Aim high, 100 KWh powerwall

What inverter is best to use

  • Singel hybride inverter

    Votes: 3 15.8%
  • Multiple hybride inverters

    Votes: 6 31.6%
  • Single inverter

    Votes: 3 15.8%
  • Multiple inverters

    Votes: 7 36.8%

  • Total voters
    19
  • Poll closed .

Menno

Member
Joined
Aug 24, 2017
Messages
52
This project started end 2017 and only a few things where know.

1. Build with 18650 cells which I salvage from broken packs.
2. Aim for 2 times my highest measured daily use, which is 48 KWh. This means a target pack of 100KWh, as the future also will have an Electric car and Motorbike planned.

In the past years some basics are came up.
3. Max load for my house is estimated between 10 and 15 Kw.
4. I do not want to ballast the batteries more than 0.5C. This means I need at least 30 KWh before I start connecting to the net.
5. Battery packs will be 14S80P which makes an average of 5 KWh per pack. They are with electronics about 30 Kg and that is easier to handle and replace. Pack size is 560mm*400mm*<70mm. The ideas is to place them on the long side.

The first 5 Kw is packed, other are underway, See picture. The pack on the back is a 7S160P. This was my practice pack and I used cells that are not deemed right (low capacity or less than 90% of original capacity) for my Powerwall and is used for charging my E-Bikes. Currently I have >14 KWh packed. This is without a couple of smaller packs and the 7S160P Which I builded to test idea's. I have a steady stream of batteries coming in and currently have tested or are in testing another about 6 KWh on cells and more to come early next years. The expectation s that I will start hooking up somewhere end 2019.

I am not sure with what kind of BMS I will start working and what kind and size invertor I am going to use. I was thinking a Hybrid inverter, any advice is welcome.
 
What do you have running that pulls 48kWh per day? I'd first take a look at that and see if you can reduce it. Then you wouldn't need such a huge powerwall.
 
I said my peak load is 48 kWh a day. My average daily use in winter is about 20. But with a could southerly wind, everyone home, some washing to be done, use of the sauna it just start going up and up. My annual use is about 8000 kWh with a 350 sqr meter house (3500 square foot), a swimming pool, spa, and 2 Sauna's. And we are with four. All runs on electricity. So I covered most of reducing my use.

There is no real issue with the size of the Powerwall. It is just a pet project to build and I will also run my future car and motor bike from it. I have the space, however it is not that big. I got my cells for free. So I just aim high. It is like a road trip, is it how you come to there and not the destination. I learn a lot, reduce the impact on the environment in the mean time. With keeping my house warm it gives me a real warm feeling.

Thank you for thinking with me. If I needed to buy the batteries is would have been very expensive.
 
Better to overbuild for capacity than to underscale. I agree.

You hot water I would see about converting to on demand, if you can (if not already done). The units are LOT better than they were 20yrs ago. For your sauna's, I would see another way of heating them other than thru electricity, or at least primarily through something else. Perhaps you can use evacuated tubes to produce hot water for the sauna (and also for the house if enough). This would go for the spa as well. Evac tubes will work to heat the water drastically, and even works in 0C weather because of the way they work.

For the Pool and Spa, I would have load limiters so that you can't run the Pool/Spa pumps while dryer/water-heater are running or other heavy loads. And vice versa. But have overrides if needed. That way you won't have 4 heavy load devices running at the same time pulling over 5kW of power at once
 
camthecam said:
Id just move into a smaller house..

Great, we not we like our house. I am not building because I need, I am building because I can.


Korishan said:
Better to overbuild for capacity than to underscale. I agree.

You hot water I would see about converting to on demand, if you can (if not already done). The units are LOT better than they were 20yrs ago. For your sauna's, I would see another way of heating them other than thru electricity, or at least primarily through something else. Perhaps you can use evacuated tubes to produce hot water for the sauna (and also for the house if enough). This would go for the spa as well. Evac tubes will work to heat the water drastically, and even works in 0C weather because of the way they work.

For the Pool and Spa, I would have load limiters so that you can't run the Pool/Spa pumps while dryer/water-heater are running or other heavy loads. And vice versa. But have overrides if needed. That way you won't have 4 heavy load devices running at the same time pulling over 5kW of power at once

Hot water is done by hotwater panel. in winter time it will be topped up between 4 and 6 in the morning. The wash machine runs only from 11pm. Mostly drying of the wash is done outside. Only on rainy days the heatpump drier start automatically after finishing the washing. The spa normal goes on only after midnight. use of the Sauna is not that often but is still uses a lot of power.

I am interested in the possibilities of the load limiters, good idea, so I can prevent some items to run when e.g the heatpump is running or cooking.
 
How are you going to charge the pack ? Solar + Wind ?

15kW inverter - get a toroid based unit and check the no-load power use as this can be very significant with some units and use 5kWh per day. Custom tuned inverters can be around 30W standby or less for a 15kW unit (not on pulsed standby). You might be able to get away with a 10kW unit depending on how long the overloads above 10kW last or build your own inverter and just put the transformer in an oil bath, just like a standard commercial distribution transformer and you can then run it at a higher loading for longer.

In one regard the battery is the easy bit.
 
completelycharged said:
How are you going to charge the pack ? Solar + Wind ?

15kW inverter - get a toroid based unit and check the no-load power use as this can be very significant with some units and use 5kWh per day. Custom tuned inverters can be around 30W standby or less for a 15kW unit (not on pulsed standby). You might be able to get away with a 10kW unit depending on how long the overloads above 10kW last or build your own inverter and just put the transformer in an oil bath, just like a standard commercial distribution transformer and you can then run it at a higher loading for longer.

In one regard the battery is the easy bit.

Charging will be Solar, and maybe on low priced night energy. Currently I only have an estimate of max use. Did some measurements already and probably can go with 10 kW. All depent of the time and height I have peaks above that. Any examples you can send a link from are very welcome.

Yes the battery from some point the easy bit, but also a lot of work. :)
 
Well, at least you got your loads sorted out :)

Load limiters would monitor your current draw. You'd have a monitor on each power cable and a relay would be used to fully disconnect a circuit if another circuit is running. That's my understanding of how they work, anyways.
 
Most of the hours of work goes into the battery, but the rest of the system is usually the more tricky bit.

These are the types of inverter board I plan on using to build my own and oil bath cool the toroid. I still need to find one that is closer to 15kW continuous rated (right FET's, QTY and board design). I have seen the boards and just trying to find out who actually makes them.

http://s.click.aliexpress.com/e/BrUq2Uo

The transformer ends up being the largest part of the cost of an inverter due to the additional cost of the high shipping weight and can be well over 50% of the inverter price.

In regards to solar I would try and put as much solar out as possible (more than you need for the peak of summer) because in winter/spring/autum that is when every kW of capacity really counts. I would estimate 15kW of solar as an absolute minimum (summer maximum of 4:1 - i.e. 4kWh for every 1kW of capacity) and probably closer to 25kW to make the most in the shoulder and winter months with some excess in a couple of months in summer, which an EV will soak up.

Try and heat the pool direct from the solar output as this could then reduce the battery size and use the pool as a thermal store or dump load for the solar.
 
It makes no sense to charge your ebike or e vehicles from your powerwall ..

If the solar feeds direct into the e vehicles you will have saved your powerwall work and it will last longer ...

Or just make sure you charge vehicles when the sun is out , then power is taken out of the powerwall into the vehicles at the same time power is going from panels into the powerwall ... so the powerwall voltage is fairly constant , the cells are neither charging or discharging and will last longer.

Bottom line , try to avoid charging e vehicles at night.

I notice that although 33 people have read this thread , only 3 have voted in the poll ...I suspect , like me , most are not sure what a hybrid inverter is , or why it should be necessary to use many ...etc

Anyone care to explain?
 
ozz93666 said:
I notice that although 33 people have read this thread , only 3 have voted in the poll ...I suspect , like me , most are not sure what a hybrid inverter is , or why it should be necessary to use many ...etc

Anyone care to explain?

Hybrid Inverters are discussed in fairly good detail in the FAQ, found on the main page in the top section.
 
ozz93666 said:
It makes no sense to charge your ebike or e vehicles from your powerwall ..

If the solar feeds direct into the e vehicles you will have saved your powerwall work and it will last longer ...

Or just make sure you charge vehicles when the sun is out , then power is taken out of the powerwall into the vehicles at the same time power is going from panels into the powerwall ... so the powerwall voltage is fairly constant , the cells are neither charging or discharging and will last longer.

Bottom line , try to avoid charging e vehicles at night.

Completely agree here. Minimize your conversions as much as possible. Charge when charging doesn't cost anything, which is when the sun is out. When it's not possible, better to use a buck converter to go from the powerwall to the ebike pack. If they are nominally the same voltage, then you'd want to use a buck-boost converter that can top off the ebike even if the powerwall is lower.
 
Nice idea to charge the bikes with a Buck inverter. Will look into that.
 
48 KWh for daily use seems quite high. Upon reading the title I though you want to build a SHTF system.
2x power aim is fine although in my case I'd go for a 3x.
Anyway, it's quite an objective you've set there, hope you complete it successfully.
 
I have already Hot water solar heating, which in summer, when temp looks to top out,will be dumped into the pool to get a nice pool temperature. Currently I have 15KW build and another coming in the next coming months. Only when I am above the 30KW I will start connecting to the grid. I have currently only about 600W solar panel. Which preferable will be updated with a solar roof.
 
completelycharged said:
These are the types of inverter board I plan on using to build my own and oil bath cool the toroid

http://s.click.aliexpress.com/e/BrUq2Uo

I looked at these and wonder, would love to learn but don't have the experience or extra money yet.

I am in the 1600 kwh monthly range as well or 50 or so a day.

If you do have a build log, would love to learn. Also any of your building, you have did your homework. I have my basic work done but know for sure that I am not accounting for everything correctly.

CB
 
Menno said:
This project started end 2017 and only a few things where know.

1. Build with 18650 cells which I salvage from broken packs.
2. Aim for 2 times my highest measured daily use, which is 48 KWh. This means a target pack of 100KWh, as the future also will have an Electric car and Motorbike planned.

In the past years some basics are came up.
3. Max load for my house is estimated between 10 and 15 Kw.
4. I do not want to ballast the batteries more than 0.5C. This means I need at least 30 KWh before I start connecting to the net.
5. Battery packs will be 14S80P which makes an average of 5 KWh per pack. They are with electronics about 30 Kg and that is easier to handle and replace. Pack size is 560mm*400mm*<70mm. The ideas is to place them on the long side.

The first 5 Kw is packed, other are underway, See picture. The pack on the back is a 7S160P. This was my practice pack and I used cells that are not deemed right (low capacity or less than 90% of original capacity) for my Powerwall and is used for charging my E-Bikes. Currently I have >14 KWh packed. This is without a couple of smaller packs and the 7S160P Which I builded to test idea's. I have a steady stream of batteries coming in and currently have tested or are in testing another about 6 KWh on cells and more to come early next years. The expectation s that I will start hooking up somewhere end 2019.

I am not sure with what kind of BMS I will start working and what kind and size invertor I am going to use. I was thinking a Hybrid inverter, any advice is welcome.

>2. Aim for 2 times my highest measured daily use, which is 48 KWh.
My 24 panel6.885Kwh array produces 44kwh / day this month of June 2019.

>3. Max load for my house is estimated between 10 and 15 Kw.
Prior to my solar system the power comapny reports mydaily hi (with 6 Tonair / 100F day and spa and regular stuff) at around 9kwh. I run several computer servers 24/7 that account for about 1500watts/hour.

image_csojud.jpg


>4. I do not want to ballast the batteries more than 0.5C. This means I need at least 30 KWh before I start connecting to the net.
My 18650 battery bank is 40kwh /780ah @ 48v. Its 14s360p and drivesa 12,000watt AIMS that delivers 240v @ 50a. At full load to the AIMS thats 48v @ 250a DC. 250a / 360cells= 690ma per cell max. The system typically draws between 200 and 350ma per cell thru the day.
My worst cell is 3amp (and best is 10amp) so that's within the 0.5C you are shooting for.

The power delivery to the house is everything active / significant powerexcept spa and air conditioner. This is computers, TV, Refrigerators, Hybrid Hot Water Heater, lights all over house, Cook Top, Kitchen outlets/appliances, offices, shallow well pump, and power tools (table saws, drills etc).

Overall, with 7Kwh PV array,40Kwh battery,and 12.000watt inverter the house (during the day in June) consumes an average of 28kwh 'directly from Panels' and another 15 from the 40kwh battery after the sun goes down and battery has charged up during the day. I have a fixed cut-off at 48v on battery bank and then automatic transfer switch takes over to supply grid.

This puts my DOD (15kwh consumption/40kwh battery)at an average of 38% toconsume everything a 44Kwh Array will deliver each day on a cycle that starts around 10:00am (inverter on at 52v) and ends around 4:00am (inverter off at 48v). That an average consumption by the house of 2750watts/hour over 16hrs.

My numberssuggest you only need 40kwh battery(or less) for daily 48kwh consumption. You may have 10kwh peek for a hour or 2 but I suspect the average is much lower.
 
Sorry for the silly question.

If you have 600W of solar how are you charging the batteries?

If its from the grid what is the advantage of storing?
Is your grid very unreliable.

I voted multiple inverters, Im installing a 5kW Victron Multiplus, they can be paralleled later when I have more battery storage if I want the ability to charge our EV at 7kW.
Our current usage is around 13.5kWh a day plus the car.
 
Jon said:
Sorry for the silly question.

If you have 600W of solar how are you charging the batteries?

If its from the grid what is the advantage of storing?
Is your grid very unreliable.

I voted multiple inverters, Im installing a 5kW Victron Multiplus, they can be paralleled later when I have more battery storage if I want the ability to charge our EV at 7kW.
Our current usage is around 13.5kWh a day plus the car.

Hi John,


There are no silly questions.


The pack is under construction. I have currently 15 KWh. Next month I will add another 5 KWh an more is underway. I have a total of about 30 KWh build or under construction. I only use one brand, type per cassette. So when I have one full it will be added to the other. I do not have it jet connected to the grid, I will do that when I have more than 30KWh in completed cassettes. The 15 KWh is now used to test incoming batteries, charging E-bikes and other packs. The 600W keeps it even in winter nicely topped up. I need to start looking what kind of inverter I need. My max load is estimated on about 15 KW and an electric car is in the planning.
 
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