Help with changes to current set up

Ectophile

Do check with your DNO (District Network Operator) before installing a larger solar inverter.  The existing system may have been capped at 3.6kW for a good reason.  3.6kW is the maximum that usually goes through without any surveys.  More than that would require prior approval.

Before spending thousands on batteries, work out if the cost savings - the difference between day rate and night rate - will ever pay back the cost of the battery.

Also make sure you aren't going to overload your supply.  Charging an EV, and running the heat pump, and charging the house batteries, and running the immersion heater all at the same time may require an excessive amount of power.

bintyandthebeast

Thanks Ectophile.

I hope to get some time this weekend to sit down and crunch some numbers to see whether additional panels and/or battery storage would work. As I’m not clued up on costs to do the work I’ll need to get a couple of quotes to help with that.

Not certain I can ask the DNO directly about the sizing of the inverter but will look into this too.

Agreed about overloading the supply. I’d asked my electrician about this and he said it would be fine with 2x ev chargers in total. We wouldn’t be using sauna overnight; hot tub is a 1.5kw heating element when it kicks in; immersion won’t be used as we’ll have the heat pump for higher efficiency; and cooker/induction hob are also not in use at cheap rate period.

Thanks for your input!

bintyandthebeast

Hi all, late addition to this thread but hoping to get some more advice. 

Fogstar have 2x batteries available at what looks to be great prices on their website for Black Friday:

Fogstar Energy 16.1kWh 48V Heated Solar Battery £1,799.99

and 

Fogstar Energy ECO 48V 16.1kWh Solar Battery £1,399.99

Would either of these be suitable for a simple swap out on my current system so I could get 2x batteries installed? I’d probably look to change whatever I need to change to get the batteries to charge / discharge at a higher rating than 3.6kw but if its a swap out may be possible myself for 1 I it’s a decouple and couple option?

QrizB

bintyandthebeast said:

Would either of these be suitable for a simple swap out on my current system so I could get 2x batteries installed?

I'm going to quote myself from earlier in this thread when we were discussing Fogstar batteries:

Your current system used "high voltage" batteries, not the 48-volt ones that many systems use. As a result it's only compatible with Fox ESS HV batteries. I've got a 16kWh Fogstar battery (not quite the one you link to, but similar). But theyre not compatible with your current inverter.

You also say:

bintyandthebeast said:

I’d probably look to change whatever I need to change to get the batteries to charge / discharge at a higher rating than 3.6kw

That'll mean replacing your current Fox ESS inverter. If you do replace the inverter, your replacement is likely to be suitable for 48-volt batteries.

Speak to a MCS-accredited installer (or your preferred electrician) and ask for a quote for them to supply and install a suitable inverter plus however many Fogstar batteries you think you need.

Solarchaser

For the DNO approval you can just try calling them, north Scotland is SSEn and their number is 0800 048 3516

I'm not sure how helpful they will be, but dont ask, dont know.
I'm southern Scotland and when I called SP energy networks thet said not to bother applying as Southern Scotland was red for generation. 

Id be happy to recommend fogstar batteries, I've run them for around 2 years now and been very impressed.
I have just shy of 60kwh of them, so like 4 of the systems you highlighted. 

Your fox batteries are high voltage, so you couldn't link them to "normal" home batteries which are usually 50V as QrizB has said.
I have a friend running the same fox system who does want to increase his capacity,  so perhaps a deal could be made there, but you would have to be replacing your inverter too, if you moved away from fox, and that won't be cheap.

Most common ac inverters have a 3kw to 3.5kw output, though I think there are some 8kw ones now.
I currently use 2 x Lux ac inverters in parallel to give me around 7kw discharge capacity which usually covers the whole house unless Mrs. Solarchaser decides she wants the oven, the hob, the washing machine and tumble dryer on at the same time 😔

The eddi diverter is a great bit of kit, and for about £50 you can add a relay board to it which does two things, 1 is it it gives inputs for 2x pt1000 temperature sensors so you can see what you water tank is at, and heat until a set temperature,  rather than the thermostat cut out, and the other is it has 2 x 16a relays which you can use as heaters amongst other things, and so you could have one of those relays run your hot tub pump on the overnight tarrif, and/or add in a side held 3kw heating element that would dip into your hot tub to heat the water also. (I've never used one, so cant endorse, but thats what id be doing).
This does however, require a knowledge and comfort level with electrics that you may not be comfortable with.

Regarding batteries and solar, I've recently (a bit over a year ago) changed from trying to consume all my solar charging batteries and heating tanks, to instead charging batteries and heating tanks overnight, and exporting everything i can, this has changed my bill from £1400 (after solar and batteries) to £-200 for the year (excluding EV charging)

bintyandthebeast

Thanks for your feedback.

in my ignorance I thought the labelling on the front of the Fox box showing 48v DC supply would mean a simple changeover. 

This box is in addition to the Growatt 3600TL Inverter (in attic). 

If we change the batteries and increase storage we would need to look at a higher charge / discharge rate. We get 5 hours overnight cheap rate and would scrape filling a single battery but any more than that would need an increase in charge rate as ours will be capped at 3700 watts. 

Our eddies being used for nighttime charge of the cylinder but we have signed off on a heat pump which is being installed in January and we will also be installing a bigger cylinder so won’t be diverting power through the day as will be cheaper to use the heat pump and take the export rate. 

I’ve asked for a couple of quotes now so will see how they come out after they come out to view what’s installed already.

Thanks again!

QrizB

Those 48V stickers are misleading and (I'd suggest) dangerously wrong.

If you look at the Fox battery modules (towards the bottom of your photo) you'll see that they are connected in series; the positive terminal of the top battery connects to the negative terminal of the one below. The individual battery modules might be "48 volts" (the datasheet suggests a 51.2V nominal voltage) but with four in series, the DC voltage at the terminals on your inverter will be over 200 volts - considerably more hazardous than 48 volts and deserving the same respect you'd give to mains electricity.

Datasheet here:

https://www.fox-ess.com/wp-content/uploads/2024/12/EN-HV2600-Datasheet-V3.5-20241119.pdf

gefnew

Fogstar Energy ECO 48V 16.1kWh Solar Battery £1,399.99 at Fogstar | hotukdeals
Is this any good for your new set up to be.