Tesla Powerwall....hint of future options?

Tesla's Powerwall may give some insight into what could be done with a new EV design. For $3000, they offer 7 kWh daily-cycle units, weight 220 lbs and capable of 2 kW continuous. Taking a wild guess at $1K or even $2K for some interface circuitry, I could envision a DC slow charger that would transfer this energy into the primary battery pack when needed. Or, with an inverter might simply provide 220 VAC to a portable EVSE for occasional use.

This approach takes advantage of the fact that a battery can be optimized for energy or for power. This design seems to emphasize energy over power and limits the output to the 3.5 or even 5 hour rate. While this doesn't help much for a freeway dash, it would allow continuous slow charging over a period of hours, whether parked or in traffic.

I'd seriously consider paying an extra $5K for an extra 7 or 10 kWh. It would make the FFE a 120 mile class car. Nothing short of Tesla or the no-longer-produced RAV4 gives this flexibility.

It only makes sense if you have extra cheap Time of Day rates vs day rates. Also good a good device if you have solar cells, because you will overproduce solar power during the day. 7 to 10kwh is only 1/3rd to 1/2 of a full charge for an EV.

In its intended use, yes, exactly.

I was thinking conceptually as a spare battery carried in the car and used as needed.

$3500 is a good price for 10kwh and a must for any solar install. In 5 years that price will get 15kwh and in 10 years 20kwh.

I use 10khw in my house on a typical day which traslate to a 3kwh solar panel install.

damania said:

$3500 is a good price for 10kwh and a must for any solar install. In 5 years that price will get 15kwh and in 10 years 20kwh.

I use 10khw in my house on a typical day which traslate to a 3kwh solar panel install.

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I was wondering about that. If one doesn't have solar, I can easily see the benefit of charging the battery at time of low rates and then using the power during the daytime peak rate periods.

But with solar...might it not be better to use solar to return the energy to the grid during mid-day (and getting a large credit) and using cheap grid energy at night? Here in Los Angeles, for example, peak rates are from 1 PM to 5 PM weekdays and by 8 PM we are down to the lowest base rates.

I'm thinking possible good plan is to install the battery, charge it up overnight, and use it to avoid the peak rates....no need for solar.

Great points about TOD use and solar! This would be great for areas that have super low TOD rates! But thinking about this further.. To justify $3500, there must be a huge differential in TOD rates. So if there's a $.20 difference in cost savings that's only $2.00 per day. * 365 days it's about $700 per year savings. That's breakeven in 5 years!

And about solar.. I guess if you're grid tied, it doesn't make any sense to have it. It only makes sense if you are off grid. Thanks for pointing it out!

damania said:

Great points about TOD use and solar![...]
And about solar.. I guess if you're grid tied, it doesn't make any sense to have it. It only makes sense if you are off grid. Thanks for pointing it out!

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We have PV solar + Time Of Use billing, so plan charging. Is a really Big help vs. electric bills.
Separate point: for rare times when utility power fails, wish we could use the solar system (run refrigerators etc.) but cannot: inverter only runs if can sync. with grid.
Other inverters could run without grid but require onsite battery system, I heard.
Tesla plan has me wondering ...

damania said:

$3500 is a good price for 10kwh and a must for any solar install. In 5 years that price will get 15kwh and in 10 years 20kwh.

I use 10khw in my house on a typical day which translate to a 3kwh solar panel cleaning Canada.

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Hello,

Can you tell me what is the cost of solar panel installation in California??