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re: trojan l-16 vs t-105 batteries- data sheet
26 feb 1999
warren lauzon wrote:
>i just dug through all the trojan literature we have, and nowhere can
>i find any information at all on how the cycles are measured.
aee (http://www.alt-energy.com) says average lifetimes of t105s and
l16s are 1200 and 900 cycles, both measured at 60% depth of discharge.
they told me this is the optimum discharge depth, in terms of their
lifetime cost per kwh of energy storage, which is surprisingly deep.
>...trojan's own literature is telling us that the l-16 is a bad deal,
>even though it costs more.
if the number of cycles alone determined their lifetime (ie they were
fairly heavily used), t105s would store 1200x6vx220ahx0.6 = 950 kwh in
their lifetime. if they cost $85, that's 8.9 cents/kwh. l16s would store
900x6x350x0.6 = 1134 kwh. if they cost $198, that's 17.5 cents per kwh.
figure 5.6 on page 91 of the 3rd edition of richard komp's practical
photovoltaics book shows that the natural log of the number of cycles
in the lifetime of lead-acid batteries decreases linearly with increasing
discharge depth. that allows predicting the discharge lifetime of a
battery at any discharge depth, given the lifetime at any two depths.
it also says says lead-acid batteries store the most energy in their
lifetime with very small discharge depths, although in that case we
need more of them for a given system, which drives up the interest
on the investment and increases the cost of shelf life wear out...
nick
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