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Combining Solar Systems?

Ferretman

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Joined
Feb 6, 2021
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6
Howdy:

So here's my situation. I have a good sized Outback-based system right now...three FX-80 charge controllers, two 4000W inverters, 36 Conergy 230W solar panels on three rows of ground mounts, 24 Outback 2700RE batteries (for a 48V system). The inverter runs 240V down to the house where it's split as needed around the house.

I'd like to add the newer solar panels (350W+) but that would necessarily require adding more charge controllers given the amperage involved. This isn't impossible...I've got the wall space....but I wanted to see if there was an option.

Could I instead install a new row of panels, tie them into a charge controller or two that can handle the higher amperage, feeding a separate battery bank? Could I connect this battery bank to the same (existing) inverters so everything basically simple has a bigger reservoir of power overall? How would the inverters handle the separate battery bank inputs....as a second string I presume?

Looking for some thoughts here...anybody here had experience doing something similar?

Thanks muchness!


Steven
 
Welcome to the forum.

First, when you have two batteries connected to the same thing (your charge controllers, inverters), they are connected to each other, so you can't think of them as "a separate battery bank." I don't see any logical reason or benefit to your imagined solution.

36 * 230W = 8280W - your current solar.

8280W/48V = 172.5A - already more the your FM80s can handle, so any added solar is beyond that which you can capture.

2700RE cells are 2228Ah with a maximum charge current of 500A. FLA/AGM/GEL batteries perform best (longevity-wise) with a target charge current of around 10-15% of the C20 rate. In your case, that's 229 - 343A. You are well under this and would best be served by adding some solar capacity AND another charge controller.

In other words, your battery bank is already too big for the solar you have.

You should add another 1-2 FM80 for an additional 80-160A of solar charging potential with suitable attached arrays.

48V * 80A = 3840W per FM80.

The above is solely based on balancing your system parameters. Your actual usage and design goals may render this analysis invalid.

Remember:

You add more solar to allow for more daily usage and to charge your batteries faster.
You add batteries to operate for longer between charges.
 
hey,
i run 3 battery blocks as seperated systems.
*each battery with its own inverter.
input is about 8 Chargecontrollers (60A each). I did not hardwire the chargecontrollers/inverters but instead
used Big Connectors to be able to switch the chargecontrollers to the battery block that needs them the most.
(the connectors are used for electrical forklifts -> https://www.picclickimg.com/d/l400/...-mit-Kupplung-Stecker-Doser-Rema-Euro-DIN.jpg )
*i split Entertainment and / Live support with those battery blocks and have one block as backup.
 
Welcome to the forum.

First, when you have two batteries connected to the same thing (your charge controllers, inverters), they are connected to each other, so you can't think of them as "a separate battery bank." I don't see any logical reason or benefit to your imagined solution.

36 * 230W = 8280W - your current solar.

8280W/48V = 172.5A - already more the your FM80s can handle, so any added solar is beyond that which you can capture.

2700RE cells are 2228Ah with a maximum charge current of 500A. FLA/AGM/GEL batteries perform best (longevity-wise) with a target charge current of around 10-15% of the C20 rate. In your case, that's 229 - 343A. You are well under this and would best be served by adding some solar capacity AND another charge controller.

In other words, your battery bank is already too big for the solar you have.

You should add another 1-2 FM80 for an additional 80-160A of solar charging potential with suitable attached arrays.

48V * 80A = 3840W per FM80.

The above is solely based on balancing your system parameters. Your actual usage and design goals may render this analysis invalid.

Remember:

You add more solar to allow for more daily usage and to charge your batteries faster.
You add batteries to operate for longer between charges.
Thank you! That confirms my "back of the envelope" calculations; I needed somebody to do that. I've always felt that the existing system didn't have enough to feed the battery bank; this helps confirm it.

I think I need more panels and (as you say) another charge controller to handle the incoming amperage. I would kinda like to bump up to an FX-100 but the price difference (when last I checked) was a pretty steep premium, so I may stick with the FX-80s. I'll have to run the numbers t here.

I'll also need to bury another conduit into the shed and I am pretty sure the combiner box we have down there is already maxed out in terms of simple space if not actual connectivity.

Will confirm all of this with my solar guy here on Wednesday afternoon.

Thank you for your help!

Steven
 
hey,
i run 3 battery blocks as seperated systems.
*each battery with its own inverter.
input is about 8 Chargecontrollers (60A each). I did not hardwire the chargecontrollers/inverters but instead
used Big Connectors to be able to switch the chargecontrollers to the battery block that needs them the most.
(the connectors are used for electrical forklifts -> https://www.picclickimg.com/d/l400/...-mit-Kupplung-Stecker-Doser-Rema-Euro-DIN.jpg )
*i split Entertainment and / Live support with those battery blocks and have one block as backup.

That's an interesting idea....did you automate the "switch" or is that a manual operation when needed?


Steve
 
Thank you! That confirms my "back of the envelope" calculations; I needed somebody to do that. I've always felt that the existing system didn't have enough to feed the battery bank; this helps confirm it.

I think I need more panels and (as you say) another charge controller to handle the incoming amperage. I would kinda like to bump up to an FX-100 but the price difference (when last I checked) was a pretty steep premium, so I may stick with the FX-80s. I'll have to run the numbers t here.

I'll also need to bury another conduit into the shed and I am pretty sure the combiner box we have down there is already maxed out in terms of simple space if not actual connectivity.

Will confirm all of this with my solar guy here on Wednesday afternoon.

Thank you for your help!

Steven

You keep calling them FX-80/FX-100. They are FLEXmax (FM). Please correct me if I'm missing something.

FM100 vs. FM80:

2X the price
25% more charge current/PV capacity
2X the PV input voltage limit (300V)
Able to be configured via Mate3

Unless you NEED the features the FM80 doesn't offer, I would stick with the FM80 as that's the far better value.

I calculated the PV wattage per FM80, but the manual indicates 4000W for 48V systems. I'd go with that.
 
You keep calling them FX-80/FX-100. They are FLEXmax (FM). Please correct me if I'm missing something.

FM100 vs. FM80:

2X the price
25% more charge current/PV capacity
2X the PV input voltage limit (300V)
Able to be configured via Mate3

Unless you NEED the features the FM80 doesn't offer, I would stick with the FM80 as that's the far better value.

I calculated the PV wattage per FM80, but the manual indicates 4000W for 48V systems. I'd go with that.
That's because they literally say that in big friendly letters on the casing and in the box they came in.

It seems like the 100 was built to work *with* the Mate 3, whereas I have a Mate 2. And as you say it's more cost effective....


Steven
 
I just can't find any reference to FX-80 or FX-100 on Outback's site.

Some Outback inverter/charger models are prefixed with "FXR," but I find no reference to "FX" in relation to any charge controller they've ever made. There are MX models, but they have been discontinued for some time.

From the FLEXmax 60/80 spec sheet:

1612798512778.png

From the FLEXmax 100 spec sheet:

1612798625871.pngf

Perhaps there's a model I can't find, but moving forward, if you add a new SCC, you will be looking for a FM80 or FM100.
 
I actually already have a couple of the FX-80s slated presently as replacements in the event of Zombie Apocalypse, so this will probably form the basis for fleshing out the system a bit more. It's down the road a bit yet; I haven't had a chance to talk to my solar guy about what I want to do, and then the digging and whatnot will take some time. I'm pretty sure that the 2" conduit that's in there right now is stuff so I expect we'll have to put in new conduit and wiring, and the addition of another box might make simplifying some of the existing wiring a bit.....not sure yet there.

I also need to see how many mount pillars (basically 6" or 8" PVC pipe cut down to around 6') I have left. Pretty sure we've got enough to handle another row though, and I had cleared the area to allow for two more when I was clearing out the scrub oak in the area. Glad I did....


Steve
 
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