On-grid domestic battery storage

1961Nick

chamelion wrote: »

are these actually worth it? what % of your generation do you actually use if you didn't have batteries?

Last year I generated 3908 kWh of which 2911 kWh was exported.

The reality is that the batteries should save around £300 pa so break is a long way in the future.

I have noticed that there is a step change in mindset since the batteries were installed & we're now careful not to waste electricity when the sun is shining. This may result in a reduction in consumption but it'll be hard to quantify.

I may consider a traffic light tariff in the future which could reduce the break even period......although this may require more batteries to work without too much intervention.

NigeWick

chamelion wrote: »

are these actually worth it?

The length of time to pay for itself will be quite long. I bought a Tesla Powerwall 2 last year because I can afford to be an early adopter.

If you intend to buy for purely financial reasons, you will need to do your sums. I have to say, it is nice to know that my FiT pays for the gas heating our home in winter and my electricity bill is minimal.

JKenH

NigeWick/Nick1961

I am interested in knowing the rate at which your batteries charge and discharge. I ask this because I did have a battery for 3 months but returned it as it had quite low charge and discharge rates and more frustratingly the discharge rate was fixed at 450watts, not flexible.

zeupater

JKenH wrote: »

NigeWick/Nick1961

I am interested in knowing the rate at which your batteries charge and discharge. I ask this because I did have a battery for 3 months but returned it as it had quite low charge and discharge rates and more frustratingly the discharge rate was fixed at 450watts, not flexible.

Hi

Oddly enough, a recent article (part of a series looking at battery benchmarking) touches on what you're describing by comparing 1kW & 5kWcharge rates - not quite what you're looking for, but the graph showing the difference between results over a day may be interesting.

Link - Home Solar Batteries: Performance Benchmarking - Pre-Analysed Datasets


HTH
Z

NigeWick

JKenH wrote: »

I am interested in knowing the rate at which your batteries charge and discharge.

I've seen my PW2 discharging at 4.5kW and accepting 3.6kW from the solar array. I've never got up to check it when charging from Economy 7 in winter. I believe maximum discharge rate is 5kW and don't know what maximum charge rate is. You could check their web site for details.

1961Nick

JKenH wrote: »

NigeWick/Nick1961

I am interested in knowing the rate at which your batteries charge and discharge. I ask this because I did have a battery for 3 months but returned it as it had quite low charge and discharge rates and more frustratingly the discharge rate was fixed at 450watts, not flexible.

The maximum charge/discharge rate of my system is 3kWh (Sofar ME3000 inverter).

JKenH

zeupater wrote: »

Hi

Oddly enough, a recent article (part of a series looking at battery benchmarking) touches on what you're describing by comparing 1kW & 5kWcharge rates - not quite what you're looking for, but the graph showing the difference between results over a day may be interesting.

Link - Home Solar Batteries: Performance Benchmarking - Pre-Analysed Datasets

HTH
Z

Thanks for that link. There are some very interesting articles on that website.

K

zeupater

JKenH wrote: »

Thanks for that link. There are some very interesting articles on that website.

K

Hi

We tend to use a one stop approach & drop in on their menu of weather options then use the (bookmarked)) satellite view options for short term decisions, such as timing of using high loads or even putting the washing out - the layout just seems to be easier than most others ...there's also a link to a 6 day generation forecast tool for a particular site in there somewhere which is sometimes useful for planning too ...

HTH
Z

mbeast

sorry to jump on this thread but somehow seems appropriate...

I'm looking at changing my standard inverters to something like the lux hybrid as i have 40 x 285w panels to fit and want to be able to set it to zero export as i wont get paid for any export.

I use around 70 kwh per day with a base load of 2.5kw per hour in summer and around 1.5kw per hour in the winter, so i'm wondering if it is worth getting 2 or 3 x lux hybrid inverters with 2 or 3 pylontech US3000 batteries per inverter, and maybe even charge them with economy 7 in the winter or would i be better to invest the cost of the batteries in something else as that might make more than i'd save on my power bills?

if anyone has a spreadsheet too that i could use then that would be great.

thanks

jcontest

orrery wrote: »

Well, no. I'm sitting in a hotel room with my portable battery I use for charging my phone when I'm out and about. It only ever gets charged, never discharged, as I keep it for 'just in case'. I just check it is fully charged before I go places.


Today, on a long coach journey around an island the phone got a hammering, so I used the portable charger, which went from 100% to 25% instantly and then lasted about 2 minutes.


I'm now cycling it end-to-end by using it as a charger and then charging it up again every night (will it help? Mmm - who knows)



I'm just making the point that a cold calculation of battery cycles won't give you the life of the battery in use, it is just one of the limiting factors that needs to be overlaid on the others.

I think the problem is that a battery (probably Lithium-whatever) loves to sit in a specific range. It likes to be used but never charged fully, never discharged low, not too much heat, and don't charge or discharge too fast too often.


If your going to discharge a system to 90% every day, then your probably better doubling the size of your system and discharging to 45%. Usable lifespan should more than double if you have two instead of one.


The numbers behind it all gets really confusing. From the losses you get during the storage and mixing in solar, economy 7, maintenance, install cost, to the fact that it also ties you to your home for the next 10-20. Solar panels will put buyers off, it shouldn't but it does. Slap £10-£15k worth of battery on the side of your home and people will really frown. If they imagine them going down as badly as their phone battery then It's understandable.


For me, we would need 2 Powerwalls, one MIGHT cut it, but unless I was able to map my solar production exactly against my consumption I can't even guess for sure. I know my annual electricity usage would put me up around 2 powerwalls. Savings for me would be quite good, around £400 a year, perhaps more but not less. So even one powerwall wouldn't pay for itself before the warranty is out (10 years IIRC). It is near price parity now for home users to time-shift the power. Mixing that with solar/wind power will help those people consume 80-90% of what they generate. Throw in smart meters and your export will go down to nothing - but I expect that change to happen regardless.