Question: Measuring Internal Resistance of small household batteries

Question: Measuring Internal Resistance of small household batteries

Hi, is there any difference in accuracy between a $3000 Hioki and a $200 Rim (Germany) internal resistance battery tester, for testing alarm or camera (lithium) and gel cel (UPS) batteries?

I have other questions: Does the meter reading differ, with the State of Charge of the battery under test?

Is such a tester worth buying, for a hobbyist? Any advice appreciated, thanks in advance.

Reply to
tunesandballoons
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You can make quite satisfactory measurements of battery internal resistance with a voltmeter and a resister. Measure the open-circuit voltage of the battery, then the voltage with the resistor. With a little bit of calculation you can figure out the internal resistance of the battery. With two meters you can simultaneously measure current and voltage, which will save some calculation and let you use a lower precision resistor.

The internal resistance of a battery does vary with charge. In fact, in theory the open-circuit cell voltage is constant and only the cell resistance changes with the state of charge. In practice many batteries don't follow this rule, but given enough time to recover even a profoundly discharged NiCd battery will read 1.2V, until you ask even the slightest current from it.

--
Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

On Fri, 14 Apr 2006 07:57:46 -0700, Tim Wescott wrote: ...

"Profoundly discharged?"

I love it! ;-)

Cheers! Rich

Reply to
Rich Grise

tunesandballoons @ yahoo.com MULTI-POSTED:

Cross-posted to sci.electronics.design, sci.electronics.components, sci.chem.electrochem.battery

Learn to cross-post.

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I guess multi-posting comes naturally when you're a spammer.

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Reply to
JeffM

"JeffM" wrote in news: snipped-for-privacy@z34g2000cwc.googlegroups.com:

Even that large crossposting looked relevant to each group posted to, and the first was especially limited to those groups likely to know.

You might not like what you saw, but it's NOT the same as the kind of spam that takes a large number of groups in alphanumeric order and hits them all, repeatedly.

I'm all for observing usenet common sense, but etiquette for its own sake is silly. This guy at least thought about what he said, and where he'd say it, and said it once.

There are worse things in the world to worry about. :)

Reply to
Lostgallifreyan

It appears you don't understand the difference between the terms *Cross-post* and *Multi-post*:

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*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-what's-going-on+*-frowned-on+*-correcting+*-polite-*-mention-*-*-*-*-*-*-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+*-Followup-To-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+*-*-_perfect_-*-*-*-*+*-*-*-*-two-groups-*-*-aren't-*-different . .

So far, so good. .

Bzzzzzt. WRONG. It could be that you *DO* know what *Cross-post* and *Multi-post* mean and are unclear on the use of the Usenet Archive (aka Google Groups). If you click on the *show options* link in the gray area which contains the OP's name, it will show you ONE group's name.[1]

In the case of the the OP's "Sustainability" submissions, this was repeated in 11 groups--an obvious spamming. If you are going to take it upon yourself to defend fools, you should at least understand the topic.

This time, His INDIVIDUAL posts to 4 groups [2] had no connection to each other.

*I* was the one who 1st cross-posted in this thread (and noted that fact). . . That *you* apparantly have never seen a response to a post which was adequately answered days--or even weeks-- before the newer response in another parallel, identical, but completely disconnected thread shows your complete lack of knowledge about what a terrible idea multi-posting is. I recommend that you read the thread at the link I provided. . . [1] This information is also available to you from within the headers of your newsreader. [2] It appears that I missed 1 of the entries in Google's search results; and only cross-posted my notice to 3 of the 4.
Reply to
JeffM

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