OT, I know, but remember that tomorrow is Pi Day, and a special one at that: as written in the U.S., tomorrow morning we'll see 3.14.15 9:26.53 (and at some unknowable instant, all the time will exactly equal pi).
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Plan: Off grid solar with a Model S battery pack at the heart
- Thread starter wk057
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- Energy Environment Policy
Tedkidd
Member
Really hope those wires and whatever else you're waiting on comes soon. I miss the frequent updates on my favorite TMC thread. Been said a bunch but this project is a-Ma-Zing.
On a lighter note, you'll be getting even more press tomorrow when Elon ends range anxiety by announcing the wk mobile power plant, hope all those cells come in and out of the basement easy.
On a lighter note, you'll be getting even more press tomorrow when Elon ends range anxiety by announcing the wk mobile power plant, hope all those cells come in and out of the basement easy.
Wire is arriving Friday morning, I'm arriving back home today. I've been traveling for the past few weeks, so, this held me up a bit too. Should be back in full swing by the weekend.
As for Elon's power plant, unless it can replace my setup with as much power for a super reasonable cost, I'll stick with my setup.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Nice! An quick ocular estimate tells this is "elephant schlong" gauge wire.
Nice! An quick ocular estimate tells this is "elephant schlong" gauge wire.
lol.
It's 4/0 gauge (212 kcmil, 107mm^2, 0.46" diameter) fine stranded UL listed wire (dual rated THHW and MTW) with 105C rated insulation (safety!). Not many places make or carry this for some reason, at least not actually UL listed (like welding cable). It's good for use in conduit per NEC, and is much easier to work with compared to 4/0 THHN. Also much safer for battery related stuff since no thick wire torque on connections.
Running behind.
I actually just completed the inverter DC wiring to the DC bus bars. I'll be using a few modules to do a small test of each inverter to make sure they all work, probably tomorrow. After I make sure everything works like it should I'll work on completing the battery rack and connecting the modules to the DC bus.
Cooling loop actually isn't a priority. It's on my list, but, my setup shouldn't require it since my max charge/discharge and under 1/4C. In my testing, after 3 hours of charging at this rate the cell temps barely climbed 5F. I will be adding the cooling loop once I complete my custom BMS setup, though.
Nothing original and basically a re-hash of other articles, but Jason has hit the broadsheets in the UK. :wink:
http://www.theguardian.com/environment/shortcuts/2015/mar/22/hacking-car-batteries-home-power-tesla
http://www.theguardian.com/environment/shortcuts/2015/mar/22/hacking-car-batteries-home-power-tesla
I've been thinking of a few things as I read your posts-
-I believe the inverters you are using shut off once voltage gets below 40v. Will this significantly limit the capacity you can get out of the modules? Perhaps a dc/dc converter could bump up the voltage coming from the modules enough to get full use of their capacity?
-Do the BMS boards on the modules appear to balance everything when you apply a charge? Are you planning on doing any inter-module monitoring (eg. monitor voltage of each of the 6 parallel groups) or are you just monitoring the voltage of the total module?
-I believe the inverters you are using shut off once voltage gets below 40v. Will this significantly limit the capacity you can get out of the modules? Perhaps a dc/dc converter could bump up the voltage coming from the modules enough to get full use of their capacity?
-Do the BMS boards on the modules appear to balance everything when you apply a charge? Are you planning on doing any inter-module monitoring (eg. monitor voltage of each of the 6 parallel groups) or are you just monitoring the voltage of the total module?
That is correct - the Model S cell's chemistry can safely go down to 2.5V loaded. But, there's a steep drop off in voltage at low discharge rates.
40V would be 3.333 per cell, or ~14% capacity lost at C/3. About ~11% capacity lost at C/6. Not too bad.
Lithium ion degrades the slowest at low voltages so ideally id like an inverter for ~2.8V (loaded) - 4.05V or 33.6V - 48.6V for 12s.
40V would be 3.333 per cell, or ~14% capacity lost at C/3. About ~11% capacity lost at C/6. Not too bad.
Lithium ion degrades the slowest at low voltages so ideally id like an inverter for ~2.8V (loaded) - 4.05V or 33.6V - 48.6V for 12s.
electrodacus
Member
I seen this on Blomberg first. I was reading trough the posts and this is a monster off-grid installation . It seems you even purchased more battery modules than the initial pack.
I live OffGrid for not that long I will have two years this spring. I use LiFePO4 for a few reasons (excellent safety, lowest amortization cost, easy to find large capacity cells 1000Ah no problem)
On my small 65sqm (700sqft) OffGrid house I was concentrating on energy efficiency and reduced use so you may find my power consumption ridiculously small (based on what I read here).
I have at the moment just 3x 240W PV panels and a 24V 100Ah LiFePO4 battery so 2.5kWh capacity. My average monthly power consumption is around 80kWh a bit smaller in November /December and usually around 80 to 90kWh the rest of the months.
On the positive side my system is extremely simple at least compared to this installation. All the electronics are inside the Solar BMS a device that I designed and build specifically for my house but is open source so "anyone" can build one.
I have now a new version on Kickstarter and this new SBMS will be able to handle a 3kW PV array and with a 400Ah battery or more it will be able to sustain about 300kWh/month extrapolating from my current data.
I will be curios what is your expected monthly power consumption?
I recently made some calculations related to amortization cost and should be about 16 cent/kWh most of this is related to battery amortization cost since that is the most expensive part.
I can give more details if someone is interested but since this forum is about Tesla I will limit my post to this.
. It seems you even purchased more battery modules than the initial pack.I live OffGrid for not that long I will have two years this spring. I use LiFePO4 for a few reasons (excellent safety, lowest amortization cost, easy to find large capacity cells 1000Ah no problem)
On my small 65sqm (700sqft) OffGrid house I was concentrating on energy efficiency and reduced use so you may find my power consumption ridiculously small
(based on what I read here).I have at the moment just 3x 240W PV panels and a 24V 100Ah LiFePO4 battery so 2.5kWh capacity. My average monthly power consumption is around 80kWh a bit smaller in November /December and usually around 80 to 90kWh the rest of the months.
On the positive side my system is extremely simple at least compared to this installation. All the electronics are inside the Solar BMS a device that I designed and build specifically for my house but is open source so "anyone" can build one.
I have now a new version on Kickstarter and this new SBMS will be able to handle a 3kW PV array and with a 400Ah battery or more it will be able to sustain about 300kWh/month extrapolating from my current data.
I will be curios what is your expected monthly power consumption?
I recently made some calculations related to amortization cost and should be about 16 cent/kWh most of this is related to battery amortization cost since that is the most expensive part.
I can give more details if someone is interested but since this forum is about Tesla I will limit my post to this.
One of Tesla's secrets is that the "coolant" is really used for heating, much more then cooling.
The use case of a Model S never really allows the cells to warm on their own in the first place due to load/charging.
The only time cooling is needed is if the car is stored at high ambient in the sun at high SOC, to prevent cell degradation.
On the other hand, they need to heat the cells for fast charging and to improve performance and efficiency.
In addition, the thermal contact between the coolant flow and individual cells is quite poor; it's basically useless other then for environmental temperature control of the cells.
The cells are designed for durability and performance and high temperature, at the determent of performance at lower temperatures, because it's more desirable to heat then cool (because they only need to be heated when driving or charging, and "free" heat is available from the inverter/motor after some driving) while cooling needs to be done to prevent degradation all the time, esp. at high SOC.
The use case of a Model S never really allows the cells to warm on their own in the first place due to load/charging.
The only time cooling is needed is if the car is stored at high ambient in the sun at high SOC, to prevent cell degradation.
On the other hand, they need to heat the cells for fast charging and to improve performance and efficiency.
In addition, the thermal contact between the coolant flow and individual cells is quite poor; it's basically useless other then for environmental temperature control of the cells.
The cells are designed for durability and performance and high temperature, at the determent of performance at lower temperatures, because it's more desirable to heat then cool (because they only need to be heated when driving or charging, and "free" heat is available from the inverter/motor after some driving) while cooling needs to be done to prevent degradation all the time, esp. at high SOC.
Running behind.
I actually just completed the inverter DC wiring to the DC bus bars. I'll be using a few modules to do a small test of each inverter to make sure they all work, probably tomorrow. After I make sure everything works like it should I'll work on completing the battery rack and connecting the modules to the DC bus.
Cooling loop actually isn't a priority. It's on my list, but, my setup shouldn't require it since my max charge/discharge and under 1/4C. In my testing, after 3 hours of charging at this rate the cell temps barely climbed 5F. I will be adding the cooling loop once I complete my custom BMS setup, though.
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