The 5AH/20H rating says you should get 5AH if you drain the battery at
250mA.  If you drain it faster you may get less than 5AH due to
inefficientcies in the battery.

Doug Butler
Sherpa Engineering


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Ammerman
> Sent: Sunday, July 21, 2002 5:41 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]:speaking of gellcell's ?
>
>
> > I thought I understood ah ratings this battery says (5ah/20h) that's a
> little
> > confusing.
> >
> > Jim
>
> ie: the batt wil provide 5ampere hours if discharged over an
> interval of 20
> hours. This would imply a current of 250ma.
>
> Bob Ammerman
> RAm Systems
>
>
> >
> > -----Original Message-----
> > From: Byron A Jeff <byron@CC.GATECH.EDU>
> > To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
> > Date: Saturday, July 20, 2002 8:38 PM
> > Subject: Re: [EE]:speaking of gellcell's ?
> >
> >
> > >On Sat, Jul 20, 2002 at 06:57:05AM -0700, Jim wrote:
> > >> Hi
> > >
> > >> Pardon my ignorance
> > >
> > >No need. You have very cogent questions.
> > >
> > >> I'm working on a home project using a 12v gellcell.
> > >
> > >One piece of information that's missing here is how are you using the
> > >battery. What type of charging you need depends on how it's
> being cycled.
> > >
> > >> It has charging info printed on it but I'm kinda new to
> charging these.
> > >> It say's cycle use 14.5 ` 14.9v (25deg c) initial current less than 2
> > amps
> > >> stand by use 13.6 ` 13.8v (25deg c)
> > >
> > >Typical...
> > >
> > >>
> > >> I have been looking at charging info on the web
> > >> I would like to use an lm317 for the charging and have already
> > breadboarded
> > >> a cicuit that will switch between the 2 voltages
> > >> How important is the temp compensation?
> > >
> > >It's important if there's a wide variation of temperature from 25C.
> > >
> > >> Can I charge it at around 1 amp without any ill effect?
> > >
> > >Not at 14.6V. This voltage will guarantee an overcharge if left
> > indefinitely.
> > >
> > >>if the charger is working properly should I be able to measure aprox
> 14.6v
> > >>when I first connect it to the battery or does it have to
> climb to this
> > >> voltage as it charges?
> > >
> > >The latter. The battery will drag the voltage down to its level as it
> takes
> > >on charge, slowly rising to the target voltage.
> > >
> > >Battery charging is serious and complicated business. Essentially
> charging
> > >under any conditions other than ideal will eventually result in battery
> > >failure:
> > >
> > >* No charge will result in a dead battery.
> > >* Undercharging will cause sulfation resulting in lowered
> capacities and
> > >  premature failure.
> > >* Overcharging will result in gassing causing premature
> battery failure.
> > >
> > >I would advise not charging your battery from 14.5V source unless you
> have
> > >a an automatic cutoff mechanism (or two) in place. I finally
> decided that
> > >float charging was the safest dumb charging course of action.
> > >
> > >A good reliable gell cell charger is high on my list of things
> to build.
> I
> > >really want a 3 stage charger with autodetion of stages (bulk,
> absorption,
> > and
> > >float) and decent indicators. What I really haven't figured
> out is how to
> > get
> > >really high current for fast charging. My 33Ahr 12V gel cell
> will accept
> up
> > >to 10A current. But finding a 10A transformer is a tough proposition.
> > >
> > >Hope this gives you some help,
> > >
> > >BAJ
> > >
> > >--
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> > >
> > >
> > >
> >
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