Mpp Solar pip max 8048 DC or AC coupled battery?

[idontknowwhatimdoing]

Hi there,

I got asked by the company I was looking at buying an EV charger if the battery is AC or DC coupled to the inverter. Assuming that the battery is connected via DC and not AC to separate charger. Does that make it a DC coupled battery?

If that is the case I can't use that smart EV charger to send excess solar to the car.

Is there a "smart charger" that has a CT that connects to battery and detects when charge is going into battery and sends a set min or max/ variable value of amps into an ac charger for the EV?

https://www.google.com/url?q=https://www.mppsolar.com/v3/catalogs/PIP-MAX.pdf&sa=U&ved=2ahUKEwiSnrj4m-n7AhVUMXAKHVZED3AQFnoECAEQAg&usg=AOvVaw19xJxBCS240It0zvrjmUP1

 

[automatikdonn]

I fear you need more details on what exactly your question is. The title doesn't match the content, so it's confusing what it is that you are asking.

Maybe try to reframe the question or update the title.

 

[idontknowwhatimdoing]

Sorry I was just reiterating what I was told by the salesperson and he said that these devices don't work with DC coupled off grid inverters. I have no idea what that means.

I just want to use the MPP Solar Pip Max 8048 inverter with the following to harvest the excess solar, or a set portion of solar in combination with the loads and house battery charging.

Energy Harvesting Wireless Sensor | myenergi Australia

harvi is an energy harvesting wireless sensor, used to help control your renewable energy usage and power your home.

myenergi.com.au

EV Charger | #1 Electric Car Charger ⚡ myenergi Australia

A truly smart solar EV charger. zappi the easiest to use car charger on the market. Approved for electric car charging. As seen on Fully Charged.

myenergi.com.au

Hope this makes sense

 

[automatikdonn]

So I am curious as to why you wouldn't just power the charger with the MPP inverter. It will pull solar and convert it directly to A/C energy if I am not mistaken.

However some simple maths tell me it may take a while to charge your EV with just one of those inverters

8000 /240 == 33.3 amps

If you are comfortable with that charge rate, then I wouldn't really worry about the EV charger being "smart" . Solar would already be provided as a direct feed at layers below the charger.

If you aren't comfortable with that charge rate, then you will need at least a small 48v battery to put a couple of them in parallel. FWIW I have 6 MPP 8048s that are mission critical to my plan of grid irrelevance.

 

[idontknowwhatimdoing]

Yeah my plan was to power the charger with the inverter, as it is off grid.

I'm happy with 8kw max charge. That will do fine to trickle it for my basic driving week to week. Its a 60kw battery and on a good day if I'm home all day it will still do a full charge.

The issue is, in low sun, how will that charger know to reduce output and not suck it out of the house battery. Without me manually adjusting it.

Ps. I only use 7kw to run the house per day.

 

[wattmatters]

Those chargers are designed for use with grid-tied PV systems, which export any energy in excess of household consumption. They are monitoring exports to the grid and adjusting the EV charging rate to keep grid exports to a minimum (up to the rated power draw of the charger), but also to avoid importing grid energy.

They are not suitable for use with off-grid inverters such as a PIP inverter. Off-grid inverters, by their very nature, do not feed excess energy back to the grid. They simply do not generate energy in excess of household demand (including charging of a battery) in the first place. Without any way to know if there is excess generation capacity, those chargers have no way to determine how much power to draw.

 

[idontknowwhatimdoing]

That's what I thought.
Thanks a lot
So what options do I have.

Is there a way that I can detect how much solar is available and/or divert a portion of charge going into the battery into the car? Acting sort of like a load dump?

Because surely the inverter must know how much potential power can be drawn to work out how much to charge the battery current wise or the inverter would just shut down every time it went to charge and there wasn't enough solar.

Would this be something that evse could do?

 

[wattmatters]

Is there a way that I can detect how much solar is available and/or divert a portion of charge going into the battery into the car?

An off-grid system can't know if there is any unrealised PV capacity. It only supplies what the load demands.

The only way to know is to apply a load to see if the system can supply it without discharging the battery.

Because surely the inverter must know how much potential power can be drawn

The inverter has no clue. It simply supplies the load, up to its maximum rated capacity. It can use solar PV and/or battery as the source to supply that load.

to work out how much to charge the battery current wise or the inverter would just shut down every time it went to charge and there wasn't enough solar.

When there is insufficient solar PV to power loads, the inverter begins to supplement that demand from the battery. If the battery is unable to supply the demand then yes, the inverter will indeed shut down.

 

[idontknowwhatimdoing]

This makes sense.
I assumed the off grid inverters could adjust their battery charge rate based on what makes solar is available. Not such a "dumb switch".

So if you set the charge rate of the house batteries in the inverter to 120A it will only start charging once that is available?

Is there a way / product that a CT can sense once the battery is being discharged / charged at a certain rate that it can then vary or stop the EV charger?

 

[wattmatters]

The difference with grid-tied system is that a grid-tied inverter is always presented with an infinite load - the grid. So it will always seek to extract the maximum power the PV array(s) is(are) capable of supplying - because that energy has somewhere to go.

All you then need do is to measure how much of that production is being exported to the grid - that is the excess energy available to be used by the household, be it to run an aircon, charge an EV or heat some water.

With an off-grid system it does not have an infinite load to dump to. So it only extracts from the PV what the loads demands, assuming the PV can supply it. If not then it will begin to draw energy from the battery.

 

[idontknowwhatimdoing]

For some reason I assumed the inverter would work out house load first, then adjust battery charge rate until there is a voltage drop or it detects that the house load is requiring battery or something. Sort of like an mppt algorithm except for charging. ?

 

[wattmatters]

I assumed the off grid inverters could adjust their battery charge rate based on what makes solar is available.

They do. To a limit.

Generally with an off-grid system you specify an upper limit to the charge current for your battery. If the battery is not fully charged and can accept charge, and the PV system is capable of supplying it, then it will charge the battery with whatever PV power is available but only up to the maximum charge current setting of the battery.

If the PV could generate more power but the battery is already charging at its maximum rate setting, then the inverter will cap production so as to not exceed that maximum charge current setting. In that case the only way to see if the PV could generate more power is to apply some load. If the MPPT can respond and supply more power, then it will. But if the PV is maxed out then the current going into the battery will reduce by the amount required to ensure the load is supplied.

 

[idontknowwhatimdoing]

Ah okay, great. That's the main thing.
So back to what I said.

Is there some sort of EVSE that will sense when the batteries are being discharged and stop /adjust charging until there is nil discharge. Surely that could be done with a simple CT? Maybe an extra CT to monitor house loads and deduct that from the max charge rate of EV?

Then all you would need to do is set a max charge rate of EV to not overload the inverter?

 

[wattmatters]

For some reason I assumed the inverter would work out house load first, then adjust battery charge rate until there is a voltage drop or it detects that the house load is requiring battery or something. Sort of like an mppt algorithm except for charging.

Here's a picture showing the solar PV output and battery charging for my off-grid system. This is from a few days ago when we had a nice sunny day and my battery needed a good charge after powering the home the night before.



You can see that the PV output follows a nice maximum production curve for most of the day.

My PV array is not capable of supplying enough power to exceed the maximal charge current limit for my battery, so while ever the battery can accept charge, it will take whatever the PV array can supply.

But a little after 3PM the battery was full and would not long accept charge. Note that steep decline in PV output. There was just nowhere for the PV energy to go, except for the limited household loads it was supplying.

A little later in the day you can see the PV output increase again - the home began to use a lot more power, so the inverter was drawing from the PV array, and production was jumping up and down trying to keep up with changes in household loads. It can't respond fast enough to such rapid changes, so the battery fills in the gaps, sometimes supplying energy, sometimes accepting a little.

Eventually it gets darker as the daylight winds down and so the battery begins to supply more of the demand and eventually it supplies all of it.

 

[idontknowwhatimdoing]

Yeah that makes perfect sense.

Essentially all I would need to do is have the smart EVSE charger treat the battery like the grid in a grid tie setup.

 

[wattmatters]

Is there some sort of EVSE that will sense when the batteries are being discharged and stop /adjust charging until there is nil discharge. Surely that could be done with a simple CT?

A CT is only for detecting/measuring AC current. For monitoring DC current in/out of a battery you either need a shunt or a Hall effect sensor (kind of like the DC version of a CT clamp).

Any sensibly designed off-grid system will have battery monitoring, so you should know whether or not a battery is being discharged, as well as the current state of charge.

 

[wattmatters]

Essentially all I would need to do is have the smart EVSE charger treat the battery like the grid in a grid tie setup.

If you can find an EVSE which can have its charge power rate remotely controlled, e.g. via automations in Home Assistant or Node Red or similar, then you can also integrate your battery shunt data and use that as an input to algorithms to control the EVSE charging rate.

 

[idontknowwhatimdoing]

Ah of course, a shunt. Not CT ?, I guess only a CT for the house / loads side. I definitely am using a shunt.

Surely someone has done this so I can copy and paste their project?

 

[wattmatters]

Plenty have installed home EV chargers, mostly grid tied though.

Some do charge their EV from an off-grid system but they would mostly expect to have sufficient capacity in their system (PV + battery) to manage that demand without much smart control other than manually deciding when to charge.

Some might have set up a smart switch which can turn a charger on or off, but not control the charge rate.

Control of charge rate is generally done by the car, not the charger. If a charger does manage this, it would need to interface with the car's charging system.

Tesla chargers/cars have an app which can control the charge rate, so it might be some of those have been able to automate it. For instance some have done so with Home Assistant being able to control the Tesla app via an API:

Optimizing use of unused Solar Power to charge a Tesla

I am now using the Tesla API to match charging to solar production. Looks pretty good. I have the following script setup to run every minute when the car is charging. service: tesla_custom.api data: command: CHARGING_AMPS parameters: path_vars: vehicle_id: '{{...

community.home-assistant.io

I've no idea whether other charger/EV combinations provide similar access to an app to control charge rate.

Not sure if this is the sort of thing you are looking for, but it's an open source EV charger:

OpenEVSE - Electric Vehicle Charging Solutions

OpenEVSE provides electric vehicle charging solutions worldwide based on SAE J1772 and IEC 61851 standards. Our experts provide components, software and services to accelerate the development of new charging technologies.

openevse.com

One guy did get his Zappi working off-grid, but it involved two inverters, not one:

Charge Your Electric Car At Home Off Grid with a Zappi

Charging your electric car at home or EV off grid is nirvana. Is it really possible to charge a Tesla or Hyundai off grid? It's good to know that you can be self sufficient and not dependent on grid connected power. The Zappi is known for self consumption but can still work off-grid connection...

www.evolutionaustralia.com.au