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

blobert · 16-11-2023 03:46PM #1

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.

16-11-2023 04:04PM

Is your ev car v2g

blobert · 16-11-2023 04:56PM

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

graememk · 16-11-2023 05:40PM

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 · 16-11-2023 08:23PM

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 · 17-11-2023 01:03AM

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 · 21-11-2023 03:34PM

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 · 21-11-2023 06:46PM

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 · 21-11-2023 07:54PM

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 · 21-11-2023 08:18PM

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 · 21-11-2023 08:53PM

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 · 21-11-2023 08:58PM

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 · 21-11-2023 09:36PM

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 · 21-11-2023 09:58PM

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 · 21-11-2023 10:00PM

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 · 22-11-2023 01:13PM

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 · 22-11-2023 01:20PM

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' · 22-11-2023 04:46PM

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 · 22-11-2023 05:31PM

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 · 22-11-2023 07:29PM

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' · 22-11-2023 07:46PM

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 · 22-11-2023 08:16PM

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 · 22-11-2023 10:00PM

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 · 22-11-2023 10:08PM

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 · 22-11-2023 10:57PM

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 · 22-11-2023 11:25PM

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 · 22-11-2023 11:42PM

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

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

unkel · 23-11-2023 12:36AM

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!