Possible to Charge 50kw+ Home Battery in 3 Hours at Night?

blobert

Hello,

We have 3 phase power in a new build and are planning to have a very large solar installation of 30-40kw, we have permission to export up to 30kw.

However the house is using a lot more electricity than modeled and so it won't be possible to achieve our plan of having an essentially off grid home without having a stupidly big installation which then will then be too large in summer months.

We were also planning to have a 50+kw battery for storing electricity from PV using a bank of these or similar.

Just looking I see with some of the EV specific night rates you get very cheap electricity for 3 hours at night (Pinergy is 5c per Kwh I think).

So what I'm wondering is, is it possible that I could potentially charge 50+kw of batteries at the cheap night rate in 3 hours? As I say I have 3 phase power but I don't know if it would involve some sort of complex/expensive charger?

This way I could be either running on "free" solar electricity or 5c grid electricity in winter which would be less painful than my current rates (no solar installed yet)

Any advice would be much appreciated.

Is your ev car v2g

blobert

Thanks, I don't think so, have Tesla Model Y and Nissan Leaf.

graememk

https://www.boards.ie/discussion/2058322831/possible-to-charge-50kw-home-battery-in-3-hours-at-night

Yes. If your inverter(s) is(are) big enough.

[Reminds me of a story in national school, "how many loads of sand is on this beach?"

"One, as long as you have a big enough trailer"]

Quite simply you'll need to be able to charge your batteries at 17kW.

What's your MIC? (It's likely gonna be 30+, if you have a MEC of 30)

Also did you go with the resistive underfloor heating? I think we said back when you were asking it's gonna be expensive!

unkel

Going off grid in Ireland isn't possible on solar PV alone. And certainly not if your heating is electric!

Charging a huge battery with cheap night rate is certainly an option. You have the 3ph grid connection and because of your export approval you can install a very powerful hybrid inverter. I currently pay 5c / kWh incl. VAT for night rate electricity between 2AM and 5AM, which is enough for me to exclusively use that cheap electricity all year round. I would still go ahead with the large PV install as the feed in tariff is extremely generous

slave1

With that sized array I’d plan to export throughout the good months to balance off the poorer ones, you could also export into the night for the better months of April to Sept via your intended battery setup. I think Mr Excel is due a visit

blobert

Thanks very much for the replies guys. So to clarify is it the inverter/s that are responsible for charging the batteries?

I might buy batteries from Aliexpress in Black Friday sale but want to make sure I don't buy something that would be wildly unsuitable.

Assuming I got somthing like 10 of these 5kw ones if my power MIC is high enough (I think it's 35+kw from memory) and my inverter can handle it I should be hypothetically able to charge 50kw of batteries in 3 hours?

Jonathan

https://www.boards.ie/discussion/comment/121396335#Comment_121396335

Unlikely to work. You'll never achieve the currents required to charge 50kWh of LV batteries. Remember power = voltage by current, so store 50kWh in three hours at 51.2V you are looking at a charge current of over 300A. 🤯

For the capacity and the currents involved, you should be looking at HV batteries, not LV batteries. These are stacked in series so the voltage increases rather than the current.

graememk

LV batteries are fine, if you have enough of them and heavy enough cables.

But figure out your inverter first before buying batteries

I know your on three phase, I'd look into sunsynk, they do 3 phase, but also they can link 3 single phase inverters together to do three phase too.

Although I'd be looking more at the 300ah batteries(15kwh) than the 5kwh batteries

unkel

https://www.boards.ie/discussion/comment/121397113#Comment_121397113

He is certified for having a pretty awesome setup like a triple Sunsynk / Deye 8.8kW that @graememk suggested

Charge your 50kWh LV batteries at near 600A, or empty to full in well under 2 hours 😎

You'd want good quality solid busbars paralleling those packs though. Not cables.

Jonathan

https://www.boards.ie/discussion/comment/121397417#Comment_121397417

Having three single phase inverters on a three phase system is far from ideal. You unless your loads are very evenly balanced, you'll likely find yourself in a situation where you end up with an empty battery on L1 inverter, but have unusable capacity remaining on L2/L3.

A three phase hybrid inverter that supports unbalanced loads solves that. There are a few three phase hybrids that use LV batteries but none that support the current require unless you parallel them.

graememk

You can run them all from the same battery pack.

(I don't see it in the manual of the sunsynk though, I've seen it in the deye manual)

Jonathan

https://www.boards.ie/discussion/comment/121397587#Comment_121397587

Seems overly messy for single phase inverters. On the other hand, it seems to be a supported configuration for Sunsynk's three phase LV Hybrid. See page 34.

https://www.sunsynk.org/_files/ugd/52fa1b_a5239db64d4d4c91b825a2440ce296aa.pdf

unkel

I've seen plenty of pics / mentions of setups with multiple Sunsynk inverters (mostly in South Africa), Keith (CEO) mentions it regularly too. Personally I think I'd prefer just a single very powerful 3ph inverter too!

I think they have more powerful ones than the one in your link @Jonathan. That one can "only" do 240A charging, which only gets about 35kWh into his 50kWh battery in a 3 hour slot

graememk

https://www.boards.ie/discussion/comment/121397743#Comment_121397743

Yeah and to get 30-40kw of inverter power, possibly paralleling them might be more beneficial

Sunsynk do a 30-50kw inverter but seem to only be able to charge/ discharge at 2x 50A, but at a high voltage, Batteries would need to be able to support that, (eg the weco batteries have a high voltage mode)

although the 8-12 can do 240 amps each at low voltage.

the 5-25k is Also high voltage.

Need to know what inverter(s) you are getting.

No idea on price but the 16kw sunsynk is 4k.

SD_DRACULA

The 16kw single phase deye hybrid supports 290a so just that + whatever non hybrids are required for the rest of the PV

https://www.deyeinverter.com/product/hybrid-inverter-1/sun12-14-16ksg01lp1-1216kw-single-phase-3-mppt-hybrid-inverter.html

Or just two of them?

waterwelly

People need to consider that electricity prices should continue to fall, so be careful basing investments on current prices.

I'm considering another battery but if prices fall close to pre Ukraine then it's hardly worth it.

S'

I'm currently looking into the Pinenergy (5c night) plan.

Will upgrading my connection from a 12kva to 16kva help in my case.

I am looking to charge the following in the 3hr window:

30kwh Battery pack connected to a Deye 8.8kW (200a charging)

EV with a 60 kWh battery pack (Zappi)

Heat 300l hot water cylinder (not essental as I have a back boiler stove)

SD_DRACULA

https://www.boards.ie/discussion/comment/121399905#Comment_121399905

Just FIY there's another 💩-show of a war just started to be used as an excuse to rip off the world...

graememk

https://www.boards.ie/discussion/comment/121401025#Comment_121401025

16kva is 80 amps and the upgrade is about 2k + whatever needs to be done in your consumer unit/tails etc.

If you count in amps

32 amps for the EV

35 amps for the deye

13 for hot water..

+ Background load!

The ev could be reduced (zappi will do that anyway)

How much do you need to cover the rest of the 21hrs

S'

Thanks @graememk Is the 16kva upgrade gone that expensive? I had €900 in my head. Might not make sense so to upgrade.

Not too concerned about load after the 3hr window if I can fill the battery and put as much into the car as possible.

unkel

https://www.boards.ie/discussion/comment/121401856#Comment_121401856

€2068 incl VAT to upgrade from 12kVA to 16kVA. A bit rich in my book.

ECO_Mental

Only thinking about this myself and working the numbers and how big a battery I will need. I imported 15,500 kWh in the last 12 months... my average over the year is 40 kWh/day but that includes the EV of on average which is 20 kWh/day

But in reality you wont be charging to 50 kWh every night there will some days you will only use 30 kWh or a lot less so you will only need to fill it by 20 kWh the following night! Also soalr PV will fill a bit of it potentialy during the day.

I know you have a big house and potentially big bills but there is dimishing returns here

unkel

https://www.boards.ie/discussion/comment/121402428#Comment_121402428

Nope.

You will want to charge as much as you possibly can every night (costing 5c / kWh). Anything you don't need you can dump to the grid next day and get paid 27c / kWh. This is extremely profitable and will drastically reduce the pay back period of your system.

jasgrif11

On dumping back do you have this automated?

When in the evening do you start to dump and is right down to 20% upto 1.59am when the cheaper rate starts?

unkel

https://www.boards.ie/discussion/comment/121402721#Comment_121402721

Automation is on my wish list! Not the highest priority for me now in the depths of solar PV winter, as I can barely charge my battery enough in 3 hours for my own use over 21 hours (while constantly trickle exporting), due to a physical cable upgrade needed first

waterwelly

https://www.boards.ie/discussion/comment/121402456#Comment_121402456

I wonder how long the 5c / 27c will last though?

unkel

https://www.boards.ie/discussion/comment/121402881#Comment_121402881

My contract is for 2 years. They basically can't touch the 5c rate as it is a fixed percentage discount (like 90% discount) of the full rate. So even if they upped the full day rate to 100c (which they won't), the night rate would still only be 10c

As for FIT, nobody knows.

Hopefully we will get a fully agile tariff structure as an option within the next few years. Where the rate can be between minus 30c and plus 100c any time of day and night, and you only know a day up front. Then the fun will really begin!

graememk

https://www.boards.ie/discussion/comment/121403097#Comment_121403097

£2.20 at the most recent octopus saving thing. It was only for an hour but..

unkel

https://www.boards.ie/discussion/comment/121403106#Comment_121403106

Bring it on 😁

https://www.youtube.com/watch?v=sEoIuqS6CNU

ECO_Mental

https://www.boards.ie/discussion/comment/121402456#Comment_121402456

f**king hell forgot about that!! 200IQ move. Need to add that into my calcs for battery.

I have a 6kW inverter what would be the limit of export to the grid before a few eyebrows are raised...

unkel

https://www.boards.ie/discussion/comment/121403675#Comment_121403675

If all you have is one 6kW inverter, then you'll be fine! 6kW is the max you are allowed to export (unless you are approved for more - have a search for NC7 here). Or to be precise: all ESB can see is the average per 30 minute slot. So as long as none of those slots ever show an export of over 3kWh, you are fine

Happy exporting 😁

blobert

Hello again, thanks for the advice on this.

I was chatting to a solar adviser about this. He's not a big fan of batteries (from environment perspectives) so was suggesting:

(1) Use my heavily insulated concrete slab as a battery of sorts, ie charge/heat it at cheaper night rates only and never have heating on during peak times. Same with hot water.

(2) Seeing as you can get paid 25c for export at the moment and in theory get night rate for as little as 5c just optimise the PV system for max export, use what you need but just get paid for exporting.

(3) He reckons night electricity will if anything get cheaper as there's tonnes of unused wind at night and this is going to increase way more with more wind coming on line. He thinks the feed in tariff will probably get worse also in that there's also relatively low demand at the time of day (summer mid day) when people are producing at home so this electricity isn't worth anything like 25c on the open market.

Anyway I don't share his views on batteries (I want to get as cheap electricity as possible and I also like the idea of using my PV from the day at night, like the idea of being somewhat self sufficient etc) so I think I might still go with the batteries.

I'm looking at getting 1/2 racks (30kw each) of these: https://www.europe.ruixubattery.com/product-page/rx-lfp48v100-19-rack-mounted-3u-module-ul1973-certified.

They are not that cheap but get very good reviews (Will Prowse chap likes them). The racks looks very good quality: https://www.europe.ruixubattery.com/product-page/ruixu-lithium-batteries-kits-15kwh-20kwh-25kwh-30kwh

They say:

RX-LFP48100 

• Nominal voltage：51.2V                                                  
• Nominal capacity@0.2C：100Ah  
• Nominal energy : 5,120Wh                                                
• Dimesion(W*D*H) :482.6x460x133mm | 19 x 18.1 x 5.23 inch                  
• Weight: ~47kg(103.6lb)                                                  
• Electrical Characteristics Working voltage range: 44.0V~56.8V             
• Recommended charging voltage:56.8V                                  
• Max. continuous charging current: 100A                                  
• Max continuous discharging current : 100 A                              
• Peak current:101~119A@5mins | 120~149A@15S                              
• Float Voltage : 54.6V                                                     
• IP Rating: IP20                                                           
• Self discharge: < 3.5% per month                                          
• Cycle Life (25oC, 0.2C, 80% DOD):≥6000 cycles               
• Parallel function: Maximum support 32 groups in parallel 
• Certification:CE/ IEC62619 / UL1973 / UN38.3 
• Warranty: 10 years       

Is this likely to be ok from a charging perspective if I was looking to be able to charge over a few hours at night assuming I find the right inverter?

I'll have to double check but I think for my application I had to pick a particular inverter to use (Solis-30K-5G), so hopefully I could swap for another one without too much issue as I think that one is max output of 50 A

And the other confounder for my plan (I forgot) is my new 3 phase meter is not a smart one so I am stuck on deemed export and can't get 5c rates etc till it's switched to smart. Which may well take ages. They were meant to start doing smart 3 phase meters at the end of this year but I suspect I could be waiting a while.

In a way I suspect the battery might work ok with deemed export in that I'd be keeping some of the electricity I'd be getting paid to export.

unkel

Your installer has a very narrow view on the environmental values of batteries. In my view batteries fulfill a crucial role in the transition to renewables in any country that doesn't have substantial hydro. It buffers when there is not enough wind / sun. I'll go a step further and state that batteries are even more important than the renewables themselves

That said, your installer is right in most other ways. If you don't get / make very cheap DIY batteries, they make no financial sense at the moment unless you charge them up with super cheap night rate and dump them into the grid during the day. In your case, until you have a smart meter, I wouldn't spend a cent on batteries and certainly not on expensive off the shelf ones installed by even more expensive official installers

graememk

https://www.boards.ie/discussion/comment/121411628#Comment_121411628

The inverter you mentioned is not a hybrid, Its just a string inverter, you cant connect batteries to it.

I agree with point 1, the slab is a battery, And will act just like a storage heater.

As for batteries, You need to figure out your inverter first, then the batteries can be matched to them.

This is a kit, but if your anyway DIY inclinded, It goes together really easily, 15kwh, under 2k gbp. https://www.fogstar.co.uk/collections/seplos-mason-kits/products/seplos-mason-280-and-x16-grade-b-envision-305ah-battery-bundle you'd have 30kwh for the price of 15.

or a prebuilt one for 2.5k gbp : (still coming soon though) https://www.fogstar.co.uk/collections/solar-battery-storage/products/fogstar-energy-15-5kwh-48v-battery

DC999

https://www.boards.ie/discussion/comment/121411628#Comment_121411628

I don’t see a future of wildly cheap night-rate energy. Would be amazing to have it of course! It’s down to supply and demand, and I see night demand increasing. An example of demand - my EV uses close to the electricity our whole house uses (ex heating and cooking). We’re gonna have a wild amount of EVs all running in that cheap slot. Heatpumps are gonna become more popular and use a lot of juice. If people have UFH, they can run them at night. And load shifting. And, and….

And that’s only residential. I’m sure many companies can load-shift at least a % of the stuff depending on the nature of their business / office / facilities.

 

 

unkel

@DC999 - I do see very cheap and negatively priced electricity. In fact it is already there in the wholesale market (and in the retail market in more mature countries like NL and UK). As we move along to more renewables, we need to have a large overcapacity in wind generation alone. While demand will grow, peak supply will grow even more.

ECO_Mental

Octopus Agile rates in the UK can pay you to take energy when there is peak surplus energy...thats where we need to be.

We actually do it here in Ireland demand response but its mostly for very large customers and it mostly peak demand reduction but they there is peak load as well.

Home Assistant routines and automations will be getting a serious work out when that comes in hopefully down the line

slave1

The principle being it cheaper to pay for “someone” to use the surplus electricity versus shutt8ng down whatever is generating the electricity