Solarexploits

I have 10 of each the higher wattage ones will be feeding a new 4kW 48v inverter, it takes a max of 3kW solar input, so 10 x 310W is just too large, hence I'm intending to use 3 x 3 series strings in parallel, which leaves me an odd 310W panel. The other 240W panels are feeding 2 x 24v solar controllers for additional battery charging, I only have 6 connected so far all in parallel It sounds as though it might be best to find another purpose for the odd 310W panel, maybe a small 24v battery with another baby charge controller I have & use it for my garage lighting, I'll do some maths, but sounds like mixing them is going to be counter constructive.

I have a couple of different panel sizes & trying to work out the optimum way of using them they are 310W, max O/C V 44.9, optimum output V 36.4, opt output A 8.52 & 240W max O/C V 37.4, opt output V29.6, opt output A 8.11 Now I realise if I "daisy chain" in series, I'm simply going to be adding the output voltages together, but say I have 2 of the 310W & 1 x 240W in series, can that cause any damage to the 240W panel due to higher current generated by the 310W panels, or does it simply reduce the output of the 310W panels slightly if at max output. Equally if I put dissimilar panels in series is the unequal voltage a problem, i'm seeing that I'm putting 36.4V in parallel with 29.6V, which my gut tells me isn't good, will I finish up with a median voltage somewhere in the middle, again, can it damage either of the panels & again, does it in effect reduce the output of the more powerful panel?

Ah! Ok, I had assumed he was purely carrying out an electrical check - after all he won't have installed it, but thanks for the info!

@RonskiThanks for the G99 form, but we should only need the G98 as it'll be below the 3.6kW export limit Can anyone tell me if it's G98 form A or form B that we need & for a DIY installation what do you put in for the "Installer details" & particularly what is required in terms of Accreditation/Qualification? I think it's form B as it will be a single inverter rather than multiple?

Ok, I think for him, that is going to be the safest & most cost effective option (might also save me a load of unpaid work!) So, just to clarify, he's with UK Power Networks, so I google to get the G98 form, we fill it out & send it in once we're ready, when do we send in the G99 & do we have to wait for approval? & once ready for operation a sparky signs it off (I have someone for that) & as long as he won't export more than 16A (is that regarded as 3840W,4kW or what?) & that's it, no inspection of anything other than by the sparky? It just sounds far too simple, I thought being grid tied involved loads of paperwork???

Is it worth going thro' the extra hassle to export, I believe you get paid peanuts now for anything going back to the grid? Where do I get the G98 application from & can the commissioning be confirmed by any properly qualified sparky?

So what inspections/certification are carried out for the G99 approval - sorry, I know zero about this, my off grid system is completely off grid, can never feed back to the mains, my grid tie system was an old MCS install back in 2011, so I had no involvement in anything other than paying for it. If he decided to go grid tied, but not bother with getting anything back for anything exported does that make the process simpler & is there any reason he can't use the second hand panels we already have? Are ther any specific mounting requirements for the panels as most of it would go on 2 separate (different heights) flat rooves & we were intending to make our own mounts?

Sorry, perhaps I didn't make it clear in the original post, he has no intention anymore than I do of being completely off grid, in the UK I really don't think it works unless you're building or modifying a place from scratch with that as the aim, even then if you want what we've come to expect as normal living, you'd need a huge array & battery bank & probably wind & a generator as backup, costs would be huge No idea how much a G99 fee is, but you then get into the whole business of electrician's inspections & sign offs, local authority notification, MCS if it's a full supplier install etc etc & with no FIT payments & the alternative being pitifully low, just doesn't seem worth all the hassle of being tied to the grid with associated formalities What I've done & what he's looking at are SH panels, we have 20 on the way, some of which top my system up & the rest for him, a relatively cheap hybrid inverter 4000/5000W & I have access to SH lead acid solar batteries dated only last year at very sensible money, I set my system up (currently 10 x 310W panels, but room for more) for around £1400, he'll be looking at a little more for his, but with the way energy prices are going that should pay back within a couple of years or so We're perfectly capable of doing the work, but don't have the formal qualifications, just don't want to do something that would come back to bite him

Had a quick look at G98/99, so far as I can see it only refers to grid tied systems - charging a battery doesn't in any way connect the off grid system to the grid any more than using a battery charger to charge batteries would surely?

Ok, so I already have several off grid panels myself operating satisfactorily with a lead acid battery bank, this has been used as a temporary installation & test bed, it is far from a "formal" installation, mine mainly runs via a couple of extension leads apart from the lighting which has been removed from the consumer unit & runs via a separate RCD A friend has now asked me to help him with a similar off grid installation, but this is definitely going to be permanent & become a fixture within his house. We are obviously somewhat more concerned with legal/insurance/electrical regs The inverter will be a 48V hybrid unit, only connection to the mains will be for occasional charging if batteries have got too low What is required in terms of switching/fuses between battery bank & inverter? & what is required from the inverter to the mains circuits, he's already assumed he'll need a 2nd consumer unit/RCD's for any circuits he wants to transfer from existing. What is needed in terms of isolation in either case - as this is all off grid, is there any requirement to notify authorities/insurers etc. If you mention specific types of switches/isolaters etc then any links would be useful to ensure we're looking at the right equipment

I would say that unless your home is exceptionally well insulated &/or your energy demands are exceptionally low, then you would be better to accept that connection to the grid is a requirement, but go for something like Octopus's GO tariff, which gives VERY cheap (currently 5p/kWh, expecting that to go up to 7.5p in Oct) overnight leccy for 4 hours (00.30 to 4.30am). If you happen to be on the Siouth coast & have room for a huge array then that would help, but Dec/Jan are always going to be particularly problematic, particularly if panels are covered in snow! I have a 4kW MCS array, installed back in 2011 which has a Solic immersion diverter giving us free hot water for around 8 months & a reduction in gas costs for the other 4 months, obviously associated reduction in all round leccy usage. I've recently installed 10 x SH 310W solar panels with lead acid solar battery backup & I have more panels arriving soon (240W Renusola). The panels/batteries & inverter are providing almost all my summer usage requirements last bill for gas & leccy combined was £36 & most of that was standing charges!. The rest is mainly cooking costs as I don't have the oven/hob/microwave on the battery system as the inverter won't cope with those loads & charging my EV (of course done on the 5p overnight) During lower solar output months I can use the cheap overnight leccy to charge the batteries, further reducing consumption of grid power when it's expensive I reckon it will defo pay for itself within a couple of years, maybe less given the way energy prices are going!

I think the Growatt stuff looks great, but struggling to find a Uk stockholder? Am I looking in the wrong places? But it looks like even the 3500W is going to be best part of a grand, the Steca also by the time you add vat & delivery is best part of £850. Re what I was originally looking at, for £350, so if we forget the PMW charger, I can buy an 60A MPPT controller for around £120 (though for a gain of 25% battery charging that's going to take a while to pay back) so for £470 that would give me what I want & it's split across 2 units so if something does go wrong then at least all is not lost in one hit. Growatt claim a 10 year guarantee, but who would I get supply from where that guarantee would be likely to actually be honoured???

Oh, shoot, told you I was prone to daft errors, I hadn't spotted that was 24V - completely defeats the object of what I'm trying to do! Why are 48V inverters so much dearer than 24V, you'd think handling less current would make them cheaper not dearer!, I'll keep looking - still open to any suggestions cheaper than Victron!

Thanks, that's just the sort of input I was looking for - I'm still at the point of making daft mistakes! Having looked at the feedback of the supplier I wouldn't buy from them anyway! So a similar MPPT unit, https://www.ebay.co.uk/itm/284861192503?hash=item42530cd937:g:HyEAAOSwaAlirdQd any comments? Will this do what I want? Also, can someone explain the hybrid/AC connection side of things to me, given that I already have an MCS 4kW array which has a Solic immersion diverter on it totally separate to the off grid stuff I'm doing now - if I use the AC connection with a hybrid inverter I assume it would only ever take anything from the AC input side if the batteries had become discharged (which I'm very careful never happens) ?

I'd agree Victron is good kit, but they want about 4 times the price for something to do the same job - kinda defeats the object of trying to save money on energy prices!

Looking for an 48V off grid inverter with a max constant supply of 3kW or so, it will rarely be used above 1500W or so, but 1. I want to over spec so it will last & 2. I want to be able to plug the vacuum cleaner/electric fire or lawnmower in without worrying about overloading anything. I currently have 10 x 310W panels going to 2 x 24V solar controllers charging 2 pairs of 12V solar 170Ah of batteries in parallel & running a (supposedly!) 2kW inverter, which is usually only running significantly less than 1kWh of power , but nevertheless sometimes draws some pretty heavy current on the panels, occasionally 40A or so, I'd like to add the last of the power circuits with exception of oven/hob & microwave so as much is off grid as possible, at least in the summer months, hence the requirement to go to 48V to reduce current draw I've been looking at this https://www.ebay.co.uk/itm/393394807847?hash=item5b98286427:g:h6AAAOSwupFgfV6I on Ebay, it appears to do everything I want (I wouldn't be running all the panels on it, I would keep to the 2400W max suggested). I assume using this I don't need to purchase separate controllers as these are already part & parcel of the unit. It seems very cheap for what it is & having already experienced Chinese ridiculous claims of 100A this 6kW that, I don't want to get burnt (possibly literally!) Has anyone had experience of Powland or Easun which are apparently the same units, or suggest any other suitable, reasonably priced unit? Thanks in advance for any info

Hope this hasn't been covered b4, but couldn't find anything on a search I'm a bit of a newbie to solar & battery storage & even more so on V2G & V2L I own a Kona Electric, '21 plate, so far as I'm aware it does neither of the above, tho' it does have a "camping mode" where you can draw power from the 12V system reasonably indefinitely as it gets topped up from the 64kWh battery, (normally charged on 5p/kWh overnight leccy) personally I couldn't be bothered with popping bonnet & hitching up jump leads to take 12v power (horrific amperages to an inverter if you want any significant load!), even if you wired in a plug/socket of some sort (probably invalidating warranty & possibly insurance!) it would still be hardly worth the faff Do any current/previous vehicles have a direct access to the battery power or are we still waiting for V2G or V2L to actually become a usable thing? Apologies for my ignorance, trying to gain knowledge!

I take power direct from the battery terminals at 24V, this powers a 24V inverter to give 230V off grid ac

Ah! Ok, that makes sense, I'm building in a separate system which automatically kicks the battery charger in should the voltage fall that low (21.4V in my case as I run 24V system). Itho' would not ever expect it to drop that far unless we had an exceptionally bad set of weather conditions, at which point I'd be switching loads off from the batteries anyway. I don't leave any essential loads like fridge/freezer on the batteries if we're away for any extended period

Doh! Of course, that's actually dead obvious, I've stated it a*se about face! I believe I've got it right about havinfg some E. or W. facing tho'?

On the solar controllers I have, they have 6 connections, + & - from batteries, + & - from panels & then a further + & minus which are labelled load (shows an icon of a light bulb) In the Chinglish instructions there is no mention of what the load terminals do, (they show a schematic of them supplying a light as an example) I have my supply to the inverter running direct from my main batteries, I can't see any difference if I measure voltage at load terminals as opposed to if I check voltage at the battery terminals. What is their purpose. do they offer some further protection to that 24V supply? Is there any advantage to connecting to load rather than batteries?

Yeah, just done exactly that, we were able to make a substantial difference with some removal/lopping a few years back, the more recent work has little effect in Summer, but will improve things slightly in Winter, unfortunately given the price of tree surgery that's going to be a Loooong payback period!

Further to all the above, I've now added the fridge/freezer & a separate freezer onto the items supplied from the off grid panels & batteries. With crappy weather as we've had like last few days, dull/overcast, it needs the battery charger run overnight for 4 hours on the 5p/unit leccy, & I've also found the Solic immersion suuply isn't quite adequate on it's own when it's as overcast as it has been. However, as long as we get a bit of sun I'm now powering the whole house with the exception of cooking, for nearly all the time, including overnight. I still need to remount panels at a better angle & have space to add a few more. Am I correct that having the panels (provided they are in parallel) at a shallower angle & with some East or West facing should lower the peak output, but extend the time I get supply?

Funnily enough that's the way I saw it, however I can draw over 1.6kW consistently without it causing any problem. With the system at 24V surely 1.6kW on the output of the inverter at 230V would need to have something like 70A on the dc supply side allowing for losses, even at 100% efficiency it's still over 66A???

So from the sound of things there's nothing I can do (reasonably cheaply) with the existing array that's going to improve output, other than if the shading could be removed/improved? I'm actually getting more out of the system now than it ever put out in the early years, but I know we were able to reduce the shading 4 years back with some tree lopping