Simple Options for Cheap 50kwh Battery Buying from China Today

blobert · 11-11-2022 8:09pm #1

Hi Guys,

We're building a house that's going to have a very large PV array (up to 50kw) and 3 phase power.

I'd like the house to be as close to off grid/self sufficient as possible and while it will produce massively more electricity than we'll use over the course of the year this will obviously be done during daylight hours/slanted way more towards summer. So I'm looking to have about 40-50kw of battery storage also to cover the usage (or most of it) when the sun is not shining. We need a big storage capacity as it's a big house that's entirely run on electricity with a lot of our usage in the evening.

Now while the PV panels should have a pretty quick payback I'm aware that batteries are questionable as to whether they will ever payback but I'd still like to have them. In saying that I'm looking to do so in as cost effective a way as possible, ie I've no interest in buying really expensive batteries from a lot of the Irish solar suppliers which can be thousands of Euro for a couple of kw.

I know that there is a lot of discussion of DIY 10kw battery installs and this is definitely the cheapest way to do things (even though the price of the batteries has gone up quite a bit since I checked them earlier this year). For instance, the cheapest I can find for singles day sale today are these. They work out at €167 per kwH

However the issue with these is (a) I'm not in a position to DIY a 50kwh battery using them myself and I doubt I can find anyone to do this for me, I suspect electricians wouldn't touch it when doing one for a paying customer as opposed to in their own home. I know the electricians working on the house or any solar installer I get to connect up our system would probably run a mile from shelves of these all attached together even if I could build it myself/get someone else to.

So what I'm leaning towards are the bigger modules of these in rack form. Yes, they are quite a bit more expensive, this seems to be the best option I can find today at €302 per kwh. While it's not far off x2 the cost of the individual batteries per kwh it's a lot easier for people to work with, has BMS etc. Ie I think if I have a rack of these I can get someone to work with them far more easily than the DIY option.

I'm assuming these batteries can work with a 3 phase system. I'm just wondering if anyone has any input/things I need to be aware of or knows of a cheaper option in rack batteries than what I've found.

Ideally I'd like to place an order today/tomorrow while the Singles Day sales is happening in China, there seems to be a decent discount to be had. But I'm also wary of buying somthing that wont work.

Any advice would be much appreciated!

Thanks

graememk · 11-11-2022 8:48pm

Re sales: there's loads of them if it's singles or whatever the next sale is, don't feel pressured into buying now, watch the price for a while,

you'll see that it doesn't change much, and you will see when you actually get a good price.

I ordered cells at the end of August, the same ones are 3-400 more now for 20kwh "on sale"

Also,do you know what inverter you are going to use? Before rushing in and buying batteries.

the_amazing_raisin · 11-11-2022 8:53pm

Okay that's an absolute monster of a system, are you heating a lava moat or something? 😂

Anyway, here's my 2 cents

So regarding capacity, this is a very much "it depends" question. You've said you want to be able to go off grid, but I will warn you that really isn't economical in Ireland. If you're getting a grid connection anyway (sounds like you are) then you're already paying for that expense, so going off grid isn't really going to save anything

However, let's take the argument they you want to be off grid capable, and you've correctly hit on the idea that this changes the math a lot. If you've no grid the live on, then you need the battery to be capable of powering everything in the house at the same time. This is the everything switches on at once scenario

There's two factors to consider, available storage and available power. Available storage is just the number of kilowatt hours you can get out of the battery, the more you have the longer you can live off grid

Available power is the amount of juice you can get out of the battery at one time. This is important because some appliances can have a significant start up load and can put the batteries under stress.

For most lithium batteries, you can safely discharge at up to 1C, or 1 times the battery capacity. So a 50kWh battery can give 50kW of instantaneous power

However you should check the data sheets to confirm this

If you want to answer the question of "how much power" then the simplest method is to add up the rated load of every appliance in your house. It could add up to a pretty eye watering number though 😜

How much capacity it pretty much similar, try to find the nominal amount of electricity used by every appliance for this instead of the peak amount. Then multiply that by the number of hours it'll be running to get the energy needs of that appliance. Add it all together, multiply by the number of days you want to be independent, and that's the battery capacity you need

Okay, so time to talk about inverters

If you've a 3 phase supply, you'll need a 3 phase inverter, or 3 inverters configured to run each phase

IIRC the smallest 3 phase connection that ESBN offer is 29kVA, so you'll need to total inverter capacity to at least match that

3x Victron Quattro 10kVA would do the job, although they aren't certified for the Irish grid

You're correct that the battery isn't 3 phase, that only exists in AC, not DC which the battery supplies

However, there's implications on how you connect the batteries to the inverter. IIRC they should share a common busbar with all the inverters and the batteries should be evenly spaced between the inverters to keep the current balanced

Incidentally, make sure your busbar is rated for something like 800A or more, there'll be a LOT of current coming from those batteries

This really isn't a system that you'd want to be doing DIY as your first outing. There's a lot of complexity that only starts to apply at larger scale so you'd want to get the pros involved

slave1 · 12-11-2022 11:56am

Subscribing to this thread!!!

JHet · 12-11-2022 12:26pm

Checkout the SunSynk youtube channel. They have a lot of videos on commercial grade setups which is basically what you've got there.

https://www.youtube.com/channel/UCirp6bMpAK7AvyKnAo-14FA

There is of course the sales pitch stuff intermingled into everything they do, but there are some great nuggets of information about important considerations for installations at scale.

I certainly found their videos very useful and informative. I can see why their products have become popular here.

blobert · 12-11-2022 1:25pm

https://www.boards.ie/discussion/comment/119863100#Comment_119863100

Thanks for that, I won't feel pressured into buying now then! But they did seem a bit cheaper than what I'd seen a few weeks ago. Probably best to work out exactly what I'm doing first.

slave1 · 12-11-2022 1:35pm

50kWh isn't outragous, there's a good few here with 20kWh setup, my thought would be more along what inverter as that will determine how much power you can suck from the batteries at any moment in time

SD_DRACULA · 12-11-2022 3:03pm

I am a firm believer in the rack mount type batteries, got 4 of them myself, plug and play all the way.

No need to mess with balancing/dodgy cells if unlucky/random BMS errors and just a ton of babysitting but your main issue is that no installer will touch the DIY setup as opposed to being able to connect the rack type of batteries yourself.

Just need a DC breaker/fused disconnect between the battery pack and inverter which any electrician can easily do.

Yes you're paying twice the price but also what is your time worth, mine is worth a lot so I paid up.

Your other issue with buying from China will be warranty, highly unlikely they will stand over it so again a bit of a gamble vs buying from a supplier which is local-ish.

Just be sure the batteries will work with the main inverters, the likes of Solis, Sunsynk/Deye, SolarEdge, Sofar, etc

Not bad for the 6kwh one:

Question remains, will you get shafted by revenue when they land

DC999 · 12-11-2022 5:14pm

https://www.boards.ie/discussion/comment/119865276#Comment_119865276

So what battery setup have you? All you say would push me away from diy.

SD_DRACULA · 12-11-2022 10:52pm

Got four of the 5kwh dyness but to be honest if there was an EU supplier with proper warranty/quick replacement not this China non-sense I would have probably went for it, could have gotten 40kwh for the price of 20kwh but prices also went up on the rack batteries quite a bit since I bought mine at the start of the year.

blobert · 12-11-2022 11:01pm

https://www.boards.ie/discussion/comment/119863116#Comment_119863116

Wow, thanks for the really comprehensive reply, I really appreciate it!

Yes the load of the house could be very large. It's a circa 450m2 bungalow with a seperate 50m2 granny flat all of which is being heated through underfloor electric heating (we intentionally went for this vs a heat pump/underfloor as it was way cheaper and we knew we'd have lots of "free" electricity if we have the huge solar array so a less efficient system won't matter as much). Likewise we'll be just using electric water heating including instant hot water for Granny flat, running 2 electric cars, cooking, I run a 4.5kw sauna pretty much every evening, my wife likes to run a tumble drier near endlessly and we may have a small endless style pool (pool heaters eat electricity). So basically very high electricity requirements and a lot of it later in the day/evening.

On the rack batteries will they work with 3 phase power ok? Ie if I did buy a bunch of them now would I be probably be able to work with them later?

blobert · 12-11-2022 11:06pm

https://www.boards.ie/discussion/comment/119865276#Comment_119865276

Thanks, yes I'd be of the opinion that on top of me probably lacking the skill, I'm not that keen on putting a lot of time into building batteries, I'm ok with paying x2 as much while still being a lot cheaper than local options

Seems the cheapest 6kw ones are sold out now so not an option sadly.

Is it just a lottery as to whether you get charged VAT? The sellers seem to claim no VAT will be charged but that seems not legal!

AMKC · 12-11-2022 11:10pm

I have bought a couple of big batteries from China not for house power but for something else. Smart Propel are very good. My only advice is watch the currency exchange when buying. Yhey deal in Dollars The Euro was at parita with the dollar for a while buts its better than that now so its a good time to buy. Wish I had waited a little longer to get my second battery but I got it at parita.

graememk · 12-11-2022 11:21pm

https://www.boards.ie/discussion/comment/119867422#Comment_119867422

Its a big "it depends"

Batteries don't care if the inverter is single or three phase, all they need to do is handle the power draw.

Although some three phase inverters need "high voltage" packs

Weco for example support this, because they can be configured in series to make the higher voltage.

A possibility is as someone mentioned, having 3 separate single phase hybrid inverters, each dealing with it's own phase and it's own batteries.

Will help you keep the balance between the 3 phases.

mickdw · 12-11-2022 11:22pm

https://www.boards.ie/discussion/comment/119867422#Comment_119867422

Interesting how you are going for the striaght electric heating, avoiding heat pump and running it on your own generated electricity.

How does building regs like that..... High energy demand but with massive renewable production on site?

unkel · 12-11-2022 11:49pm

@blobert - just beware of the rack batteries. All they are is just cells inside with a BMS and an enclosure. With a very substantial price markup. And a lot of the time, they use far inferior cells than the ones we buy to make our own batteries. I could show you some lovely pictures of bloated, degraded, pouch cell internal packs from often highly recommended Pylontech batteries.

If you are not in a super hurry, start watching some vids from the likes of Will Prowse or Off grid garage on YouTube. Then decide for yourself to either make the battery packs yourself or go with the rack batteries.

blobert · 13-11-2022 12:20am

https://www.boards.ie/discussion/comment/119867517#Comment_119867517

Thanks, we are actually technically putting in a heat pump (an air to air air conditioning unit) and a lot of the rationale for that is just for the sake of the BER. Despite the fact we're building a house to beyond passive standards that will produce way more electricity than it consumes in a year it would have a terrible BER rating without it.

We were going to have a very fancy Danish air to water heat pump, underfloor heating everywhere but it was crazy money, about €60k I believe, while the electric underfloor heating is somthing like €7k. It also didn't make sense to have really efficient heating system as despite being massive the house in theory has a really low heat load of less than 4kw (I don't fully trust the modeling so we're putting in 9-10kw of electric underfloor) so I'd be long dead before I'd ever make up the savings in having the more expensive/efficient system. The air to air heatpump/aircon is €7k installed and in theory we can use it to heat the place or part of it with a really high COP (higher than air to water) but I prefer underfloor heating to heating through the air. The other advantage of the electric underfloor in the screed/concrete is that it can just be on when the PV is generating (if at all in winter!) and the concrete will retain the heat. So I'm thinking we could just run the heating during the day (literally flicking it on/off if there is PV power) to keep the house at a fairly constant temperature.

blobert · 13-11-2022 12:24am

https://www.boards.ie/discussion/comment/119867602#Comment_119867602

Thanks Unkel,

As discussed I think the main worries with the DIY route is that I'll have a massive load of batteries taped together that no electrician will want to go near.

I also think I'd struggle to find someone to build it for me, I'd imagine they'd be worried that if my children get electrocuted when messing with it that I'd sue them.

Have watched some of the Will Prowse videos but I think building it is beyond my pay grade and also somthing I'm not that interested in spending time doing.

unkel · 13-11-2022 12:44am

It certainly isn't above your pay grade, but if you aren't interested in getting into this stuff and if you are willing to pay an extra €800 for a kitted battery that would take a couple of hours of your time to put together yourself, fair play! My brother in law gets a man in to assemble Ikea flat pack kits all the time, although he generously pays them €20 per hour, not the €400 per hour you are paying 😂

ELM327 · 14-11-2022 9:49am

Listen, I'm aiming for something similar to you - albeit we don't have 3 phase yet. Take it from me, there's plenty of advice on this forum, listen to some of it before doing anything!

Those rack batteries are essentially the exact same as the calb cells. Just getting a box with a fancy connector with 16 of the calb cells in it - and with a BMS. To be honest I'm betwixt and between what to buy myself too. I currently have 20kWh of dyness batteries which I will be selling and replacing with a larger array.

unkel · 15-11-2022 2:03am

https://www.boards.ie/discussion/comment/119871652#Comment_119871652

Not quite. The rack batteries typically have lower quality, lower capacity cells in them than the 200Ah CALB cells.

SD_DRACULA · 15-11-2022 10:16am

https://www.boards.ie/discussion/comment/119875741#Comment_119875741

Or higher quality if you lose the battery lottery and get a bunch of dodgy cells delivered like it has happened for a few people here.

You can also usually hook up a serial cable to the rack batteries and check the voltages to confirm if they're good but yeah it would be nice to "see what's inside" for monitoring the cells for swelling etc, something you can easily see with the CALBs.

It's a gamble either way I suppose.

unkel · 15-11-2022 10:25am

I haven't heard about bad cells from PWOD official store. Also measuring the voltage doesn't say much about if a cell is good or not. There is no swelling on the CALBs but I have seen swelling on lots of other LiFePO4 batteries, the worst probably on the Pylontechs. They have 3 packs of 10 tiny pouches inside the US2000 (2.4kWh). I worked a few of them (that were already slightly swollen) very hard in the last week or so (but within spec or thereabouts) and they are now so fat they look ready to vent if pushed any more. I've retired them from active service 😂

ELM327 · 15-11-2022 10:34am

https://www.boards.ie/discussion/comment/119875741#Comment_119875741

That depends on what you purchase and where from, but watching some named brands on Will Prowse's teardown videos you can find them on ali express. The Trophy, SOK, and EG4 batteries were all given great reviews by him and showed what cells etc were in. Of course, anyone can slap any combination of cells and a BMS into a fancy box and you don't know what you're getting. But in the same way, anyone can sell those blue cells too.

unkel · 15-11-2022 10:45am

That's what I'm saying. That's why myself and others have been recommending for years to only get your CALB cells from PWOD official store.

Sure most cells are fine - particularly when lightly used. But the 200Ah CALBS simply are the best and they can't be found in any of those rack batteries. Sure you would need to be some man to lift a rack battery with 16 CALBS as it would weigh well over 100kg 😂

Also battery cells are expensive so mine have to work very hard for a living. I'm not going to buy 20kWh of cells if 10kWh would have been more or less enough.

blobert · 15-11-2022 7:08pm

Thanks Guys,

If I managed to build a mega 50kw CALB 200Ah cell battery myself or had someone else do it for me what do I need from a electrician to connect it up/certify it?

Ie what can be DIYed and what requires the input of a qualified electrician?

Looks like the cheap battery options are gone now till the next sale in any case so I'll have time to work out what I'm doing

graememk · 15-11-2022 7:33pm

When going that big, possibly 2-3 sets of 20kwh especially when sizing bms's for them.

Time to binge the off grid garage I think his battery is about 40kwh.

unkel · 15-11-2022 8:43pm

@blobert - "what requires the input of a qualified electrician?"

Connecting the inverter to the grid in its own new group / RCBO in your consumer unit is a job for the electrician. You can do everything else yourself, from building the battery to hanging the inverter and doing all the cabling, BMS, balancers, DC and AC disconnects.