tesla pwer wall

[mahendra]

I have been looking at the Tesla Powerwalls lately but still skeptical since tesla was the company that demonstrated what not to do with lithium.

[Westbranch]

they don't seem particularly well suited for 24/7/365 use in a PV system...

There was a good investigations and discussion of the ''P Wall'' on NAWS but I can't locate it with the new search engine...

found it!  http://forum.solar-electric.com/discussion/343395/tesla-battery/p1

[mahendra]

good thread .i figured  there was something fishy about them.

[Powerplay]

Westbranch : Thank you for the link about the Tesla Power Wall.  It will be interesting to see where battery tech goes in the next few years.  Most of the objections to TPW in the other forum seemed to stem from poor cost effectiveness related to safety limits that were required and an odd anti-Tesla sentiment which seemed unrelated to the topic.  I'm interested in energy storage solutions that reduce the weight, cost, fragility, short life span and hassle etc. from mostly a scientific perspective.  Safety is also a concern so it is an interesting topic in general.  And I noticed Midnite has a charge mode for lithium Battery, so fun topics.

[Westbranch]

my hope, though I doubt it will happen any time soon, is for a cost per Kw of storage from LiFePO4 packs...  Even with more production and use I am hesitant to count on it... and now with the falling price of crude oil...    

As to the safety aspects If a solar power system is well planned out and the LIFE bank is in line with the inverter and power demands and the CC is programmed  properly,  with a bottom balanced bank without a BMS, there should be no safety worries. 

I am not so sure a top balanced bank falls into that category with out an expensive BMS, if even then...

[tecnodave]

BYD.  (Build your dreams) , a Chinese company has opened a factory in Lancaster, California that is building all electric City Transit Busses for the North American markets, They have gotten National Transportation Safety Commission approval to operate these busses on American highways. They are powered by LFP!   Not Baby busses these are 40 feet and 60 feet articulated busses with capacities of 40-66 persons!    Run all day on one charge in transit service!   BYD also builds tractor tuggers for port facilities,  (they move 40 foot container trailers around loading docks etc.). These are in use in LA and Oakland terminals, also LFP powered, they also produce the Cherry all electric city car in China, LFP powered.     Take that Tesla!

Warren Buffet being no ones fool has invested LARGE in BYD!

This is the kind of boost that LFP needs, now only if they will build a LFP factory here.

td

[Cniemand]

I've watched a few videos on those BYD buses. Snazzy stuff!

I am not sure the TPW is that horrible of a proposition. As I calculated it, it is a little cheaper per kWh than when I purchased my bare LFP cells a couple years back. I am not sure about how it works in a full time usage environment. What it will freely give up at any one time.  What will be seen in the next year or two is a major dropping of Lithium Battery prices as the Tesla Giga Factory opens up and starts ramping up production of those millions of 18650s. 

We may find that it does come out cheaper to build packs with thousands of tiny cells rather than the large Prismatic bricks those of us that use LFP have been accostomed to.

The other side with the TPW was that it came with a warranty of ten years? That takes out the whole equation of whether in real life you get 2000 cycles @100 %DOD 3000 @80%DOD or 5000 @ 70%DOD

Cloud

[Cniemand]

My system has been up since june 2013. If I take the total aH of production (that the local app tells me) and then divide it by the 100aH capacity of the battery bank I come out with 570 cycles. (In the first two years I did not flex the ability of the system to really use everything available. Averaging 2-3 kWh per day on a 2000 watt array. The past year or so I have taken liberty to use an electric space heater for a diversion load. Seeing a handful of days of over 10 kWh collections. ) I have once used 100%DOD on the pack. (In the beginning when I was working out what the true charging parameters should  be. In that time I would guess less than a half dozen uses of 90%DOD. Rarely do I ever see my pack at 80%DOD or beyond (including those mentioned above)

Typically in the morning before the sun comes back we are in the 50-60%SOC range. So, if the data sheets are to be believed I would expect that I am in the 3-5000 cycle life range.

I shall let you all know how well I did when I get there! ha.