Solar battery and V2L

[johnb80]

Hi John and others,

Secondly they have strongly advised against charging the batteries other than via the BMS (Solax battery management system).

The BMS should be built in to the battery housing and by connecting your charger to the vacant BATT+ and BATT - connections you will be charging via the BMS. In all likelihood what will happen is the energy from your charger fed from the MG will supplement the battery power going to the inverter, in other words the energy being taken from the batteries will be reduced when demand is high. Only when lightly loaded will you be actually charging your house batteries. An easy check would be to put a voltmeter on the vacant BATT + and BATT - connections and see if you see 53V (ish) when the system is running. I'm confident you will and feeding power in there is no different to what your inverter does. Then again do bear in mind what I was told on here 'You're just some bloke in Lincolnshire advising against what experts have said' so there we go Caveat Emptor LOL.

 

[T1 Terry]

The other thing to be aware of, the MG V2L is only 220vac at best, the Victron inverter charger that we use, can be set down to 220 VAC output and accept in down to 195 VAC. With the MG charging at 10 amps and the toaster, air conditioner and whatever else running at the time, the Victron 5000 VA holds the voltage up at 220 VAC drawing from the 12V Sodium ion 600Ah 12V battery, yet on mains power, the voltage drops to 205 VAC Might be the 5mm² conductor 15 metre extension cord plugged into the 15 metre 2.5mm² conductor extension cord causing that voltage drop

T1 Terry

 

[Everest]

Secondly they have strongly advised against charging the batteries other than via the BMS (Solax battery management system).

Then again do bear in mind what I was told on here 'Youre just some bloke in Lincolnshire advising against what experts have said' so there we go Caveat Emptor LOL.

The old woman from East Anglia concurs with your feedback, @johnb80!

The BMS will be within the battery pack - I can't even get my head around why Solax would imagine that you would not be charging via the BMS.

 

[AmperaE]

Thanks Terry, I'll look into that. I'm not that keen on adding new switches. I've already got a huge MTS to switch between grid and inverter EPS. And what's the point having an inverter with a second ac input if doesn't work unless you implement dry contact. I'm going to complain about this first.

 

[AmperaE]

The old woman from East Anglia concurs with your feedback, @johnb80!

The BMS will be within the battery pack - I can't even get my head around why Solax would imagine that you would not be charging via the BMS.

Beats me, but I'm not really experienced in this field

 

[T1 Terry]

Worth checking the manual to find out what the dry contact relay is designed to do. If it is marked as a generator input, it's purposes is generally to trigger a starting sequence for the generator once the SOC or battery voltage drops to a certain amount, or some are configured to start the generator if mains power is lost.
The inverter manual will have a section about how the dry contacts work and how they are triggered.
I don't know how you would wire it to turn the MG on as a V2L supply once the dry contacts relay is triggered, that was why I was recommending using a change over switch and setting the MG to power the V2L so the whole process was a manual operation .....

T1 Terry

 

[johnb80]

The problem using the generator input is that it's very likely to overload the supply from the MG whereas using the MG to power a battery charger you can set an almost constant load max'd out just under the capability of the MG.
I've set ours so that it draws a constant 2.5 kW and it runs fine, on days of special demand eg Christmas day, I've had it running and it supports the house batteries adding a useful 30kWh extra in the day.

 

[wattmatters]

The problem using the generator input is that it's very likely to overload the supply from the MG whereas using the MG to power a battery charger you can set an almost constant load max'd out just under the capability of the MG.
I've set ours so that it draws a constant 2.5 kW and it runs fine, on days of special demand eg Christmas day, I've had it running and it supports the house batteries adding a useful 30kWh extra in the day.

This is the way.

There are multiple conversion losses of course but when used on an occasional basis or when the energy originally used to charge the car was free / very low cost then it doesn't matter much.

I think the most I drew from the car was 22 kWh over an afternoon and night providing supplemental energy to the home battery during an extended grid outage.

In my new place I won't have this option with the battery system I'll have (Sigenery). It will have capability for a generator input via the gateway but I suspect it will fall foul of the E-N link issue if using V2L as the supply source.

I still have a standard generator. It's an area I will explore in the year ahead. If there is a way to make the V2L a suitable replacement for a generator, we'll have 2 x MG EVs which can supply supplemental energy if needed.

 

[T1 Terry]

The resistor size in the V2L restricts the amount of current that can be drawn. A 2k resistor limits the output to around 10 amps @ 220vac. A 470 ohm resistor increases the draw limit to around 34 amps @ 220 VAC.
The MG itself limits how low the SOC can go before it turns the V2L function off.
This means, as long as the cable from MG to the inverter is a sufficient mm² area conductor, there are no other issues to worry about.

I've used 5 mm² conductor cable, mostly to avoid voltage drop, my Victron inverter is programmable so we have restricted the input current to 12 amps so an overload is not possible if plugged into a caravan park supply.

I plan to make my V2L plug today, so I'll report how it goes ..... there is something seriously wrong with our mains supply and the voltage drops to 185 VAC quite often through evening/night, so we are looking at trying to stabilise the supply voltage by using the MG4 battery over night .....

T1 Terry

 

[johnb80]

The resistor size in the V2L restricts the amount of current that can be drawn. A 2k resistor limits the output to around 10 amps @ 220vac. A 470ohm resistor increases the draw limit to around 34 amps @ 220vac.

Where is the inverter for this, onboard the MG or in the adapter?

The MG itself limits how low the SOC can go before it turns the V2L function off. This means, as long as the cable from MG to the inverter is a sufficient mmsq area conductor, there are no other issues to worry about.

Caveat above

I've used 5mmsq conductor cable, mostly to avoid voltage drop, my Victron inverter is programmable so we have restricted the input current to 12 amps so an overload is not possible if plugged into a caravan park supply.

Yep, same here but what does the inverter do if the demand is greater than the supply can feed, trip it's output?

I plan to make my V2L plug today, so I'll report how it goes ..... there is something seriously wrong with our mains supply and the voltage drops to 185vac quite often through evening/night, so we are looking at trying to stabilise the supply voltage by using the MG4 battery over night .....

That doesnt sound so good. Good luck

 

[T1 Terry]

The inverter is part of the AC onboard charger, just being driven in reverse, so the MG4 system has full control of what is happening and takes its instruction from the value of the resistor in the V2L plug. This includes interpreting if it is a charging source input or a V2L output and just how much to output as far as current. Other bits control how deep the battery is discharged and can be programmed via the touch screen.
It's a pity the output voltage is only 220 VAC and not 230 or 240 VAC, but it is what it is ..... so we just have to work with what we have.

At some later date, I want to dive into how the DC side works. Apparently, the V2G uses the DC output and converts that to grid power. I haven't seen one of these miracle devices yet or found any information regarding anyone doing a deep dive into one.

My interest is in direct DC charging the battery from solar, to minimise the losses, but with so many projects on the go at the same time, that one is well towards the back burner at the moment ...... there and not forgotten, and still simmering enough for a thought bubble to surface every so often

T1 Terry

 

[wattmatters]

At some later date, I want to dive into how the DC side works. Apparently, the V2G uses the DC output and converts that to grid power. I haven't seen one of these miracle devices yet or found any information regarding anyone doing a deep dive into one.

Sigenergy's DC charge modules are V2G ready. It's the networks and car manufacturers who need to approve its use. Essential Energy have been testing its V2G capability with a Ford Lightning.

Vehicle to grid milestone: Electric ute trial paves way for EVs to be batteries on wheels

A landmark trial with a Ford F150 Lightning electric ute has paved the way for vehicle-to-grid technology to be used across one of Australia's largest electricity networks.

thedriven.io

 

[johnb80]

The inverter is part of the AC onboard charger, just being driven in reverse, so the MG4 system has full control of what is happening and takes its instruction from the value of the resistor in the V2L plug.

I dont believe it can be that simple in all honesty, theres a world of difference in taking in AC, convert to DC and taking DC, converting it back to AC. I cant imagine anywhere there will be commonality of circuit blocks etc.

This includes interpreting if it is a charging source input or a V2L output and just how much to output as far as current. Other bits control how deep the battery is discharged and can be programmed via the touch screen.
It's a pity the output voltage is only 220 VAC and not 230 or 240 VAC, but it is what it is ..... so we just have to work with what we have.

Given that the DC voltage will be 400V or more, it should be easy, in fact preferable to run at higher voltage.

At some later date, I want to dive into how the DC side works. Apparently, the V2G uses the DC output and converts that to grid power. I haven't seen one of these miracle devices yet or found any information regarding anyone doing a deep dive into one.

Its going to be nothing more than an inverter with a high voltage DV in, not unlike the solar inputs to an inverter now. It will need a bit of logic to get the contactors to close but that's not insurmountable.

My interest is in direct DC charging the battery from solar, to minimise the losses, but with so many projects on the go at the same time, that one is well towards the back burner at the moment ...... there and not forgotten, and still simmering enough for a thought bubble to surface every so often

A lot of effort for little return.

 

[T1 Terry]

The MG4 SR 51 has 104 LFP cells, a nominal voltage of 333V DC and a fully charged voltage of 380V DC, although the 3.65V per cell is rarely reached because a cell will exceed the 3.65V DC mark and cut the charging, before the other cells reach 3.6V DC.

At the moment, we live in a Winnebago 33ft motorhome and hope to be on the road at the end of the month. We will only have solar power to charge both the 600Ah @12.8V nom. of Sodium ion house battery I just installed, and the MG4 51 as the "tanker" to store as much battery capacity as we can collect, to carry us through the poor solar days.

Relying on the max amount of solar you can squeeze onto the roof of a motorhome, means you can't afford to waste any of it. If I build a solar array with an open circuit voltage of just over 380V DC, by the time the MG battery has reached fully charged, the solar output voltage will have been reached so zero current will flow ..... the battery can't overcharge, but it will get a tapered charge current reduction from 3.42V per cell onwards, ending with a trickle charge by the time the cells reach 3.65V.
No losses converting a high solar voltage to 12V via MPPT, then the losses converting that to 230V AC, feed that into the MG4 charging port and add the losses converting it back into a maximum of 380V DC.

The 10 solar panels will put of 2500W, about 7 amps @ 380V, a full 6 hrs charging will bring it up from 20% SOC to fully charged ......

We can get that and more in summer over here, but being so far south in winter, we get about 2.5 peak sun hrs, so we plan to head north for winter and south to Tasmania for summer to see the BiL that we haven't seen since the wedding, 20 yrs ago ........

That's the plans, I'm rapidly approaching 70 and so far, nothing in those 70 years has ever gone to plan, so I'm not expecting much to change

T1 Terry

[ Edit moderator: 230vdc -> 230V AC ]

 

[johnb80]

The MG4 SR 51 has 104 LFP cells, a nominal voltage of 333V DC and a fully charged voltage of 380V DC, although the 3.65V per cell is rarely reached because a cell will exceed the 3.65V DC mark and cut the charging, before the other cells reach 3.6V DC.

Sounds like a little active balancing needs to be done.

At the moment, we live in a Winnebago 33ft motorhome and hope to be on the road at the end of the month. We will only have solar power to charge both the 600Ah @12.8V nom. of Sodium ion house battery I just installed, and the MG4 51 as the "tanker" to store as much battery capacity as we can collect, to carry us through the poor solar days.

Sounds like a plan

Relying on the max amount of solar you can squeeze onto the roof of a motorhome, means you can't afford to waste any of it. If I build a solar array with an open circuit voltage of just over 380V DC, by the time the MG battery has reached fully charged, the solar output voltage will have been reached so zero current will flow ..... the battery can't overcharge, but it will get a tapered charge current reduction from 3.42V per cell onwards, ending with a trickle charge by the time the cells reach 3.65V.

DC to DC booster? get the supply voltage higher, theyre pretty efficient nowadays and whats lost in electronics loss would be gained by quicker charging.

No losses converting a high solar voltage to 12V via MPPT, then the losses converting that to 230V AC, feed that into the MG4 charging port and add the losses converting it back into a maximum of 380V DC.

Good job you dont have a Taycan LOL

The 10 solar panels will put of 2500W, about 7 amps @ 380V, a full 6 hrs charging will bring it up from 20% SOC to fully charged ......

We can get that and more in summer over here, but being so far south in winter, we get about 2.5 peak sun hrs, so we plan to head north for winter and south to Tasmania for summer to see the BiL that we haven't seen since the wedding, 20 yrs ago ........

Safe trip, hope all works as it should.

That's the plans, I'm rapidly approaching 70 and so far, nothing in those 70 years has ever gone to plan, so I'm not expecting much to change

You sound just like me.

 

[T1 Terry]

Sounds like a little active balancing needs to be done.

Sounds like a plan


DC to DC booster? get the supply voltage higher, theyre pretty efficient nowadays and whats lost in electronics loss would be gained by quicker charging.


Good job you dont have a Taycan LOL


Safe trip, hope all works as it should.


You sound just like me.

I have to rely on whatever cell balancing the MG4 uses for their LFP batteries, I doubt it's active balancing where they shuffle capacity from the high voltage cell to the low voltage cells, that would be quite a complex system to have 104 induction coils, then link them to balance between the coils, then link back to the cell to either discharge for the lower cell or charge for the high cell/s. I would expect they just use the basic resistor load to burn off a bit of the capacity on the high voltage cells ..... and hope the low voltage cells catch up on the next charge cycle.

As far as the Winnebago and travelling, we have at least 2 yrs to kill while we wait for a new house to be built after the fire that took out the last motorhome and house ...... that's 2 yrs from when the insurance company finally stops buggerising around and actually parts with the $$ ..... fire was last July .....


I'll look into the DC to DC voltage booster idea. The Victron solar MPPT controller is limited to 250vdc open circuit, so if I could step that up to close to 400vdc, that might work better ...... a plan for later .... only have 4 days until we plan to hit the road ......

Funny you mention the Taycan, I was looking at adding a electric motor to either run in the tailshaft or in front of the 6.8ltr V10 fuel guzzler, and it required a 700vdc nom. battery, I'd have to tow a 30 ft trailer to get enough panels to generate the 800vdc to charge that, 21 panels and a 5.25kw solar array

Tried to solder in the new 470 ohm resistor between the earth pin and the PP sensing pin in the CCS2 plug to get the higher output V2L working, the grid voltage was so poor I couldn't get the soldering iron hot enough, so I'm charging the house battery pack and I'll try again tomorrow using the inverter .....


T1 Terry

 

[johnb80]

I have to rely on whatever cell balancing the MG4 uses for their LFP batteries, I doubt it's active balancing where they shuffle capacity from the high voltage cell to the low voltage cells, that would be quite a complex system to have 104 induction coils, then link them to balance between the coils, then link back to the cell to either discharge for the lower cell or charge for the high cell/s. I would expect they just use the basic resistor load to burn off a bit of the capacity on the high voltage cells ..... and hope the low voltage cells catch up on the next charge cycle.

Thats not generally how it's done, I made my own simply by having a power mosfet from each battery to discharge it as required, connect to a simple boost converter, charge a supercap. Then disconnect from the high cell and connect to the low cell and discharge the supecap into the low cell. Works like a dream, 4 amps active balancing.

As far as the Winnebago and travelling, we have at least 2 yrs to kill while we wait for a new house to be built after the fire that took out the last motorhome and house ...... that's 2 yrs from when the insurance company finally stops buggerising around and actually parts with the $$ ..... fire was last July .....

Jeez thats not so good.

I'll look into the DC to DC voltage booster idea. The Victron solar MPPT controller is limited to 250vdc open circuit, so if I could step that up to close to 400vdc, that might work better ...... a plan for later .... only have 4 days until we plan to hit the road ......

All sonds good, enjoy your road trip.

Funny you mention the Taycan, I was looking at adding a electric motor to either run in the tailshaft or in front of the 6.8ltr V10 fuel guzzler, and it required a 700vdc nom. battery, I'd have to tow a 30 ft trailer to get enough panels to generate the 800vdc to charge that, 21 panels and a 5.25kw solar array

Go for it, I look forward to the build thread

 

[T1 Terry]

Thats not generally how it's done, I made my own simply by having a power mosfet from each battery to discharge it as required, connect to a simple boost converter, charge a supercap. Then disconnect from the high cell and connect to the low cell and discharge the supecap into the low cell. Works like a dream, 4 amps active balancing.

Jeez thats not so good.


All sonds good, enjoy your road trip.


Go for it, I look forward to the build thread

We might have our wires crossed here, are you talking about balancing the MG4's LFP battery or a house battery?

I've been using induction coil charge - equalise - discharge - repeat for around 8 yrs, once I found a manufacturer that made a product that worked independently to the BMS.
We used ZHC from 12V to 48V off grid battery systems, I think the biggest was 1200Ah @ 48V..... has functioned faultlessly for around 5 yrs now, the same with all the systems we have used these cell equalisers on .... well, except for a system the owner decided they'd redo the battery wiring and ignored the directions to insulate the terminals if they were removed and mark where each one went so they were fitted back in the correct place, the unit basically tried to balance a 12V configuration with a 3 V cell and simply fused itself internally .......

There is another system that has had some good reviews, Deligreen, never used them myself, I don't like capacitor type balancers, they often either don't work from day one, or fail over time.

The longest continually operating ZHC equaliser I have is on our old Mazda 3500 converted motorhome and I fitted it in 2015 I think, it's still doing a great job, it's my emergency inverter power supply and over flow fridge when it doesn't all fit in the Winnie fridge

T1 Terry

 

[johnb80]

We might have our wires crossed here, are you talking about balancing the MG4's LFP battery or a house battery?

House battery, I would have thought the MG would have active balancing for sure.

I've been using induction coil charge - equalise - discharge - repeat for around 8 yrs, once I found a manufacturer that made a product that worked independently to the BMS.

Yep mine sits on the same battery terminals as the BMS.

We used ZHC from 12v to 48v off grid battery systems, I think the biggest was 1200Ah @ 48v ..... has functioned faultlessly for around 5 yrs now, the same with all the systems we have used these cell equalisers on .... well, except for a system the owner decided they'd redo the battery wiring and ignored the directions to insulate the terminals if they were removed and mark where each one went so they were fitted back in the correct place, the unit basically tried to balance a 12v configuration with a 3 v cell and simply fused itself internally .......

There is another system that has had some good reviews, Deligreen, never used them myself, I don't like capacitor type balancers, they often either don't work from day one, or fail over time.

Mine still appears to be working and isnt showing any signs of distress.

I can imagine early failures of commercial units if they dont use decent capacitors, the caps are worked hard.

 

[T1 Terry]

Thats not generally how it's done, I made my own simply by having a power mosfet from each battery to discharge it as required, connect to a simple boost converter, charge a supercap. Then disconnect from the high cell and connect to the low cell and discharge the supecap into the low cell. Works like a dream, 4 amps active balancing.

Jeez thats not so good.


All sonds good, enjoy your road trip.


Go for it, I look forward to the build thread

So, it's up and working, should I do a photo thing describing how I did it and showing the result .... starting with a disclaimer that this is only how I did it and not an instructional post and any information used is at your peril and no responsibility is implied or accepted.

Would the moderator team be ok with that .... or would they prefer not to take the risk ......

T1 Terry