FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Science and Technology » Chem » Electrochem » Battery
Measuring cell resistance
Post new topic   Reply to topic Page 1 of 1 [3 Posts] View previous topic :: View next topic
Author Message
Evgenij Barsukov
science forum Guru Wannabe


Joined: 09 May 2005
Posts: 137

PostPosted: Sun May 21, 2006 3:42 pm    Post subject: Re: Measuring cell resistance Reply with quote

DaveC wrote:
Quote:
I'm told that an ESR (equivalent series resistance) meter can be used for
measuring resistance of cells, an indication of cell life expectancy. Of
course this is only if the meter has high input impedance and is not
diode-protected.

My question is how valuable is this information in determining remaining cell
life? Is such a measurement useful? For all chemistries? Only some?

Should the measurement be taken with cell charged? Discharged?

If you want to use it for correlation with state of health,
it is better to always do it in the same state, preferably
charged.

Effective resistance that you will see depends on the time
of load application, because battery impedance is a function of
frequency (or time, if it is in time domain).

It is preferable to look at voltage drop after fixed time, in
each test time should be same. At high frequencies (1kHz, time - 1msec)
you will only see ohmic resistance. At longer times you will see
effect of battery material, so it is more informative.
Depending on how much time you can spend, you can use 10 sec
or better 100 sec.

Not all battery chemistries have easy correlation between impedance
at state of health (although Li-ion battery does). The best correlation
can be achieved if you look not at one point (say 10 sec), but at
several points (say 1, 10, 100 sec).
If you just want to have rough estimate like "dead vs alive" one
point will be enough, but if you need to get quantitative correlation
on capacity with say 15% accuracy, things become much more complex
and probably not for home project.
There is plenty of patents on that, which can be downloaded for
free from US Patent office web-site.

Regards,
Yevgen
Back to top
Mark W. Lund, PhD
science forum addict


Joined: 24 Mar 2005
Posts: 64

PostPosted: Mon May 15, 2006 5:32 pm    Post subject: Re: Measuring cell resistance Reply with quote

It is hard to know what you mean, there are a couple of ways to measure
the ESR.
The first is straightforward, you have do discharge the battery into a
known resistance
and measure how much of the voltage drop is across the resistor and how
much
is across the battery. This is usually done by discharging across two
different resistances
to isolate the battery resistance.

The second way is to capacitively couple an AC signal into the battery
and measure
the AC impedance. This sounds like what you are describing.

Best regards
mark
Back to top
Usenet user
science forum Guru Wannabe


Joined: 06 May 2005
Posts: 166

PostPosted: Wed May 03, 2006 5:14 am    Post subject: Measuring cell resistance Reply with quote

I'm told that an ESR (equivalent series resistance) meter can be used for
measuring resistance of cells, an indication of cell life expectancy. Of
course this is only if the meter has high input impedance and is not
diode-protected.

My question is how valuable is this information in determining remaining cell
life? Is such a measurement useful? For all chemistries? Only some?

Should the measurement be taken with cell charged? Discharged?

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 1 of 1 [3 Posts] View previous topic :: View next topic
The time now is Tue Nov 21, 2017 6:21 am | All times are GMT
Forum index » Science and Technology » Chem » Electrochem » Battery
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts can anyone help me complete this voltage cell Howard610 Electrochem 0 Wed Nov 22, 2006 12:07 pm
No new posts Estimating Errors in Measuring Volume arguani Math 0 Tue Aug 29, 2006 2:11 am
No new posts Measuring Background Noise Doug Acoustics 3 Wed Jul 12, 2006 12:53 pm
No new posts CRV3 lithium maximum cell voltage vs. RCRV3 tjones77@gmail.com Battery 0 Sun Jul 02, 2006 2:32 am
No new posts "The Impossibility of Measuring the Velocity of Light" Dlo Relativity 0 Thu Jun 29, 2006 11:44 am

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Electronics forum |  Medicine forum |  Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums  |  send newsletters
 


Powered by phpBB © 2001, 2005 phpBB Group
[ Time: 0.1964s ][ Queries: 20 (0.1813s) ][ GZIP on - Debug on ]