Re: Charge & Discharge waveforms of lead acid battery Vs Super Capacitor


"auto boost" <yhotracy@xxxxxxx> wrote in message
news:1148400298.866007.201530@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I've an application where I need to know the charging and
discharging response time of lead acid battery used in autos. Can you
be kind enough to show me how to obtain this data. In particular, I
want to compare the charging and discharging response waveform between
lead acid battery and super capacitor which has an ESR of about 70
milliohms.
Thank you in advance.
Go to a battery manufacturers website. Most have graphs of the curves for
their batteries. There are a _lot_ of variables though. Batteries are a
chemical device, and give a very flat output voltage for most of their
discharge. However their ability to deliver power at high currents, falls
faster than a simple 'resistive' loss, as a result of limitations in the
rate of chemical action (also the actual resistance of the cell changes as
it discharges). This gives a curve called the 'Peukert curve', which
characterises how batteries perform at higher discharge rates. Batteries
also have quite complex charge requirements, with many types undergoing
accelerated decay if charged wrongly.
A capacitor conversely has a relatively simple linear discharge, and can
be charged by a simple voltage source, with a current limit to prevent
damage.
The battery has the big advantage that more of it's discharge cycle is
spent at relatively higher voltages, making it simpler to make efficient
use of the power.
http://www.national.com/appinfo/power/files/f19.pdf for an 'overview'
about batteries, and:
http://www.homepower.com/files/battvoltandsoc.pdf

Best Wishes


.

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