# lowest cycle cost battery

C

#### colin

Jan 1, 1970
0
Hi,

Whats the cutting edge in lowest cost per kwh of 'cycled energy' storage
these days ?
ie the cost of 1khw storage / cycles in a liftime ?

SLA are quite cheap, but dont last so long,
nicad more expensive but probably more cycles,
Im not sure about the other types lithium etc,
as theyr not readily available off the shelf so hard to get a good cost to
compare,
maybe super cap?

I had a crazy idea to work out economics of storing electricity at cheap
rate and be able to use it during the day.
plus it would be a good ups.

A water tower might be good if there was one handy.

Colin =^.^=

J

#### Jeff L

Jan 1, 1970
0
colin said:
Hi,

Whats the cutting edge in lowest cost per kwh of 'cycled energy' storage
these days ?
ie the cost of 1khw storage / cycles in a liftime ?

SLA are quite cheap, but dont last so long,

If properly taken care of and not deeply discharged, they can last a very
long time (there are some in service for 20+ years and usually only get
changed due to routine maintenance).

1) since some batteries such as Li ION age whether they are used or not.
2) it depends on how much they are discharged. A lead acid will survive a
lot longer and store a lot more energy if discharged only 20% compared to
80%. In other words adding capacity to a batter bank for the same load and
charger will exponentially extend the life of the batteries
3) how well they are charged. Some charger algorithms are very abusive,
while others help extend life
4) temperature at which they run.
5) Quality of the cell
6) many other not as significant variables

E

#### Eeyore

Jan 1, 1970
0
colin said:
A water tower might be good if there was one handy.

Even better when it rains ! Free power.

Graham

C

#### colin

Jan 1, 1970
0
Jeff L said:
If properly taken care of and not deeply discharged, they can last a very
long time (there are some in service for 20+ years and usually only get
changed due to routine maintenance).

1) since some batteries such as Li ION age whether they are used or not.
2) it depends on how much they are discharged. A lead acid will survive a
lot longer and store a lot more energy if discharged only 20% compared to
80%. In other words adding capacity to a batter bank for the same load and
charger will exponentially extend the life of the batteries
3) how well they are charged. Some charger algorithms are very abusive,
while others help extend life
4) temperature at which they run.
5) Quality of the cell
6) many other not as significant variables

well the numbers for SLA dont add up favourably,
wikipedia quotes 7-18WH/$with a durability of <1000 cycles so thats 6c per khw wich is more than the cheap rate savings. seems the other types come out worse. Colin =^.^= J #### John Barrett Jan 1, 1970 0 colin said: well the numbers for SLA dont add up favourably, wikipedia quotes 7-18WH/$ with a durability of <1000 cycles
so thats 6c per khw wich is more than the cheap rate savings.

seems the other types come out worse.

Colin =^.^=

I'd compute it based on years of service -- do the numbers for 5,7, and 10
years average battery life and see where that puts you -- as long as you are
not deep cycling the batteries -- you will get more cycles out of them --
which is why I keep talking about oversizing the battery bank.

I've got one 7 year old bank that is regularly discharged to 25% and
occasionally to 50% (2-3 times per month) that is still going strong... I
dont anticipate needing to replace any of the cells for at least 2-3 more
years.... (based on "new" cells charging to 12.8v and the worst cell is the
bank is currently topping out at 12.6v)

the key is a VERY good charging circuit to maintain the battery health and
avoiding deep discharge

since you are talking about an off-grid application, dont forget to include
the cost of inverters in the cost estimate.. and seriously consider running
the banks at 48V which will require charge balancing -- which was discussed
in another thread a few days ago.

C

#### colin

Jan 1, 1970
0
John Barrett said:
I'd compute it based on years of service -- do the numbers for 5,7, and
10 years average battery life and see where that puts you -- as long as
you are not deep cycling the batteries -- you will get more cycles out of
them -- which is why I keep talking about oversizing the battery bank.

I've got one 7 year old bank that is regularly discharged to 25% and
occasionally to 50% (2-3 times per month) that is still going strong... I
dont anticipate needing to replace any of the cells for at least 2-3 more
years.... (based on "new" cells charging to 12.8v and the worst cell is
the bank is currently topping out at 12.6v)

the key is a VERY good charging circuit to maintain the battery health and
avoiding deep discharge

since you are talking about an off-grid application, dont forget to
include the cost of inverters in the cost estimate.. and seriously
consider running the banks at 48V which will require charge balancing --
which was discussed in another thread a few days ago.

well it would be 1 cycle per day,
as its storing cheap rate electricity every night,
so 1000 cycles is ~3 years,
yes I apreciate what you said about under utilising,
and this may decrease the cost per kwh cycle significantly,
but ive not seen any figures to go on.
also I havnt started to consider anything financial like return on capital
etc,
or cost of equipment wich presumably would outlast the batteries many times
as it doesnt look like the batteries are even going to break even.
I think it needs to be closer to around 1c per kwh of storage to make it
worthwhile.
if it was this cheap then the power companies would probably be using them
for this very purpose anyway.

ofc if the inverter isnt pretty efficient it will throw away any benefits.

Colin =^.^=