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25-03-2015 7:02am

3000 cycles on the outside for those Panasonic cells.

nokia69 · 01-04-2015 4:45am

‏@elonmusk
Major new Tesla product line -- not a car -- will be unveiled at our Hawthorne Design Studio on Thurs 8pm, April 30

will most lightly be a home battery system using Lithium ion cells

nokia69 · 01-05-2015 5:01am

http://www.teslamotors.com/presskit/teslaenergy

The Tesla Powerwall is a rechargeable lithium-ion battery designed to store energy at a residential level for load shifting, backup power and self-consumption of solar power generation. The Powerwall consists of Tesla’s lithium-ion battery pack, liquid thermal control system and software that receives dispatch commands from a solar inverter. The unit mounts seamlessly on a wall and is integrated with the local grid to harness excess power and give customers the flexibility to draw energy from their own reserve.

The battery can provide a number of different beneﬁts to the customer including:

Load shifting – The battery can provide ﬁnancial savings to its owner by charging during low rate periods when demand for electricity is lower and discharging during more expensive rate periods when electricity demand is higher
Increasing self-consumption of solar power generation – The battery can store surplus solar energy not used at the time it is generated and use that energy later when the sun is not shining
Back-up power – Assures power in the event of an outage
The Powerwall Home Battery increases the capacity for a household’s solar consumption, while also offering backup functionality during grid outages.

The Powerwall is available in 10kWh, optimized for backup applications or 7kWh optimized for daily use applications. Both can be connected with solar or grid and both can provide backup power. The 10kWh Powerwall is optimized to provide backup when the grid goes down, providing power for your home when you need it most. When paired with solar power, the 7kWh Powerwall can be used in daily cycling to extend the environmental and cost benefits of solar into the night when sunlight is unavailable.

Tesla’s selling price to installers is $3500 for 10kWh and $3000 for 7kWh. (Price excludes inverter and installation.) Deliveries begin in late Summer.

Powerwall specs:

Mounting: Wall Mounted Indoor/Outdoor
Inverter: Pairs with growing list of inverters
Energy: 7kWh or 10kWh
Continuous Power: 2kW
Peak Power: 3kW
Round Trip Efficiency: >92%
Operating Temperature Range: -20C (-4F) to 43C (110F)
Warranty: 10 years
Dimensions: H: 1300mm W: 860mm D:180mm

01-05-2015 12:54pm

$0.55 per kW hour lifetime at installer costs for 7kW.
Smaller than the average house consumption.
Proprietary system.

envaction · 10-11-2015 1:11am

That is actually a pretty interesting thing to think about. Being able to use a car battery to power your home. I think that it would be something cool to think about, but I don't know who actually has the time for that. I mean if you could hire someone, then it might be worth it. But in the end is it worth? Would anyone here do it?

Jim Martin · 10-11-2015 1:24pm

Anyone know if the Tesla deliveries began as expected at the end of the summer?

Sh1tbag OToole · 12-11-2015 10:23pm

I don't think it makes a whole lot of sense to bring in a massive battery pack designed for average household consumption. Shouldnt the aim be to reduce the power consumption as much as possible, then come up with a few ways of generating power at different times (solar, wind, TEG modules) then get the smallest battery pack you can get away with?

13-11-2015 7:46am

Sh1tbag OToole wrote: »

Shouldnt the aim be to reduce the power consumption as much as possible,

Couldn't agree more.

Sh1tbag OToole wrote: »

then come up with a few ways of generating power at different times (solar, wind, TEG modules)

Hahaha TEG modules, I spent 3 weeks giving myself a crash course in thermoelectrics to try to get them gizmo-tronics working. Stupid money for miniscule return. There's a technology still in it's infancy.

Sh1tbag OToole wrote: »

then get the smallest battery pack you can get away with?

Largest you can afford is usually more prudent, they're not really expandable after commissioning.

Sh1tbag OToole · 13-11-2015 9:16pm

Sir Liamalot wrote: »

Couldn't agree more.

Hahaha TEG modules, I spent 3 weeks giving myself a crash course in thermoelectrics to try to get them gizmo-tronics working. Stupid money for miniscule return. There's a technology still in it's infancy.

Largest you can afford is usually more prudent, they're not really expandable after commissioning.

Did you try any of the power harvesting IC's designed for TEG's? There are some commercial TEG generators out there that you attach to your stove but they're still a bit expensive although the price of the modules has come down.

Expanding ones battery capacity is only a problem these days because most charge controllers and inverters only do 1 channel.

13-11-2015 9:29pm

Nah spent weeks researching TEGs and thermodynamics, I spec'd a system for myself that worked out about €35 per watt iirc.

PV is €1 p/w
Wind is about €3 p/w

Not at all a battery is just a bunch of cells you don't have two batteries you have one larger battery.

Lithium cells need to be completely discharged, rebalanced and recharged to add additional cells to a bank.
LA depending on usage may never come right as the newer stronger cells are discharged by the older weaker ones.

Sh1tbag OToole · 13-11-2015 9:45pm

Sir Liamalot wrote: »

Nah spent weeks researching TEGs and thermodynamics, I spec'd a system for myself that worked out about €35 per watt iirc.

PV is €1 p/w
Wind is about €3 p/w

Not at all a battery is just a bunch of cells you don't have two batteries you have one larger battery.

Lithium cells need to be completely discharged, rebalanced and recharged to add addition cells to a bank.
LA depending on usage may never come right as the newer stronger cells are discharged by the older weaker ones.

Probably still better to keep the old and the new separate so

The ones I saw were about $500 for 50wt, this was a few years ago now. They were a bit sparse on the details but I can only assume it was TEG-module based. It would provide power when it's being used at a time of the year when solar and wind might not generate much. It will be interesting to see if they'll get cheaper again.

13-11-2015 10:18pm

Two medium batteries aren't as good as one larger one. It's an internal resistance thing.

TEG's will get cheaper. Few car companies looking at building thermopiles on the exhaust system to save a couple of horse power by not running alternators.

You can get peltier modules salvaged from cooler boxes and run them backwards if you want to tinker with some. They're even worse than TEGs ~3% efficient but you could make a stove fan or something from them.

Wind, hydro, CHP are all much better value.

It's easy be a net exporter of energy with PV alone. Generation in the Winter is only really an issue for the off gridders.

Sh1tbag OToole · 17-11-2015 6:53pm

Sir Liamalot wrote: »

Two medium batteries aren't as good as one larger one. It's an internal resistance thing.

TEG's will get cheaper. Few car companies looking at building thermopiles on the exhaust system to save a couple of horse power by not running alternators.

You can get peltier modules salvaged from cooler boxes and run them backwards if you want to tinker with some. They're even worse than TEGs ~3% efficient but you could make a stove fan or something from them.

Wind, hydro, CHP are all much better value.

It's easy be a net exporter of energy with PV alone. Generation in the Winter is only really an issue for the off gridders.

Ah sure feck it if someone is running their house off a battery when they have a perfectly good grid connection they're living a life of perpetual sin. There is no way that would make sense even if the rate of wear on the battery is 1% of what it is now. You definitely wouldn't appreciate the few watts from a TEG module unless you're off the grid

17-11-2015 10:00pm

Perfectly good grid connection? :rolleyes: They lose half the energy they convert. A substantial amount of it is redeemed from hydrocarbons. They don't support micro-generators. Three phase costs an arm and a leg....

The point of a battery I find is to develop a tangible sense of the energy we use and how to increase efficiency. Once an appreciation of how difficult it is to cultivate electrons is achieved then, I find at least, the easiest way to make systems work is not to waste so much.
Load shifting could be a great benefit to the national generators whereby instead of having to build more to cater for peak demand we can distribute the load evenly on the existing ones and reduce the need for peaker plants operating at near idle.
Personally I'd much rather see micro grids sprouting up rather than pylons.
For me it's not about a financial return just a reliable system.

nokia69 · 04-02-2016 10:20pm

Sir Liamalot wrote: »

3000 cycles on the outside for those Panasonic cells.

http://blog.evandmore.com/lets-talk-about-the-panasonic-ncr18650b/

To estimate the number of cycles that the cell can undergo in its lifetime, we charge it at a maximal current of 0,5C and discharge at a current of 1C at 25 degrees Celsius and then we count the number of charge/discharge cycles until the cell degrades down to 70% of its initial capacity (2250mAh). In the case of these cells, the number is about 500 cycles.
500 cycles? But that’s (relatively) low! Yes. But what is not shown on the spec sheet is that when you partially charge and discharge, degradation of the battery capacity is reduced. Thus, you can do over 40 000 charge/discharge cycles when going from 30% to 70% only. Or over 35 000 charge/discharge cycles from 20% to 80%; 28 000 cycles from 10% to 90%; 15 000 cycles from 8% to 92%, 7500 cylces from 6% to 94%, and the capacity reduction goes faster and faster, finally reaching 500 cycles when recharging from 0% to 100%.

05-02-2016 10:21pm

nokia69 wrote: »

... but once they stay inside the middle 60% then the cycles don't matter....
...if you have the right cell chemistry then in both cases the batteries could last just as long, doing cycles once a day or once a week won't make a difference, change of 20% to 60% makes no difference

Same goes for for LA except they can take more than double the abuse of full discharges and it's 50% to 100% they rather live, now calculate the price per Wh end user cost compensating for the reduced discharge and see who's on top..

Have a look at that OPzS datasheet again Nokia, that's the cycle life to 80% rated capacity based on lab tests from a manufacturer.

Capt'n Midnight · 06-02-2016 12:26am

Peak demand here is when people arrive home from work. So I'd reckon a lot of them would be expecting to be putting their cars on charge.

From a user point of view the difference between day rate and night rate is about 10c a unit. BUT if you drive to work in the morning and you want to charge it before 11pm then you may not be able to use that stored energy.

From an economics point of view one of the main selling points of lots of charging car batteries is that you could potentially shed a lot of demand very quickly. But again that's only if they are charging at peak demand instead of night rate.

nokia69 · 06-02-2016 7:28am

Capt'n Midnight wrote: »

Peak demand here is when people arrive home from work. So I'd reckon a lot of them would be expecting to be putting their cars on charge.

I think most people start charging after 12 to get the night rate

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