Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,690
DC couple meaning SCC takes power from PV and applies it to battery. AC couple, GT PV normally goes through grid tie inverter to grid; if you want battery, a separate bidiretional inverter connects battery to grid.
More popular these days are high frequency inverters with high voltage bus. PV feeds bus, inverter to/from grid connects to bus, internal DC/DC converter connects battery to bus.
Data comm in this case meaning SCC, shunt, inverter talk to each other (or an analog shunt connects to one of them.) This is also done with lithium battery BMS (closed loop), although sometimes open loop, only relying on voltage.
Some systems, like hybrids or all-in-one, will be easier to set up and should have integration of internal components taken care of.
Batteries may have a preferred charge current (especially flooded lead acid) or at least a max current. You can limit PV array or charge controller to avoid exceeding that. But better if you can have lots of PV power available for when AC loads use it, but regulate battery charge current.
A hybrid should have battery current setting built in. Systems with separate inverter and charge controller usually can't achieve that unless there is a battery current sensor (shunt) and communications. Victron and Midnight offer that. My SMA take care of that because AC coupled, but if DC coupling (direct battery connection) is used, then it has to be dealt with.
I struggle with computers too, and I used to design them. Communiations and PV equipment, it is more about data cables (sometimes custom), correct polarity, terminators, pullup/down, compatible equipment ... Yes, lots of ways to do things wrong.
My equipment comes with RJ45 paralleling cables and terminator plugs, with diagram of how to connect. That much is easy. Some of the other connections are a bit more involved.
You can start with a simple inexpensive system, maybe relegate it to some niche application when you start over and build something big with more capability. Or you can estimate what you'll want in the future, come up with an architecture concept, try to research and indentify a product line to fit your plans.
I started 20 years ago with grid-tie Sunny Boy from a retailer, knowing they had Sunny Island battery inverter only in Europe at the time. It turned out to be a top quality product, and in recent years I acquired their newer model Sunny Island. It is a bit behind in the time of use/peak shaving features now made popular due to utility companies trying to make PV a bad deal, but still works well for net metering and backup during grid failures.
My main system is whole house. PV creates 3x as much power as batteries get charged with, so when grid is down, central A/C can run; if not needed the PV harvesting is reduced. If grid is up, the excess is backfed.
I'll be installing the lastest SMA inverters for family & friends. As grid tie PV for now, but if they want battery backup it can be added (at a premium price, for BYD batteries.)
"Would it be best to stick with all the same brand of components or is it easy enough to mix and match?"
To a great extent, I think within one brand will be more trouble-free.
For some systems (especially AC coupled), lithium batteries seem to cause problems. Charging has to slow down as cells get full. Some brands like my SMA list supported batteries, and minimum capacity.
For communications, I think with few exceptions it needs to be single brand. There seem to be some things like SunSpec for reporting and gross level control (grid support) that will probably do what they need. But you want something that charges at the correct rate and never causes battery to disconnect. Plenty of threads here on that topic.
More popular these days are high frequency inverters with high voltage bus. PV feeds bus, inverter to/from grid connects to bus, internal DC/DC converter connects battery to bus.
Data comm in this case meaning SCC, shunt, inverter talk to each other (or an analog shunt connects to one of them.) This is also done with lithium battery BMS (closed loop), although sometimes open loop, only relying on voltage.
Some systems, like hybrids or all-in-one, will be easier to set up and should have integration of internal components taken care of.
Batteries may have a preferred charge current (especially flooded lead acid) or at least a max current. You can limit PV array or charge controller to avoid exceeding that. But better if you can have lots of PV power available for when AC loads use it, but regulate battery charge current.
A hybrid should have battery current setting built in. Systems with separate inverter and charge controller usually can't achieve that unless there is a battery current sensor (shunt) and communications. Victron and Midnight offer that. My SMA take care of that because AC coupled, but if DC coupling (direct battery connection) is used, then it has to be dealt with.
I struggle with computers too, and I used to design them. Communiations and PV equipment, it is more about data cables (sometimes custom), correct polarity, terminators, pullup/down, compatible equipment ... Yes, lots of ways to do things wrong.
My equipment comes with RJ45 paralleling cables and terminator plugs, with diagram of how to connect. That much is easy. Some of the other connections are a bit more involved.
You can start with a simple inexpensive system, maybe relegate it to some niche application when you start over and build something big with more capability. Or you can estimate what you'll want in the future, come up with an architecture concept, try to research and indentify a product line to fit your plans.
I started 20 years ago with grid-tie Sunny Boy from a retailer, knowing they had Sunny Island battery inverter only in Europe at the time. It turned out to be a top quality product, and in recent years I acquired their newer model Sunny Island. It is a bit behind in the time of use/peak shaving features now made popular due to utility companies trying to make PV a bad deal, but still works well for net metering and backup during grid failures.
My main system is whole house. PV creates 3x as much power as batteries get charged with, so when grid is down, central A/C can run; if not needed the PV harvesting is reduced. If grid is up, the excess is backfed.
I'll be installing the lastest SMA inverters for family & friends. As grid tie PV for now, but if they want battery backup it can be added (at a premium price, for BYD batteries.)
"Would it be best to stick with all the same brand of components or is it easy enough to mix and match?"
To a great extent, I think within one brand will be more trouble-free.
For some systems (especially AC coupled), lithium batteries seem to cause problems. Charging has to slow down as cells get full. Some brands like my SMA list supported batteries, and minimum capacity.
For communications, I think with few exceptions it needs to be single brand. There seem to be some things like SunSpec for reporting and gross level control (grid support) that will probably do what they need. But you want something that charges at the correct rate and never causes battery to disconnect. Plenty of threads here on that topic.