Solar PV battery options

Thanks. If you hear of anyone that wants to part with one please let me know...

After binge reading 83 pages here I'm really impressed with the depth of knowledge that you guys have shared here!

I'm planning to pull the trigger on a decent sized array on a garage I'm building and go done the DIY battery route. I'm consuming about 16MW per year so committed to a 10KWhr battery and likely a second. That would give me 2x 16s packs.

I have a question regarding inverters. Should I stick with an installer provided hybrid like to solis 6KWhr (with 100A charge/discharge) or opt for dedicated storage inverters?

Can I plug both packs into the solis or would the second pack requir a dedicated inverter?

Thanks!

I was planning on installing the PV inverter in the garage next to a sub consumer unit and run grid power & cat6 in ducts to the main CU.

That would put the PV inverter in the same location as the batteries.

The advantage of a separate storage as I understand it would be increasing my ceiling for charge from grid & discharge current to load.

Any other advantages in having a battery string on a storage inverter? Monitoring, IFTTT, tweaking, etc?

I'll likely run with just the PV inverter to get started. Just ordered 32x 200Ah from PWOD so distilling the shopping list from this discussion next...

@runner2011 For the Dyness, the capacity will double, but charge and discharges RATES would be unchanged I would expect

@theRed73 and ME3000 can only charge from the grid at a rate of 3kW, so it could be that a Hybrid may be able to charge at a higher rate. A separate Storage Inverter gives you a bit more control - like charging a car or heating water before a battery.

Thanks for the reply .. Maybe I didn’t word it quite right .. if I have 2*50A batteries In parallel then the max draw could be 100A so where previously I could power a sustained ~2.5kw draw when 2 are connected it could be ~5kw rather than Solely a 2.5kw draw for twice the length of time ?

Thanks for the reply.. phew.. .. yup I get the peak output on the inverter and I’m ok with that as I knew about it when I bought it.

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Guy up north with puredrive,5kw,2400£, collected.

i wasn’t sure if that was a good price?

We really need to calculate what 5kw battery can expect to save in year. That price might be the "market rate" but does it even pay for itself over 10 years? Ie can u save 240 a year? I know it could last longer than 10 years... but some sort of benchmark to measure costs/value.

Either FIT OR nightrate plus summer charging. Whatever is most....

I wrote a little app last year to calculate this stuff. Two different methods, but since it's better to export (with FIT) than it is to store in the battery, let's change "method 2" to 365 days charging.

So about 8 years to payback a 5Kwhr battery costing €2400 with €0.28 day and €0.078 night rates. This is assuming you do this every single day. Fill up your battery at night and use those 5kwhr during the day. In reality you won't do that as I'm sure you will take vacations and not be in the house etc. so let's call it 10 years.

I think we need more context? To whom was that directed to ddonq1412? What file etc?

I'd be slow to go for a large battery though. Despite what I mentioned above, this was strictly a payback using night time during day rate scenario. It doesn't include FIT or anything. I think a small-medium battery is a good thing for a house (in general) but a massive battery would be something that I think people should think long and hard about unless going the DIY route, which while it isn't as hard as you might think, it's not for everyone

Unfortunately my little app is integrated with my solar installation, so I'd have to decouple it to give it out. But one thing that you forgot in your calcs, is that you have to take care of the "depth of discharge". i.e. if you buy a 5Kwhr battery, you can't go from 100% to 0%, it's more like 100% to 10% if you want the battery to last. You won't kill it in 1 go if you did go from 100%->0%, but it's not good for it.

So your "usable capacity" of a 5kwhr battery is about 4.5Kwhr. Some people recommend that you go from 100% - 20%, so your usable capacity is only 4Kwhr, but I think it's ok to "push it" a little. Hence your break even point is something longer than you have.

Course, this assumes stable rates, in reality we'll (probably) have €0.30+ rates maybe even as much as €0.40 in the future, especially likely for the 2-3 hrs of peak usage when we are all on smart meters.

Everyone is different though. For me, it's wasn't completely about a "break even" point in time. I had the money last year and now, going forward, those winter bills won't sting as much as I can make them €80-90 every 2 months lighter with my 8Kwhr battery by "load shifting" them to night rate.

@bullit_dodger thanks for the comments on the usable battery, I hadnt considered that

@graememk you're right I hadnt considered the higher rates of these smart tariffs and 24 cents for a night unit is eye watering. Did I read something before though on here that you can get an exemption from a smart meter but still get the FiT by reading your own meter? Or will an energy company just not give you the FiT unless you install a smart meter? Given the prices of smart tariffs Im determined to avoid having one until they become mandatory.

And obviously running the house on battery power from a car is a non goer if the charger alone would cost 2-3k and not even be certified which Id guess might then invalidate my house insurance in the event of a fire. Its a pity though as Im a low user of both the car and electricity so if a reasonably priced solution did come along that was safe and certified then it would be an interesting option. But ultimately it would be scuppered by being forced on to much higher smart tariffs compared to the tariff Im on now (30c//9.5c)

Took longer than expected but finally collected the batteries on Thursday.

All intact and well packaged.

Checked charge and cell levels on the internal BMS, no need to hook up anything at this stage as all can be checked on the integrated menu/screen.

Getting these up a stira attic staircase is a pig of a job, get help as they are heavy at 48kg. My impatience got the better of my and I decided to manhandle two up myself!!!!!health and safety would have had a field day🤔 thought my weight and battery combined would have gone through a tread...

Powered down the inverter and hooked everything up before powering back up. Selected User Defined battery type and inputted the parameters provided, saved, exited and all was good. Battery level on the Solis tallied with that shown on the internal BMS. Have been told that a future Solis firmware will have the battery type pre-defined.

Charging and discharging looking good so will run for the weekend before tidying everything up and securing the batteries in there final position.

Although I ordered all the cables I forgot to specify an amphenol surlock connector on one end of the cable for connecting to the Solis. Managed to get a set of cables from an electrical wholesaler and have ordered the surlock connector for the cables I have.