Nameste from India!

I've been following this forum for as long as I remember, staying incognito and gathering as much information as I could to begin my solar experience. As such, some mistakes were made, mostly drastic, some not so much. But, I'm hoping to fix these one at a time.

Let me begin with my setup that I started with, early in March :

• 1x Axpert 24v PWM 3kVA (marketed as 'Flin Lite' from Flin energy here in India)
• 6x 255w 24v Solar Panels in parallel (Vikram Eldora rated for 15.67% efficiency)
• 2x 200AH c20 flooded lead acid from Luminous (Redcharge 25000, suitable for deep discharge)

Firstly I went with 24v with the only reasoning being... not wanting more than 2 batteries and the 24v Axpert was inexpensive. I deeply regret this mistake today.

Secondly, the batteries turned out to be OK, but perform worse because they're not rated for the amount of loads I run in the evening. Rookie mistake - I take out approximately 750w to 800w at peak with continuous being 350w to 400w. These batteries are only rated for 240w together if I understand things correctly (10amp load over 20 hours => 200ah) but apparently the capacity loss is too much when I pull more.

Here's how it looked like (everything's in the balcony, with ample ventilation and protection from outside elements.... I think) :

 

Problem numero 1:

The inverter does not display the amount of solar energy it's able to extract... or pull, or whatever. The only thing I get to see is DC amps being used by loads, DC amps being pulled from the battery, and DC amps being put into the batteries. To fix this, I used @Manie's ICC software for Windows, but it was only supporting MPPT and not the PWM model I had. But, it was able to display the amount in watts being delivered to load + being used to charge batteries which was enough for me to come up with some numbers.

The numbers were not good.

I was only able to get 600w at max throughout the day, no matter how much load I put into the inverter. At one time, with peak sun and 1000w being used, the inverter continued to take 400w from the batteries.

Problem numero 2:

The batteries. At first I thought I had dead ones as the voltage would go below 23v (preset to switch to Grid on Axpert) when I only used 1.5kwh. If I understand correctly, each battery has 2.4kwh of usable energy. I have two of them, which should give me 4.8kwh at near dead state no? Turns out these c20 batteries aren't so useful when I pull out too much since my peak usage is 750 to 800w. More than 3 times the rated wattage for these batteries.

Anyway, in an attempt to fix this, I contacted Flin (the distributor for this inverter) and they offered 0 support so I set forth to fix these issues.

Fixing numero 1:

I wanted to go MPPT. Flin did offer one, but owing to the support I've had thus far and the fact that I wanted to get more out of it, I went with Victron Energy's 150/70 MPPT along with their Bluetooth dongle. In order to setup this right, the panel configuration was changed from 6 Parallel to 3 parallel strings of 2 panels wired in series each. 3x2.

This allowed me to monitor the kind of energy I'm able to extract, and I've had as much as 1200w of peak output. Nice, double the output from 600w previously. The Axpert at this point is only used as an inverter, with MPPT taking care of all the solar production. Axpert's back to grid voltage was still 23.

Fixing numero 2:

I bought a Victron BMV-702 to monitor the kind of amp hours I'm putting in, plus taking out. Without data, blaming the battery is unfair. I also installed a HA01 battery balancer - should have gone HA02, but oh well.

Turns out, I'm only able to extract 60ah out of the batteries when the voltage hits 22. I'm able to extract more if I lower the load, but to my regular loads, it's impossible.

New problem...

• The Axpert sucks at automatically falling back to grid and back to battery, as it depends on voltage readings and that's highly inaccurate and my loads are unfair to the battery. I tried to use ICC to automate this but in the end, my usage is more than what the batteries are able to provide. Bad!
• Not able to extract all the energy from the sun in the day, since my usage is very limited and mostly we tend to use at night. Production ranges from 4 to 6kwh with max peak at one point being 7.1 for the system with MPPT.

==================================================================================================

If you've read until here, thank you for putting up with my nonsense. For others who prefer a TLDR:

• I went with 24v system, regret mistake
• Got Victron MPPT 150/70 to minimize damage cos of the PWM Axpert not producing enough
• Got Victron BMV-702 to monitor batteries, regret buying c20 batteries, or rather not enough for the amount of loads taken out

==================================================================================================

Thus, here I am with all of my mistakes laid out fair and square, pleading guilty to not following recommendations. Thus, I want to fix this, and going 48v Axpert is not an option since I ended up getting an independent MPPT anyway.

Here's what I'm thinking (wallet does not like it) :

Option 1 

• Get Victron Multiplus 3000 48v
• Replace batteries with 4x c10 rated batteries (since the load I take out at peak is 80amps @ 12v divided by 4 gives me 20amps per battery so 4 batteries in 48v rated c10 should be exactly the capacity I need, correct?)
• RPI based CCGX, I don't want to buy the actual CCGX..
• Get HA02, and maybe a desulfator to keep the batteries in shape

 

Option 2

• Get Victron Multiplus 3000 48v
• Get 2 more same batteries - they will still be below my usage requirements since they drop amp hours so badly if I pull more
• RPI based CCGX

 

Option 3

• Keep the Axpert, properly configure ICC to take data from BMV
• Get 2 more same batteries and add them in parallel - attach another HA01 (do these keep things in line when there are different strings involved?)

 

Some Victron specific questions I have :

• Multiplus 3000 has another output port that disconnects when the grid is down - so I'm able to add something big, like an air conditioner or a water heater. Will these applications use Solar + Grid in the morning?
• Can I program the Multiplus to take out only X amount of watts from the batteries and take the rest from Grid when Grid is still available?
• I want to make sure the Muiltiplus does not feedback to the Grid, as I have a digital meter and it spins the same way no matter if you take the energy or give it back. Net metering is not an option at the moment. It's possible to make sure this doesn't happen right?
• Can the inverter be paired with the RPI with an mk3 to usb cable do I need something else? How's the detection like?
• Realistically, how much of an overload can I put on this since it can be grid-parallel without affecting the batteries?

Any other further recommendations is also highly appreciated. Since Victron is involved, I'll page @plonkster and @The Terrible Triplett to be involved in this one big mess of a thread.

Special thanks to Jason @Energy and @plonkster for helping me with the registration!

Edited June 4, 20177 yr by 9xsolar
Added victron questions

59 minutes ago, 9xsolar said:

The batteries. At first I thought I had dead ones as the voltage would go below 23v (preset to switch to Grid on Axpert) when I only used 1.5kwh. If I understand correctly, each battery has 2.4kwh of usable energy. I have two of them, which should give me 4.8kwh at near dead state no? Turns out these c20 batteries aren't so useful when I pull out too much since my peak usage is 750 to 800w. More than 3 times the rated wattage for these batteries.

Anyway, in an attempt to fix this, I contacted Flin (the distributor for this inverter) and they offered 0 support so I set forth to fix these iss

I doubt any supplier will help you out, some might offer to sell you more and/or better batteries, at best. Caveat Emptor as they say in Latin. Lead batteries usually don't want to discharge at more than C5 for short intervals, or C10 for longer intervals. This means 850W for short periods and 400 Watt for longer periods. Even though they are capable of 4800wh, they really don't want to release all of that in one hour (C1), they prefer to do it over 5 hours or longer (C5-C10), and ideally over 20 hours (C20).

59 minutes ago, 9xsolar said:

Multiplus 3000 has another output port that disconnects when the grid is down - so I'm able to add something big, like an air conditioner or a water heater. Will these applications use Solar + Grid in the morning?

That output is fairly useless in an off-grid scenario. The reason why it is there is so that loads that you don't want to discharge the battery can still benefit from the automatic transfer switch in the device. This is especially useful with the Quattro, which has two inputs as well: One for the grid and one for the generator. The second output will be live whenever one of the inputs have power on it. In addition, when you run grid-interactive (ESS, or PowerAssist), loads on the second output can benefit from PV power or battery assistance. The scenario where you would use this is your typical yacht or campervan: Your shore connection can only manage 16 ampere, but you need 20 for short periods to handle the air conditioner. The air conditioner might be on the second output, but the inverter can still do PowerAssist to provide the missing 4 ampere to loads on the second output. Similarly, with ESS (energy storage system), loads on the second output will be powered from PV/battery as long as the grid is there (up to the configured maximum), but once the grid goes out so does the second output.

59 minutes ago, 9xsolar said:

Can I program the Multiplus to take out only X amount of watts from the batteries and take the rest from Grid when Grid is still available?

This is implemented in the CCGX software (called Venus, it's just Linux under the skin). To do this, it must run grid-interactive, what is called ESS mode. You have to carefully check local regulations for the grid-connecting of embedded generators, additional anti-islanding might be required.

Long story short, yes the Multi can do this. I do this in the evening, my Multi only takes 250W from the batteries (ie 10A, around the C20 rate) and the rest from the grid.

1 hour ago, 9xsolar said:

I want to make sure the Muiltiplus does not feedback to the Grid, as I have a digital meter and it spins the same way no matter if you take the energy or give it back. Net metering is not an option at the moment. It's possible to make sure this doesn't happen right?

Yes, two ways. If all the loads are on the inverter output, you configure the CCGX to run "without grid meter" and it will use the internal current sensor in the inverter and avoid feedback. You can also mount a separate current meter, and the software will always adjust the power so it never feeds back. Victron currently uses the Carlo Gavazzi ET112 meter for that, which at 76 Euro is affordable enough. You will need a USB->RS485 cable as well to connect the meter to the CCGX/Rpi.

1 hour ago, 9xsolar said:

Can the inverter be paired with the RPI with an mk3 to usb cable do I need something else? How's the detection like?

The Rpi changes isn't yet fully in the official release (I can help you in the mean time, though it should be done by the time you get there), but there are some changes for automatic detection of hardware that makes this work out of the box. In a full ESS setup, you need the modbus meter (the CG ET112 I referred to above), the RS485 USB cable, one or more vedirect-usb cables (for the BMV and the MPPTs), and the mk3-usb dongle. For a minimal setup you will need at least the mk3 and one vedirect-usb cable (for the BMV).

1 hour ago, 9xsolar said:

Realistically, how much of an overload can I put on this since it can be grid-parallel without affecting the batteries?

In grid interactive mode (aka ESS) you are limited only by the transfer-switch capacity of the inverter. So if you have the 48/3000/35 model, that's 48V, 3000VA, 35 ampere. 35A at 230V is around 8kva. So that would be the limit while the grid is around. Without the grid, you can do 3kva continuous and up to 6kva surge (for about a second).

2 hours ago, plonkster said:

I doubt any supplier will help you out, some might offer to sell you more and/or better batteries, at best. Caveat Emptor as they say in Latin. Lead batteries usually don't want to discharge at more than C5 for short intervals, or C10 for longer intervals. This means 850W for short periods and 400 Watt for longer periods. Even though they are capable of 4800wh, they really don't want to release all of that in one hour (C1), they prefer to do it over 5 hours or longer (C5-C10), and ideally over 20 hours (C20).

Yep, I understand it now. Was quoting the inverter supplier for lack of inverter support though. I was confused when it switches between Grid and Battery as the loads increase within a few hours at best.

 

2 hours ago, plonkster said:

The air conditioner might be on the second output, but the inverter can still do PowerAssist to provide the missing 4 ampere to loads on the second output. Similarly, with ESS (energy storage system), loads on the second output will be powered from PV/battery as long as the grid is there (up to the configured maximum), but once the grid goes out so does the second output.

That's perfect for me, but is there a way to make sure only PV is used and not Battery for something that big of a load? Only on the 2nd output.

 

2 hours ago, plonkster said:

This is implemented in the CCGX software (called Venus, it's just Linux under the skin). To do this, it must run grid-interactive, what is called ESS mode. You have to carefully check local regulations for the grid-connecting of embedded generators, additional anti-islanding might be required.

Long story short, yes the Multi can do this. I do this in the evening, my Multi only takes 250W from the batteries (ie 10A, around the C20 rate) and the rest from the grid.

Yes, two ways. If all the loads are on the inverter output, you configure the CCGX to run "without grid meter" and it will use the internal current sensor in the inverter and avoid feedback. You can also mount a separate current meter, and the software will always adjust the power so it never feeds back. Victron currently uses the Carlo Gavazzi ET112 meter for that, which at 76 Euro is affordable enough. You will need a USB->RS485 cable as well to connect the meter to the CCGX/Rpi.

A bit confused.

If I run under ESS mode, by default, will the inverter Feed-in? If I disable Feed-in through Venus, is that enough to make sure it doesn't really feedback or is the energy meter a requirement nonetheless?

I'm already in the midst of setting it up without the inverter, have 2x VE.Direct to USB for MPPT and BMV. Just need to find a way to power the RPI nearby haha.

Really appreciate your input!

I can sort of answer all the questions together. When the inverter is in ESS mode, the distinction between input and output largely disappears. The transfer switch closes and the input is latched to the output, whatever the inverter pushes back goes to the output as much as the input. If there is a power outage at this point, the transfer switch opens (disconnecting the input from the output) and the inverter drives only the output.

In ESS mode, various algorithms control how much energy it pushes back. The basic idea is that you want to use no grid electricity, as in zero. If there isn't enough PV power, then the difference comes from the batteries (it doesn't care what side of the inverter you have the load connected to, since it doesn't distinguish). The idea is better self-consumption, when there is too little sun, you take the difference from the battery. When there is more sunshine, you recharge the batteries. The whole time it will try to keep the grid at zero. You can however configure an inverter maximum, so that it will only attempt to do this up to a certain maximum.

In order to zero the grid input, it needs to know how much is being imported, and for this it can use one of two methods. One method is an external grid meter, which you mount right after your main switch before any other circuit in the house. This means you can even push energy back to loads that are NOT connected to one of the outputs, but it will still avoid grid feedback by attempting to hit zero at the meter.

But you can also use the internal current sensor inside te inverter. This is on the input side, the Multi cannot distinguish between current on first and second output, only current on the input. If it uses the internal current sensor, the effect would be that nothing is ever fed back from the input.

But you also have to remember that the inverter plays catchup. In a modern home, loads aren't steady, they vary all the time. Both the inverter and the prepaid meter work on a sort of average over a small time window to determine the exact power flow. The result: when the inverter aims for zero, it sort of hovers around it, sometimes pushing back a little, other times drawing a little, more or less evening out at zero. This isn't too much of a problem with dumb meters that can't sense the direction of flow. It is a problem with meters that trip when there is reverse flow.

So one final thing: Currently, in Venus, there is no way to limit the feedback strictly to what is available from PV. There is a long and complex reason for this that has to do with how difficult it is to estimate the amount of available PV. It is not a big problem though. I deal with it my setting a high SoC limit, say 95%, and then also setting a maximum discharge limit of between C10 and C5. So it sometimes discharges the battery a bit to offset the hot water cylinder... and I'm okay with that, that's what self-consumption is about. It will only use the top 5% of the battery... which is negligible.

What should also be clear after this epic I just wrote, is that ESS works much better with Lithium Ion batteries.

I see Plonkster has replied. You are in good hands 9xsolar.

The 24v system was not the issue. The limited batteries with the high evening loads was the gremlin.

But, I am not saying to keep it, you have started to replace it. So I am saying keep in mind the "Wants" vs "Needs" ito the cost of any battery bank if you have access to affordable utilities. Batteries are not cheaper than utilities, keep the bank lean and mean if you can.

As per Plonk above, in my opinion, what he has done is nirvana. Expensive yes, but plug and forget with top of the range equipment that is not only grid tied but has (can be extended) battery backup if utilities go back to being disrupted. 

3 minutes ago, The Terrible Triplett said:

what he has done is nirvana.

Oh I am two expensive steps away from heaven. I need a Lithium battery (working on that) and finally I want to replace the 1600VA inverter with a 3kva. My experience so far shows I will score far more by spending money on good batteries than on a larger inverter. I mean, check this out:

With my small 1.6kva inverter I can offset more than 50% of my consumption, if I add enough PV and battery. With a 3KVA I could likely offset over 80%.

Now THAT Plonkster, makes sense i.e. a solar decision backed by a thorough analysis of your data over time.

And not 5 4 3 because.

Respect.

Ps. Talk to me if you 1600va comes up for sale. Have all the parts bar the Ziehl to do the same as you have done. My 1600VA can become pure off grid to use the Trojans for +-8 years still, with cheap 2nd hand batts on a small Multiplus system.

Hello 9xsolar, 

I am surprised that you didn't get support from Flin as typically they are known to provide good support. I am connected with people at Flin Energy. Can you send by PM your name and serial number of inverter? I will forward the info and get someone from their side to contact you.

fyi, your battery cables seem to be too thin to carry up to 100 Amps current. You are likely having good amounnt of losses with those cables. 

14 hours ago, 9xsolar said:

Nameste from India!

 

Option 1 

• Get Victron Multiplus 3000 48v
• Replace batteries with 4x c10 rated batteries (since the load I take out at peak is 80amps @ 12v divided by 4 gives me 20amps per battery so 4 batteries in 48v rated c10 should be exactly the capacity I need, correct?)
• RPI based CCGX, I don't want to buy the actual CCGX..
• Get HA02, and maybe a desulfator to keep the batteries in shape

 

Option 2

• Get Victron Multiplus 3000 48v
• Get 2 more same batteries - they will still be below my usage requirements since they drop amp hours so badly if I pull more
• RPI based CCGX

 

Option 3

• Keep the Axpert, properly configure ICC to take data from BMV
• Get 2 more same batteries and add them in parallel - attach another HA01 (do these keep things in line when there are different strings involved?)

 

Some Victron specific questions I have :

• Multiplus 3000 has another output port that disconnects when the grid is down - so I'm able to add something big, like an air conditioner or a water heater. Will these applications use Solar + Grid in the morning?
• Can I program the Multiplus to take out only X amount of watts from the batteries and take the rest from Grid when Grid is still available?
• I want to make sure the Muiltiplus does not feedback to the Grid, as I have a digital meter and it spins the same way no matter if you take the energy or give it back. Net metering is not an option at the moment. It's possible to make sure this doesn't happen right?
• Can the inverter be paired with the RPI with an mk3 to usb cable do I need something else? How's the detection like?
• Realistically, how much of an overload can I put on this since it can be grid-parallel without affecting the batteries?

Any other further recommendations is also highly appreciated. Since Victron is involved, I'll page @plonkster and @The Terrible Triplett to be involved in this one big mess of a thread.

Special thanks to Jason @Energy and @plonkster for helping me with the registration!

Morning @9xsolar

You have purchased an independent SCC so you should have solved a weakness of the Axpert, namely its tendency to overshoot. 

Further purchases of inverter hardware is not going solve your dilemma. Batteries unfortunately is where you have to spend your money. Depending on how hard you have used your batteries you may need to purchase 4 batteries and resell the 2 you have as seconds. You need to accurately determine you over night draw and have 200% of that watthour value in batteries (battery string voltage x Ah) This will give you a maximum of a 50% DOD. At discharge levels higher than this your batteries will be very short lived.

Make sure you understand the risks of parallel battery strings (read SuperDIY's guide in the download section).  

40 minutes ago, Chris Hobson said:

Batteries unfortunately is where you have to spend your money.

I tend to agree. I get the feeling he wants to rectify the 24V mistake at the same time, which is a good move if you can afford it. But to do that, you would have to invest in new inverter hardware at the same time.

My gut feeling is also to stick with what you have hardware wise (at least in the short term) and get a better battery, but if you want to buy the batteries so that a future upgrade to 48V is possible, then it's going to mean two strings, which of course is once again not the preferred way. Unfortunately a balancer is not going to fix problems with charge distribution between two parallel strings. It can however buy you a few months of time of you go this way, so I would not write it off immediately.

It all depends on your budget. If you can afford Lithium batteries, even buying a small one now (2kwh) with the option of extending it later could be beneficial, but Li batteries go with complex BMS systems that often use canbus communication and since you already indicated that you want to avoid the cost of the CCGX... you're probably looking at lead acid.

How efficient would this ESS be, if the Grid has terribly bad voltage fluctuations? It's a daily affair that my voltage drops from 230 to 200, then to 170, back to 190 etc... it's a constant nightmare in the evenings.

Lets say, for example, I have setup Venus to do self consumption only upto c10 rating of the batteries, or something like 700w continuous - and we've got the air conditioner running on the 2nd output apart from all the other things that are in the main 1st output.

Will the inverter match the Grid voltage in an attempt to sufficiently provide battery wattage to both of the outputs?

As far as controlling feedback, there is no 'right' way to do it, so it can work with either the internal sensor or the external meter, right? Just trying to make sure I understand things correctly.

6 hours ago, flltech said:

Hello 9xsolar, 

I am surprised that you didn't get support from Flin as typically they are known to provide good support. I am connected with people at Flin Energy. Can you send by PM your name and serial number of inverter? I will forward the info and get someone from their side to contact you.

Appreciate your gesture, but I feel like it's a little too late since I've already fixed 80% of the problem with the Axpert. I was only getting 600w out of my 1500w worth of panels. The addition of Victron MPPT seems to have solved that. It might just be PWM... who knows.

The other problem is the lack of battery SOC, which the BMV is there for, and with some proper configuration, I could get the ICC software to work alongside. The only issue I have now is the batteries are not rated for my usage, which is sad.

6 hours ago, flltech said:

fyi, your battery cables seem to be too thin to carry up to 100 Amps current. You are likely having good amount of losses with those cables. 

I'd like more feedback on this please. That's 25 sq.mm cable there as recommended by Flin, for this 24v system. When I measure solar input with what's being used on inverter + going into batteries, there's atleast 60w to 80w worth of difference. I thought these were DC to AC losses.

What's the correct cable in my case?

3 hours ago, Chris Hobson said:

Morning @9xsolar

You have purchased an independent SCC so you should have solved a weakness of the Axpert, namely its tendency to overshoot. 

Further purchases of inverter hardware is not going solve your dilemma. Batteries unfortunately is where you have to spend your money. Depending on how hard you have used your batteries you may need to purchase 4 batteries and resell the 2 you have as seconds. You need to accurately determine you over night draw and have 200% of that watthour value in batteries (battery string voltage x Ah) This will give you a maximum of a 50% DOD. At discharge levels higher than this your batteries will be very short lived.

Make sure you understand the risks of parallel battery strings (read SuperDIY's guide in the download section).  

Thank you @Chris Hobson

If I do the maths right, is this the way forward?

My peak usage is around 750w to 800w, sometimes it's continuous like this for an hour. Other times it's less than half of that, so around 400w to 450w. For clarity sake, let's say my usage is 80A DC in 12V continous - that should be around 960w (keeping in mind the DC>AC losses). 

4x 200AH C10 rated batteries (i.e 20A over 10h each) - this should technically give me 4kwh of usable power, considering 50% DOD, and well within the battery's rated specs. Is that correct?

It would be difficult for me to get larger batteries, since larger ones come only in 2V and that means too many of them.

3 hours ago, plonkster said:

I tend to agree. I get the feeling he wants to rectify the 24V mistake at the same time, which is a good move if you can afford it. But to do that, you would have to invest in new inverter hardware at the same time.

My gut feeling is also to stick with what you have hardware wise (at least in the short term) and get a better battery, but if you want to buy the batteries so that a future upgrade to 48V is possible, then it's going to mean two strings, which of course is once again not the preferred way. Unfortunately a balancer is not going to fix problems with charge distribution between two parallel strings. It can however buy you a few months of time of you go this way, so I would not write it off immediately.

Yes, I really want to fix this 24v since the batteries don't meet my specs. Shame on me for not figuring this out at first, but sooner or later I gotta fix this. On the other side, If I were to just buy better batteries, keeping the same inverter, I gotta find 400ah 6v batteries. I don't know if anyone here makes them.

That way, I don't need to upgrade the inverter and can stick with ICC.

Otherwise, adding another pair as parallel means sticking new batteries with old.. on top of being parallel. I don't know when things will go wrong since all I read here is parallel is bad

3 hours ago, plonkster said:

It all depends on your budget. If you can afford Lithium batteries, even buying a small one now (2kwh) with the option of extending it later could be beneficial, but Li batteries go with complex BMS systems that often use canbus communication and since you already indicated that you want to avoid the cost of the CCGX... you're probably looking at lead acid.

Yeah, lithium is way too expensive for me right now. In comparison, 4kwh 'lead acid @ 50% DOD' would cost me around 60K while '2.2kwh @ 80% DOD' will cost me 150k. More than twice for half of what I could potentially get. But, I understand this isn't apples to apples comparison.

Let's just say, I want to go lithium and get 1 pack of 48v - single battery of 2kwh. If I were to extend this down the line, that means paralleling, and isn't that kind of bad?

There's a car manufacturer here (Mahindra I believe) that uses 48v 220ah lithium battery in one of their cars. The cost of that brand new would be around 250k. Since it's a pack for a car, I would assume it comes with all the electronics that manages the charging right? Would something like that be suitable?

1 minute ago, 9xsolar said:

How efficient would this ESS be, if the Grid has terribly bad voltage fluctuations? It's a daily affair that my voltage drops from 230 to 200, then to 170, back to 190 etc... it's a constant nightmare in the evenings.

Okay, bit of background theory. A grid-tied inverter is not supposed to do voltage control. It merely injects current into the existing power network. When running ESS, the inverter runs grid-tied and will follow the grid voltage. It will however disconnect and go into invert mode if the voltages go out of the configured range.

Additionally, sudden changes in voltage or frequency are seen as islanding events and the inverter might disconnect based on those grounds too. Whenever it does this, it will drop output 2.

Fwiw, all grid-tied inverters will have this problem. ESS really isn't suitable for a bad grid, for that it would be better to run off the grid.

Another way is to run with grid-fallback: You run purely from battery and/or PV, but if there is a large load, you drop back to the grid (if available). The multi can switch back to the grid in under a second. As explained earlier, a 3kva multi can surge up to 6kva for a second, which means this setup should work fine up to 6kva. In addition, you need no anti-islanding measures, because you're not running grid-tied.

10 minutes ago, 9xsolar said:

It would be difficult for me to get larger batteries, since larger ones come only in 2V and that means too many of them.

Trojan L16RE-B is 370Ah, 6V. There is a 420Ah model as well, but that one has shorter cycle life if I recall. For the most part you are right though: Above 200Ah the denominations become smaller and the options fewer.

12 minutes ago, 9xsolar said:

There's a car manufacturer here (Mahindra I believe) that uses 48v 220ah lithium battery in one of their cars. The cost of that brand new would be around 250k. Since it's a pack for a car, I would assume it comes with all the electronics that manages the charging right? Would something like that be suitable?

Is that as in two and a half Lakh as you guys say? Cause that's 50k ZAR which is cheap compared to what we'd pay for that. We'd pay up to 100k ZAR for a 10Kwh battery like that.

I know Mahindra well. They sell the pick-up trucks here, called the Scorpio and the Bolero. And there is an old Jeep-like one as well, of which there is a joke: It has a top speed of 120km/h... straight down a mineshaft. I think it has an old Peugeot Diesel engine in it :-)

Aaanyway, back to the battery: The pack itself usually has some kind of internal cell balancing, either active or passive, but usually it also needs to talk to the external charger or load to communicate certain critical conditions. If any of the cells in the pack is critically low, it has to notify the inverter to shut down to prevent damage to that cell. Similarly, if any cell is too high, it has to let the charger know to stop charging to prevent damage to that cell. For this reason, there is usually a layer of communication between the pack and the outside world. There are of course simple ways of doing this, which involves a large contactor/relay which simply disconnects it. Point is, your inverter has none of that functionality, it would have to be built/developed for it. In the car, this management is likely incorporated into the computer systems of the car.

It's still an exceptional price, if it is 250k INR!

There's two guys on Youtube who does that kind of thing. The one is named "DIY Tesla PowerWall" and the other is called "jehugarcia". They build their own packs from cells and make videos about it.

28 minutes ago, plonkster said:

Okay, bit of background theory. A grid-tied inverter is not supposed to do voltage control. It merely injects current into the existing power network. When running ESS, the inverter runs grid-tied and will follow the grid voltage. It will however disconnect and go into invert mode if the voltages go out of the configured range.

Additionally, sudden changes in voltage or frequency are seen as islanding events and the inverter might disconnect based on those grounds too. Whenever it does this, it will drop output 2.

Fwiw, all grid-tied inverters will have this problem. ESS really isn't suitable for a bad grid, for that it would be better to run off the grid.

Ouch, that means more problem for me, haha. Let me explain what I'm trying to do with Victron inverter, maybe there's something else other than ESS and is not grid-tied that could help?

Right now, most of our usage is at night, and the batteries reach float at 10, 10:30ish in the morning. Our morning usage is OKish, but I would really like to use up 100% of whatever solar I could manage. I thought running some of the Aircon loads will help with that, apart from keeping the batteries topped up for night usage. Here's my generation pattern so far..

 

It should be able to generate close to 7 or even more, but I'm missing out on it as there's no additional load.

Additionally, the voltage fluctuations only happen at the evening when there is no solar, so part of ESS could still help? All I want is to utilize the most of sun. 

28 minutes ago, plonkster said:

Another way is to run with grid-fallback: You run purely from battery and/or PV, but if there is a large load, you drop back to the grid (if available). The multi can switch back to the grid in under a second. As explained earlier, a 3kva multi can surge up to 6kva for a second, which means this setup should work fine up to 6kva. In addition, you need no anti-islanding measures, because you're not running grid-tied.

Can it run like hybrid instead? For example, there's 700w of power on the main output, and 1kw of power on the secondary output (i.e aircon) - it can supply the 700w with solar, and whatever else solar has left to offer for the 1kw and topup the rest with Grid.

28 minutes ago, plonkster said:

Is that as in two and a half Lakh as you guys say? Cause that's 50k ZAR which is cheap compared to what we'd pay for that. We'd pay up to 100k ZAR for a 10Kwh battery like that.

I know Mahindra well. They sell the pick-up trucks here, called the Scorpio and the Bolero. And there is an old Jeep-like one as well, of which there is a joke: It has a top speed of 120km/h... straight down a mineshaft. I think it has an old Peugeot Diesel engine in it :-)

Haha, yeah, same Mahindra. Scorpio and Bolero

250K is the sticker price for their customers, I did not ask it in more detail but it's definitely in that range.

I've also been following the powerwall scene and 18650's... but even that is expensive if I can't find used batteries, and I'd rather go with new ones. I even mastered a grand plan to buy lots of Xiaomi power banks that come with LG 3500mah 18650's. But the cost of it turned out to be more or less same with what manufacturers demand for a new pack... lol. Flawed plan.

8 minutes ago, 9xsolar said:

Can it run like hybrid instead? For example, there's 700w of power on the main output, and 1kw of power on the secondary output (i.e aircon) - it can supply the 700w with solar, and whatever else solar has left to offer for the 1kw and topup the rest with Grid.

When running grid-fallback it can't run as a hybrid, unfortunately.

Watch the ESS webinar to get more info on that.

Nice webinar, I really like the ESS mode, but with grid not being stable, there's no other alternative right? If I don't run ESS, will the 2nd output act just like a Grid while the main output acts as Off-grid and run only on battery/PV?

At least with this I might be able to measure how much energy the aircon drinks I guess.

2 hours ago, 9xsolar said:

the 2nd output act just like a Grid

The second output is connected to the inverter output while the grid is available. It might as well be connected directly to the grid.

There's a heap of things to explain here, for example in the inverter programming (this is on the inverter itself, no CCGX required) you can configure it to ignore the ac input, to pretend it is not there. In some setups we use this to force the inverter to run from PV/batteries, for example, we might configure it so that it uses the battery down to a specific depth of discharge, or as long as the load stays below some limit. I'm mentioning this only to point out that even in this case, where the grid is available but you force self-consumption, it will still take output 2 down (as far as I know). So literally output 2 is only on when the grid is on, which I pointed out earlier isn't incredibly useful outside the use case it is designed for: PowerAssist.

PowerAssist was a Victron first, as I explained, that helps a boat/yacht/barge or RV that's stuck in some backwater harbour/caravan park with a weak AC supply by extracting the difference from the batteries. It will do PowerAssist even for loads on output 2. But PowerAssist is where you help a weak grid with the batteries. What you want to do is help the batteries with the grid, but your grid connection appears to be unstable (rather than weak).

On my inverter I only have one output, and I don't miss the other one at all. Cause this ain't a boat. Well... in a good rainy year the earth gets so soggy that I sometimes joke and say the house floats on a pool of thick mud... but other than that, it is not a boat :-)

I'm starting to realize the 2nd output isn't what I imagined it would be, not even close to a rainbow that would've extracted all of the sunshine. In retrospect, I doubt I'd need 2400w worth of an inverter for loads less than 1000w.

If I still want to go towards 48v, the Multiplus 3000 is the bare minimum. If not, I'm starting to think 24v isn't such a bad idea in itself, but lower capacity battery definitely is.

Coming back to the options I'm thinking about now..

• Multiplus 48/3000 in off-grid. Can experiment with ESS and voltage fluctuations, but mainly off-grid with 4 batteries.
• Multiplus, something like 24/2000 and continue with the same batteries for a few more months, but using proper battery discharge wattage and rely on grid under ESS. This means I could kiss 48v good bye and when upgrading the batteries, can go for 6v higher capacity ones... if they exist here and stay 24v.
• Multiplus, something like 24/1600 and same as above....
• Multiplus, something like 24/1600 and upgrade to a lithium battery (albeit lower capacity... sigh) cos $$ saved on not buying a 3000.

My head's gonna explode

7 hours ago, 9xsolar said:

I don't know if anyone here makes them.

Trojan, batteries we like, is also available in  India.

http://tools.trojanbattery.com/dealers.aspx

 

 

What's your use case. What problem are you trying to solve? That's what I like about the ESS webinar, it starts out right there with the different systems, 1) No grid available, 2) grid available but unstable, 3) stable grid available but frequent failures, 4) stable grid. ESS works well with the last two options, which is where South Africa is in most areas.

You'll have to make a call based on what percentage of the day the grid is unstable. If it only does so in peak times, for example, a few hours a day, then maybe it will work?

Time to collect more data, me thinks? Get the CG ET112 meter so long, with the RS485 cable and let an Rpi running Venus log your grid values for you. Then you get frequency, voltage and consumption values :-)

Hoping to get the RPI up and running soon.

Is it advisable or even possible to have a voltage stablizer in between the Multi and Grid?

2 hours ago, 9xsolar said:

Is it advisable or even possible to have a voltage stablizer in between the Multi and Grid?

What would such a thing look like? :-)

Uhm, not sure if that's sarcasm or not, but there are voltage stablizers for air conditioners that handle more than 1kw easily. And since I only have loads upto that much, it would make sense to connect the inverter to the output of the stablizer, and input of the stablizer to Grid.

Something like this :

1 hour ago, 9xsolar said:

sarcasm

No it wasn't. Other than an online UPS, I am not aware of something that can just lift the voltage and make it all clean. Thanks for the picture, always good to know what people are up to.

1 hour ago, 9xsolar said:

voltage stablizers

Looks like a buck/boost arrangement with a transformer and multiple taps to raise/lower the voltage. Can't say how it would work, I think when it switches the inverter will see it as an islanding event and disconnect for 60 seconds (depending on configuration), so it's not going to be plain sailing. I'm really not familiar with this kind of setup to be honest.

Alright, I'm finally finalizing on these things >

• Multiplus 1600 24v 40/16
• Continue with same batteries with ESS set to discharge wattage of 200w (20amps?) - if the need to upgrade arises, I can go for 6v batteries

Some last minute questions...

• Doess the MPPT 150/70 have an upper limit of 2000w under 24v? Would it hamper upgrade ability down the line?
• Is the energy meter really required? I don't want to spend more if the Multiplus can indeed take care of not feeding-in on its own. However, if not, will get it. 
• Will 1600 version be enough to be able to overload it with, say total of 1700w when it's grid parallel under ESS?

Just a bit confused about the energy meter so far.