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Best value battery system?

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I currently have a solax 3.6kw solar inverter, what's the best approach to add a battery to the system?

Replace the inverter with hybrid or have an AC connected system?

Is fogstar the best value at the moment, which inverter is preferred and do they have any wireless CTs?
4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
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  • ed110220
    ed110220 Posts: 1,609 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Combo Breaker
    edited 3 July at 6:28PM
    The best value I know of is the Seplos battery sold by Fogstar, 16.1 kWh for £1749.99. Or a little less if you buy it as a kit and assemble it yourself. It's sold by Fogstar but not to be confused with their own Fogstar branded battery which is a bit more expensive but still very good value.
    Solar install June 2022, Bath
    4.8 kW array, Growatt SPH5000 inverter, 1x Seplos Mason 280L V3 battery 15.2 kWh.
    SSW roof. ~22° pitch, BISF house. 12 x 400W Hyundai panels
  • QrizB
    QrizB Posts: 18,292 Forumite
    10,000 Posts Fourth Anniversary Photogenic Name Dropper
    edited 3 July at 6:31PM
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Vodafone BB / iD mobile. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 34 MWh generated, long-term average 2.6 Os.
    Not exactly back from my break, but dipping in and out of the forum.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs, Best kettle!
  • ed110220
    ed110220 Posts: 1,609 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Combo Breaker
    QrizB said:
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    Yes, I was assuming price/kWh. The Seplos will need a hybrid inverter and it doesn't give you access to Octopus intelligent tariffs, but I still think it combined with one of the "EV tariffs" eg Octopus Go or EON Drive is hard to beat 
    Solar install June 2022, Bath
    4.8 kW array, Growatt SPH5000 inverter, 1x Seplos Mason 280L V3 battery 15.2 kWh.
    SSW roof. ~22° pitch, BISF house. 12 x 400W Hyundai panels
  • Netexporter
    Netexporter Posts: 1,967 Forumite
    1,000 Posts First Anniversary Name Dropper
    Fogstar recently had the 15.5kWh batteries at £2000, again, but I think they're sold out. They were that price last Black Friday, if you can wait until the next BF.


  • NedS
    NedS Posts: 4,525 Forumite
    Fifth Anniversary 1,000 Posts Photogenic Name Dropper
    QrizB said:
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    Location is also important - where is the battery going to be sited?
    For example, I wouldn't want to stick a Fogstar outside. Besides the IP weatherproof ratings, there's also the issue of thermal management of the cells. No point having a huge battery that won't charge in winter when the weather drops below zero. If installing outside, this would be my primary concern.

  • Netexporter
    Netexporter Posts: 1,967 Forumite
    1,000 Posts First Anniversary Name Dropper
    edited 3 July at 8:54PM
    NedS said:
    QrizB said:
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    Location is also important - where is the battery going to be sited?
    For example, I wouldn't want to stick a Fogstar outside. Besides the IP weatherproof ratings, there's also the issue of thermal management of the cells. No point having a huge battery that won't charge in winter when the weather drops below zero. If installing outside, this would be my primary concern.

    The 15kWh Fogstars have got automatic heating,
  • QrizB
    QrizB Posts: 18,292 Forumite
    10,000 Posts Fourth Anniversary Photogenic Name Dropper
    NedS said:
    QrizB said:
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    Location is also important - where is the battery going to be sited?
    For example, I wouldn't want to stick a Fogstar outside. Besides the IP weatherproof ratings, there's also the issue of thermal management of the cells. No point having a huge battery that won't charge in winter when the weather drops below zero. If installing outside, this would be my primary concern.

    The 15kWh Fogstars have got automatic heating,
    Some of them do, some of them don't.
    There was no heating in the Seplos Mason kit that I built.
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Vodafone BB / iD mobile. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 34 MWh generated, long-term average 2.6 Os.
    Not exactly back from my break, but dipping in and out of the forum.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs, Best kettle!
  • ed110220
    ed110220 Posts: 1,609 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Combo Breaker
    QrizB said:
    NedS said:
    QrizB said:
    "Value" is a tricky proposition, as there's more to it than price-per-kWh.
    Some people will say that the best value is from a battery that's compaltible with Intelligent Octopus Flux, which means Tesla / GivEnergy / SolarEdge / Enphase.
    Others might say that, if you can buy the same battery capacity as a PW3 from Fogstar plus a hybrid or AC-coupled inverter and save £5k, it'ls going to take a lot of tariff-specific gains to make up for the extra outlay.
    You'll find folk in both camps here, gently ribbing each other.
    Location is also important - where is the battery going to be sited?
    For example, I wouldn't want to stick a Fogstar outside. Besides the IP weatherproof ratings, there's also the issue of thermal management of the cells. No point having a huge battery that won't charge in winter when the weather drops below zero. If installing outside, this would be my primary concern.

    The 15kWh Fogstars have got automatic heating,
    Some of them do, some of them don't.
    There was no heating in the Seplos Mason kit that I built.
    I think this refers to the Fogstar branded batteries rather than the Seplos ones that Fogstar also sell. They have similar specs and people tend to talk about them interchangeably but they are different things. The Seplos kit I got doesn't have heating, so if the Fogstar does that might be worth considering if you're putting it in an unheated place.
    Solar install June 2022, Bath
    4.8 kW array, Growatt SPH5000 inverter, 1x Seplos Mason 280L V3 battery 15.2 kWh.
    SSW roof. ~22° pitch, BISF house. 12 x 400W Hyundai panels
  • Spies
    Spies Posts: 2,267 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    I would likely need a qualified electrician to install as I don't have a dedicated circuit I could use, unless I swapped my solar inverter for a hybrid, what would be a good hybrid inverter with local access that would support the fogstar battery?
    4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
  • Netexporter
    Netexporter Posts: 1,967 Forumite
    1,000 Posts First Anniversary Name Dropper
    I'm going to use an 8kW Sunsynk (DNO permitting) so I can fill 2 batteries easily in a 4 hour cheap window. Also it has the facility for islanding in the event of a power cut (which are fairly frequent here).
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