Chris,
You need to look at the link... they look at the costs over a 10 year
period.
Including battery bank replacement for the Lead Acid batteries. Lead
Acid is still cheaper.
And I think their prices for Lead Acid batteries are inflated. I would
also consider using a Lead Acid forklift battery (or multiples).
They are made to be rebuilt.
Sure they are heavy. And that might be an issue for some, but if you
have a tractor with a loader, or a forklift, then that is really not an
issue.
Dave
On 5/16/2019 6:24 PM, Chris Albertson wrote:
Let's see your parts list for a 13.6 KWH system and let's look at the cost
over a 10 year period. List the charger/inverter and the frame and
housing.
When you do you costing assume the system is used cycled daily. Design in
enough margin so that tyou system still meets speciications after 10 years
of use. Itmust still have 13.6 KWHafter 10 years of daily cycling.
Yes, this can be done with LA.
You can get the initial cost way low but you can't run it for 10 years
without replacing all the batteries 3 or 4 times. That is the problem is
lead-acid batteries, it is their very limited number of cycles. You can
work out different designs. If the goal is only low initial cost then you
will find you need a VERY frequent battery replacement schedule. You can
greatly reduce the number of times you need to replace each cell over the
10 year period if you double the initial cost.
You can't claim LA is lower cost until you look at the total cost
of ownership, not just the up from cost. It is possble to get very low
up from cost or you can also "cheat" assume the system is only used for
backup power a few times a year. But realistically you need to look at
costs of a system that is actually used over an extended period.
So, you have to make a spreadsheet or punch buttons on a calculator. A
LA cell is good for about 300 cycles to 50% discharge before it looses bout
1/2 it's capacity. SO Youfigure maybe we only go to 40% and extend this
is 400 cyccles and buy 2X as may calls so we still meet specs after 400
cyccles. Then you work out how many batteries you need using them to
only 40%of their rating and stating with 2X over capsity. You are
"shocked" at the cost so you think about designing a yearly schedule where
you add a few batteries everyyears and remove a few every year, but maybe
you don't add and removethe same number, so long as you kee the same 13.6
KWH spaec. Work this over a 10 year period.
The up front cost means nothing because you can make that very low but it
will cost you a LOT later. I doubt you can do $6,700 total cost over 10
years.
On Thu, May 16, 2019 at 12:03 PM Dave Cole <linuxcncro...@gmail.com> wrote:
https://www.wholesalesolar.com/blog/lead-acid-vs-lithium-batteries/
This solar company wrote up this analysis regarding Lead Acid vs Lithium
and generally recommend Lead Acid for off grid residential use.
I went through their analysis and the only problem I had with it is that
their lead acid batteries are over priced.
Which, if their Lithium batteries are priced right, means that Lead Acid
is by far the best way to go.
I think their numbers for a Crown Lead Acid bank was $2800. I did some
numbers and figured I could create a deep cycle bank of the same
capacity for about $1800.
Making your own power wall or Lithium battery pack is certainly a
possibility, but as mentioned cell balancing circuity is required.
I have a sailboat and participate in several sailboat lists and the
overwhelming way to go for house power on a larger sailboat is to use 6V
golf cart batteries.
The cost per power stored is cheaper than using 12 volt batteries and
golf cart batteries are true deep cycle batteries which are commonly
available.
A lot of 12 volt deep cycle batteries are compromised designs.
Now if these batteries were in a mobile device, like a car, that would
be an entirely different comparison since weight is a big deal in a
mobile device.
But these are for a stationary application.
Regarding the power wall concept. The idea of having 20+ KWHR of stored
energy in my house is a little daunting.
If a short circuit occurs and the batteries melt down, your house could
be gone.
I'd put the battery bank in an outbuilding. If something shorts out and
the battery bank melts down, the little building may burn but my house
won't.
Dave
On 5/14/2019 2:11 PM, Kirk Wallace wrote:
On 5/14/19 9:33 AM, Dave Cole wrote:
I've been planning to put up an array on my roof. But I have plenty
of space so I may do a ground level install.
It would be a lot easier to maintain.
FLA batteries seem to be the general recommendation for a constant
use residential install.
In my opinion, lead-acid batteries of any format are far inferior to
lithium. LA batteries need to be at full charge most of the time or
they will degrade and with good management will only last about 5
years. I ended up running my generator to charge my FLA batteries in
the evening if the solar had not brought them up during the day. So I
ran the generator most days. Lithium batteries don't like to be fully
charged so now I don't need to worry about topping up before I go to
bed. Lead-acid batteries typically have a cycle life in the hundreds
of cycles where lithium battery cycle life is in the thousands or
more, and end up being cheaper in the longer term. On the other hand,
Lithium batteries are easy to kill if they are over or under charged,
so a proper battery manager/protector/balancer is a must. Otherwise
they have a wide charge range and don't mind be anywhere within that
range. I have been using these with good success for a while:
https://kit.com/jehu/lithium-battery-sources-july-2018/1274926-johnson-controls-24-
https://www.mobile-solarpower.com/solar-charge-controllers.html
(Epever 40 amp)
I've had chargers trash batteries when they failed. I sure wouldn't
want that to happen to $10K worth of Lithium batteries!
Weight isn't an issue.
Dave
... snipped to end
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