Keeping the lights on when the grid is down

[Entilzha]

Hi folks,

I'm new here, and I haven't done much in the way of prepping other than stashing some long-life food and some water and batteries etc.

I'm in the process of arranging solar panels and a backup battery (Tesla Powerwall) for my home. This was partly because it is greener and I'm becoming a bit of a tree hugger, but also because I thought it would be useful if there is an extended power outage. Imagine my disappointment when I find out that when the grid is down the solar panels won't work, it's not even allowed to charge the batteries in case it completely fills it and tries to send excess onto the grid.

Obviously we'll be able to use whatever power is still in the Powerwall but with no way to refill it that is not really a solution. Does anyone know of a way to either enable the solar panels to continue working (safely - i don't want to kill the guy trying to fix the the outage!) or another way to charge the Powerwall maybe via portable solar panels?

I do also have a small poweroak solar generator and 120w folding panel. That won't last long if I want to keep the fridge/freezer on though.

What would you do?
Larger solar generator (I hear the ecoflows are decent)?

cheers!

Si

[British Red]

I don't know who told you that a powerwall cannot charge when the grid is down, but I suggest that you find a different company to install it!

https://www.tesla.com/support/energy/po ... er-outages

If you have solar, your Powerwall can recharge from your solar system to run your home from solar and Powerwall even when the grid is down. A traditional solar system without a Powerwall does not function during a grid outage

[jennyjj01]

Hi folks,

I'm new here, and I haven't done much in the way of prepping other than stashing some long-life food and some water and batteries etc.

I'm in the process of arranging solar panels and a backup battery (Tesla Powerwall) for my home.
What would you do?
Larger solar generator (I hear the ecoflows are decent)?

cheers!

Si

Hi and Welcome,

That you have any food stash puts you ahead of the curve. Well done.

How far are you down the solar route? Committed to buying anything? It's a scary marketplace with a lot of salesmen, of various levels of integrity!

I'm one of a few here pottering around with Solar: Tiny scale home mashup. A few hundred pounds just for minimal freezer and lights resiliance.

You need to decide why you want solar and what you want it to do. Grid tied? Off grid or hybrid offer very different features.

An off the shelf, full roof commercially fitted system that is grid tied is close to useless in a long term or even short term grid down situation. If you are getting batteries, then why grid tie it? You probably can, but it will be expensive: But you don't need to. Selling power back to the network is no longer worth it IMHO unless you are really overprovisioning on panels. Beware any salesman that makes a song and dance about the money the grid will pay you
Provisioning the right number of panels and the right sized battery are mission critical. make sure that your advisor fully works with you on designing that. If you are going for a full fitted system, then batteries is the only way to be fully resiliant. Don't believe everything the salesmen tell you. YOU decide what you want it for? Resiliance against long term outage? Cheaper daytime electricity? Complete grid down independence?
If you have, or are getting an electric car, that will be central to your plan.https://www.nuvisionenergy.co.uk/solar-inverters
There are MUCH cheaper batteries than those Tesla ones. You are paying for the name.

https://www.dragonsbreathsolar.co.uk/pr ... r-storage/

[Vitamin c]

I'm looking at a solar set up that could keep a hgv truck battery charged up so if you know what you're doing please tell in a solar for dummies way .

[jennyjj01]

I'm looking at a solar set up that could keep a hgv truck battery charged up so if you know what you're doing please tell in a solar for dummies way .

Hi Vitamin_c,
That one is dead easy. You will need just two things: a PWM charge controller at about £9 and a modest sized solar panel of probably about 100W capacity, costing up to £100. Add in a bit of cable and a mounting kit and you're good to go.
The hardest bit, and its pretty simple, is figuring out how much energy you need to put into your battery. E.g. will you just be trickle charging it to stop it naturally leaking to flatness, or will it be getting drained by lights or equipment such as a tv or chiller.
The 100 panel I mounted on my garage was designed for a truck or caravan. the mounting kit was simply a cartridge of glue. Wiring consists of a fat two wire cable from panel to controller, and another fat two wire from the controller to the battery. You could use 30A 'twin and earth' or 13A cable from any DIY place. Some kits come with silly leads with crocodile clips.

Since you are not trying to make 240V mains, you won't need an inverter.

A 100W panel would probably be fine for just trickle charging. Maybe even a pair or quartet of 25W ones
If the truck battery is 24V, you'd need a nominally 24V panel, which would have operating voltage in the region of 30V to 40V. Don't buy a single 12V one for a 24V battery. The charge controller would be dual voltage. You could use a pair of 12V panels and I'd suggest that as the best option.

Example:
Cheapest Charge controller £9
A good 12V panel for £71
or
https://www.amazon.co.uk/Renogy-Monocry ... B07HR6RSB9

24V solar panels are a bit more rare, so you could easily just install TWO 12V panels and wire them in series. (Series just means take the + from one panel and connect it to the - of the other and take the other + as - to the charge controller.

Two of These https://www.amazon.co.uk/gp/product/B08 ... UTF8&psc=1 wired in series would give you 50W, or four in series-parellel would give you 100W

Beware the panels and kits on ebay where they quote absurd and dishonest energy values for £30 kits. If they are little panels with tie down holes in the corner, they will be low wattage.
Surface area is a good guide to what rating they really are. 500mm x 400mm would be about 25W. 600mm x 1200mm for a 100W. If they are much smaller than that, they are lying.

Here's an off the shelf 24Kit, but at only 30W and £211 and with short leads, it's poor value
https://www.amazon.co.uk/SOLPERK-Mainta ... B08S6M3CVK

Message me if you want explanation in even simpler terms.

[bobble]

Jennyjj01, many thanks for that easy to understand info on solar! Just starting to put a little solar set up together. Very helpful!

[Vitamin c]

Thanks
Jenny.

[jennyjj01]

Jennyjj01, many thanks for that easy to understand info on solar! Just starting to put a little solar set up together. Very helpful!

Happy to help, by Personal Message or in thread. It can be a bit daunting at first, so I'm happy to show how cheap and easy it is to get 'something'
And you can be sure I won't encourage you to spend a lot of money, because I'm tight as.

Here's where I did the shopping list for my first set up back in April.
Ample for keeping a car battery trickle charged and charging up AA batteries and lamps

25W panel ~ £30 :
cheap controller £9 :
Blagged car battery £0
And a few £££ spent on lamps and rechargeables. This would ample for keeping a bunch of lamps charged.

[jansman]

Hi folks,

I'm new here, and I haven't done much in the way of prepping other than stashing some long-life food and some water and batteries etc.

I'm in the process of arranging solar panels and a backup battery (Tesla Powerwall) for my home. This was partly because it is greener and I'm becoming a bit of a tree hugger, but also because I thought it would be useful if there is an extended power outage. Imagine my disappointment when I find out that when the grid is down the solar panels won't work, it's not even allowed to charge the batteries in case it completely fills it and tries to send excess onto the grid.

Obviously we'll be able to use whatever power is still in the Powerwall but with no way to refill it that is not really a solution. Does anyone know of a way to either enable the solar panels to continue working (safely - i don't want to kill the guy trying to fix the the outage!) or another way to charge the Powerwall maybe via portable solar panels?

I do also have a small poweroak solar generator and 120w folding panel. That won't last long if I want to keep the fridge/freezer on though.

What would you do?
Larger solar generator (I hear the ecoflows are decent)?

cheers!

Si

You don’t appear to have introduced yourself in the New Member Section. Please do so, as your posts will not be allowed otherwise. Thank you.

[Entilzha]

Good info thanks.

Searched on the subject and found the equivalent UK link says something similar but subtly different. I've reached out to Tesla support for clarification. My engineer thinks this might be disallowed in the UK (blocked at firmware/software level) even though the tech supports it, but is going to look deeper.