[OT] More on Batteries

[Brian Densmore]

To me a battery is "dead" when it no longer provides sufficient 
current to power a device it should power. After ten days according to
your calculation you have 4.2 Volts. Try making a mobile robot that
requires 
12 volts run on that. Again though, as was noted in another post, it is
power 
we should be talking about and not voltage. But a transistor that flips
on at 
5.7 V won't flip on in this scenario. I don't believe Jonathon was
talking
about voltage, but about power. 

i.e.
day 0) 1200 mAH
day 1) 1200 - (1200*.1) = 1080
day 2) 972 = 1080 - (1080*.1) 
day 3) 874.8
day 4) 787.3
day 5) 708.6
day 6) 637.7
day 7) 574.0 (now at less than half the power it originally had, 
       I doubt any device would be working now that required 1200mA)
...

I think perhaps the 10% should have been 
more like 1%, or .10%, but I'd still like to know the source of this
data.

Brian

> -----Original Message-----
> From: Steven Elling [mailto:ellings at kcnet.com]
> Sent: Tuesday, May 13, 2003 1:25 PM
> To: Brian Densmore; kclug at kclug.org
> Subject: Re: [OT] More on Batteries
> 
> 
> On Tuesday 13 May 2003 12:16, Brian Densmore wrote:
> > > Stored batteries will loose up to 10% of their charge per
> > > day.  Obviously, any
> >
> > That would make a battery dead in 10 days. I find that hard
> > to believe.
> 
> That would be 10% of the 'remaining charge'. i.e.
> 
> 12V - (12V * 10%) = 10.8V
> 10.8V - (10.8V * 10%) = 9.72V
> 8.748V
> 7.8732V
> 7.0859V
> 6.3774V
> 5.7397V
> 5.1658V
> 4.6493V
> 4.1844V
> 3.7660V
> 3.3894V
> 3.0505V
> 2.7455V
> 2.4710V
> 2.2239V
> 2.0016V
> 1.8015V
> 1.6214V
> 1.4593V
> 1.3134V
> 1.1821V
> 1.0639V
> .9576V
> 
> Which means the battery would be effectively dead after 24 
> days when it has 
> less than 1V of charge.  Is that believable for some battery 
> types? Maybe.
> 
> However, what about alkaline batteries?  I'm looking at some 
> Rayovac's that 
> have Dec 2009 written on them.  What about lead-acid 
> batteries?  I've had 
> lead-acid batteries in cars that sat for over 6 months and 
> were still able 
> to crank over the engine.
>