On-grid domestic battery storage

Solarchaser

My experience with two separate battery systems can give the same problem as you have with battery +immersion.
The growatt responds slower than the sofar, so when the load drops off, the growatt is still pushing wattage, which the sofar sees as excess solar and starts to charge.

I understood you could set the immersion to look for 10 seconds (or whatever you chose) of export before deciding to switch itself on.

If that's not the case. Then I'll be stopping looking at heat stores.

Unless I can get a system capable of parralelling, that can cover the 9kw shower with batteries and then activate an immersion with solar when bats are full, and available for much cheapness.... but I think that is simply nirvana lol.

I have 6kwh of batteries on the system I can monitor, and it says I'm on 50% just now, so it will last till morning now, that will be about the 10th time this year.
I'd say in about 30% of this year the battery has been discharged 20% or more throught the day keeping up with loads that go above what the solar can cover, and then recharging when the load is off.

Croft12 if you are on a decent fit payment, it may make more sense to get an AC battery inverter like the sofar me3000sp as it doesn't affect how much fit you get paid, if its non fit, then a hybrid inverter will probably be better.

Based on my own experience I'd avoid growatt, Ive had an sph3600 for almost 6 months and it just doesn't work right, hasn't since new, and has slowly gotten more broken, (it now doesn't charge its batteries at all) and growatt are horrendously poor at any kind of service.

mmmmikey

Solarchaser wrote: »

I understood you could set the immersion to look for 10 seconds (or whatever you chose) of export before deciding to switch itself on.

If that's not the case. Then I'll be stopping looking at heat stores.

My immersion controller is a Solic 200 and doesn't have this feature, I'm not sure if others have. Also, the Solic 200 has a zero-export threshold so turns itself on before others, which might be coming into play.

Having said that, this issue is easily resolved (for me) by putting the battery into "only charge" mode before switching the Solic-controlled immersion heater on, then switching back to normal mode when the water is heated and switching the immersion heater is off. Once I've proved this works and found the best time of day to do it, I can automate it with timers easily enough.

Not the best way to do it, because the possibility is that house-load exceeds solar generation when the battery is in only charge mode and I end up using energy from the grid. But in my case this is hardly an issue and is only like to mean a small amount of grid consumption in the shoulder months (if at all) as long as I get the timings right.

Also worth noting, I did my sums on the basis of charging the battery overnight on e7 low rate, saving me ca. 15p per unit and anything I do with solar saving ca. 21p per unit is a bonus.

Thanks, Mike

Reed_Richards

I don't have an immersion heater but if I turn on the kettle then the battery takes several seconds to ramp up its output and when the kettle goes off it exports to the grid whilst ramping down. If electric cars behaved this this laggy way they would be miserable to drive.

1961Nick

mmmmikey wrote: »

My immersion controller is a Solic 200 and doesn't have this feature, I'm not sure if others have. Also, the Solic 200 has a zero-export threshold so turns itself on before others, which might be coming into play.

Having said that, this issue is easily resolved (for me) by putting the battery into "only charge" mode before switching the Solic-controlled immersion heater on, then switching back to normal mode when the water is heated and switching the immersion heater is off. Once I've proved this works and found the best time of day to do it, I can automate it with timers easily enough.

Not the best way to do it, because the possibility is that house-load exceeds solar generation when the battery is in only charge mode and I end up using energy from the grid. But in my case this is hardly an issue and is only like to mean a small amount of grid consumption in the shoulder months (if at all) as long as I get the timings right.

Also worth noting, I did my sums on the basis of charging the battery overnight on e7 low rate, saving me ca. 15p per unit and anything I do with solar saving ca. 21p per unit is a bonus.

Thanks, Mike

It should be fairly simple to build something to interrupt the iBoost clamp signal when the battery is charging or discharging.

Joe might be able to sketch a circuit out for you?

1961Nick

Reed_Richards wrote: »

I don't have an immersion heater but if I turn on the kettle then the battery takes several seconds to ramp up its output and when the kettle goes off it exports to the grid whilst ramping down. If electric cars behaved this this laggy way they would be miserable to drive.

I solved that problem by fitting a boiling water tap (1.2kWh) & binning the kettle......actually it's in the loft for emergencies.

orrery

Reed_Richards wrote: »

If electric cars behaved this this laggy way they would be miserable to drive.

I'm assuming you know that isn't the case already. In fact, it is petrol and diesel cars that behave in this laggy way, and they are indeed miserable to drive (once you've driven an EV). Positively agricultural.

mmmmikey

1961Nick wrote: »

It should be fairly simple to build something to interrupt the iBoost clamp signal when the battery is charging or discharging...

Yes, set me thinking, thanks Nick. All I need to do is control a relay on the Solic 200 output using a current clamp on one of the Powervault consumer unit tails and a bit of simple circuitry. I just need to switch the immersion off when the Powervault is doing anything - doesn't matter whether it's charging or discharging so very simple circuitry. May do something with a Raspberry Pi as I have a spare one that I played with last year - a bit of overkill but I'll be able to see what it's doing remotely and extend it to do other more intelligent control at a later stage if I want to. Not top of the list though, a fun project one day....


In other news, data from the Powervault suggest that it is working as expected but I need to run it a bit longer and reconcile the data with my supply meter.

mmmmikey

1961Nick wrote: »

I solved that problem by fitting a boiling water tap (1.2kWh) & binning the kettle......actually it's in the loft for emergencies.

Sounds like a good idea, not something I've ever considered. Does boiling really mean boiling - is it actually very near boiling or just very hot (important to a fussy tea drinker ). Also, could you put a water filter in the supply? Thanks, Mike

1961Nick

mmmmikey wrote: »

Sounds like a good idea, not something I've ever considered. Does boiling really mean boiling - is it actually very near boiling or just very hot (important to a fussy tea drinker ). Also, could you put a water filter in the supply? Thanks, Mike

“Very near boiling” is a pretty good description...high nineties. Ours came with a cartridge water filter & I believe it’s pretty standard to prevent limescale. It’s called an “Insinkerator 3 in 1” & there are usually some listed on amazon if you want the full details.

Reed_Richards

orrery wrote: »

I'm assuming you know that isn't the case already. In fact, it is petrol and diesel cars that behave in this laggy way, and they are indeed miserable to drive (once you've driven an EV). Positively agricultural.

Yes I did know this. But knowing battery vehicles are capable of instant power I was curious as to why the battery in my solar system cannot, or is not allowed to, do the same.