OK, here is one for you. Surrette doesn't seem to have the Peukert exponent
for the L16H on their site but the spec sheet does have the capacity for
draw times from 1 hour to 100 hours. Using that and the formula on the site
you referenced solved for n (Peukert) gives a Peukert exponent of 1.22 which
when plugged into the original formula tracks almost exactly to the Surrette
specs until the draw gets extremely large or extremely small so it appears
that my math was correct.

However, using the formula in the back of the Link 20 manual working from a
reserve minutes at 25A of 870 I get 1.44. If you plug 1.44 for Peukert into
the original formula you do get the stated 870 minutes @ 25amps but the
calculated capacities do not track the Surrette spec at all. .

It appears that the Peukert formulas must be taken with a grain of salt.

Incidentally, I got a price on a set of four Surrette S-530 (L16H) batteries
delivered to Macon from DC Battery Specialist in Miami for only $20 more
than the local price for a set of Trojan L16Hs. Actually less with sales
tax and way less than any internet source with shipping.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"chuck" wrote in message
...
Glenn Ashmore wrote:
Interesting question came up this evening perusing the Surrette L16H
battery specs. The specs say they have a 20 hour rating of 400AH and a
50 hour rating of 476AH. Almost 20% more. That is to be expected as
total amp hours increase with slower draw rates. The 20 hour rate is
used to compare one battery against another but if in normal good
practice a bank is only discharged from90% to 40% over 24 hours, wouldn't
it be more appropriate to use the 50 hour rather than the 20 hour rating
when estimating the actual usable amp hours?.


Discharging from 90% to 40% in a 24 hour period could have been done at a
one hour rate, a 20 hour rate, or some combination that even includes a 50
or 100 hour rate.

Technically, what you need to do is find Surrette's Peukert equation for
the L16H and divide the period into rough blocks and use the approach
nicely outlined he

http://www.smartgauge.co.uk/peukert2.html
SmartGauge Electronics - A proper explanation of Peukert's equation
(Peukert's Law)

Chuck

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