LEAD ACID BATTERY
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From: budgie on 1 Apr 2006 07:04 On Sat, 01 Apr 2006 08:42:56 GMT, Robert Baer <robertbaer(a)earthlink.net> wrote: >budgie wrote: > >> On 31 Mar 2006 13:26:58 -0800, "RHRRC" <h.lewis(a)connect-2.co.uk> wrote: >> >> (snip good stuff) >> >> >>>'C' is merely a short-hand way to refer to the capacity of a battery at >>>its declared (20hr) discharge rate. >> >> >> Sorry, couldn't let that one go through to the keeper. >> >> 'C' refers to the capacity of the battery at the rate that (superficially) is >> the one-hour rate. >> >> i.e. the 13Ah battery's 'C' is 13A. >> >> C/20 is the discharge rate of 13/20 for that battery i.e. 650mA. >> >> and as the O/P's required current is 700mA the redcution in performance would be >> absolutely marginal, giving his target of 12 hours almost spot-on. > One might think that, but he has voltage constraints that requored a >more thorough analysis... I fully appreciate that. The comment was relating to the definition of C and how it can cause major mis-calculation.
From: budgie on 1 Apr 2006 07:05 On Sat, 01 Apr 2006 08:44:01 GMT, Robert Baer <robertbaer(a)earthlink.net> wrote: >budgie wrote: > >> On Sat, 01 Apr 2006 08:47:10 +0800, budgie <me(a)privacy.net> wrote: >> >> >>>and as the O/P's required current is 700mA the redcution in performance would be >>>absolutely marginal, giving his target of 12 hours almost spot-on. >> >> >> >> Aaarrrggghh! My turn to stuff up! Ignore that line, >> >> Particularly if the O/P really meant: >> >> " I have to design a voltage source ( +/- 18volts, 13A )" > So? Use of three 6V batteries in series gives 18V. You totally missed the point. 13A? or 700mA?
From: RHRRC on 1 Apr 2006 07:10 budgie wrote: > On 31 Mar 2006 13:26:58 -0800, "RHRRC" <h.lewis(a)connect-2.co.uk> wrote: > > (snip good stuff > > >'C' is merely a short-hand way to refer to the capacity of a battery at > >its declared (20hr) discharge rate. > > Sorry, couldn't let that one go through to the keeper. > > 'C' refers to the capacity of the battery at the rate that (superficially) is > the one-hour rate. > > i.e. the 13Ah battery's 'C' is 13A. > <snipped> Sorry to say you are in error. The nominal 'C-rate' of a 13Ah battery is 13amps. As previously stated 'C' is a capacity - not a current - that is why C is used rather than A or I!
From: John Fields on 1 Apr 2006 09:23 On Fri, 31 Mar 2006 22:40:34 GMT, Robert Baer <robertbaer(a)earthlink.net> wrote: >------- SNIPped for brevity and sanity ------ > Get off your asinine rants about google groups and posting "rules" >that do not apply to any of the answers or posting(s) related to this >message. > Either give a decent answer *without* unrelated griping, or SHUT UP. --- I'll do precisely what I want to, and that includes commenting ("ranting" if you like) on the evils of top-posting and the inability of some Google groupers to post considerately to forums which have customs they seem incapable of accepting or appreciating. If you find any of my posts annoying or not to your liking, in any way, or you find me irritating, then I suggest you learn how to use your newsreader's filter(s) and simply plonk me. At least that way you won't feel compelled to gripe about my griping and there'll be that much less noise here. -- John Fields Professional Circuit Designer
From: budgie on 1 Apr 2006 21:49
On 1 Apr 2006 04:10:42 -0800, "RHRRC" <h.lewis(a)connect-2.co.uk> wrote: > >budgie wrote: >> On 31 Mar 2006 13:26:58 -0800, "RHRRC" <h.lewis(a)connect-2.co.uk> wrote: >> >> (snip good stuff >> >> >'C' is merely a short-hand way to refer to the capacity of a battery at >> >its declared (20hr) discharge rate. >> >> Sorry, couldn't let that one go through to the keeper. >> >> 'C' refers to the capacity of the battery at the rate that (superficially) is >> the one-hour rate. >> >> i.e. the 13Ah battery's 'C' is 13A. >> ><snipped> > >Sorry to say you are in error. > >The nominal 'C-rate' of a 13Ah battery is 13amps. > >As previously stated 'C' is a capacity - not a current - that is why C >is used rather than A or I! FFS what extreme pedantry. "C" vs "C-rate" indeed. Just ahve a quick look at the usage of 'C' in describing charge rates. You'll be scratching to find many references to 'C-rate'. And your line: " 'C' is merely a short-hand way to refer to the capacity of a battery at its declared (20hr) discharge rate." was so wonderfully precise? Review your other line: "The nominal 'C-rate' of a 13Ah battery is 13amps." Try reading the two in conjunction. |