Solar PV battery options

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.

That app is the Solis app. There are 2 Solis apps available Solus Cloud and Solis Home. That one is the Solis Cloud app.

Virtually all the inverters have an app of some description to show you the telemetry of what's happening in the system.

All of what you say is possible, without having to write sophisticated custom automation. You can set charge/discharge times on your battery so that it only discharges during day time rates, where it's needed of course. meaning that you can charge it via the solar panels from say 8am to 7pm, and then when it's dark, the battery will keep you going until night time rates kick in (midnight in the summer)

@THE ALM You really should use the default option to specify the battery type. This is really for Lead Acid's, for the inverter to "guesstimate" the SOC%. You really want the inverter being dumb and learning everything from the BMS of the battery modules.

No default option selectable, with the Solis manual and battery manufacturer both stating to select 'User Defined' and input battery parameters.

I'll chase up when the battery will be added to the Solis firmware but all seems to be working well with both the battery and inverter displaying the same readings.

My apologies, I meant User Defined. That is generally for Lead Acid's when you don't have a BMS. The power curve of Lead Acid's is quite different to LiFePO4's.

I expect you have connected the BMS to the inverter, but it will be doing absolutely nothing.

The BMS should tell the inverter about the voltages and the cell capacities.

Did you try various battery types on the inverter, to see if one worked ?

I'm only saying all of this because I started with a HEYO / DALY BMS. The inverter was all over the place with guessing the SOC%. I was really only getting to use about 70% of the batteries capacity. The Seplos changed everything

I'll keep an eye on it and check the readings on the inverter and the battery bms to see how they tally and see what battery capacity we are seeing with the charging and discharging.

Sent a request to Solis to see what they say.

Actually I just watched his video of assembling the 48V kit

https://youtu.be/igO3Q8lK7H0

Looks like a well made kit, but I really hope they've improved the packaging.

The kit he got didn't have any manual or documents and the bag of screws wasn't properly held in place and ripped open, spilling all over the inside of the kit

I need to watch the follow up video to see how he got past the BMS communication issues

Good to hear, let us know how you get on with the kits, I'm considering getting a couple myself

Seplos are a bit of a weird company it seems. They seem to be trying to act something like a parts manufacturer, and get local distributors to handle the customer support side of things

They seem to get dragged into being a consumer focused company though, and I think they're still building up the support side of things to match

In general their stuff does seem good, I like how they're trying to build in some features for DIY users that you'd only see on the expensive batteries

Jaysis, you going off grid?

That better be paired with at least 30kw of panels 🤣

Okay, time to start an argument 😁

PWOD store vs OYE store, what's your opinion?

They each seem to have people saying they're great and folks saying they're scam artists

From what I can tell PWOD is more expensive generally, so maybe that's a sign that they're ripping people off or a sign that OYE is selling second rate garbage.

Kind of hard to tell when both their stores look mostly the same and they're selling generic looking blue lithium cells

What has your experience been?

Have a look at the ratings for PWOD official store. That will say it all. I wouldn't buy anywhere else tbh