Adding solar panels? considerations, issues, advice please!

I have 20 panels on 2 strings... 320w each = 6.4kw total
Not on FIT

Givenergy 5kw Gen 1 inverter
3 x 8.2kw batteries

I have room for up to 5 more panels.

1. Can I add 5 panels without other upgrade to inverter?
2. Do additional panels need to be 320w or can they be higher? How to check compatibility - or not an issue?
3. I'm assuming adding to existing strings to make
   2 x 12 panels
   Or 1 x 12 and 1 x 13
   Any views on whether that's ok ....or not?
4. DNO has so far capped me at 5.5kw. Any chance of getting that upped (without a payment)? Cap is probably not a problem as I don't often exceed cap due to non-optimal angle/orientation. And will try to fill batteries and use for own needs otherwise too.
   Shoulder periods additional production should make it worthwhile.

Any other comments or considerations?

I think the max power listed on the datasheet for a gen 1 inverter rated at 5kw is 6.5kw. Also not sure I understand the cap question. If the inverter is 5kw is this not the cap already built in?

Ben472 thanks!

i'm not sure if the max DC 6.5kw means a max and exceeding will be an issue and cause tripping? or if max is exceeded it will be "clipped" and simply not used... and lost?

1. if former case... can i add a small 4 or 5 panel string with a small inverter (givenergy or other) ... ideally would feed batteries but no problem if export excess production and/or self consumption are only options

2. If latter case... i don't think that's a problem. During such peak production its not likely to be huge or often. may be able to use excess myself (if the system can supply it)... but if i lost that prod completely then not toooo worried as I say ... shoulder periods are likely to be far greater

3. for capping... actually i don't know! i'm not sure as production is used for:
   i) self-consumption
   ii) fill batteries
   iii) export to grid
   i'm not sure if all 3 cannot exceed 5kw in total? I think they can... is that 6.5kw? or??

e.g.

if self consumption 1.4kw + batteries fill 2.6kw... what is max output to grid?

Again not exceptionally worried as I don't think that's a massive lost. But if a DNO upgrade to allowance is possible that's a start.... secondly what can I produce needs to be used most effectively

I believe the dno are primarily interested in the export to grid limit. This is the basis of the decision regarding g98, g99 fast track or full g99 applications. I don't believe they are that interested in capping induced by the inverter at all. With regard to max power for the inverter I would think this may invalidate warranty clai,s if there are issues but one for givenergy to advise on.

Tim Adams If you want to add more panels, you could consider adding another inverter (HY3.6?) and putting the additional 5 panels on one string, giving an additional 2kWp (5 x 400). Depending on the voltage of your existing panels, it may not be worth changing those strings as your existing inverter can handle all the output. We reduce the battery charge rate this time of year to extend the export window.

With new inverters coming onto the market, you might be able to pick up a second hand Givenergy hybrid although the new cost isn't that expensive. Of course this option would assume you'd transfer one of your batteries to the new hybrid, thereby increasing your in-house PV/battery capability from 2.5kW to 5kW or 6.1kW, depending on the inverter.

Adding panels to your existing installation wouldn't affect your G99 or DNO export limit but adding another inverter would, so a new application would be required. Givenergy don't recommend installation of dual inverters but there are plenty of dual AC-connected inverter owners who are generally happy with their plant, other than occasional cross-charging. Dual hybrids aren't recommended either but, apart from jacking up grid voltage during export, our dual hybrids play very nicely.

Tim thanks for the input. its very helpful to gather such thoughts as it will help me discuss options with installer...

Interesting thread, let me highjack it for a thought experiment.

Last year, i had the GivEnergy Gen1 5kw inverter, 8kwp shared between on two strings (one facing Easterly, the other facing Westerly) however the unit burnt out in May. I suspect overloaded and overcooked, looking at the spec it indicates max total at 6.5kw.

Ive changed the inverter to the Gen2 5kw, the good news on this next generation inverter looks to be a higher spec and allow for each string to have 7.5kwp, the other good news is that there is still some space on the roof - would be a shame not to use it right.
Adding some additional panels should make us balance in the spring and autumn months, and if we finally get an EV will be ready with the extra home made power.
So my understaning is if i lift each string to be around 6-6.5kwp (so still within the spec) the excess above 5kw generated would just be clipped and dissipate.

If adding a few more panels - should i aim for the same type of panels as the original configuration? or isnt that so important. i suspect the new panels would need to have optimisers on them but would rather not retrofit optimisers on existing panels.
If i have the same inverter as before i dont need to chase additional paperwork with the grid.

Of course this is all ahead of talking with a qualified installer etc,

CharlieSays You also need to look at the max input voltage. Excess power (within reason) will just be clipped but excess voltage can cause issues. I'm no expert on that so check with your installer, but I believe max voltage is a key parameter. To give an idea, we have 12x2 410w panels on E/W arrays which are within about 7 or 8 % of the max input voltage of a 5kw Gen 2 at peak generation potential.

CharlieSays I suspect overloaded and overcooked,

Perhaps also look at providing some forced air cooling to avoid the same happening again? Easy enough to do with either pc fans, or vehicle dashboard fans, and a readily available £8 temperature controller thermostat with sensor.

sponev
Interesting- that adds another upper limit on what i can do, i guess as panels are added in series i add the max output V of the panel spec together to get a value, and that just needs to be below the inverter max V. A couple less than i originally calculated.
Are they ever configured in parallel?
Thanks

SilverArt
Thanks SilverArt - yep i rigged up a fan blowing air above the head exchange and had that running throughout summer, i also stopped importing during the early hours and just had exporting excess as i was generating rather than trying to time the peaks and troughs for optimal cashflow. Both of these made a big difference.

CharlieSays Are they ever configured in parallel?

No, not in domestic situations.

Also bear in mind that the PV voltage is going to be considerably higher in cold weather so you need to do the calculation for the lowest temperature you're likely to see - for most of the UK that's around -10C.

CharlieSays I would recommend consulting someone more expert than me, I have a working knowledge but that's about it. Also the point about cold, bright days mentioned above which can make a difference. Plus you need to take into account the max input you'll see as it's an E/W config - as a rule of thumb 80% but you need to have it calculated properly for your own config to make sure you don't wreck the inverter. Also check the open circuit Vmax to see if that matters.