

Then there is a buck converter, so that if the battery is a bit full, the fixed transformer ratio doesn't make too high a bus voltage. That's three power conversion processes when inverting from battery or solar to power loads.

So if I've got that right, it takes the DC, steps it up to 400VDC using some kind of inductor (we had an argument here about that, re transformerless inverters being so much "better" :-P), but because that step-up is fixed ratio it bucks down again from 400VDC before it chops it up into AC?

So just to check then the three conversion processes are:

1. Buck converter from solar onto 48V DC bus

2. Boost converter (isolated or not?) from 48VDC to ~ 400VDC, probably 1:8 ratio?

3. Adjustable Buck converter from ~400VDC (I would thing between 360 and 480) to ~325VDC

After that then will follow the "chopping stage" where 325VDC peak is turned into 230VAC RMS.

 

6 hours ago, Coulomb said:

I believe, but am yet to confirm, that they use the TI trick for charging from the mains.

I could google this (and I did in fact) but google is being clever and thinks I'm looking for Texas Instruments stuff. Can you elaborate on the "TI trick" because I am curious as heck :-)

 

18 hours ago, The Terrible Triplett said:

So I would hazard and say if older charge controllers pushes max onto the bus and not back down, that it is faulty.

I think the issue here should be considered in the light of an "incorrectly" sized array, where the battery is sized much too small for the solar array that's connected to it. Normally you deal with this by configuring the charge controller to a safe maximum. If you however ALSO have a large inverter connected to the DC bus, and you actually intend using that power directly without pushing it into the battery, then you must allow the charge controller to go above that maximum, so that the new limit is set to the maximum battery charge current PLUS whatever is being used. This is in fact what the Axpert does, and what jdp is now concerned about... :-) All that is happening here is the charge limit on the charge controller is dynamic. Us people with separate charge controllers can't do this sort of thing... we have to set the charge controller to a safe limit, use a smaller array, or get larger batteries. That's our reality... well, unless you take out the dosh and buy a Victron with all the interconnecting equipment.

36 minutes ago, plonkster said:

... is the charge limit on the charge controller is dynamic.

Assuming all the Voltronic models are this clever, which I sincerely hope is the case.

 

36 minutes ago, plonkster said:

Us people with separate charge controllers can't do this sort of thing... we have to set the charge controller to a safe limit, use a smaller array, or get larger batteries. That's our reality... well, unless you take out the dosh and buy a Victron with all the interconnecting equipment.

So Plonkster, "Us" now not only being Blue but Separatists to boot. 

Seriously, for "Us" it just means we do our sums for the loads we need powered, then we spec the bank for the load, then the panels to make it all work and then we get really clever ... we use Eskom as backup to reduce the cost of the battery bank to auto switch back, thereby reducing the cost of the batteries, panels and inverter required. 

8 minutes ago, The Terrible Triplett said:

Assuming all the Voltronic models are this clever, which I sincerely hopes is the case.

 

So Plonkster, "Us" now not only being Blue but Separatists to boot. 

Seriously, for "Us" it just means we do our sums for the loads we need powered, then we spec the bank for the load, then the panels to make it all work and then we get really clever ... we use Eskom as backup to reduce the cost of the battery bank to auto switch back, thereby reducing the cost of the batteries, panels and inverter required. 

I like how you just have to keep convincing yourself

9 minutes ago, The Terrible Triplett said:

Seriously, for "Us" it just means we do our sums for the loads we need powered

Well yeah, for "Us" it means staying old school, which is not a bad thing. But I tell you, batteries are expensive... and I would really love to use my inverter's hybrid capabilities. And it CAN be done, the technology is all there... it's just <insert expletive> expensive. I mean, I could implement this tomorrow using hub-4 and some clever code (I'm not yet sure how to hot-adjust the VE.Can mppt controller, but it can be done)... but I need to spend 8k on anti-islanding first (thank you Jacob <insert another expletive> Zuma and your <insert third expletive> Gupta cronies). I can console myself that the Voltronic doesn't have the hybrid capability and can't even push back to begin with... but man, this really is like being the guy with the Porsche at the Race Track, looking at the guys down the pit lane with the old Escort having way more fun than me... :-)

On the other hand, I remember Andre (from Victron) commenting on how people want to go racing on Marie-biscuits. Perhaps being the Porsche Driver isn't a bad thing.

7 minutes ago, plonkster said:

Well yeah, for "Us" it means staying old school, which is not a bad thing. But I tell you, batteries are expensive... and I would really love to use my inverter's hybrid capabilities. And it CAN be done, the technology is all there... it's just <insert expletive> expensive. I mean, I could implement this tomorrow using hub-4 and some clever code (I'm not yet sure how to hot-adjust the VE.Can mppt controller, but it can be done)... but I need to spend 8k on anti-islanding first (thank you Jacob <insert another expletive> Zuma and your <insert third expletive> Gupta cronies). I can console myself that the Voltronic doesn't have the hybrid capability and can't even push back to begin with... but man, this really is like being the guy with the Porsche at the Race Track, looking at the guys down the pit lane with the old Escort having way more fun than me... :-)

But Plonkster, the switchback to Eskom and back to inverter to save on batts, sorted that yonks ago, so what is the problem still?

6 minutes ago, plonkster said:

Well yeah, for "Us" it means staying old school, which is not a bad thing. But I tell you, batteries are expensive... and I would really love to use my inverter's hybrid capabilities. And it CAN be done, the technology is all there... it's just <insert expletive> expensive. I mean, I could implement this tomorrow using hub-4 and some clever code (I'm not yet sure how to hot-adjust the VE.Can mppt controller, but it can be done)... but I need to spend 8k on anti-islanding first (thank you Jacob <insert another expletive> Zuma and your <insert third expletive> Gupta cronies). I can console myself that the Voltronic doesn't have the hybrid capability and can't even push back to begin with... but man, this really is like being the guy with the Porsche at the Race Track, looking at the guys down the pit lane with the old Escort having way more fun than me... :-)

They have it's the green one: infini

http://www.voltronicpower.com/oCart2/index.php?route=product/product&path=24&product_id=73

I like this bubble bursting

4 minutes ago, viper_za said:

They have it's the green one: infini

http://www.voltronicpower.com/oCart2/index.php?route=product/product&path=24&product_id=73

I like this bubble bursting

Ja like everyone going out now and replace their current inverters with Inifini's. 

With Victron we just add the parts ... did I just hear a POP in Pretoria!!! 

6 minutes ago, The Terrible Triplett said:

so what is the problem still?

I have a 900W array pushing into 200Ah batteries. Do the math. 200*0.13 = 26 amps. 900W/23V (lets say they are empty) is almost 40 amps. So that's 20%... which is sort of acceptable for short periods, so I am at my limit. I literally have to buy batteries next. These voltronic people, in the mean time, are running 3kw arrays with 200ah batteries. That is kind of cool...

Edit: No worries though. We'll fix this... and it'll be open source to boot too.

1 minute ago, The Terrible Triplett said:

Ja like everyone going out now and replace their current inverters with Inifini's. 

With Victron we just add the parts ... did I just hear a POP in Pretoria!!! 

Nah happy to have no grid connection if they decide to add a connection fee here like in the Cape, so with the money for the Infini I'll add another Axpert and panels.

Lovely plan

 

POP POP POP

31 minutes ago, viper_za said:

They have it's the green one: infini

http://www.voltronicpower.com/oCart2/index.php?route=product/product&path=24&product_id=73

I like this bubble bursting

I was just about to remind him about that. 

Must say, brand choices have always been fascinating to me. I am a big Toyota fan, for example. Pretty much top of the list whenever I buy cars. But then recently my wife wanted a Suzuki Swift, which is also a lovely vehicle... at least from the same country. So reason why I am thinking of this... I used the rather poor analogy above of a Porsche racing driver. Truth of the matter is, a Porsche is a nightmare to own! Expensive, breaks all the time, you should see what a set of tyres costs, etc. I feel the same way about pretty much any German vehicle. Owned a BMW for one horrible year. Lovely to drive, absolute pain to maintain once they get old. So that was a poor analogy. I think my choice of inverter rather mirrors my choice of vehicle. Have you seen what Toyota charges for a new car now? Almost half-a-mill now for a RAV4... and then these vehicles often don't even have an ipod interface or bluetooth for your phone or stuff like that... so in some ways it mirrors the Victron situation: For the price, I'd expect it to have all that stuff. Yet somehow we continue buying them ... :-)

So why do we continue buying these overpriced Toyotas? Because they don't give you k*k. So I laugh at Jeremy Clarkson, way back in 1997 in one of the very early Top Gear programs he had to test one... decided to race it against a Golf GTi to show that you should in fact be *misserable* in your jappo-box... and then the Corolla won the race. So he decided to evaluate it on handling and said that that too... couldn't really be faulted at that level. So finally all he could say is that he hated it for being boring... well... I owned one of those Corollas (1998 1.6 with the 4A-FE engine). Most reliable thing I've ever owned. When I sold it at 213 000km it still had the original exhaust, alternator, water pump, etc in it. Save for the clutch, it was factory original.

That's why we buy overpriced boring jappo-boxes.

I like to think I bought the Victron for the same reason. Reality isn't as simple. Back in 2013, the Axpert was practically unheard of... the Victron was the only thing that could be paralleled, and I practically drooled about the programmability (Virtual Switch and later Assistants). Come to think of it... there is STILL no inverter with this level of extensibility.

Plonkster, I had same Toyota, actually had that one and then two newer models after it in a row ... company use, so 2 years, 180 000km's per car.

By that mileage they had to be traded in, all three needed their 5th gears replaced, was worn out due to +-160 000 kms driven at high speeds all over the country. 

I got a Tazz 1.3 for the wife way back then, also now at 200k +, still all original, cheaper as can be to maintain.

Unless you have experienced that reliability, the boringness, low maintenance, everything keeps going right ... you cannot explain, same as the Victrons.

You 'get it' or you don't.