Battery choice

[pau1phi11ips]

I don't think that would be a viable amount for the grid to pay for storage and feedin if it was guaranteed to continue id buy a shedload of lithium and forget putting them in the motorhome just as an investment.

I'm not getting paid for feeding back to the grid. Just charging the battery at 5p/kWh and then using that for the baseload of the house during the day when it's 15p/kWh. See the post above.

It means it's made average price is 8.62p/kWh for the whole day.

 

[Raul]

It's using a Victron Multiplus II inverter in the van.

I'm on Octopus Go tariff, it's 5p/kWh for 4 hours at night. This is enough time to charge the battery up from 15% to 95%. Then it starts discharging back onto the grid to cover the baseload of the house. You can set whatever power you want on the Multiplus to put back on the mains, it's usually on around 180W - 220W.

It's acting as a grid-tied inverter in this case, it syncs to the mains frequency and then ups the voltage just a touch to make that the preferred source for appliances in the house.

The images below show power used by the house without the van system and when it's working.

When I finally get around to fitting the 600W of solar I have to the van the power from the MPPT will be used straight by the inverter when there's enough sun.

Nicely done, the multi 2 and multi grid can feed into the grid. Just don’t feed more than you use local. Otherwise you will supplying the neighbours from your battery. We don’t have grid, so it’s much easier to use the van as a reserve when house bank goes low on dark days.

 

[Tombola]

pau1phi11ips
Love it

So what sort of electrical gear s needed to tell the house electrics to use the van, Ive got a fair bit of lithium and loads of roof space thet I have 3 x 200w panels waiting to go on.
I did have my large kitchen frdige just running off basics coming from the van for a while, thinking it was at least something while my van was sat on the drive, but Id be very intrested in something similar to yours idea.

 

[The Wino]

I'm not clever enough to know but wouldn't some of the energy you produce just leak into the grid rather than be used in your house. How does it know how much power to feed in unless you actually turn off the mains supply.

 

[Raul]

He knows his base load, and adjusts the multi to feed below that value. That way the feed in is used all, and a bit from the grid to make up the difference.

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[pau1phi11ips]

pau1phi11ips
Love it

So what sort of electrical gear s needed to tell the house electrics to use the van, Ive got a fair bit of lithium and loads of roof space thet I have 3 x 200w panels waiting to go on.
I did have my large kitchen frdige just running off basics coming from the van for a while, thinking it was at least something while my van was sat on the drive, but Id be very intrested in something similar to yours idea.

I just plug the Multiplus into a regular household socket on the ring main. You don't need to do anything to house electrics.

I've described it using the analogy that the electricity is water to some people and they seem to have got it so I'll try that here.

Imagine your house wiring is water pipes and the mains supply is a big water tank. You plug something in and turn it on and it's like a tap for the big mains tank water. The Multiplus in the van syncs it's output frequency up to the mains AC sine wave and acts like a another water tank, but it raises it slightly higher than the mains tank (higher voltage). Now when you turn on the tap again, the water will flow from the Multiplus source first because it's higher up. There's a flow control on the Multiplus to limit the flow (current), like it can increase or decrease the pipe diameter at the touch of a button, so it will use power from this first but only up to a point. Then the rest of the power will come from the mains.

The meter on the mains just measures the flow from the mains or to the mains so I try to get this as close to zero as possible.

That make sense? A few people I've told about it have been surprised that both power sources can be connected together without things blowing up but it's really what the Multiplus is designed to do.

At the moment I can just set the Multiplus at 200W output and it'll sit there all day feeding that back into the house and I know it won't feed more back into the grid than I'm using. That's primarily because I have tiny heater in the office that's on all day in the winter. I work from home so the heating in the rest of the house isn't usually on if I can avoid it. It's a different case in the summer when I'm using less power. I had a ET112 meter fitted after the smart meter. This can talk to the Multiplus in the van via wireless ZigBee (I haven't got this working yet tho) and the power the house is using will be the measuring point instead of the power in/out of the Multiplus. Instead of setting the Multiplus to -200W (constantly feeding 200W out), I will set it to 0W with a max feed-in of 500W. Then the Multiplus will try track and try match the house usage between 0 and 500W.

 

[Raul]

You could use a energy meter or current sensor ( Carlo gavazzi) and have the power dinamic controlled. I used current sensor on AC coupled to feed into multiplus with a fronius. The multiplus current sensor has to big resolution and can only limit up to a point. The Carlo Gavazzi works with rs485 into GX control, and can work dinamic.

 

[pau1phi11ips]

I mentioned that at the end of the last paragraph above. The ET112 is fitted but not linked up to the Multiplus yet

 

[Raul]

I mentioned that at the end of the last paragraph above. The ET112 is fitted but not linked up to the Multiplus yet

Sorry missed that as I was typing.

 

[pau1phi11ips]

Sorry missed that as I was typing.

I've also got a Fronius sitting in my loft that I found cheap on eBay last year. My house roof isn't a good aspect for solar but thinking about adding ~2.5kW in the garden this year. Got a corner plot so the garden's massive and there's already a workshop in the far corner with a 32A mains supply to it.

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