On-grid domestic battery storage

EVandPV

Finally got our Pylons hooked up to the Lux ac controller today, yay !
Must say, the Lux is a great piece of kit. Great monitoring/remote control options.
Just a shame there's no sun here to top them up.

1961Nick

During the summer months my Pylontechs remained in balance & a full charge was pretty much consistent at 11.75 kWh. However, since I started overnight grid charging they’ve been going further & further out of balance to the point where a 100% charge was only 9.8 kWh. That missing 2kWh is like losing a battery! After a manual balancing at 50% SOC - turn off dc to the inverter & unplug the comms leads - I’m back to an 11.5 kWh overnight charge.

I think the problem is that they never get an opportunity to balance as they’re either charging, discharging or empty. The balancing works best at mid cycle & they obviously have to be idle for it to happen. Summer provides that window when there’s enough solar for the house but not enough for battery charging to commence ... about 30 minutes most days.

During balancing, the SOC indicator flashes on the batteries that are charging, is static on the ones discharging and will go out when the process is completed. This can take an hour if they’re badly out of balance.

EVandPV

1961Nick wrote: »

During the summer months my Pylontechs remained in balance & a full charge was pretty much consistent at 11.75 kWh. However, since I started overnight grid charging they’ve been going further & further out of balance to the point where a 100% charge was only 9.8 kWh. That missing 2kWh is like losing a battery! After a manual balancing at 50% SOC - turn off dc to the inverter & unplug the comms leads - I’m back to an 11.5 kWh overnight charge.

I think the problem is that they never get an opportunity to balance as they’re either charging, discharging or empty. The balancing works best at mid cycle & they obviously have to be idle for it to happen. Summer provides that window when there’s enough solar for the house but not enough for battery charging to commence ... about 30 minutes most days.

During balancing, the SOC indicator flashes on the batteries that are charging, is static on the ones discharging and will go out when the process is completed. This can take an hour if they’re badly out of balance.

Nice tip there Nick, cheers.
Haven't started grid charging mine yet as still waiting to get on Octopus Go but I'll bare that in mind.
I take it balancing is therefore controlled by the Pylontech BMS ?

1961Nick

EVandPV wrote: »

Nice tip there Nick, cheers.
Haven't started grid charging mine yet as still waiting to get on Octopus Go but I'll bare that in mind.
I take it balancing is therefore controlled by the Pylontech BMS ?

The BMS does a fine job of balancing during the summer. When I added the 5th battery the BMS has it in sync within 24 hours.

It’s certainly something to keep an eye on if you’re planning to grid charge during the winter.

EVandPV

1961Nick wrote: »

The BMS does a fine job of balancing during the summer. When I added the 5th battery the BMS has it in sync within 24 hours.

It’s certainly something to keep an eye on if you’re planning to grid charge during the winter.

If you added a delay at the end of grid charging before discharging started, would that allow the Pylons to balance ?
Mine will only take a couple of hours to charge to 100% and I won't need them to discharge until the end of the Go period at 4am so that would give them about 2 hours.

1961Nick

EVandPV wrote: »

If you added a delay at the end of grid charging before discharging started, would that allow the Pylons to balance ?
Mine will only take a couple of hours to charge to 100% and I won't need them to discharge until the end of the Go period at 4am so that would give them about 2 hours.

That may work but I don’t know how effective balancing is with the charge level at 100%? Mine were getting to 100% with 30 minutes still left on the ‘Go’ period & they clearly weren’t using it for a sync. Balancing seems to work best around 50/60% charge.

EVandPV

1961Nick wrote: »

That may work but I don’t know how effective balancing is with the charge level at 100%? Mine were getting to 100% with 30 minutes still left on the ‘Go’ period & they clearly weren’t using it for a sync. Balancing seems to work best around 50/60% charge.

Or set the DOD to 50% temporarily.

joefizz

1961Nick wrote: »

This can take an hour if they’re badly out of balance.

Thanks Nick, very useful info.
Just to add slightly unrelated but noticed last Jan when installing new fully charged batteries to 20-25% ones that balancing took nearly a day and they didnt balance from the batteries but rather charged the lower charge ones from the mains. The BMS did this automatically, much to my surprise!

rugbyleaguesmate

Hi all

In big handfuls are batteries at a place where they pay back yet? I've been holding back but recognise the benefits of a battery.

I have a 6.72kw solar PV south facing (purchased through good advice on here) and recently I have purchased an EV.

For those that have jumped in and purchased batteries, how long until they payback purchase/install cost?

thanks in anticipation

Ian

1961Nick

rugbyleaguesmate wrote: »

Hi all

In big handfuls are batteries at a place where they pay back yet? I've been holding back but recognise the benefits of a battery.

I have a 6.72kw solar PV south facing (purchased through good advice on here) and recently I have purchased an EV.

For those that have jumped in and purchased batteries, how long until they payback purchase/install cost?

thanks in anticipation

Ian

I’ve had mine 11 months now & they’re on target to save £300 in the first year which suggests a 15 year ROC in simple terms. That’ll probably rise to £340 in the 2nd year with a full 12 months of Octopus Go & more familiarity of usage patterns.

There are some hidden savings though ... it’s now 1.00am & I can hear the dishwasher & washing machine going, both consuming off peak electricity. We’re also conserving energy when there’s a surplus of solar generation rather than wasting it. The ‘use it or lose it’ mindset has gone now that we can use it after sunset.