[RE-wrenches] Lithium Ion Phosphate for grid back up
James Surrette
james at surrette.com
Mon Aug 22 08:54:04 PDT 2011
Hi Dave,
We've been doing some work in this field - all of which is preliminary
at this time. By no means would I consider myself an expert but a few
things I have garnered over the past couple of years.
1) Most Iron Phosphate (jelly roll or prismatic) are relatively low
capacity resulting in lots of cells to generate meaningful capacity.
2) Nickel Magnesium Cobalt (NMC) provides a more stable platform (less
temp rise) and significantly higher capacity per cell. This allows for
fewer cells resulting in easier monitoring and management of each cell.
3) To echo everyone else BMS is the key to success however, this gets
increasingly more difficult if you have 100's of cells.
4) NMC technology is retailing for ~$1800 kwh or ~60k for a 700AH,
48VDC system (includes BMS).
Regards,
Jamie
>>> "Dave Palumbo" <dave at independentpowerllc.com> 8/21/2011 10:14 PM
>>>
We have a potential client for a net metered PV with battery backup
system with a serious interest in using lithium ion storage batteries. I
do not know of any systems that have used these batteries yet. From some
quick calcs I come up with 105 LiFEYPo4 3.2 volt cells. 7 strings of 15
cells for 700 AH at 48 volts. Price is quoted at $ 125 per cell.
Here’s a link the client forwarded from his research.
http://currentevtech.com/Lithium-Batteries/Thundersky/Thundersky-40ah-cell-p24.html
What are the reasons why these are not being used in home power
systems? The web site states 3,000 cycles at 80% DOD vs. 750 cycles for
typical gel storage batteries.
Also, what are your favorite inverter(s) for grid tied with battery
backup?
David Palumbo
Independent Power LLC
462 Solar Way Drive
Hyde Park, VT 05655
www.independentpowerllc.com
NABCEP Certified PV Installer
Vermont Solar Partner
23 Years Experience, (802) 888-7194
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