I was talking to a tesla owner the other day. He was saying that when the car battery capacity drops to 80% that it might be practical to replace them with the newer lighter ones and use the old ones for a home solar system. Apparently they retain their high efficiency so they would be really useful where weight is not a concern.
[This message has been edited by dratts (edited 05-02-2015).]
First they say fully automated as if it has everything to connect to grid but then state no inverter. So it is really just a battery and thats great but not fully automated. An inverter and a controller is needed for Solar/gen/mainline inputs not to mention an auto switch for when main line power is down.
I am still very interested in the Battery. If you could get a Tesla 4/5 door or the suv for 40 grand would you buy one?
I wish they would take the Model T approach.
[This message has been edited by pokeyfiero (edited 05-02-2015).]
Sounds like a business opportunity. Provide the required extra components and the labor, add in the battery and you are in business.
I read you can get a 10 kw/h version but it didn't say how long it would last running at 10 kw/h. Anybody see those numbers?
Answered above, but also remember the 10kw is for backup only and only rated to cycle weekly. The 7kw is meant to cycle daily. Max discharge rate has a role in this too. You may only be able to draw x amount of amps, for y amount of time. I would like more information on the batteries themselves. Do they have a automated BMS?
You can buy a GB industrial forklift battery that has a 20 hr rate of 1206 amps @24v for $3400, That is 28kw if my math is right. This means you can draw 60 amps for 20hrs @ 24v. http://gbindustrialbattery....ications_Zone15.html
[This message has been edited by dennis_6 (edited 05-03-2015).]
Answered above, but also remember the 10kw is for backup only and only rated to cycle weekly. The 7kw is meant to cycle daily. Max discharge rate has a role in this too. You may only be able to draw x amount of amps, for y amount of time. I would like more information on the batteries themselves. Do they have a automated BMS?
You can buy a GB industrial forklift battery that has a 20 hr rate of 1206 amps @24v for $3400, That is 28kw if my math is right. This means you can draw 60 amps for 20hrs @ 24v. http://gbindustrialbattery....ications_Zone15.html
Problem is that home circuits run at 120-240 volts. After A/C conversion and a step-up transformer, that forklift battery will not last long.
Problem is that home circuits run at 120-240 volts. After A/C conversion and a step-up transformer, that forklift battery will not last long.
People use them off grid all the time, with a inverter, no step up transformer required. They last around 10-20 years in that application, they just need to be sized correctly. They are much heavier duty than pretty much all of the typical solar batteries, and in a offgrid application they last longer than a forklift. In a forklift they are good for 5-10 years. Cons are heavy, require watering, and more temp sensitive than lithium. Much better bang for the buck, than lithium though. BTW, Tesla system also requires a inverter, so net loss is the same, doesn't matter if you are going up or down, and both are converting DC to AC
I can't remember where I read it, but the two different battery sizes also have different continuous draw ratings. They're designed for different types of load, rather than just being two sizes of the same type of battery.
First, there's this little thing called Peukert's law, which states that the faster you drain a battery, the less energy you get out of it. Hence why a 28kw lead acid battery has been suggested, rather than a 5 or 10kw/h...that 5 would probably be more like 2kw/h under a heavy strain, the 10 would likely be more like 6. You have to size the battery appropriately (many times larger than you might expect) to get a decent "return" on your charge. It's the same when charging the battery. This also means/is why the battery gets "tired" quickly, and won't put out as much as it does when "rested".
With lithium, you still have to size it properly -- it has to be big enough to sustain the output you plan on putting on it without overheating and it has to be big enough to have enough run-time -- but the Peukert effect is so minor that it can pretty much be ignored. If you drain it at 120 amps or 12 amps, you'll get roughly the same amount of energy out of it. They don't get tired. Your main concern, depending on the exact chemistry, is thermal runaway, or thermal expansion damaging the cells.
Second is self-discharge. Lead acids are bad for this, especially certain chemistries....like the ones commonly used in deep-cycle flooded batteries, like that forklift battery. You need to keep a constant trickle charge on it, or use it relatively soon after charging, if you want to get most of what you put in to it back out again. Recharge it every month if you want it to have a charge when you need it. AGM batteries are much better for this. Charge once every 6 months or so. And lithium are better yet. Hence your lithium battery in your smoke detector lasts the life of the smoke detector (10 years).
Third, are the number of discharge cycles you can get out of it, assuming you use it properly. Golf-cart type deep cycle lead acid batteries might get you 300 charge/discharge cycles out of them, if you discharge them 80%. If you discharge them 100% or beyond, you'll be lucky if you get in to the double digits. After that, the battery will not hold more than 50% of its original capacity. That big bugger mentioned is probably good for 1000 or so. Whereas with lithium, to 80%, can give you 1000 to 5000 cycles. And that's down to 80% capacity at the end, not 50%.
There are pros and cons to both. But since weight & size doesn't matter in a house, and because the lithium are stupidly expensive, I'd lean towards lead acid, despite the lithium being, as far as I can tell, far superior. However, if efficiency was an absolute must, I'd have to consider the higher upfront cost of a lithium setup. Since it will get more cycles, and it will waste less energy charging and discharging than the lead-acid, it might pay for itself in the long run. I doubt the lead acid will, even if it's cheaper. That efficiency will make a whole lot of difference if you're on a solar setup...
I can't remember where I read it, but the two different battery sizes also have different continuous draw ratings. They're designed for different types of load, rather than just being two sizes of the same type of battery.
The Powerwall comes in 10 kWh weekly cycle and 7 kWh daily cycle models, both of which are guaranteed for 10 years and are sufficient to power most homes during peak evening hours. http://news.discovery.com/t...the-grid-1505011.htm
From Tesla press kit it list the specs the same for both models....
Powerwall specs:
Mounting: Wall Mounted Indoor/Outdoor Inverter: Pairs with growing list of inverters Energy: 7 kWh or 10 kWh Continuous Power: 2 kW Peak Power: 3.3 kW Round Trip Efficiency: >92% Operating Temperature Range: -20C (-4F) to 43C (110F) Warranty: 10 years Dimensions: H: 1300mm W: 860mm D:180mm
First, there's this little thing called Peukert's law, which states that the faster you drain a battery, the less energy you get out of it. Hence why a 28kw lead acid battery has been suggested, rather than a 5 or 10kw/h...that 5 would probably be more like 2kw/h under a heavy strain, the 10 would likely be more like 6. You have to size the battery appropriately (many times larger than you might expect) to get a decent "return" on your charge. It's the same when charging the battery. This also means/is why the battery gets "tired" quickly, and won't put out as much as it does when "rested".
With lithium, you still have to size it properly -- it has to be big enough to sustain the output you plan on putting on it without overheating and it has to be big enough to have enough run-time -- but the Peukert effect is so minor that it can pretty much be ignored. If you drain it at 120 amps or 12 amps, you'll get roughly the same amount of energy out of it. They don't get tired. Your main concern, depending on the exact chemistry, is thermal runaway, or thermal expansion damaging the cells.
Second is self-discharge. Lead acids are bad for this, especially certain chemistries....like the ones commonly used in deep-cycle flooded batteries, like that forklift battery. You need to keep a constant trickle charge on it, or use it relatively soon after charging, if you want to get most of what you put in to it back out again. Recharge it every month if you want it to have a charge when you need it. AGM batteries are much better for this. Charge once every 6 months or so. And lithium are better yet. Hence your lithium battery in your smoke detector lasts the life of the smoke detector (10 years).
Third, are the number of discharge cycles you can get out of it, assuming you use it properly. Golf-cart type deep cycle lead acid batteries might get you 300 charge/discharge cycles out of them, if you discharge them 80%. If you discharge them 100% or beyond, you'll be lucky if you get in to the double digits. After that, the battery will not hold more than 50% of its original capacity. That big bugger mentioned is probably good for 1000 or so. Whereas with lithium, to 80%, can give you 1000 to 5000 cycles. And that's down to 80% capacity at the end, not 50%.
There are pros and cons to both. But since weight & size doesn't matter in a house, and because the lithium are stupidly expensive, I'd lean towards lead acid, despite the lithium being, as far as I can tell, far superior. However, if efficiency was an absolute must, I'd have to consider the higher upfront cost of a lithium setup. Since it will get more cycles, and it will waste less energy charging and discharging than the lead-acid, it might pay for itself in the long run. I doubt the lead acid will, even if it's cheaper. That efficiency will make a whole lot of difference if you're on a solar setup...
Agreed, and with electric vehicles, lead acid is a loss cause. Very little Lithium in the off grid world right now, its difficult to find supporting electronics. I like the power wall, but at this point it is not cost efficient. Average household usage is 29kw a day, You would need 3 units for a backup solution and 4 units in a solar setup.
Agreed, and with electric vehicles, lead acid is a loss cause. Very little Lithium in the off grid world right now, its difficult to find supporting electronics. I like the power wall, but at this point it is not cost efficient. Average household usage is 29kw a day, You would need 3 units for a backup solution and 4 units in a solar setup.
I'm reading that an average house is consuming around 15-18kw per day.
I'm reading that an average house is consuming around 15-18kw per day.
If having gas for heat, may drop it more.
It may be for some regions, I went with the eia number. In 2013, the average annual electricity consumption for a U.S. residential utility customer was 10,908 kilowatthours (kWh), an average of 909 kWh per month. Louisiana had the highest annual consumption at 15,270 kWh, and Hawaii had the lowest at 6,176 kWh. http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3
First they say fully automated as if it has everything to connect to grid but then state no inverter. So it is really just a battery and thats great but not fully automated. An inverter and a controller is needed for Solar/gen/mainline inputs not to mention an auto switch for when main line power is down.
I am still very interested in the Battery. If you could get a Tesla 4/5 door or the suv for 40 grand would you buy one?
I wish they would take the Model T approach.
the inverter is left out because most systems you would use this with already have one. and, the "automated" part is the charging maintenance. While you can just dump raw juice in, carefully selecting cells for charging is much more efficient, and extends cell life.
the inverter is left out because most systems you would use this with already have one. and, the "automated" part is the charging maintenance. While you can just dump raw juice in, carefully selecting cells for charging is much more efficient, and extends cell life.
Most inverters can't handle the voltage of the Tesla pack.
Because most inverters are small? Is there any reason that inverters can't be sized to the job?
Because most inverters run off of 12-72v input, the Power wall was reported at 350-450v. To use a standard inverter you would have to convert to AC, put it through a step down transformer, and then convert back to DC. Size has nothing to do with, there are very powerful inverters on the market, just the wrong input voltage.
Tesla most likely did this to sell you a inverter also. There are a few advantages though, wiring can be very small gauge, do to high voltage, low current of the battery. Losses in wiring from battery to inverter should be minimized also, but neither are anything to write home about.
There is nothing all that powerful about the powerwall, in fact it is far to small to get much range if used for a electric car, not to mention that its 2kw continual output is only 2.6hp. So it could put out 2kw to the motor controller which has losses, to the motor which has losses, and to the drive train which has losses, and you might get 1.8hp for 3.5 hours out of it. It really is just a rich eco toy at this point. It will cover short blackouts, and allow you to buy electricity off peak to store, till off peak times. Nothing more really. Think of it as a 2kw generator, that can run 3.5 hours, before you refill it.
Here are the specs on a very powerful inverter, it takes 48 volts dc in, and cannot operate on Tesla's powerwall.
Includes: GS4048A Inverter, mounting bracket, remote temperature sensor, hardware kit and manual. Radian Series InverterThe new Outback Radian A series Inverter/Charger inherits the hallmark features of the original design including: Dual AC inputs for grid/generator flexibility; unparalleled surge capability and operational stability; easy field upgradeability and stacking capability for large systems; easy-to-use configuration wizard; and multi-mode operational flexibility.
In addition, both models have a new Advanced Battery Charging (ABC) profile option to support leading edge technologies such as Lithium-Ion and others. Both incorporate Outback's GridZero technology - a superior level of intelligence in energy management for self-generation and self-consumption programs, providing precise balance between using stored energy, and solar and utility power, to overcome surges and load spikes when needed. GridZero makes it possible for a smaller inverter/battery system to perform like a much larger one, when required. In addition, the new Radians are ideal for use in complex utility environments such as California and Hawaii.
Both models also support AC-coupling through a compatible Outback Load Center to provide an economical solution for upgrading existing grid-tied systems to battery-back up capability.
FEATURES: Grid-Interactive and Stand alone capability in the same package GridZero Technology optimizes the balance between stored and renewable energy sources - minimizing grid dependence and allowing users to get the most out of their investment Advanced Battery Charging (ABC) supports leading edge technologies including lithium-ion 8000W and 4000W of continuous power in the two models Simplified stacking design for flexibility to upgrade to a 12kW system Field adjustable input/output voltage and frequency boundaries Unsurpassed surge capacity 120/240V Split-Phase Voltage Dual AC inputs
[This message has been edited by dennis_6 (edited 05-05-2015).]
I'm not familiar with solar cells, but doesn't home wind generators output at 350V-400V?
Some can in much the same way, a unregulated car alternator does. It puts out 3 phase AC which is regulated and turned to a proper DC voltage. The problem with the Tesla units is they are putting out 350-450 volts DC, not 3 phase AC.
This is from a listing for a 300V wind turbine, the item of interest is this... http://www.magnet4less.com/...D_q8UCFQGNaQodmxYAyQ GinLong Grid Tie Controller and Dump Load Included: The Ginlong controller with dump load is used to rectify frequency-variable output voltage of the wind turbine generator to DC voltage before feeding into the grid tie inverter. This item turns the variable frequency (3 phase) A/C into DC at a normal voltage. From the specs on the turbine.... Generator 300V Brushless 3 phase PMA with high performance Neodymium MagnetsGenerator
You would need to convert to A/C, run it through a transformer, convert to a proper DC voltage and then feed it into a inverter. There would be a lot of loss. So unless the Tesla inverter is really cheap, or you can find a really good deal on some oddball industrial inverter, using a forklift battery, or building a LifePo4 pack of the proper voltage, would be more economical. Forklift battery will be much cheaper, and there are automatic watering systems.
[This message has been edited by dennis_6 (edited 05-05-2015).]
