Off peak grid tied storage with ac coupled inverter

[Drewby80]

Hi all

I am currently looking at fitting an AC coupled storage inverter, something like a Sofar ME3000SP and programming it to charge on off peak electricity on Octopus GO @ 7.5p per kWh and using it to charge a big bank of prismatic lithium cells or LG Chem cells in a home made storage rack.

The web is littered with salvage EV packs that are significantly cheaper per kW than the likes of Pylontech server rack packs etc.

The problem is that all of the grid tied inverters seem to be tied to either their own manufacturers battery packs which are circa £5k for 10kW of storage or will only work with off the shelf packs that are equally pricy.

Is there a grid tied inverter solution out there that will work with an off the shelf BMS that enables you to build your own storage pack?

I would like to build a 30kW pack that chargers nightly and supplies 90% of my power demands but is grid tied so when my power demand exceeds the inverters output capacity it imports from the grid to supplement the load requirements.

Is this possible, and if so what kit would I need to do this with?

 

[Ampster]

Is there a grid tied inverter solution out there that will work with an off the shelf BMS that enables you to build your own storage pack?

Yes there are many choices, The most common search term is Hybrid GT inverter. I recently saw a description that covers some of the most important functionality,
"A bidiretional solar battery powered inverter". AC coupling is a functionality that varies by manufacturer and that is the functionality you would need to leverage your existing GT inverter{s}. Some brands available in the US that are UL Listed are Outback, SolArk, Schneider, SMA and a few others. Any inverter will work with almost any BMS that has some way to disconnect the Battery from the inverter.

I would like to build a 30kW pack that chargers nightly and supplies 90% of my power demands but is grid tied so when my power demand exceeds the inverters output capacity it imports from the grid to supplement the load requirements.

All of that would be determined by the settings in the inverter. The battery is just a dumb device that receives power (charges) and serves loads {discharges}. The inverter typically has modes that determine if it charges from the grid, solar or both. The bidirectional feature described above is how it can import from the grid to support load requirements.

 

[Gareth79]

I am doing exactly the same research at the moment, and don't seem to have a firm handle on what is a good grid-tied inverter for relatively small "DIY" type packs (also specifically to the UK). I mainly want to shift spare solar generation to the batteries (using Home Assistant to monitor export and manage the charging), and then likewise top up using Octopus Go.

I'm planning something like 12x 280Ah batteries from Jenny Wu/Docan, which would total about US$1500 shipped for 10kWh capacity - significantly cheaper than off-the-shelf systems (obviously excluding BMS etc). I'd think this is a better bet than using salvaged cells.

 

[Gareth79]

To update this, I decided on the Sofar ME3000SP since there's several ESP8266/32 integrations to monitor and control it, and there's plenty of people who have used it with LiFePO4 so I shouldn't need to do much work to get it set up. It's not currently in stock anywhere in the UK but the distributor has stock from the 19th July, so I placed an order with a retailer who suggested they will be getting some of that supply. Ordering direct (from Midsummer Wholesale) it's £982, but a retailer is listing it for £622, which I'm hoping they will honour!

I have 16x 280Ah cells on the way from Jenny Wu, no idea when they will arrive though!

 

[israndy]

Why did you go with a Solar Inverter if you are AC charging, are you also in need of a solar inverter?

 

[Gareth79]

Why did you go with a Solar Inverter if you are AC charging, are you also in need of a solar inverter?

The ME3000SP? It's a not a solar inverter, it's purely AC input/output. It comes with CT clamp so you can set it up to detect and charge export, but you can use it standalone too, and have time based overrides etc, or just control it using the serial/CAN interface.

 

[1Watt]

The ME3000SP? It's a not a solar inverter, it's purely AC input/output. It comes with CT clamp so you can set it up to detect and charge export, but you can use it standalone too, and have time based overrides etc, or just control it using the serial/CAN interface.

Hi Gareth79, have you got any further with this project? I'm also in the UK and looking to do the exact same thing. Hoping to learn from your experience.

 

[Gareth79]

Hi Gareth79, have you got any further with this project? I'm also in the UK and looking to do the exact same thing. Hoping to learn from your experience.

Been reading about the possible blackouts over the winter? :D

It's trundling along! I just managed to get hold of an ME3000SP, it's a "refurbished" one from south-west-renewables on ebay, although I have a pre-order in for a brand new one from a supplier too. I THINK it should be able to do everything required with it's built-in functionality

My EVE cells are still on the way. I have a Daly BMS ready to go. I'm not sure about mounting the batteries, I will probably build 2x steel trays for 8x cells each in blocks of 4, with threaded rod and plastic end panels or something. I can weld, sort of, well enough to make something anyway...

 

[1Watt]

Been reading about the possible blackouts over the winter? :D

It's trundling along! I just managed to get hold of an ME3000SP, it's a "refurbished" one from south-west-renewables on ebay, although I have a pre-order in for a brand new one from a supplier too. I THINK it should be able to do everything required with it's built-in functionality

My EVE cells are still on the way. I have a Daly BMS ready to go. I'm not sure about mounting the batteries, I will probably build 2x steel trays for 8x cells each in blocks of 4, with threaded rod and plastic end panels or something. I can weld, sort of, well enough to make something anyway...

It sure would be nice to have power during a blackout!

Do you mind if I pick your brains? I'm still new to the battery side of things.

Background: A couple of weeks ago I finished building my own grid-tie 2.4kW PV array with panels in my garden and a standard Growatt (non-hybrid) inverter. It's worked out really well and is significantly over producing. At the same time I also installed a iBoost to dump the extra energy into my hot water tank - this has worked out really well, essentially dropping the need for my gas boiler at the moment.

Next I would really like to add a battery but I have questions.

My inverter doesn't have connections for a battery so an AC battery solution is my only option. This lead me to the ME3000SP.

Am I right in thinking I could install the ME3000SP, connect it to LiFePo4 cells and program it to be charged from my solar array using a couple of clamp meters to detect excess power?

I see that you mentioned a BMS, where does this fit into the equation?

Sorry for the newb questions.

 

[Gareth79]

Am I right in thinking I could install the ME3000SP, connect it to LiFePo4 cells and program it to be charged from my solar array using a couple of clamp meters to detect excess power?

I see that you mentioned a BMS, where does this fit into the equation?

Sorry for the newb questions.

Yes, that's exactly what I will be doing, I have a Growatt inverter myself too, it should work exactly as you say. The BMS is not absolutely required for a system to work, but it monitors the voltage of each individual cell and balances the charge, to prevent overcharging or excessive discharging, and also the system as a whole, so basically it is required if you want the cells to last.

 

[1Watt]

Yes, that's exactly what I will be doing, I have a Growatt inverter myself too, it should work exactly as you say. The BMS is not absolutely required for a system to work, but it monitors the voltage of each individual cell and balances the charge, to prevent overcharging or excessive discharging, and also the system as a whole, so basically it is required if you want the cells to last.

Thanks so much for your input Gareth, I'll find a primer on setting up the BMS with the LifePo batteries as those two parts are readily available. I can't find a ME3000SP anywhere, i think I'm a year late to the party!

When your kit arrives it would be great if you could document the build and installation, there seems to be very little on this, especially for UK installations.

 

[KJA2001]

Does a Daly BMS work with the ME3000? Has anyone actually done this? My understanding was that a BMS that emulates a pylontech battery was required.

 

[Gareth79]

Does a Daly BMS work with the ME3000? Has anyone actually done this? My understanding was that a BMS that emulates a pylontech battery was required.

It's not required, I believe the ME3000 can work independently, the other option is a bridging device (ESP8266/32). However I then read that the Seplos BMS is the best solution and have pre-ordered one when they are back in stock.

As a general update, I bought a used ME3000SP, and then my back-ordered one shipped, so I returned the used one. I have build a "tray" from box section steel to hold the batteries, but need some more sheet steel to do the next part. I'm planning to get some SurLok Plus connectors for battery cables, which is what Pylontech seem to use.

 

[mrfish]

Hi,

Sorry, I'm a newbie too and also very late to the party. Having said that, I've been enjoying having panels installed since 3 days before the FIT was initially slashed, so although late to the party, been enjoying (some of) the benefits for years.

Having recently been shopping and bought an EV, couldn't help but think that some of the solar excess could go into the car so I've bought a power meter and when there's an excess of 6a, charge can go there when it's plugged in, however, there's still a lot of energy going back to the grid; and all of it when no one's home and the cars not plugged in!

I've taken a look at installing a DC coupled battery system (https://soltaro.com/faqs-frequently-asked-questions/dc-coupled-battery-system) but believe that as my Fronius IG-TL inverter is not a hybrid, it's not possible, hence AC's probably the way forward.

I've read a lot about AC coupled systems being expensive to install, and I'm sure that walking into a Tesla shop, it probably would be! Especially with energy costs rising, (reasonable) cost isn't putting me off a DIY system. So I've been feverishly surfing for an economical solution and this...

Am I right in thinking I could install the ME3000SP, connect it to LiFePo4 cells and program it to be charged from my solar array using a couple of clamp meters to detect excess power?

...perhaps with a BMS. As above, there seems to be very little on this in the UK so it would be great to see any 'as builts' or build ideas - energy bills are about to go crazy .

 

[MisterB1959]

Hi,

Sorry, I'm a newbie too and also very late to the party. Having said that, I've been enjoying having panels installed since 3 days before the FIT was initially slashed, so although late to the party, been enjoying (some of) the benefits for years.

Having recently been shopping and bought an EV, couldn't help but think that some of the solar excess could go into the car so I've bought a power meter and when there's an excess of 6a, charge can go there when it's plugged in, however, there's still a lot of energy going back to the grid; and all of it when no one's home and the cars not plugged in!

I've taken a look at installing a DC coupled battery system (https://soltaro.com/faqs-frequently-asked-questions/dc-coupled-battery-system) but believe that as my Fronius IG-TL inverter is not a hybrid, it's not possible, hence AC's probably the way forward.

I've read a lot about AC coupled systems being expensive to install, and I'm sure that walking into a Tesla shop, it probably would be! Especially with energy costs rising, (reasonable) cost isn't putting me off a DIY system. So I've been feverishly surfing for an economical solution and this...

...perhaps with a BMS. As above, there seems to be very little on this in the UK so it would be great to see any 'as builts' or build ideas - energy bills are about to go crazy .

have a look on you tube for stuart pittaway - he is in the uk and is going through a similar process

 

[MisterB1959]

Thanks so much for your input Gareth, I'll find a primer on setting up the BMS with the LifePo batteries as those two parts are readily available. I can't find a ME3000SP anywhere, i think I'm a year late to the party!

When your kit arrives it would be great if you could document the build and installation, there seems to be very little on this, especially for UK installations.

where in essex? i am in Clacton and just starting on the journey ..... off to collect a Sofar inverter today !

 

[CrossStreet]

I am in the UK South Yorkshire and building an 8kW system. The 28kWh battery is ready, but it turns out it's hard to find an electrician to upgrade my CU and connect the inverter. So I am at this stage. (I could wire AC myself, but in the UK one needs a licenced electrician to do certain things)

 

[Gareth79]

So an update - the system is mostly set up and working ok!

The Seplos BMS is working well. The only real issue I had was that my sytem is set up in 2x packs and the link cable between them was too long, and causing a higher voltage on the first cell of the second pack. I rewired the pack (flipped the busbars) so that the cells linked at at the front, and switched the 25mm cable for 50mm, and now it works perfectly.

The ME3000SP is very good too, the KEY thing when setting one up is to "freeze" the CT direction. I didn't with mine, and it all worked ok when the solar exported it detected it as a load and tried to export to match it!

I am using Home Assistant and have the Seplos BMS linked in using ESPHome. The ME3000SP didn't have any ESPHome integration but I am writing a Modbus configuration to monitor and control it (currently a WIP). There is an MQTT bridge for it, but I try and use ESPHome wherever possible. Then it will be possible to directly control the charging/discharging from Home Assistant, eg. as a timer, and also shut it off before a full charge based on solar predictions for the following day.

 

[Gareth79]

The current HA setup. The ME3000SP is a work-in-progress, I'm still figuring out the modbus registers.

 

[CrossStreet]

It's good that you can weld and use metal. I had to use some plywood for compression.