Charging house battery with MG4?

[MickeySw]

would you need a grid connection for bidirectional charging though?

No, but you’ll need a very ‘beefy’ off-grid setup to be able to power a standard EVSE, never mind a rapid charger.

I just don’t think the MG4 V2L is a robust enough system for an off-grid system, not robust enough to recommend someone buying it for that purpose anyway.

Agreed, it was never designed for that purpose, but it’s very useful to support the house battery in case of an extended power outage, (post #10)

 

[Everest]

would you need a grid connection for bidirectional charging though?

Good question. I get the impression that the terms V2G, V2H and V2L are not that well defined and no-doubt different equipment supplies will use the terminology in different ways. AFAIAA, V2G and V2H systems that can supplement the house's grid supply will operate in a similar technical manner to grid-tied solar/ESS inverters. As such, they will require a stable grid with a fixed AC frequency and voltage to synchronise with. Plus, of course, the ability to detect when the grid fails and stop production (anti-islanding), primarily for safety reasons.

V2H systems that can operate 'off-grid' are essentially the same as the 'back-up' AC output from a regular solar/ESS inverter. In that case, they will generate their own voltage and frequency and can be used to power household loads that are connected to an essential-loads circuit. The important thing is that back-up load circuit cannot be grid-tied; it must be either on its own circuit or isolated from the grid via a manual or automatic transfer switch, when needed. Plus, of course, all the issues of earthing will come into play, as already discussed on various other threads.

 

[wattmatters]

would you need a grid connection for bidirectional charging though? I just don’t think the MG4 V2L is a robust enough system for an off-grid system, not robust enough to recommend someone buying it for that purpose anyway.

As an occasional source of power to supplementary charge a home battery during a long grid outage it's perfectly fine.

 

[wattmatters]

would you need a grid connection for bidirectional charging though?

That will depend on the system.

e.g. a Sigenergy birectional DC charge unit can operate while off-grid, but it's a module sandwiched between the battery stack and the inverter - it's an integral component of the Sigenstor system.

If you have a bidirectional charger that's on its Pat Malone, then it likely will need a grid signal to operate.

 

[T1 Terry]

G = Grid

Means the grid operators have full access to your battery at DC levels.

The only time the grid supplier can demand access, is when you use the home battery subsidy scheme ...... no such thing as a free lunch or money for nothing, or any truth in the term, "I'm from the govt and here to help you".

There are sites that explain how they will help you to be an energy supplier in the electricity grid and you give them access to you battery capacity and they sell it at the best price and recharge as needed at the lowest price.

I know people who have built their own approved solar/battery/grid tied system that have it set up on rental properties and use these companies to utilise their system and provide a second income from the rental property. The renter gets no electricity bill assistance from the solar or the govt and the whole thing is tied into the rental agreement contract.

There is nothing stopping a renter from trading in the energy market using their EV as the energy storage unit, so, buying a write off and parking it in the shed and connecting the battery up to a V2G, as long as the house owner approves for the wiring back to the main power board, and buying when the price is cheap and selling when the price is high, you just need a good landlord .....

It might be a future enterprise for unit dwellers who own their property and can get the body corp to agree to it ...... making money for little effort seems to help in these matters, set up a battery in their locker area and wire it into their power system and trade on the energy market, or even assist with their power bill by using the cheap stored power during peak power price periods and recharging when the power is cheap.

T1 Terry

 

[T1 Terry]

would you need a grid connection for bidirectional charging though? I just don’t think the MG4 V2L is a robust enough system for an off-grid system, not robust enough to recommend someone buying it for that purpose anyway.

I guess our time on the road will test this theory out. We plan to use it every time we free camp, can't see the difference between 7kw ac charging each day and 7kw AC discharging each day, it's just the same system operating in reverse. Easier on the battery because the discharge is limited to a max of 7kw, less than a 7.5% load on an SR 51 kw LFP battery, that is extremely light throttle driving and the battery only ever discharges to a max of 20% SOC on a V2L ....

T1 Terry

 

[Corindikev]

There was a thread about 18 months ago when someone tested the V2L capacity and got the full 32 Amps (7.4 kW) discharge fine. They had a kettle boiling, a toaster running & a 1 or 2 bar electric heater all going at the same time. As mentioned it is the limitations of the discharge adapter that determines what can be drawn.

I bought a 32 Amp discharge adapter from Aliexpress in September 24 when i bought the car & I can draw far more than 10 amps. I have never tried to pull 32 amps as the connector has one of those universal 3 pin sockets & I think it would get pretty hot even if I ran it through 6mm² cable. It is very solid & only cost $40.00 but needs a 32 amp discharge socket & this would have raised the cost somewhat.

Not long after I got the adapter it was taken off the market & replaced with a 15 amp version.

 

[Everest]

I just don’t think the MG4 V2L is a robust enough system for an off-grid system, not robust enough to recommend someone buying it for that purpose anyway.

Agree when using the V2L directly. The maximum current is limited so, once you have more than a few inductive loads connected to it, it would likely trip due to not being able to deliver the surge required. The solution, is to use the V2L to 'trickle' feed / top up existing ESS battery system as @wattmatters and @Bricktop X PWR have been doing successfully as detailed on other threads.

There was a thread about 18 months ago when someone tested the V2L capacity and got the full 32 Amps (7.4 kW) discharge fine

Sure it has been demonstrated as working and @Stageshoot powered his whole house using that configuration (V2L Test. 7kW output...)

BUT... if the CCU fails I suspect that MG will quickly see from their logfiles that excess power had been drawn on the AC output and, quite reasonably, decline warranty replacement.

Pat Malone

LOL - had to look that one up!

 

[wattmatters]

Not long after I got the adapter it was taken off the market & replaced with a 15 amp version.

I'd prefer a 15 A option, just a bit more flexible. Can still plug regular plugs into it, but I also have an excellent 15 A extension cables with 2.5 mm^2 wire.

Used the V2L yesterday as we had a longish grid outage (a nasty one at that, the grid dropped to 80 V) and our home battery system is still ~ 4 weeks from being installed.

 

[T1 Terry]

The adaptor I made is capable of the full 7kw, but we have the Victron Multiplus II set to a max of 12 amps input at the moment, but I did remove the cabinetry I'd made so I could plug a cat 5 cable in, so I can plug the adapter and either the 'puter or the phone into it and adjust that higher or lower.

I think any system using the MG4 V2L as a back up, should have that load assist feature via the inverter and house batteries to smooth out any serious overloads, rather than maxing out the V2L resulting a voltage drop.

To each their own, the MG4 combined with the Victron and house battery is enough to power my mig welder while the full house functions are still being powered, that is another advantage of using the heavier gauge cable in the extension lead, no voltage sag stuffing up the welders .... just my crap skill level to blame now

T1 Terry

 

[siteguru]

Bear in mind that the OBC on the 51 (at least - probably also applies to the single phase 64) is rated to 6.6kW and not 7 or 7.4kW.

 

[T1 Terry]

Bear in mind that the OBC on the 51 (at least - probably also applies to the single phase 64) is rated to 6.6kW and not 7 or 7.4kW.

So only 30 amps @ 220vac ...... I feel cheated

T1 Terry