Solar PV battery options

bullit_dodger · 05-08-2022 10:59PM

The "open circuit" voltage does vary a little from manufacturers. I think this is because some are 60 cell panels others are 72 cell panels etc.

My Qcell G9's are 45.1v open circuit - but you have the basic theory right, albeit that limit is per string. Word of caution, I'd also not be "right at" the limit. unkel mentions it above, but it's dependant on temperature, so you want to give yourself a bit of a buffer. That's why many of us could "fit" 13 panels, but in reality 12 is the max as otherwise you'd regularly be getting max voltage alarms every other day.

Another good thing about doing it yourself, is that you can add on the panels as you see fit. Add a couple of panels. See the difference it makes....add some more etc.

insular1 · 06-08-2022 07:17AM

https://www.boards.ie/discussion/comment/119434585#Comment_119434585

Sorry to clarify so if VOC is 50 per panel is it max 600/50=12 per inverter or 12 per string?

championc · 06-08-2022 07:32AM

So max 600v for the inverter overall, and max 520v for any one string is the way I understand it

graememk · 06-08-2022 08:57AM

600V per string. (with a solis inverter)

I have 24 panels, 12 on each string.

unkel · 06-08-2022 09:03AM

https://www.boards.ie/discussion/comment/119435578#Comment_119435578

"Another good thing about doing it yourself, is that you can add on the panels as you see fit. Add a couple of panels. See the difference it makes....add some more etc."

Indeed, but only if they are identical panels in the same string, otherwise the whole string performs as if it were made up of the lowest spec panels. I have that problem myself unfortunately, can't wait to get it sorted.

redmagic68 · 06-08-2022 09:07PM

Hi quick battery question. Complete amateur and novice so go easy. I’m very close to pulling the trigger on a solar system with dyness batteries. 9.6k bank. They are similar to pylontech which from what I’ve read here aren’t special just wondering what you guys thought. It’s with a company so that’s what they use but if they’re totally useless I’d have to reconsider.

it’ll be. 7.2kw 20 x jinko solar panels with a 6kv sofar hybrid inverter, eddi and the 9.6k dyness.

I see bullit dodger is here too so he’ll love to see me and my toddler type solar questions again . But I’m learning.

bullit_dodger · 06-08-2022 09:25PM

Ach man, we all had to learn from somewhere. While I've an engineering background, most of my solar knowledge comes from the likes of unkel and Graememk and a few others knocking about before I came, and we're all still learning. Strenght of boards.ie is the sharing of the knowledge, we don't do that and respect people who don't know things as well as others......we might as well give up and call it a day.

One thing most people will advise though is make sure you get a good few (more than 1-2) quotes ideally from some of the more regular well known "value" companies out there. There's the one I used myself as well as the supplier from Enniskillen. As for dyness, no I've not heard of anything particuarly bad about them. Mostly all the battery suppliers "do what they say on the tin". Sure, some of them will cycle more than others, but for most consumers any of them will do the job.

yankinlk · 06-08-2022 10:53PM

Have a dyness 9months. Flawless.

lafors · 08-08-2022 08:03AM

Rebuilding eventually and planning ahead for battery initially and then add solar down the road.

Was looking at the battery, didn't want the hassle of building my own (though could do it) and contacted bslbatt to get a price on their 10kWh 200A battery that was mentioned here a while back. Back then iirc the battery landed (to Ireland, not delivered or installed) was around 1.5k. They have an Irish supplier now and the price for delivery in Ireland is €4490. Good luck with that!

Build my own it is!

jumpin jack · 09-08-2022 01:47PM

Hi there,

I'm a newbie to the Solar PV world so please forgive my lack of knowledge. I want to build a system to give me some independence from the grid providers and to reduce my impact on the environment. I have a lot of space facing due south that I can fill with a ground mounted solar system. I'm thinking a 15->20Kw array and a 15Kw+ battery system could give me this. I have recently upgraded my heating system to air to water (A pair of 12kw Krono Therm units) and I charge my EV at night using night rate electricity.

What kind of panels , inverters, optomisers, batteries etc. would you guys recommend, I want to build this system myself and get my electrician to finish off and certify the rig.

Thank you.

ColemanY2K · 09-08-2022 02:40PM

https://www.boards.ie/discussion/comment/119449731#Comment_119449731

Hi JJ

I'm in a similar boat. I received planning earlier in the year and intend to embark on something similar although nowhere near as grand as to what you're planning.

The FAQ thread at the top of the Renewable Energies section is a good place to start. WRT panels there's no difference as far as I can see between the various brands. You figure out your total wattage (15 to 20 in your case) and then select whichever panel is the cheapest per watt. The one thing I would recommend regarding panels is to research the different types e.g. PERC Mono Half Cell versus Poly bla bla bla. The same seems to be the case with inverters. With a battery you'll be needing a hybrid. Which one is up to you but the most common on boards appears to be Solis. As for batteries ...well this is where a bit more research is needed. I noticed a couple of experienced posters dissing pylontech recently and perhaps rightly so. You'll need to do your own research on the matter however a good place to start would be on page 1 of this thread. Another thing to note is the feed in tariff (FIT) is now making large battery systems less appealing.

There's a couple of Irish wholesalers selling PV kit online, solartricity is one such business. I have been touch with a number of retailers on alibaba who appear to be extremely competitive. If you can wait two months for the gear to arrive then alibaba could be worthwhile option. Below is a quote I got this morning.

I'm considering ditching one of the batteries from the quote because of the FIT and because the passive house I have designed needs less than 15kw over a 24hr period (reducing battery storage from 20kw to 10kw) and the roof mounting system. That would bring the quote down to circa $8,000 (shipping will be about another 500 quid) which is give or take the same in euros. I'll build my own ground mounted unit and do all the other donkey work myself. One word of warning...the quote excludes VAT and custom duties. Best to allow the guts of 30% on top of whatever quote you receive just in case.

pv.JPG

championc · 09-08-2022 07:35PM

Max inverters permitted to be connected to the grid are

Single phase = 6kW

3 Phase = 10kW

You can oversize on panels. Best fit for batteries= twice the panels kWp

bullit_dodger · 09-08-2022 08:11PM

Isn't 3 phase export limit 11kw mate?

+1 on the oversize panels for inverters, but word of caution that there is a max voltage that you have to remember. Also with that size system you might want to be looking at 3 phase as single phase would be multiple inverters and a bit of a mare :-)

Also a thing to remember on the battery (and one that I'm sort of suffering myself with) is make sure you have adequate charging/discharging rates. My own battery is limited to 2.6Kw and while I can ask for that limit to be removed, it also voids the guarantee that they give for the 10 year timeline. Charging a 20Kwhr with only 2.6Kw would be a pain in the hoop.

ColemanY2K · 10-08-2022 10:51AM

https://www.boards.ie/discussion/comment/119451329#Comment_119451329

OK... just so i understand correctly, i can have multiple inverters but only one of them is permitted to be connected to the grid? if export is capped then theoretically there's a limit to the amount of power which can be sold to the grid in a given year. i am considering upping the proposed size of the array to 15kW, a battery of 10kW and lashing whatever excess is produced back to the grid at 14c per kWh (for example) but if there's a cap i could potentially be over producing and by not having enough storage sending it to the grid for free.

have i got the above right?

championc · 10-08-2022 11:21AM

A 5kWp array can fill a 10kW battery.

Think about it - 15kW generating one third power will fill the battery in less than two hours.

The cap before being taxed via BIK is €200

IMO, It's absolutely nuts even considering something that big. Can you honestly consume 50kWh per day - about 40 during Solar hours (since you'll only be storing 10kWh) ?

You still will have ESB and the Standing Charge - and it's that that is the killer

bullit_dodger · 10-08-2022 12:31PM

+1 on what championc mentions.

We see people rock in with 50Kwhr/day or there abouts with ~7-8Kwp so if you double that you'll be close on 100kwhr/day in summer. Winter you could probably use it with a heat pump etc, but of course then you have the opposite problem of too little production when you need it most.

Unless you've some "good" (subjective) reason like a bit of crypto mining, going three phase to support 15kwp is a level that's beyond most people here. That's not to say that it's undoable, but you'll be "off script" as they say :-)

If you were thinking of a top end kick ass system, I'd probably go two strings of 12x400 watt panels, hooked into a 6Kw single phase inverter. So 9.6Kwp in panels, and then couple that to a 20Kwhr battery. Be pricey doing that battery off the shelf, but if money was no object. otherwise DIY battery. The Fit of €0.14 or so will help you, but that nonsense about €200 before BIK kicks in is sad.

Keep it single phase, but if you have experience with 3 phase, then you have access to stuff/knowledge that I wouldn't have.

ColemanY2K · 10-08-2022 02:44PM

i might considering installing three strings in order to isolate two during the very high generating season and then switch them on in the darker months...the ROI could be pitiful mind you 😂

plenty to ponder, thanks gents.

bullit_dodger · 10-08-2022 02:59PM

Your welcome!

Although if you install something......hell I'd never isolate them out. Worse case you'd get a FIT payment which you'd have to pay a Benefit in kind on, but you'd still be earning coin on the panels. Albeit lower than what it should be without that BIK nonsense.

If you're isolating them because your worried about the 6Kw export limit, most inverters can set the max to export (which naturally enough on a 6Kw is 6kw by default), if you generate more, you'll only "pull down" 6Kw into the inverter from the panels.

unkel · 10-08-2022 03:46PM

Not BIK, income tax. At your marginal rate, which for many people will be around 50% if you take social charges into account too. But there is a significant exemption. I could be wrong here but was it €400 per year? The overwhelming majority of people with PV will not export that much, so they won't pay any tax on what they get paid as a feed in tariff.

bullit_dodger · 10-08-2022 03:50PM

True - income tax would probably be a more appropriate tax than benifit in kind.....although the main point was don't isolate them out. Yes it would mean that you don't have to pay tax, but then you also wouldn't be generating as much income as you could. Seems a bit wasteful to install panels and then not use them. No?