Add additional battery with or without more panels?

[L2]

Currently running 14 x 395w Trina panels with a 3.7 H1 inverter and 5.2kw HV2600 batteries and considering adding additional batteries as helpfully suggested by @Will but now I’m thinking whether to add a few panels at the same time to get the VAT off and would be grateful for some advice.
Will the H1 3.7kw inverter cope with anymore panels as it’s already undersized for my array? If it will cope with more, how many watts extra and would they best on the opposing direction of my main array (so they’d be NW facing) or on a small roof projection I have which would be SW facing but maybe only big enough for 2 panels?

I was looking into adding battery capacity and some were suggesting this is only worth it in the first year of ownership, is this true or can capacity be added and benefitted from at any point? I’ve only had them 6 months so far but it would be good to know whether I definitely need to get on with ordering upgrades if I want them or if there’s more flexibility in this?

I’d also be interested to hear if anyone has talked to an installer about exchanging V1 for V2 BMS for their HV2600 and whether this is going to be mean a lot of downtime with no battery available or will they send the V2 and then allow return of the V1 so no downtime?

Thanks for any help or advice, I’m very willing to take on board anything people can offer to get the best out of my system

[Will]

Hey,

On batteries - you can technically add batteries at any time but the larger the delta in new vs old batteries the worst perfomance you'll get, it's noting worth losing sleep over however. It's recommended to installers to scale within the first year if possible.

On solar - Inverters are limited by solar string voltage so its not about the number of panels but how they are wired. It's common for a solar strings in the UK to be one long serial curcit going into each solar MPPT port but you can have strings of parallel panels to keep the voltage within spec.

I believe the tax free grant would be on a complete system. i.e solar, inverter and batteries but I could be wrong.

If your current system has surplus power that you're exporting I would simply add more batteries. Solar returns are low but battery returns are high normally.

[L2]

Thanks Will, that’s very useful to know. I’m tempted by the extra batteries as we are fully cycling each day so reducing their life span but after some significant lifestyle changes we’re now much lower users than we were (6-8kWh per day) and even this month are using only 1-2 kWh from the grid each day (in the summer that was down below 0.5 kWh a day) so I’m thinking I may let it get further into the winter to see what we’re using, especially if we have a bit of time to decide on battery additions so I can see what makes financial sense..

I hadn’t understood the MPPT wiring capabilities to keep the voltage down so that’s reassuring to know.

Fortunately I managed to get on Agile Outgoing and Agile Incoming (low standing charge version) so we’ve benefitted extremely well from our exported electricity this summer and if I could guarantee those rates I would be less interested in more battery power(!) but I can see that long term, covering our usage as much as possible in all weathers via either Solar or topping up on cheaper TOU tariff is going to be the best option rather than relying on very high export rates.