more on Tesla battery packs

Hi Mex,

It is not clear that the powerwall unit can be stand alone with no grid tie.

For me, it has several strikes against it.

First the inability to charge below -20 c (-4 f). That is a deal breaker for me.

Second the price of the 10 k unit plus inverter is apparently going to be 7400 plus 2000 for the inverter.

Third, one would have to find an installer willing to work to modify the unit to be installed horizontally in an RV (under the bed does NOT appeal to me).

Fourth, LiPo (which, admittedly, is a different chemistry) is showing loss of capacity due to heating. The technomedia folks are down about 25% from their original capacity of 500 amp-hours after 3.5 years of use. It looks as if 43 C (110 F) is too hot for LI chemistries to handle.

Fifth, it is becoming clear that Li batteries do NOT like being floated at 100%. They are happiest if they are bouncing between 85 to 95%.

Sixth, the suggested charging voltages have dropped down to 13.8 for maximum cycle life. So much for being able to "shove" current into them rapidly.

Seventh, Musk says he has orders for powerwall units that will keep his not yet existent factory busy for 18 months.

Eighth, Li cell prices have not dropped at all in the last four years.

Ninth, until recently large capacity (500 amp-hours per cell, and up) have not been available. Now that they are, for someone in areas where temperatures are moderate, it may make sense--but not yet financially.

My feeling is that Musk is trying to stifle other cheaper battery chemistries by jumping in to monopolize the market. Of particular interest is a new Aluminum based battery than can be rapid charged at rates of 1000 C, (if you can find big enough conductors and a power source, that is!).

I need batteries I can use in the next year. I may try to delay that to a trip south, and I'll most likely go to AGM. It is so far down to the ground these days, and my experience with battery watering systems was a total flop. DAMHIK *grin*

pianotuna wrote:
Hi Mex,

I have zero details about the inverter other than price.

There has been an immense amount of R&D for large array to 240VAC 60 Hz and 220 VAC 50 Hz co production.

What disturbs me is the thought of a huge array dedicated solely for 120 vac use via an inverter. Some high voltage inverters RELY on line frequency synchronization to trigger the co generation line tie inverter to work. No Hz sense lead, no workee.

High voltage discrete components are expensive.

I guess I am asking for someone to guide me to an autonomous 480 volt to 120 volt 2Kw inverter. Autononous is a vital requirement. Stand alone.

Direct from Tesla Motors link above:

Models
10 kWh $3,500
For backup applications
7 kWh $3,000
For daily cycle applications

You will probably want the 7 kW for daily cycling in an RV. Probably two if air conditioner is involved.
Yes add inverter and install will more than double the price.

Hi Mex,

I have zero details about the inverter other than price.

Hi smk,

I read $74xx.xx for the 10 Kwh powerwall, plus inverter, plus installation. Or you can lease it for 10 years for $5000.00 (not sure if that includes the inverter or not).

Some how I don't think they would lease to an RV owner unless the RV no longer had wheels to go places.

Inverter will supply the voltage required by the application.

Home grid tie in the USA is 240 vac. Backup power would surely be 120/240 vac service.
Industrial probably 3 phase 480 or 600 volts.
Utility I have no idea but probably 600+ and just stepped up with a transformer to the main or local switching voltage.

The Tesla battery supplies 350 to 450 volts DC that can easily be accommodated by an inverter. Most home solar grid tie go to 500 or 600+ vdc input using MPPT so very flexible input.

http://www.solarcity.com/residential/backup-power-supply

http://www.teslamotors.com/powerwall

This is not your DIY stack of wet cell batteries. Your solution will be engineered and installed by professionals and yes that cost money. Last I read was close to $7,000 option on your total system install. Probably more if just stand alone.

Horse Diaper time...

What voltage does the inverter render?

Hi,

The inverter needed for the Powerwall is $2k. Too rich for my blood.

Why stop with just the battery pack. Any normal hybrid vehicle has the battery pack and the inverter to control output to any voltage you want. Most automotive hybrid battery packs are 480 volts.
mm49

Not a bad price at all for 5.3 kwh.

If I had these in the RV, would Tesla let me use their high-speed charging stations?