How to test power tool battery pack?

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  #1  
Old 01-09-21, 08:17 AM
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How to test power tool battery pack?

Hello,

I am wondering how to properly test 3 - battery packs that I have around my home which are used my cordless power tools (drill, circular saw, etc). These 3 packs are for a Craftsmen set of power tools and from the attached pictures, you can see they are 19.2V.

I know that simply putting a volt meter across the terminals on the battery pack will not properly measure the state of the battery. I do have a battery tester that I purchased online to test my car or boat battery, so I'm wondering if this might work? If it an option, how do I test? If this will not work, what do I need in order to properly test / measure the state of these power packs?

Any help is greatly appreciated.

Thanks in advance!




 
  #2  
Old 01-09-21, 08:33 AM
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That is a 19v battery and the meter only goes to 16v. Go to Harbor Freight or a dollar store and pick up a cheap multi-meter.
 
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Old 01-09-21, 08:38 AM
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Thanks for this.... I have a couple of multimeters in my home, but how do you measure without a load? I believe some kind of load needs to be applied (but maybe not).
 
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Old 01-09-21, 09:22 AM
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Modern Battery Pack Basics

Measuring voltage on modern battery pack is at best, a rudimentary indication of status.

Batteries/pack originally were just a string of cell wired in series. If one cell went bad, string voltage dropped by its valve.

Modern battery packs have complex electronic circuits between the cells and output terminal. Sometimes cells are OK and electronics board is bad.

Lithium packs often have 2 or 3 3.6 volt cells in parallel, then 5 of wired in string for 18 volt.

When a cell goes bad, others in pack are still good. Cells can be replaced or remaining good ones used elsewhere.
 

Last edited by doughess; 01-09-21 at 09:48 AM.
  #5  
Old 01-09-21, 09:24 AM
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Your old battery tester is designed for lead acid batteries which work differently from NiCd.

For what you have best is to give it a full charge then measure voltage without a load to get an idea of status. Those 19.2s are made of multiple batteries and normal failure is one of the batteries fails/shorts so overall no longer measures 19 volts.

Most don't go further but a simple load test would be to run the battery with your device for a couple minutes and measure the voltage afterwards.

@doughess: the OP has an old battery that is a simple string.
 
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Old 01-09-21, 09:40 AM
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An exact number like a voltage reading really isn't important and doesn't tell you much. I wouldn't bother "testing" the batteries. Do they take a charge? Do they power your tools for a reasonable amount of time? If you answer no to either it's bad. If you answer yes to both then it's good enough.
 
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Old 01-09-21, 10:20 AM
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I think very few nicad packs are still around these days. I recycled my 19.2ís a decade ago.
ie. Iím not optimistic they are good.
 
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Old 01-09-21, 10:58 AM
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That pack is from 2004. It would be reasonable to assume it's at or past the end of its useful life.
Most of those older packs use sub-C nicad cells which you can get to rebuild the pack. When you base the cost of the replacement cells vs the cost of those packs.... it would be more cost effective to just replace the pack.
 
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Old 01-09-21, 11:39 AM
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You may not test those tool batteries using a tester for car batteries. The test will draw a heavy current that might cause the batteries to oveheat.

There is no easy and quick way to test the tool batteries for holding a charge without specialized equipment that few of us have..
 
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Old 01-09-21, 12:14 PM
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you can often find NI MH packs to replace your existing NI CAD and they work with your charger probably not worth messing with trying to fix when you can buy new battery packs and there not very expensive in this case.
 
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Old 01-09-21, 03:05 PM
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Tread question, how to test battery pack did mention specific technology.Testing NiCad, Ni MH and lithium battery packs is not very informative as to condition.

Lithium far outperform others on a cost and energy basis. See data in chart:

https://sinovoltaics.com/learning-ce...gy-of-battery/

Why bother with Ni Cads or NiMH? DH has replaced NiCad cells in battery packs with lithium cells from scrapped from old units, greatly improving power and usage time.+

If old battery pack has electronics board, discarded it and wired cells directly to pack terminals. How to charge that pack is another issue.
 
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Old 01-09-21, 04:28 PM
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If old battery pack has electronics board, discarded it and wired cells directly to pack terminals. How to charge that pack is another issue.
This one example of what not to do.

We are focused on a nicad battery pack because that's what it says right on it. You cannot substitute Li ion batteries for nicads without specifying how to charge them. It's not enough to just say "charging is another issue" as li ion batteries charged on a nicad charger will explode.
 
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Old 01-10-21, 07:46 AM
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Thank you everyone for all of the suggestions.... it looks like the best (and safest) idea is just to buy a set of 2 new batteries for under $30 which is much cheaper than I thought they would be.
 
 

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