Ben,
Good points. I have a 10kWh solar array with 40kWh lead acid backup. Power
interruptions in my area are not infrequent. This system kept the
essentials of the house running for the week the power was out with Sandy.
"... but lead acid batteries are notorious for going tits-up after just a
few years."
Depends on application. For an undersized pack with frequent, deep
discharges (i.e. you're avg EV)...yes. For emergency backup (infrequent
discharges) or off grid night use (not deep discharges)...not so much.
As I mentioned I got two years of EV use, beating the s**t out of a lead
acid pack, PLUS another three years as emergency backup. My current lead
acid pack, not used in an EV, is sized pretty well for my house. So I
honestly expect between 10-20 years before having to replace. Who knows
what lithium will cost or what the battery chemistry dujour will be at that
point.
"...lithium batteries...usable service life similar to that of a
mortgage..."
Eh...maybe. I've had one lithium cell (CALB) in a pack of 48 fail within
the first couple years.
I think we're still in the early stages of large format lithium and don't
have long term data yet. Very manufacturer dependent. I trust Tesla and
hope that what you say is true. Luckily the 85kWh Model S pack has a very
good warranty!
Barry
-----Original Message-----
From: Ben Goren
Sent: Friday, May 01, 2015 12:57 PM
To: [email protected] ; Electric Vehicle Discussion List
Subject: Re: [EVDL] Tesla plugs into new market with home battery system
On May 1, 2015, at 9:34 AM, via EV <[email protected]> wrote:
While Lithium batteries make a lot of sense for vehicles where energy
density to weight is a big deal, I'm not sure of the advantage for
stationary installations. Cost for Lithium is still a big issue. An
~40kWh pack of deep cycle, lead acid batteries that provide battery backup
for my house costs ~$5k.
Yes, but how long will those lead cells last? Indications are that,
especially when gently used in climate-controlled settings, lithium
batteries have the potential to have an usable service life similar to that
of a mortgage, but lead acid batteries are notorious for going tits-up after
just a few years. If you get five years from $5,000 of lead acid but fifteen
years from $14,000 of lithium, the lithium is the better investment.
Especially if coupled with a generator or (PH)EV that can serve as a backup
for extended periods of low input and high demand, and depending on the size
of the PV array, a surprising number of people could drop off the grid with
20 kWh of batteries and many could with 30 kWh. Most should be able to with
40 kWh with many not needing the genset at that point.
If you're paying on the order of $15 - $20 / month for grid connection fees,
it doesn't make sense to spend $10,000 or so on a battery to drop off the
grid. But many utilities are trying to structure their rates such that, even
if you're at or over 100% net generating capacity, you'll still cut them a
check for $50 - $100 / month...and suddenly, hey-presto, that $10,000 to
drop off the grid makes the same kind of financial sense that the initial
solar investment did.
Things are about to happen fast. Barring apocalyptic scenarios of whatever
variety, most of us will live to see the day when a grid connection is as
anachronistic as a landline telephone is today.
b&
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