I think this is getting confusing.
Sometimes you guys are stating readings reported by a battery, and then you refer to parameters set within the inverter.

Measuring SoC is tricky.
Doing so over long periods of time without re-defining it by charging the battery(ies) to 'full' is nigh on impossible.

Let's assume that the figures you're stating here are within plus/minus 5%
almost all the 'inaccuracies' we've just discussed are actually within the range of acceptability.

Firstly, I agree with @ggw  that it's the inverter which is 'in control'.

but then let's consider this...

Posted by: @adrianmc

↑

Can the battery force charge its self 

Theoretically it's possible, but I haven't heard of that being implemented.

The BMS in that battery would need to have been pre-loaded with the command-set for your particular model of inverter.
It would then need to select the Modbus command from that set and send it to the inverter across the CAN or RS485 connection.

The inverter could then start charging the battery from the grid...

... until something else then happened.

And what is that something else?

Does the battery initiate another command?
At what point?
How can it know its SoC accurately enough whilst still being re-charged at high current?

Or would the inverter intervene anyway?
Might it read its own configuration settings and stop the grid-charge because a particular parameter had been reached?

Matching batteries and inverters is normally not undertaken at that level.

They wouldn't normally send commands to each other.
Their 'compatibility' is rarely more than just sending data from the battery to the inverter, which you can then see on the inverter's App.

Our hybrid inverter is a sunsynk, and while it states the SOC monitored by the (Seplos mason) battery I’m pretty sure it uses its own voltage measurement to indicate full/empty, and takes emergency measures based on it.  The voltage levels it uses are “hidden” - you have to swap to batt=Pb voltage control, set the levels, then swap back to Li bms.  Weird, and when it works (it is), it’s not something I’d like to mess with.

Hi,

I have been reading all the posts abotu Fogstart 15.5 kwh battery. I would like to get one without solar. Ideally I would like someone to install but I don't see anyone at the moment.

What is the max charge and discharge power from this battery, from the spec sheet it says 200A, but not about peak/continuous charge and discharge power? Somewhere I don't recall it was mentioned that it is under 2kw that seems quite low.

If I want to DIY install can I not go over 3.6kw inverter? Do I have to get G99 prior before if I want any thing higher?

Thank you.

Hi @littlefinger and well done for finding an appropriate topic in which to post 🙂 

Firstly, the Fogstar storage batteries have no direct connection to either the grid or to solar panels.
You require a separate inverter to achieve that.

The 200A maximum charge/discharge from Fogstar's batteries is a feature imposed by  the inbuilt Battery Management System (BMS) from Pace.

That 200A is the maximum sustainable current.
It's unlikely that you'd ever want to pull that many amps from your battery.

200A at 52v is over 10kW.
I don't know from where you got the 2kW figure. It's not correct.

The limit of 3.68kW and G99 are factors which apply to inverters which export to the grid.

If you wish to do a DIY installation and you don't intend sending power back to the grid, then neither of these issues is relevant.

Tell us a bit more about what you'd like to achieve, preferably without too much technical stuff!
We can get more technical when we understand what you'd like to do.

@transparent Wow that was quick. Thank you.

Below is the reply from Fogstar I just received 

forums can be a minefield of misinformation.
So the max input in Kw for a 200A bms is 2.4Kw
It's a little over 2.4 as lithium operate at 13.2v (meadan voltage range) 

So in answer 

2.4Kw (2400w) max charge and discharge.

Hope this clarifies.

Any resources on how to calculate there figures from spec sheet?

At the moment I have install home battery storage at lower cost and came to know about Fogstar battery.

After reading this thread and other online forums it looks like Sunsynk Hybrid inverter is good choice.

My immediate goal is to shift my grid import to off-peak, while keep my options open for future expansion for extra batteries and Solar. There is possibility of getting EV but not right now.

From what I understand, G99 is required even if you do not want to export if inverter is over 3.68kW

I'm thinking of having either 8kW Ecco Hybrid Inverter or 8kW Hybrid Inverter (not sure what the difference, except for one is smaller than other) or Sunsynk-LifeLynk-XL. 

Would G99 approval specify how much one can export? That is can I get approval to export without solar so if I add solar later I do not have to apply again. 

Cheers

That reply from Fogstar is in response to a question about a battery rated at 13.2v,
which tells me that it's probably four LiFePO4 cells in series.

The Fogstar 15.5kWh battery bundle uses sixteen LiFePO4 cells in series, each rated at 3.2v (nominal):

Power in watts (or kilowatts) = Volts x Amps

Yes the SunSynk 8kW inverter is a good choice for an off-grid system.

The SunSynk inverters do have the capability to export to the grid.
So you would still need to obtain G99 consent from your DNO, even 'tho you will configure the export to be Zero.

That's the most common arrangement for SunSynk installations in the UK.
You state the inverter model number on the G99 Form, and the DNO will look this up on the ENA Database.

SunSynk's export-limitation feature has already obtained ENA approval to operate with Zero-export.
So you will be given G99 approval regardless of the power-rating of the inverter.

Once you have DNO consent for Sunsynk inverter(s) operating with Zero-export, you do not need to reapply if

• you add solar input
• you add another SunSynk inverter in parallel configuration
• you add further battery storage

Your off-grid system might then look something like this: