Stijn
New member
- Joined
- Jun 29, 2020
- Messages
- 6
As mentioned in my introduction post (https://secondlifestorage.com/showthread.php?tid=9620) I promised a plan of my future (to build) system, and I would like your opinions and what I can improve about it!
I hope you like a long read!
Index:
1) Testing the cells
2) Solar panel arrays
3) Electronics, MPPT, inverters, controller etc.
4) Battery Packs + BMS
5) Outdoor Battery Storage
6) Questions
1) Testing the cells.
Thus far I tested several hundred 18650 cells and have currently 150 cells that have passed al my tests.
- First I do a visual check on rust/oxidation (failed = recycle bin).
- Second I do a voltage check, this must be <1.0V (>1.0V recycle bin).
- Third I do an internal resistance test >250mOhm (<250mOhm recycle bin).
After that they get cued for the test bench.
On my test bench I have 8 pre-charging slots at 1A and 4 adjustable slots (currently 500mA). After charging the cells are discharged-tested on 3 Opus BT-C3100 V2.2 (with fan mod). When the cells are tested they get recharged on 8 slots at 1A. All powered with an old ATX computer power supply and fused in the little box with I/O switch. Cells are regularly checked for temperature and heaters are going to the recycle bin. I also have two 10-Ohm 17W resistor discharge slots in case I have to discharge some cells to 0V safely before recycling them.
Tested and charged cells are stored, <1000mAh, 1000-1800mAh and 1800-2000mAh. Only the<2000mAh cells are numbered and registered in my Excel sheet. Cells with 80%+ capacity of the original capacity still left will be used in the power wall. The lower capacities cells (<2000mAh) and higher capacity cells with less than 80% capacity of the original capacity left are stored and are used for other projects. After a month or so I will remeasure the voltage of the cell with the same multimeter to see if the cell is discharging and how much. Attached a screenshot of my Excel file with all the data.
2) Solar panel arrays
Currently there are no solar panels installed but the plan is to start with 9. I dont have a particular solar panel in mind, for my calculations I used an 325Wp solar panel with 85% installation efficiency. During operation 34,2V max, 9,94A max and an open circuit voltage of 41,1V.
These 9 panels are going to be mounted on a ramp (3x3) on the flat roof of the garage, hopefully giving us around 2,5kWatt peak. In the future this will be expanded with another 12 panels also mounted on a ramp (2x6) on the flat terrace roof. The roof on the house doesnt have much space for panels because of a large dormer, only space for 3 panels, maybe 6 with some shadows. All these panels are pointed SW (The Netherlands, northern hemisphere), but I could place another 9 on the NE roof for the morning and midday sun but that wouldnt be very effective and there are some trees there.
So for now the 9 panels on the roof of the garage and in the next couple of years another 12 panels on the roof of the terrace when its build giving us almost 6kW peak total. We are living in a urban part in an terraced house so not much options to place the solar panels unfortunately.
Sketchup drawing above, everything to scale except the roof/dormer.
3) Electronics, MPPT, inverters, controller etc.
I was looking for a complete system with MPPTs and inverters. It didnt have to be a all-in-one system, a modular system also works. Or even preferable actually, if there is a breakdown I only have to repair/replace one part and not the entire all-in-one system.
My eye fell upon the brand Victron, a Dutch company specialized in MPPTs, inverters, battery chargers and all accessories which can communicate with each other. Victron equipment has proven itself in all kind of demanding installations like on trucks, trailers, RVs and boats. It may cost a bit more than other brands or systems but generally I prefer to spend a bit more the first time on good equipment then replacing it a couple of times because of breakdowns or incompatibility.
Below a electrical diagram of the main power distribution of my house and especially everything concerning the MPPTs, inverters, solar panels and other bits like switches, shunt trips, circuit breakers, power cables and communication cables.
MPPT: Im going to start with the 9 solar panels, one Victron MPPT (150V/70A) with spare capacity for the other 12 panels. When all 6+12=21 panels are installed I have a theoretical max open voltage of 123,3V and 69,6A @100% just under the max capacity of the Victron MPPT. The future panels on the roof (3 or 6) and maybe on the NE side (9-12) also get an identical Victron MPPT just in case one breaks down I have some redundancy and can swap them depending on which PV set generates the most power.
Inverters: For my inverters I choose the Victron Multiplus-II, it is capable of charging a battery but Im not going to use that function. It does have the capability to communicate with 2 other Multiplus-II units to supply a 3 phase system like I have (and use for our breathing-air compressor to refill scuba tanks) in this house. It also has the capability to use a energy storage system like I plan to use consisting of my 14S100P 18650 battery pack with BMS communicating with the Victron system. When equipped with a current sensor on the main infeed line the system automatically regulates the currents so there is no ingoing/outgoing current from the grid. Im currently installing only one Multiplus-II and will add two later when there are more solar panels installed and the battery pack is expanded to 2P or 3P (14S100P). Im connecting it to the third phase because of the relative constant power draw (500-800W) day and night powering my server rack (UPS/NAS/Server/computers etc.) and other domotics and control systems giving it a extra UPS function when on batteries. On phase 1 and 2 are my ovens (2500W and 3500W) so a lot of peak power there. I picked the 5000W version so hopefully I can be self sufficient one day (5000/230=21,7A) with grid power backup.
Controller: For controlling all the Victron equipment I require a controller, I picked the Venus GX because of the capabilities it has regarding the MPPT/Solar/Inverters and a Energy Storage System. I dont need a direct display or some of the other functions the other controllers have. It also has the capability to communicate with the Batrium BMS system.
Fusebox: The fusebox needs to be expanded with circuit breakers for the ingoing and outgoing current for each Victron Inverter. In case of repairs, defects or other unforeseen times the bypass switch can be used to completely bypass the Victron/battery/solar installation. After the bypass switch the circuit breakers are powering the house and the large circuit breaker for the garage. Every circuit breaker and residual current circuit breaker is equipped with a feedback contact to indicate if a breaker tripped to the PLC and domotica system. And a overvoltage protection of course in case a lightning strike hits the power grid nearby (if it hits the house directly I have more problems then just the electronics).
All this will be build in my house below the staircase, the cables from the solar panels from the garage will enter the house (20m cable) and from the roof (10m cable) and the battery outside (8m cable). The cables from the battery (with shunt trip) are connected to the 48V busbar together with the incoming power from the MPPTs and outgoing power to the inverter with knife fuse + holder for each inverter. Furthermore some disconnect switches to disconnect the solar power cables, the Victron controller controlling it all and some wire tray to route all the cables neatly.
The diagonal line across the wall is the line the stairs would be, I removed the stairs for this print screen otherwise you barely would see anything interesting.
*The wires going into the floor are going into and through the crawl space below the house and a tube dug in the ground going to our garage.
* I didnt draw all the smaller power cables, communication cables and other smaller cables, just the PV and 48V cables.
4) Battery Packs + BMS
In the beginning the system will have to do with a 14S100P battery pack, with a average cell capacity of 2,5Ah I will have a theoretical capacity of 51,8V, 250Ah and 13kWh (rounded). Enough to sustain the day/night load mentioned earlier of 500-800W through the day and night. Later when I gathered more cells I will add multiple parallel packs to this one expanding the capacity to 26kW (2P) and 39kW (3P).
The BMS will probably be a Batrium BMS system with 14 Longmods, ShuntMon. Its not the cheapest out there but I really like the interface and positive stories out there. And although not officially supported it does communicate with the Victron controller according to user experiences online.
I dont think I need the Expansion Board right now, but who knows in the future.
5) Outdoor Battery Storage
In case youve read my introduction, Im also a volunteer firefighter and unlike a lot of people I really dont want to have the 18650 cells operating within the house. The amount of potential energy stored in the cells with the amount of smoke and heat generated when it goes south gives me not much time to escape the house in case of a emergency. Ive been in house fires fighting the fire from the inside but even with a relative small fire in the living room or kitchen the amount of heat and smoke is deadly very fast, even without the cells burning too.
And although the fire will be evenly intense at least the heat and smoke are going up in the atmosphere and are not accumulated inside the house. I rather lose the battery pack and the housing of it along with some plants and garden fencing outdoors instead of all my stuff, house of loved ones sleeping under the same roof. The same for the garage with all our diving equipment and other stuff we have laying around there.
So the batteries will be stored/operated outside of the house. I havent really chosen an enclosure for the batteries yet. I really like the weatherproof cabinets we have in The Netherlands used by telecom, cable, power and fiber providers placed in the streets but they are extremely rare second handed. Buying a new one will cost around a 1000 for a 1000x800x300mm (WxHxD) sized cabinet, a bit to expensive for my taste. I will keep my eyes open for a second handed one but my hopes arent very high.
Ive also been looking at metal garden sheds, they are weather proof and even larger than the outdoor cabinets, but not as sturdy. I dont have the room to place a container, our garden is only 8x10 meters. A small cabinet can be placed in the garden, but a large container is no option. And although Im not a carpenter Im able to build my own box/shed from wood.
The only really big thing thats been bothering me about outdoor storage is the operating temperature. The weather in The Netherlands can vary from -10 degrees Celsius in the winter to +35(40) degrees Celsius in the summer but not really swing more then 15-20 degrees in 24 hours unlike some other places in the world. If I build a cabinet myself from wood I can insulate it and the winters would be more easily manageable with a simple electrical heater keeping the storage above freezing but to install an air conditioning unit is a bit overdone. We dont have an air conditioning in our house so there is no possibility to blow some cold air though a tube into the battery cabinet.
Ive attached a drawing of a insulated cabinet I made with the possibility to store 3P-14S100P battery packs with some room in front of the battery packs for fuses, busbars, switches and pack monitoring. The bottom row is empty in the event some water or other dirt gets in unintentionally. Its just a draft for now and will definitely change until I feel satisfied about it.
6) Questions:
Some questions are already in the text above bust mostly not, but to summarize them:
1.1: How can I make sure the cells are the right voltage like 30% charge for storage? My current charges only charges to 100%.
2.1: If my calculations are correct the 9 solar panels will produce a max of 2486Wp (3x3x325W@85%), minus the 700W nominal load the batteries will be charged with 1786Wp. At 51,8V pack voltage (14x3,7V) this will be 34,48A in total and 344mA per cell, without nominal load 479mA. I think this is a great charge current per cell, but when I add the extra 12 solar panels the charge current goes up to 984mA with and 1199mA without the nominal load and this looks a bit high to me. Does this mean I have to extend the battery first before adding the solar panels? Or is it possible to manipulate the charging current for the batteries to an acceptable current and deliver the residual current back to the grid?
3.1: I dont have any specific questions about the third chapter/part for now, just want to know your opinion, improvements and thoughts!
4.1: The cell cutoff voltage varies from brand/cell to brand/cell, some are 2,5V but others 3,0V. Can I combine them as long as I keep the pack voltage above 3V or is it best to exclude them and use a lower 2,7V minimal for example for a little bit more capacity?
4.2: Same question as above but now with the upper voltage. Some cells I tested work great until 4,15V (ish) and then start to warm up with 110mA current still flowing through it never reaching the 4.2/4.3V maximum. Exclude them and go to 4.2V max or keep the max voltage at 4,1V?
4.3: Do I need the Batrium expansion board? I only have the shunt trip and no further equipment so far, am I forgetting something?
5.1: Whats the best temperature to operate the battery packs? During the winter the temperature can be minus 10 degrees Celsius but a simple heater (with thermostat) will help with that if the batteries themselves wont generate enough heat while (dis)charging. But how do I manage condensation? Or the hot days like this week while Im typing this (33-37 degrees Celsius in the shade, 20-25 degrees in the night). Do I need active cooling (like an airco) for the cells or is a simple fan enough blowing in outside air?
5.2: What's the best enclosure to house the batteries outside? Metal shed with wood on the inside on a steel frame, or all metal frame? I'm concerned about the rain getting in, the temperature inside (hot or cold), condensation and although we see them rarely mouse, rats and other local animals.
Only one question left: When I start building, would you like to see regular build updates in a project topic or not?
Ask me anything about the project, materials or choices I've made. Tips, tricks and improvements are always welcome!
Greetings, Stijn.
I hope you like a long read!
Index:
1) Testing the cells
2) Solar panel arrays
3) Electronics, MPPT, inverters, controller etc.
4) Battery Packs + BMS
5) Outdoor Battery Storage
6) Questions
1) Testing the cells.
Thus far I tested several hundred 18650 cells and have currently 150 cells that have passed al my tests.
- First I do a visual check on rust/oxidation (failed = recycle bin).
- Second I do a voltage check, this must be <1.0V (>1.0V recycle bin).
- Third I do an internal resistance test >250mOhm (<250mOhm recycle bin).
After that they get cued for the test bench.
On my test bench I have 8 pre-charging slots at 1A and 4 adjustable slots (currently 500mA). After charging the cells are discharged-tested on 3 Opus BT-C3100 V2.2 (with fan mod). When the cells are tested they get recharged on 8 slots at 1A. All powered with an old ATX computer power supply and fused in the little box with I/O switch. Cells are regularly checked for temperature and heaters are going to the recycle bin. I also have two 10-Ohm 17W resistor discharge slots in case I have to discharge some cells to 0V safely before recycling them.
Tested and charged cells are stored, <1000mAh, 1000-1800mAh and 1800-2000mAh. Only the<2000mAh cells are numbered and registered in my Excel sheet. Cells with 80%+ capacity of the original capacity still left will be used in the power wall. The lower capacities cells (<2000mAh) and higher capacity cells with less than 80% capacity of the original capacity left are stored and are used for other projects. After a month or so I will remeasure the voltage of the cell with the same multimeter to see if the cell is discharging and how much. Attached a screenshot of my Excel file with all the data.
2) Solar panel arrays
Currently there are no solar panels installed but the plan is to start with 9. I dont have a particular solar panel in mind, for my calculations I used an 325Wp solar panel with 85% installation efficiency. During operation 34,2V max, 9,94A max and an open circuit voltage of 41,1V.
These 9 panels are going to be mounted on a ramp (3x3) on the flat roof of the garage, hopefully giving us around 2,5kWatt peak. In the future this will be expanded with another 12 panels also mounted on a ramp (2x6) on the flat terrace roof. The roof on the house doesnt have much space for panels because of a large dormer, only space for 3 panels, maybe 6 with some shadows. All these panels are pointed SW (The Netherlands, northern hemisphere), but I could place another 9 on the NE roof for the morning and midday sun but that wouldnt be very effective and there are some trees there.
So for now the 9 panels on the roof of the garage and in the next couple of years another 12 panels on the roof of the terrace when its build giving us almost 6kW peak total. We are living in a urban part in an terraced house so not much options to place the solar panels unfortunately.
Sketchup drawing above, everything to scale except the roof/dormer.
3) Electronics, MPPT, inverters, controller etc.
I was looking for a complete system with MPPTs and inverters. It didnt have to be a all-in-one system, a modular system also works. Or even preferable actually, if there is a breakdown I only have to repair/replace one part and not the entire all-in-one system.
My eye fell upon the brand Victron, a Dutch company specialized in MPPTs, inverters, battery chargers and all accessories which can communicate with each other. Victron equipment has proven itself in all kind of demanding installations like on trucks, trailers, RVs and boats. It may cost a bit more than other brands or systems but generally I prefer to spend a bit more the first time on good equipment then replacing it a couple of times because of breakdowns or incompatibility.
Below a electrical diagram of the main power distribution of my house and especially everything concerning the MPPTs, inverters, solar panels and other bits like switches, shunt trips, circuit breakers, power cables and communication cables.
MPPT: Im going to start with the 9 solar panels, one Victron MPPT (150V/70A) with spare capacity for the other 12 panels. When all 6+12=21 panels are installed I have a theoretical max open voltage of 123,3V and 69,6A @100% just under the max capacity of the Victron MPPT. The future panels on the roof (3 or 6) and maybe on the NE side (9-12) also get an identical Victron MPPT just in case one breaks down I have some redundancy and can swap them depending on which PV set generates the most power.
Inverters: For my inverters I choose the Victron Multiplus-II, it is capable of charging a battery but Im not going to use that function. It does have the capability to communicate with 2 other Multiplus-II units to supply a 3 phase system like I have (and use for our breathing-air compressor to refill scuba tanks) in this house. It also has the capability to use a energy storage system like I plan to use consisting of my 14S100P 18650 battery pack with BMS communicating with the Victron system. When equipped with a current sensor on the main infeed line the system automatically regulates the currents so there is no ingoing/outgoing current from the grid. Im currently installing only one Multiplus-II and will add two later when there are more solar panels installed and the battery pack is expanded to 2P or 3P (14S100P). Im connecting it to the third phase because of the relative constant power draw (500-800W) day and night powering my server rack (UPS/NAS/Server/computers etc.) and other domotics and control systems giving it a extra UPS function when on batteries. On phase 1 and 2 are my ovens (2500W and 3500W) so a lot of peak power there. I picked the 5000W version so hopefully I can be self sufficient one day (5000/230=21,7A) with grid power backup.
Controller: For controlling all the Victron equipment I require a controller, I picked the Venus GX because of the capabilities it has regarding the MPPT/Solar/Inverters and a Energy Storage System. I dont need a direct display or some of the other functions the other controllers have. It also has the capability to communicate with the Batrium BMS system.
Fusebox: The fusebox needs to be expanded with circuit breakers for the ingoing and outgoing current for each Victron Inverter. In case of repairs, defects or other unforeseen times the bypass switch can be used to completely bypass the Victron/battery/solar installation. After the bypass switch the circuit breakers are powering the house and the large circuit breaker for the garage. Every circuit breaker and residual current circuit breaker is equipped with a feedback contact to indicate if a breaker tripped to the PLC and domotica system. And a overvoltage protection of course in case a lightning strike hits the power grid nearby (if it hits the house directly I have more problems then just the electronics).
All this will be build in my house below the staircase, the cables from the solar panels from the garage will enter the house (20m cable) and from the roof (10m cable) and the battery outside (8m cable). The cables from the battery (with shunt trip) are connected to the 48V busbar together with the incoming power from the MPPTs and outgoing power to the inverter with knife fuse + holder for each inverter. Furthermore some disconnect switches to disconnect the solar power cables, the Victron controller controlling it all and some wire tray to route all the cables neatly.
The diagonal line across the wall is the line the stairs would be, I removed the stairs for this print screen otherwise you barely would see anything interesting.
*The wires going into the floor are going into and through the crawl space below the house and a tube dug in the ground going to our garage.
* I didnt draw all the smaller power cables, communication cables and other smaller cables, just the PV and 48V cables.
4) Battery Packs + BMS
In the beginning the system will have to do with a 14S100P battery pack, with a average cell capacity of 2,5Ah I will have a theoretical capacity of 51,8V, 250Ah and 13kWh (rounded). Enough to sustain the day/night load mentioned earlier of 500-800W through the day and night. Later when I gathered more cells I will add multiple parallel packs to this one expanding the capacity to 26kW (2P) and 39kW (3P).
The BMS will probably be a Batrium BMS system with 14 Longmods, ShuntMon. Its not the cheapest out there but I really like the interface and positive stories out there. And although not officially supported it does communicate with the Victron controller according to user experiences online.
I dont think I need the Expansion Board right now, but who knows in the future.
5) Outdoor Battery Storage
In case youve read my introduction, Im also a volunteer firefighter and unlike a lot of people I really dont want to have the 18650 cells operating within the house. The amount of potential energy stored in the cells with the amount of smoke and heat generated when it goes south gives me not much time to escape the house in case of a emergency. Ive been in house fires fighting the fire from the inside but even with a relative small fire in the living room or kitchen the amount of heat and smoke is deadly very fast, even without the cells burning too.
And although the fire will be evenly intense at least the heat and smoke are going up in the atmosphere and are not accumulated inside the house. I rather lose the battery pack and the housing of it along with some plants and garden fencing outdoors instead of all my stuff, house of loved ones sleeping under the same roof. The same for the garage with all our diving equipment and other stuff we have laying around there.
So the batteries will be stored/operated outside of the house. I havent really chosen an enclosure for the batteries yet. I really like the weatherproof cabinets we have in The Netherlands used by telecom, cable, power and fiber providers placed in the streets but they are extremely rare second handed. Buying a new one will cost around a 1000 for a 1000x800x300mm (WxHxD) sized cabinet, a bit to expensive for my taste. I will keep my eyes open for a second handed one but my hopes arent very high.
Ive also been looking at metal garden sheds, they are weather proof and even larger than the outdoor cabinets, but not as sturdy. I dont have the room to place a container, our garden is only 8x10 meters. A small cabinet can be placed in the garden, but a large container is no option. And although Im not a carpenter Im able to build my own box/shed from wood.
The only really big thing thats been bothering me about outdoor storage is the operating temperature. The weather in The Netherlands can vary from -10 degrees Celsius in the winter to +35(40) degrees Celsius in the summer but not really swing more then 15-20 degrees in 24 hours unlike some other places in the world. If I build a cabinet myself from wood I can insulate it and the winters would be more easily manageable with a simple electrical heater keeping the storage above freezing but to install an air conditioning unit is a bit overdone. We dont have an air conditioning in our house so there is no possibility to blow some cold air though a tube into the battery cabinet.
Ive attached a drawing of a insulated cabinet I made with the possibility to store 3P-14S100P battery packs with some room in front of the battery packs for fuses, busbars, switches and pack monitoring. The bottom row is empty in the event some water or other dirt gets in unintentionally. Its just a draft for now and will definitely change until I feel satisfied about it.
6) Questions:
Some questions are already in the text above bust mostly not, but to summarize them:
1.1: How can I make sure the cells are the right voltage like 30% charge for storage? My current charges only charges to 100%.
2.1: If my calculations are correct the 9 solar panels will produce a max of 2486Wp (3x3x325W@85%), minus the 700W nominal load the batteries will be charged with 1786Wp. At 51,8V pack voltage (14x3,7V) this will be 34,48A in total and 344mA per cell, without nominal load 479mA. I think this is a great charge current per cell, but when I add the extra 12 solar panels the charge current goes up to 984mA with and 1199mA without the nominal load and this looks a bit high to me. Does this mean I have to extend the battery first before adding the solar panels? Or is it possible to manipulate the charging current for the batteries to an acceptable current and deliver the residual current back to the grid?
3.1: I dont have any specific questions about the third chapter/part for now, just want to know your opinion, improvements and thoughts!
4.1: The cell cutoff voltage varies from brand/cell to brand/cell, some are 2,5V but others 3,0V. Can I combine them as long as I keep the pack voltage above 3V or is it best to exclude them and use a lower 2,7V minimal for example for a little bit more capacity?
4.2: Same question as above but now with the upper voltage. Some cells I tested work great until 4,15V (ish) and then start to warm up with 110mA current still flowing through it never reaching the 4.2/4.3V maximum. Exclude them and go to 4.2V max or keep the max voltage at 4,1V?
4.3: Do I need the Batrium expansion board? I only have the shunt trip and no further equipment so far, am I forgetting something?
5.1: Whats the best temperature to operate the battery packs? During the winter the temperature can be minus 10 degrees Celsius but a simple heater (with thermostat) will help with that if the batteries themselves wont generate enough heat while (dis)charging. But how do I manage condensation? Or the hot days like this week while Im typing this (33-37 degrees Celsius in the shade, 20-25 degrees in the night). Do I need active cooling (like an airco) for the cells or is a simple fan enough blowing in outside air?
5.2: What's the best enclosure to house the batteries outside? Metal shed with wood on the inside on a steel frame, or all metal frame? I'm concerned about the rain getting in, the temperature inside (hot or cold), condensation and although we see them rarely mouse, rats and other local animals.
Only one question left: When I start building, would you like to see regular build updates in a project topic or not?
Ask me anything about the project, materials or choices I've made. Tips, tricks and improvements are always welcome!
Greetings, Stijn.
