To Charge or not to charge
Bobodude Registered Users Posts: 12 ✭✭
I am sure this situation has raised it's ugly head before but I have searched the site and have not found a satisfactory answer to my delema. I am putting in my own grid tie system with a Xantrex sw4048 inverter and a Outback FM80 charge contoller. My quandry is how to program the SW4048 not to charge and let the FM80 handle the charging? Do I just put the setpoints on the SW at a high point out of the range of normal charging for my 48v bank of Lifeline AGM's? I don't see any way to disable the charge function in the SW inverter. Does anyone out there have this same setup? A list of setpoint settings would be greatly appreciated.
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Are you sure it's an SW series and not an XW series inverter? I understood that the SW series is no longer produced, and never did meet grid tie application UL 1741 requirements. I have an SW4048 and it came with a grid tie interface separate from the inverter (never used....off grid).
To answer your question, I think you would have to have the inverter in SELL mode, not FLOAT mode. The owner's manual lays it all out quite understandably at any rate.
I think there are different versions of the SW too--You need the right manual/software interface information too (as I remember?).
I bought a Trace power panel in 2007 and installed it on a wall in the rear garage of a new house I built, but I ran out of money to finish the install so it has been bypassed ever since. It is a new SW4048, has never been turned on, waiting for better times. I know it is obsolete but it is certfied with the GTI and I can hook up to the grid here in Nevada. I just wanted to use the Outback FX80 due to the high pv voltage I need to feed the 80 plus feet distance from the panels to the house. I will puruse the manual again to check the "sell" mode details. I think I was trying to understand how the inverter and the charge controller will interact and not fight each other.
The FM80 has a lot of flexibility. Probably more so than the SW. I'd suggest setting up the SW as it needs to be for sell-back and adjust the FM80 accordingly. You may have to put the Float Voltage up higher than normal to maintain 'sell'.
I have a similar setup with a SW4024 with MX60 charge controller. You will need to set the FX80 to around 1 volt higher then the SW float voltage. My Fork Lift batteries call for 28 volts float, so I have my MX set to 28.8 and my SW set to 27.6. The float voltage will bounce around 28 volts and the MX will stay in MPPT mode. Even with temp comp on both MX and SX I still need to lower the SX's float voltage during the winter to around 27.2 to keep the MX60 from going to float which you don't want. It is just somewhat of a balancing act which depends on temp and array size.
when I had my sw hooked up to grid, I would set the charge voltage and float voltage 1-2 volts below what the charge controller was set at
I would also , just to make sure I wasnt using grid to charge, lower the charge amps
menu starts on page 33 of the manual, or page 55 of the pdf
also try this first ...menu 11 grid ac1 amps set to zero, that will cause your inverter to not use grid voltage and only sell back if the sell mode is on, if you have a separate main breaker box that the inverter supplies, you wont be able to do this
sorry about the link to a competitor....it had the manual I was looking for
Not a problem for the purpose. The information is appreciated.
Here is the SW manual from the "discontinued products" section of the Xantrex website.
(I've always recommended it as an "Idiot's Guide" to solar/battery systems.)
The SW was/is quite a piece of work. (I mean that in a good way)8)
Things you should know about the SW when you decide on your settings for grid tie:
- The Menu 11 "Set Grid (AC1) amps AC" determines the maximum current the inverter will allow to be drawn from the grid.
- The Menu 10 "Set Max Charge amps AC" determines the maximum charger AC current (not the DC current) The DC current will be diffferent based on battery voltage.
If the batteries are charging via the AC source and the combined total of the AC charging current and the AC Load current reach the "Set Grid (AC1) amps AC" setting, the charger will back-off and prioritize the Loads.
If, while the grid is connected, the AC loads exceede the "Set Grid (AC1) amps AC" setting, the inverter will "assist" by providing additional power to the loads from the battery. This can make it so that the AC Load output can have a higher potential current than the AC input connection.
- The Menu 17 "Set Battery Sell volts DC" setting is independent of "Set Grid (AC1) amps AC" and of "Set Max Charge amps AC" and it is NOT affected by temperature compensation.
- The Menu 10 "Set Float volts DC" setting is affected by tempurature compensation and it is independent of the "Set Battery Sell volts DC".
You can set the "Set Float volts DC" setting to an appropriate "at rest" battery voltage and minimize charging from the grid. As the sun comes up and brings the battery voltage up, the "Set Battery Sell volts DC" setting will become a daily "float" voltage setting for the batteries. (Not Temp comp'd)
If you want your batteries to receive a bulk charge you can use the green "GEN MENU" button. From the manual- "If you are battery charging - in FLOAT charge - from the utility or a manually controlled generator, you may initiate another BULK charge by moving the cursor through EQ."
Lower left corner of the SW control panel:
Attachment not found.
Watch out if you ever get the error message "I'm sorry, Alex; I'm afraid I can't do that."
I often find myself singing "Daisy Bell" when I shut down SWs.:roll::D:blush:
I've looked at my SW4048 for almost 8 years, daily, and I never noticed that in the corner. Someone was a Stanley Kubrick fan. boB? Robin?
"I'm sorry Ralph, I can't do that" (quote from my inverter's imaginary dialogue with me when I want it to do something) Now I know why!
I knew there were a few sw owners out there. Thanks all for the input. I have to find a real quiet corner of the house and imerse myself in the sw manual to understand all of it's settings. I just want to keep the batteries in full charge and sell the rest. We are hung out on the end of a 12kv feeder that is 19 miles from the sub bkr and we get hit with outages on a regular basis. We had 3 outages last yr lasting over 8 hrs each. Thats the price you pay for living in paradise.
Just another thought:
Your inverter is a bit small for your (21) 255 watt PV modules.
Your SW4048 only has a back feed power rating of 3211 watts with 90.5% efficiency.
Your inverter may not always "keep up" with being able to sell all of your PV. This will sometimes cause your battery voltage to rise above the inverter's sell voltage setting. This can cause the FM80 charge controller to go into Absorb, and possibly to float, and start regulating PV current for the rest of the day. Be sure the FM80's float settings are higher than the inverter's (non temp comp'd) sell voltage. The FM80 will not stop absorb charging based on amps if >3kW is selling. It will stop on on amps if the grid is out. You may want to set the minimum absorb time to 90 minutes. The FM80 still may reach float on cool sunny days. I don't think you can avoid this except by doing a manual "force bulk" once you pass the high solar power production part of the day. (ie. after 2: pm +/-)
The logs in the FM80 record absorption and float times, max and min battery voltage for the last >180 days. You can look back and see how well your settings are working.
Yes I have a bit of excess pv but I figured it was easier to install more panels than I need now then going back later. I also would hit max sell earlier in the day to make up for loss in the late afternoon as the sun goes down behind mountains close to me in the west at around 5 pm in mid summer. Please correct me if I'm wrong but the FX80 should baseline out at 80 amps and back off the excess. Down the road I will swap out the 4048 after it's useful life and install one that will be able handle all the installed pv plus a bit more. I think the output watts has got to be more than 3211. It's rated for 33 amps out X 120v = 3960 ? Fm80 max out = 80 x 48 =3840. Maybe during bulk charge of the bats but with full bats where is the extra amps going? I guess I am not looking at this in realistic mode but hopeful mode.
The link has the weighted inverter output ratings for every (CA) approved grid tie inverter. These ratings are based on lab tests "performed by a Nationally Recognized Testing Laboratory in accordance with the protocols adopted by the Energy Commission." As I understand it, these standards have been adopted by all other US jurisdictions.
Near the top of the page is a link to the Performance Test Results for the approved inverters. Here is the summary for the SW4048:
It shows the actual tested performance and the efficiency at different power levels.
If you look at the spec sheets for many battery inverters it shows the maximum AC output rating. Unfortunately this is not necessarily the continuous rated "Sell" rating. Keep in mind that your FM80 can put out 80 amps of PV power at the actual battery voltage. If your inverter is set to sell at 53.6vdc (default), 80 amps from the charge controller will be 4288 watts. More than a kW over the tested sell rating of your inverter.
If you look at it as 3211w (Tested inverter sell rating)
Divided by the "Sell" volts 53.6
Your max battery sell amps = 59.9 amps
If you have trouble with your FM80 charge controller shutting down with "Batt Full" in the lower right corner of the display, you can probably fix this by setting the max charging amps to 60 in the FM80. You will still get a lot of use out of the extra PV (5355 watts STC). You will have your full 60 amps earlier/later in the day, and you will have better output in poor conditions.
Thanks Alex. Your apparent extensive knowledge is appreciated. The first link is a 404 but the second is ok. Yes I see the facts. Test results don't lie. I was not aware of these test results. You think you have bought 4kw but the fine print always gets ya. I defineatly have to babysit the system closely for a while to fine tune. I am going to use the RH Engineering package to monitor the inverter and log it's readings to better understand whats going on. I am presently waiting for word on our state's incentive program details but from what I have heard from others who have gone thru the ringer, it is almost not worth it. The restrictions are pretty heavy including an extra revenue meter before any load taps and C2 electrician install. That leaves us DIY in the cold. But if you just go the net metering, the AHJ signed off permit is acceptable. Go figure.