Solar battery and V2L

[AmperaE]

@Everest
I just checked the voltage of the v2l. It's 217V ac. The grid reading is 248V. Is that difference within tolerances?

Suppose I'm switching to an isolated charger, will my batteries (2x 5.3kWh Solax T-BAT-SYS-LV-D53 battterypack). allow a second dc input? Will that not interfere with the BMS etc.

 

[siteguru]

217V is right near the bottom of the -6% tolerance for a nominal 230V supply. (-6% / +10% = 216.2V to 253V)

 

[Everest]

@Everest
I just checked the voltage of the v2l. It's 217V ac. The grid reading is 248V. Is that difference within tolerances?

Yes it is (just), as @siteguru confirmed

Suppose I'm switching to an isolated charger, will my batteries (2x 5.3kW Solax T-BAT-SYS-LV-D53 battterypack). allow a second dc input? Will that not interfere with the BMS etc.

If galvanically isolated, it is fine - that's what Chargeverters and similar devices are used for. But, you will need to consider the maximum charge current and fusing aspects, as I mentioned in post #8 in this thread..
things that @Everest said about charging batteries...

 

[wattmatters]

2x 5.3kW Solax T-BAT-SYS-LV-D53 battterypack). allow a second dc input?

Presumably they are nominally 51.2 V battery packs, typical 16S LFP configuration.

Will that not interfere with the BMS etc.

BMS is internal to the battery however it may be communicating with the inverter. Even so, it won't matter, just set the charger to a modest voltage (e.g. ~55 V) and it will stop charging before the BMS needs to do anything.

Ensure you have an appropriate fuse between the charger and the battery (it may have one built in depending on what you are using).

The idea is just to provide some supplemental charge, not be a primary source of energy.

 

[AmperaE]

@wattmatters Thanks for your explanation. Solax however claims you need to use their T-BAT-Charger, which is not compatible my LV inverter :-(

 

[wattmatters]

Solax however claims you need to use their T-BAT-Charger

Well they would.

I don't know all that much about Solax kit, are the battery modules operating in series or in parallel? If they are in series then yes you'd need to stick with a charger they suggest.

 

[AmperaE]

I think it's master/slave, but the batteries level between themselves.

Li-ion Solax-LV
Max Charge Current: 50A
Max Discharge Current :100A
Bat Online Cnt : 2
Battery Parallel Mode :Converge

Master/Slave Settings: Single
Parallel Numbers : 0

 

[Everest]

Datasheet for that product suggests regular 16S configuration with nominal voltage being 51.2V.

SolaX T-BAT-SYS-LV D53 | LV Battery For Solar Energy Storage_Our Products_SolaX Power

Discover the SolaX T-BAT-SYS-LV D53, a versatile residential energy storage solution with 5.3 to 85.1 kWh capacity, easy installation, remote monitoring, and over 6000 cycle life for ultimate convenience and durability. Contact us today!

www.solaxpower.com

 

[AmperaE]

Datasheet for that product suggests regular 16S configuration with nominal voltage being 51.2V.

SolaX T-BAT-SYS-LV D53 | LV Battery For Solar Energy Storage_Our Products_SolaX Power

Discover the SolaX T-BAT-SYS-LV D53, a versatile residential energy storage solution with 5.3 to 85.1 kWh capacity, easy installation, remote monitoring, and over 6000 cycle life for ultimate convenience and durability. Contact us today!

www.solaxpower.com

I'll try to get solax to confirm this. I guess I must connect a charger to the free bat+ and bat- ports on the second battery pack.

 

[AmperaE]

@Everest Which LifePO4 charger would you recommend, suppose I want to power it from my MG4 V2L, which is limited to 2,2kW (~ 10 Amp at 217V AC) ? Would something like this work: LiFePO4 Charger (Fogstar Energy) - 48V 35A ?

I need to connect the charger to the left view of pack (Solax T-BAT-SYS-LV D53). Probably Bat+ and Bat- and leave the BMS and Com unused ?

 

[wattmatters]

What is the output of your V2L adapter/cable/socket?

Mine is only ~ 2.2 kW max, so putting 35 A into a battery would be pushing it (once you account for the conversion losses).

But if your V2L and associated cables are ~3.5 kW max, then 35 A into the battery would be fine.

 

[johnb80]

@Everest Which LifePO4 charger would you recommend, suppose I want to power it from my MG4 V2L, which is limited to 2,2kW (~ 10 Amp at 217V AC) ? Would something like this work: LiFePO4 Charger (Fogstar Energy) - 48V 35A ?
View attachment 36581
I need to connect the charger to the left view of pack (Solax T-BAT-SYS-LV D53). Probably Bat+ and Bat- and leave the BMS and Com unused ?

The Fogstar power supply should be under the maximum rating of your V2L, Even if you assume it's output voltage rises to 55v to achieve 35 amps and 90% efficiency it sneaks in at 2.13 kW. I would expect higher efficiencies than 90%.

If you feel thats too close, get an adjustable power supply instead and adjust the voltage out and/or current limit so that it take the maximum load you feel comfortable with. I do exactly this with out MG5 and have no issues at all, the car providing great support for the batteries I have. I use a converted server power supply to provide my power for the V2L to Batteries.

If you're comfortable dealing with Alliexpress, I've never had a problem, bargains can be had like this:-

Power Supply

I've just ordered one for a similar project for my mate.

Good luck.

J

 

[Everest]

@Everest Which LifePO4 charger would you recommend

One that is adjustable with regard to output current and voltage and needs to be of a galvancially isolated design. As @wattmatters and @johnb80 have said, the Fogstar one is too much current IMHO. It is also lacking in any detail whatsoever with regard to output voltage.

As I mentioned in my post #8 you will need to consider maximum charge rate that your BMS supports and match (or adjust) the charger to not exceed that current when your inverter is running on full charge rate.

I note there are no fuses shown in your diagram and the wiring of your two LiFePO4 packs is sub-optimal; a diagonal architecture is recommended. In view of your question, a read of the excellent Victron Wiring Unlimited guide (link below) would be worthwhile to understand fusing requirements, cable sizes and a diagonal wiring configuration (see page 18).

https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf

 

[johnb80]

One that is adjustable with regard to output current and voltage and needs to be of a galvancially isolated design. As @wattmatters and @johnb80 have said, the Fogstar one is too much current IMHO. It is also lacking in any detail whatsoever with regard to output voltage.

I actually said that IMHO it was just under the max rating of the V2L supply and therefore OK, assuming poor conversion performance too.

As I mentioned in my post #8 you will need to consider maximum charge rate that your BMS supports and match (or adjust) the charger to not exceed that current when your inverter is running on full charge rate.

This isnt quite so relevant, in the operation the current from the power supply will be feeding the inverter and any surplus will be battery charging. I haven't seen any domestic inverters charge capacity less than 3 kW. Just checking the specification of the battery, 100 amps is the maximum charge rate so not an issue here at all.

I note there are no fuses shown in your diagram and the wiring of your two LiFePO4 packs is sub-optimal; a diagonal architecture is recommended. In view of your question, a read of the excellent Victron Wiring Unlimited guide (link below) would be worthwhile to understand fusing requirements, cable sizes and a diagonal wiring configuration (see page 18).

Whilst the theory is spot on the reality and practical use it isn't such a big deal especially when you consider that only two packs are involved and the extra cable length to achieve the diagonal type wiring introduces further resistance and losses. The very short interconnects negates some of the theoretical benefits IMHO.

https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf

What a great find, it's a good read and covers just about everything battery, inverter and wiring related, thanks for sharing.

My setup for this would be to get an adjustable power supply, put a fuse rated at 30 amps in the cable at the battery end or mounted near the battery end. Use the batteries down to about 50% and with a 3kW load on the inverter switch on the power supply, increase the voltage of the power supply until it reaches the 30 amps or so that is required. When the load is removed / reduced on the inverter, more charge will go into the batteries, as the SOC increases the current will reduce considerably until it becomes no more than a trickle of a few amps. My external power supply configured like this never charges my battery to 100%, it does however provide back up power to boost the capacity when the house batteries start to drop to 85% or less, the further they drop the more load the power supply takes on which is a perfect way for the system top operate IMHO. The voltage changes as the battery SOC falls is very small but works well with adjustable PSU's as per above, my PSU terminal voltage is set at 53.1V. My batteries (EVE LiFEP04) have a terminal voltage of SOC 90% 53.2V and 70% 52.9 you can see the very gentle take up of load as the SOC drops and it will run into current limit when the max output of the V2L is reached, it just sits there supplying 3 kW and the batteries supply the shortfall.

 

[T1 Terry]

The Victron gear has the facility to program in the shore power max current and the voltage range, so it can be tuned to suit the low voltage and limited current.

T1 Terry

 

[wattmatters]

I had a small all-in-one inverter charge controller I used as a supplemental source of energy for the home battery. Charge current was programmable in 10 A increments and the charge voltage also adjustable in 0.1 V increments.

I used to set it at 20A or 30A and left the charge voltage at something modest, something in the 54-55 V range.

It was originally controllable with Solar Assistant and Home Assistant (with all parameters remotely adjustable), but sadly the comms card died so it was controllable only by the front panel display. Not that it mattered as it really didn't need settings to be changed. Whenever I needed it I just plugged it in and it kept all the settings. I hooked up an Anderson connector to make it easy to connect/disconnect from the battery if needed (I already had a spare fuse on my DC busbar to connect it to).

Not an endorsement at all, but this sort of thing as an example:

VEVOR Hybrid Solar Inverter Charger 6000W 220/230V Built-in 120A MPPT Controller | VEVOR AU

Shop VEVOR Hybrid Solar Inverter Charger 6000W 220/230V Built-in 120A MPPT Controller at lowest price, 2-day delivery, 30-day returns. Shop now at VEVOR.

www.vevor.com.au

Just connect V2L output to the AC input and DC battery connection to your LFP battery (via a fuse rated to protect the cable). Set battery type to LIB and the default settings are perfectly fine for a standard 16S LFP battery.

Defaults:
Charge current: 30 A (adjustable)
Charge voltage: 56.4 V (adjustable)

 

[AmperaE]

Thank you all very much for the detailed info. Much appreciated. I'm going to mull it over. It's all fairly new to me. I'll report back my progress.

 

[johnb80]

Thank you all very much for the detailed info. Much appreciated. I'm going to mull it over. It's all fairly new to me. I'll report back my progress.

It really isn't as difficult as some would have you believe. Good luck, look forward to hearing what you decide. If you need any further help / advice, don't hesitate to reach out.

 

[AmperaE]

It really isn't as difficult as some would have you believe. Good luck, look forward to hearing what you decide. If you need any further help / advice, don't hesitate to reach out.

Hi John and others,

I've been in contact with Solax a number of times.
They have confirmed that I can use the GEN port of my inverter only for a generator that supports Dry Contact communications. That rules out every simple generator and also V2L. And renders the GEN port of my top of the range inverter pretty useless.
Secondly they have strongly advised against charging the batteries other than via the BMS (Solax battery management system).
During an extended power cut that leaves me with no other option than to run an extension cable into the house and plug in some of the essential devices.

Maybe Solax can modify their firmware for this inverter. I'm going to try Solax Benelux as they seem to have a better reputation.

 

[T1 Terry]

The dry contact just means it will provide a signal to start a generator, nothing to do with feeding power in through this connection point. What you will need is a 3 position changeover switch to select between mains power and the MG V2L power, if the SOLAX inverter isn't smart enough to switch between one or the other, that way you won't end up with two supplies, with very likely different positions in the sinewave, attempting to power the inverter resulting in possibly 415v and a very messy wave form, and an inverter, MG DC to AC inverter and a mains supply, some what compromised ......

By using the 3 position change over switch, a din rail mount switch is the easiest and neatest switch to add to your power board in the meter box, you could even just wire it into the same position as the mains AC feeds in, then you get to choose who supplies the power to run the house and charge the house battery ......

T1 Terry