chilly2
New Member
- Joined
- Sep 14, 2021
- Messages
- 150
Hello,
So I've been going back and forward on this situation for a while.
- My array is just over 3000w of 260w panels.
- Heavily shaded by neighboring trees, just one small part of my property is good for solar.
- Even then a chimney stack obscures part of it until late morning.
- I have two zero export 2kw grid tie inverters. Cheap, low startup VOC (45-90v) and high amp limit (30a), good for the shading situation.
Thus the array is actually two arrays, each 1500W 2S3P. Each set of two panels totals 61v, 8.3a, so 61v 24.9a per inverter.
This works fine, but...
1. I'm nagged by the desire to send excess production to a battery for overnight use. On a non AC day (June-Aug) there's a lot thrown away.
2. a recent storm knocked my utility power out for just over 7 days. (in 100F outside, that was fun). The grid tie inverters were obviously useless.
I had already been considering adding a separate SCC with a better VOC range and 48v battery. When the storm arrived I rush purchased a 12/24/48v 60a SCC, 12v 100a LifePO4 and 12v inverter. They kept lights, fans, electronics, the microwave, kettle and coffee maker working and I learned a lot about off grid vs grid tie during that week, including not run a 12v 100A BMS past 100A+ for minutes at a time for those last three devices. Needless to say a 2nd battery will be on the way to even it out if I do nothing else I'm asking about here.
So what am I asking?
The power is back, the grid tie inverters are working, and the 12v setup can cover emergencies. Great. But you know how it is with solar when you get the bug for it! I could...
1. Add the 48v battery / batteries with the grid ties.
The SCC I purchased for the storm handles 12/24/48v at 60a and up to 150v PV. I could use the SCC to charge a 48v LifePO4 e.g. EG4 LL and feed the grid ties, shifting the excess to the evening hours. That said, I can't program the grid ties for time of day. They'll just do what they do until the battery voltage is below a defined cut off and wake back up when it's at a reboot voltage (they have no SOC / RS485 ability which maybe will make Li problematic). I think I could fully charge one battery, possibly two (I have 500w-750w of additional panel space I could put up if I do this). Given the grid is normally fairly reliable outside of the recent prolonged outage, it means a ~$1500 purchase for the 48v battery as I have everything else now, and it would make a dent in the evenings when power usage peaks.
2. Ditch all the current kit and get an all in one / hybrid.
The grid tie inverters have a 30a limit but I limit them to 25a so as not to wear them out. It equates to about 1400W from one and 900W from the other as it has this odd reboot behavior over 17A so I capped it in the configuration. So if I have a couple of things on in the house and then I put the coffee maker on it's easy to exceed 2300W. I could replace the dodgy grid tie so they'll both handle 25a but at 51.2v that's still only 2560W total. A higher watt hybrid say 5000 or 6000w, or perhaps a pair of 3000s, with sufficient battery will 100% cover those spikes.
My concerns are...
If critical loads exceed the hybrid inverter rating, e.g. inverter is 3000w and the loads hit 6500w, will it just pull the extra 3500w through from the grid via the AC in terminals or will I have to constantly watch that the loads never exceed 3000w lest the inverter shut off and beep?
The grid ties do take a bite out of the dryer and furnace blower when they're on. If I can't have said devices in a critical loads panel, I may actually be doing worse, unless I decide I only care about lights, outlets and electronics.
If I get one that can handle split phase 120/240 that seems to mean an idle draw of at least 100w+ which for my small array is excessive. Is it the transformer doing that?
I've been looking at the Growatt SPF 3000TL LVM-48P which Signature Solar sell as it has the low VOC start up (60v) and tiny idle load. Alternatively, if I keep using the SCC mentioned above and not the MPPT in a hybrid, maybe I could use a different hybrid (EG4?) that would otherwise have been unusable because of a 125v or more MPPT start up, but it just feels messy.
3. Do the things in option 1, but also purchase a basic 48v inverter (or inverter/charger) and have it on standby until the next storm, like a generator. Extension cords to the rescue, or maybe if I can find a suitably trustworthy inverter I can later hard wire it to a transfer switch.
What would you do and do you have any particular devices / wiring schematic in mind?
So I've been going back and forward on this situation for a while.
- My array is just over 3000w of 260w panels.
- Heavily shaded by neighboring trees, just one small part of my property is good for solar.
- Even then a chimney stack obscures part of it until late morning.
- I have two zero export 2kw grid tie inverters. Cheap, low startup VOC (45-90v) and high amp limit (30a), good for the shading situation.
Thus the array is actually two arrays, each 1500W 2S3P. Each set of two panels totals 61v, 8.3a, so 61v 24.9a per inverter.
This works fine, but...
1. I'm nagged by the desire to send excess production to a battery for overnight use. On a non AC day (June-Aug) there's a lot thrown away.
2. a recent storm knocked my utility power out for just over 7 days. (in 100F outside, that was fun). The grid tie inverters were obviously useless.
I had already been considering adding a separate SCC with a better VOC range and 48v battery. When the storm arrived I rush purchased a 12/24/48v 60a SCC, 12v 100a LifePO4 and 12v inverter. They kept lights, fans, electronics, the microwave, kettle and coffee maker working and I learned a lot about off grid vs grid tie during that week, including not run a 12v 100A BMS past 100A+ for minutes at a time for those last three devices. Needless to say a 2nd battery will be on the way to even it out if I do nothing else I'm asking about here.
So what am I asking?
The power is back, the grid tie inverters are working, and the 12v setup can cover emergencies. Great. But you know how it is with solar when you get the bug for it! I could...
1. Add the 48v battery / batteries with the grid ties.
The SCC I purchased for the storm handles 12/24/48v at 60a and up to 150v PV. I could use the SCC to charge a 48v LifePO4 e.g. EG4 LL and feed the grid ties, shifting the excess to the evening hours. That said, I can't program the grid ties for time of day. They'll just do what they do until the battery voltage is below a defined cut off and wake back up when it's at a reboot voltage (they have no SOC / RS485 ability which maybe will make Li problematic). I think I could fully charge one battery, possibly two (I have 500w-750w of additional panel space I could put up if I do this). Given the grid is normally fairly reliable outside of the recent prolonged outage, it means a ~$1500 purchase for the 48v battery as I have everything else now, and it would make a dent in the evenings when power usage peaks.
2. Ditch all the current kit and get an all in one / hybrid.
The grid tie inverters have a 30a limit but I limit them to 25a so as not to wear them out. It equates to about 1400W from one and 900W from the other as it has this odd reboot behavior over 17A so I capped it in the configuration. So if I have a couple of things on in the house and then I put the coffee maker on it's easy to exceed 2300W. I could replace the dodgy grid tie so they'll both handle 25a but at 51.2v that's still only 2560W total. A higher watt hybrid say 5000 or 6000w, or perhaps a pair of 3000s, with sufficient battery will 100% cover those spikes.
My concerns are...
If critical loads exceed the hybrid inverter rating, e.g. inverter is 3000w and the loads hit 6500w, will it just pull the extra 3500w through from the grid via the AC in terminals or will I have to constantly watch that the loads never exceed 3000w lest the inverter shut off and beep?
The grid ties do take a bite out of the dryer and furnace blower when they're on. If I can't have said devices in a critical loads panel, I may actually be doing worse, unless I decide I only care about lights, outlets and electronics.
If I get one that can handle split phase 120/240 that seems to mean an idle draw of at least 100w+ which for my small array is excessive. Is it the transformer doing that?
I've been looking at the Growatt SPF 3000TL LVM-48P which Signature Solar sell as it has the low VOC start up (60v) and tiny idle load. Alternatively, if I keep using the SCC mentioned above and not the MPPT in a hybrid, maybe I could use a different hybrid (EG4?) that would otherwise have been unusable because of a 125v or more MPPT start up, but it just feels messy.
3. Do the things in option 1, but also purchase a basic 48v inverter (or inverter/charger) and have it on standby until the next storm, like a generator. Extension cords to the rescue, or maybe if I can find a suitably trustworthy inverter I can later hard wire it to a transfer switch.
What would you do and do you have any particular devices / wiring schematic in mind?
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