diy solar

diy solar

Schneider system design wasteland......no one knows anything.....

Nicely done. I had FLA for 25 years, kept the lights on, but I don't miss them one bit.My last set of Trojan L-16s are now in the well shed, driving an old Trace SW and my 240v pump.
Using refurbished BYDs and new Gyll 200s for the house now. LFP (carefully wired/installed) are a robust solution. And more affordable all the time. Best.
 
Yes, Hydrogen is very corrosive!
The batteries are inside a LEXAN box, with a fan creating positive pressure into the box.
A vent to the outside allows the gas to escape w/o incident!

Hydrogen, not so much (although it can embrittle steel containment vessels, not that you have any here.)
It is the sulfuric acid I would worry about.

I would do negative pressure, not positive pressure.
 
With AC coupling, if your inverter does what mine does, the additional PV on AC will be used to charge batteries if and only if necessary to hit target charge current. DC coupled PV normally dumps all it can onto the battery cables (although Victron with a battery shunt can regulate it.)

Ideal is to charge battery at a constant optimum rate, and vary power harvested from PV to maintain that and supply loads.

Micro inverters are an option. String inverters are another. Lots of used and new-old-stock units out there, just need to set parameters for "offgrid" or frequency-watts. I've been able to buy Sunny Boys for about $0.10/watt. Your selections may be more limited if you are required to have "Rule 21" or similar.
 
The Schneider XW-MPPT has an option to limit the DC output current to a % of the max. With a big array, I do that to manage the charging current into FLA. Once the battery current drops below the max CC output (dependent on amount of sun or the current limit) the CC will increase its output as necessary to hold the target battery voltage. You can see that happen in the attached plots at around 12:30PM. No extra shunt is required. The XW inverter/charger has the same option to limit max charge rate.
PV_AC_Summary.png
BatterySummary.png
We tend to get wild PV output fluctuations on partly cloudy days like the one around 10:30am in the plot.
I'm looking forward to the transition to LiFePO4 batteries later this fall. I don't have pvdude's sweet watering setup so I'm looking forward to avoiding that task.
 
I might be a little concerned with lead-acid cells under inverters if inverters are pulling air through them. I worked for inverter company and have seen first hand how caustic atmospheres can destroy PCBs. Otherwise looks great!
OK who did you work for? spill the beans and give us real data in regards to inverters....
 
OK who did you work for? spill the beans and give us real data in regards to inverters....
I worked for Parametrics/ABB, TB Woods, and AC Technology/Lenze. These were all 3 phase inverters for motors. Very much like what use to run the house, except no output filters. Raw PWM goes to the motor windings and the motor inductance is what filters the current into reasonably sinusoidal. did inverters for 30 years. Last 10 spent doing converters and batteries for military and aerospace.
 
I worked for Parametrics/ABB, TB Woods, and AC Technology/Lenze. These were all 3 phase inverters for motors. Very much like what use to run the house, except no output filters. Raw PWM goes to the motor windings and the motor inductance is what filters the current into reasonably sinusoidal. did inverters for 30 years. Last 10 spent doing converters and batteries for military and aerospace.
OK, I am not worthy... just a loose foot soldier slinging his sword at passing idiots... So what can i do to make things better? I was strangely enough looking at cheap Chinese inverters out of annoyance at magnum, outgback zantrex and schneider.
 
OK, I am not worthy... just a loose foot soldier slinging his sword at passing idiots... So what can i do to make things better? I was strangely enough looking at cheap Chinese inverters out of annoyance at magnum, outgback zantrex and schneider.
I really can't advise on what to buy. I was running Aims but took a lightning strike. Replacing with a Growatt.
 
Thanks to GVSolar for the links to the Schneider AC coupling docs!
AC coupling now makes more sense.
Still seems bizarre to imagine connecting two separate AC sources together and nothing explodes.

However, back in ancient times, we had two 24 cylinder quad turbo-Diesels powering a facility.
Output of a zillion watts went into a giant Square-D synchronizer, all 1970 technology, worked great.
Ok, now there is software for that.

Anyway, it looks like I need to stay w/ DC coupled, as this is off-grid, and I already have invested in DC coupled equipment.
So unless there is some other compelling reason, I will continue to expand this system to it’s limits,
within the DC coupled model.
 
If your battery inverter supports AC coupling, should be easy to add a GT PV inverter that works with it. GT means it synchronizes to AC line (your inverter) and adds current while following voltage.
That should mix-n-match with your existing DC coupled equipment, can be economical, and adds AC output power.
e.g. you might find a Sunny Boy 5000US for $500, $0.10/watt. It would probably get two strings of PV panels (small gauge wire, no fuses needed), and add up to 5000W to available AC during the day.
Even new model GT inverters may cost only a bit more than another Conext XW MPPT 100-600, and deliver additional AC at higher efficiency (compared to PV --> 48VDC --> AC)

Your XW Pro is an inverter/charger, it already will draw AC from grid or generator input as needed to charge batteries. With GT inverter on its output, it will draw from there.
The additional feature to support AC coupling is that it will raise frequency above 60 Hz to say when it wants less. Mine settles somewhere between 61 Hz and 62 Hz, to get something between 100% and 0% of available PV converted to AC.

If your inverter + SCC already commands SCC to reduce output as needed to regulate charge current, you would also be fine with just DC. If your inverter does this without a battery shunt, it may be the inverter measures its own battery current and communicates with SCC for its battery current, and adds them together. So if for instance you programmed 40A max charge current, if inverter was consuming 10A it would have SCC deliver 50A, leaving 40A for the battery. This would only work without unmonitored currents like additional loads. (My SMA system can work without a shunt if only DC coupled SCC like Midnight Classic that it talks to, or with shunt for arbitrary sources and loads.)

With a lead-acid battery, there is a preferred charge rate. My AGM do want at least 0.2C, otherwise need longer absorption time. FLA may want 0.12C.
When you put in LiFePO4, it will probably accept 0.5C maximum, but only around 25 degrees C. BMS should implement low-temperature charge cutout, perhaps at zero degrees C. However, 0.5C charge rate is too high when cold, needs to be something like 0.1C or 0.15C down around 10 degrees C.

I haven't heard of BMS or SCC that adjust charge current according to temperature. What I would do is program SCC/inverter for a maximum charge current of perhaps 0.15C or 0.25C, and set a higher temperature charge cutout compatible with that current.

You want all available PV harvested by SCC (or GT PV inverter) and delivered to AC loads, while regulating battery current to what is desired. Most systems with separate DC coupled SCC can't do that, but apparently Conext can. Victron can do it with a battery shunt and controller (should work with any inverter.) Hybrids should do it because they contain both SCC an inverter, can measure battery current. AC coupling can do it because inverter/charger knows battery current.
 
You want all available PV harvested by SCC (or GT PV inverter) and delivered to AC loads, while regulating battery current to what is desired. Most systems with separate DC coupled SCC can't do that, but apparently Conext can.
Just to be clear, it might, but I'm not saying that the Conext system can do this. The XW-MPPT60 SCC delivers power to maintain the desired voltage settings for bulk / absorb / float. The hardware / firmware I have does not independently regulate battery current although you can set an overall current limit. This would also limit the current available to the inverter. If the inverter draws more than the PV output the voltage will drop so battery charging current will decrease. At some point, battery capacity will be used to make up the difference.

The Conext battery monitor has an external battery shunt, but I have not seen an option where the XW-MPPT60 SCC uses that data to independently regulate the charging current. Not sure about the latest hardware and firmware.

Adding a lot more panels and pushing the possible charge current well over 100A on a 445AH battery bank during bulk charging seems risky to me.
 
If you connected a generator, would XW Pro convert just enough power from AC to DC so that, when combined with current from Conext SCC the battery charge current would hit target value?

If so, AC coupling should perform the same. Then there could be 5kW DC coupled PV and 5kW AC coupled PV, while limiting battery charging to no more than 5kW regardless of SoC. The additional 5kW from AC coupled would be available for loads.
 
Based on the Schneider documents provided in post #16 by GVSolar, Schneider does not want a generator connected at the same time AC coupling is active.

My system has no grid or generator connection. I wanted to connect the generator, but the Schneider XW Pro
relay only handles 60A from the generator connection, any my generator outputs 90A.
 
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That shouldn't be a problem, so long as you don't connect an AC load that draws more than 60A.

You could connect it through a fuse/breaker. Maybe that would be sufficient protection - is it just a relay and PCB traces? A short term overload, including surge to start a motor, is probably OK. Fuse blows after a long delay at moderate overload.

My Sunny Island measures AC current, and if over 56A (or whatever has been programmed), it will invert from battery to limit input current. It will also open the relay to protect against overcurrent. In a grid-tie system, we have to limit AC coupled PV wattage so 56A won't be exceeded.
 
If you connected a generator, would XW Pro convert just enough power from AC to DC so that, when combined with current from Conext SCC the battery charge current would hit target value?
Based on my older XW6048 and MPPT60s, when the generator starts, the XW charger current is added to the SCC charger current. Adjusting the charge voltage target controls the interaction. For example, if the generator is running and the XW6048 is in bulk charge at 61.0V, unless the SCC is charging to a higher voltage its current will drop depending on the difference in voltage. If the XW charger and SCC voltage are both set to 61.0V and the batteries are only at 56.0V, the currents will add to try and force 61.0V. Excitement may follow ;-)
 
My system has no grid or generator connection. I wanted to connect the generator, but the Schneider XW Pro
relay only handles 60A from the generator connection, any my generator outputs 90A.
It seems like you could wire up the generator with a 40A 240V breaker as a failsafe then adjust the XW Pro AC settings and Charger settings to limit how much it pulls from the generator. That would let you charge at up to 6kW with another 3.6kW pass through. You could open a ticket with Schneider to verify this approach. They are slow sometimes but have answered my recent questions.

When my 9kW generator runs, the XW6048 will pull 7-8kW from it with 6kW going to the charger and the balance passed through to loads. I set the input current limit a little lower than max since starting a large motor (cabinet saw) when running at full charge slows the generator enough to push it out of spec. This makes the inverter drop the generator until it re-qualifies the incoming AC.

Here are the XW setting options. You can specify the input breaker and also the max charging current. My generator is on AC2 and there is no grid input on AC1. There is a 50A breaker at the generator and the input limit is set a little lower at 45A.
 

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Based on the Schneider documents provided in post #16 by GVSolar, Schneider does not want a generator connected at the same time AC coupling is active.

My system has no grid or generator connection. I wanted to connect the generator, but the Schneider XW Pro
relay only handles 60A from the generator connection, any my generator outputs 90A.
True. I use my generator very occasionally - so I leave the SW gen input disconnected by default. That way, I can be ac coupled by default. When I wish to charge with a genny, I first disconnect the ac couple input - then connect the genny input breaker. Truth be known, with the additional AC coupled input, I haven't had to genny charge my batteries in over a year. Easy to set up the disconnect.
I do have to remember to start the genny from time to time, or it will get persnickety and won't start (don't ask me how I know that).
I used to start it more often to pump water to my gravity fed tank, but I now I mostly do that with used panels/tracker and an old Trace inverter. Works great.
 
FYI: Combox graphic of intermittent clouds & sun. Running mini-split AC, window AC, and charging car (110v charger). AC & DC coupled - Schneider SCC's and SW4024 playing nice together.
Screen Shot 2021-09-09.png
 
I think you seriously underestimate the ability for air and it's contaminants to leave a non glanded cable entry/exit point,, ESPECIALLY when you've pressurized it....
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I don't have a photo of all the silicone sealant that was used everywhere (like cable openings), but I did try to deal w/ all those leaks!
 
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