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chuck chuck is offline
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First recorded activity by BoatBanter: Nov 2006
Posts: 41
Default 20 hour vs. 50 hour battery rating

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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