390 minutes Reserve Capacity @ 25 amps
110 minutes @ 75 Amps to 5.25V

Aren't most tests/determinations done at 20 amps?... thought I saw that somewhere. -Mel Knott ----- Original Message ----- From: Hal Wyman <twl2@halwyman.com> Date: Monday, August 4, 2003 12:48 pm Subject: TWL: RE: Battery specification > Well, 390 minutes at 25 amps would be 25*390/60 amp-hours or 162.5 > amp-hours. > 110 minutes at 75 amps would be 75*110/60 or 137 amp-hours. > > The reason these numbers are different is that battery capacity is not > linear with load, i.e., if a battery will deliver 1 amp for 100 > hours it > won't necessarily deliver 10]0 amps for 1 hour. Higher currents > decreasethe total energy available from the battery. I believe > batteries are > generally rated at below 25 amps, so that the first number would > be a > conservative estimate of amp-hours. > > > > > -----Original Message----- > > From: trawler-world-list-bounces@lists.samurai.com > > [trawler-world-list-bounces@lists.samurai.com] On > > Behalf Of Paul Goyette > > Sent: Monday, August 04, 2003 5:51 AM > > To: Trawler World List > > Subject: TWL: Battery specification > > > > > > This should be an easy one, but I can't seem to find the > > answer online: > > > > How do you convert/calculate battry AmpHours from either of these: > > > > 390 minutes Reserve Capacity @ 25 amps > > 110 minutes @ 75 Amps to 5.25V > > > > Just trying to figure out how many AmpHours in my GolfCart > > batteries! _______________________________________________ > > http://lists.samurai.com/mailman/listinfo/trawler-world-list > > > > To Unsubscribe send email to > > trawler-world-list-request@lists.samurai.com > > Include the word "Unsubscribe" (and nothing else) in the > > subject or body of the message. > > > > > > > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/trawler-world-list > > To Unsubscribe send email to trawler-world-list- > request@lists.samurai.comInclude the word "Unsubscribe" (and > nothing else) in the subject or body of the message. > >

<<Aren't most tests/determinations done at 20 amps?... thought I saw that somewhere.>> The standard test load for deep cycle batteries to determine "amp hour capacity" is to load the battery at a rate that will discharge it in 20 hours, the "20 hour rate". In other words, a golf cart battery of 220 AH would be discharged at 11 amps, and would be fully discharged (to 10.5v) in 20 hours. Using a standard discharge time instead of a standard discharge rate (say, 25 amps) lets us sensibly compare small and large batteries. Discharging both at one common amperage rate unfairly penalizes the smaller battery, due to Peukerts' effect. ===== Mark Richter, M.E., aboard M/V Winnie the Pooh, "Mark's Mobile Marine" electrical systems repair & consulting. Homeport Stuart, FL Verizon cell 772-631-7408, free after 9PM & weekends.

----- Original Message ----- From: "Mark Richter" <Richter-Pooh@rocketmail.com> > <<Aren't most tests/determinations done at 20 amps?... thought I > saw that somewhere.>> > > The standard test load for deep cycle batteries to determine "amp > hour capacity" is to load the battery at a rate that will > discharge it in 20 hours, the "20 hour rate". Thanks for the clarification, Mark... right unit, wrong parameter... ;-) -Mel