Can someone tell me how to do a load test on small single cells?

[frankiee]

I read once apon a time of how big the resistors had to be to do a "load test" on small cells such as AA, AAA, C, and D cells.
I think it also gave the time limit to do a test.

Can someone tell me how to do a load test on small single cells?

 

[itsmoked]

All load tests are based on putting a specfic load on a power source and then noting the resulting voltage the source can supply. A key thing with small batteries is using them up in the process. Part of the reason the battery companies put those lame "testers" on the sides of the batteries. They hope you test the batteries often!

So if you want to know what load to put on what battery, you need to check the makers web site for engineering info on capacity and maximum recommended current draw.

Is this a personal thing you want to do or part of a product you are working on?

 

[frankiee]

This is a personal thing I wish to know but I hope that it can help me maintain and troubleshoot equiptment better.
For instance. Electric 12 volt starter system fails to start a engine. One possible tool I could use is a load test on the battery. I could also use a load test on the starter battery as part of maintanance once every 6 months to see if the battery had the ability to put out amperage and maintain sufficient voltage when needed.
Back to the single cells.
I often want to load test my flashlite batteries to see if they are still on the strong and ready side. If I turn on the flashlight, the light comes on and sometimes it can die 5 minutes after because the batteries were old or worn out. I would like to test other things also.
So I figure that if I could load test the cells with a load tester that is calibrated for for lets say twice the average draw and maintain a minimum voltage of (lets just say a number) 1.2 volts then perhaps I could assume it was good and I could feel that I trust my flashlight to work when needed.
I once seen on how to do it in a small soft cover book from Radio Shack. I think it was called "Engineer mini notes" but I can't find the book anymore and I forget the infomation( was many years)
So, I am here wondering and asking if there is a way to load test single cells to know if they are at full capacity or near the end of their capacity.
Thanks for any information given.

 

[itsmoked]

Ah... Well stated for a change.. Thanks.

So you have two cases.

The starter battery tester is kinda tough to just create because the power level of the test is large. Generally the best method is to lay hands on a real starter battery tester. The standard is called a VAT28. It is a nice big box with a large rheostat on it with two meters. You crank the rheostat up until a certain current is read. You note the voltage. Then you time it for like 15 seconds and note the voltage and current. Stop the test and read a table.

You could see if you can find a VAT28 on on ebay or any other tester for that matter. Search ebay for [battery tester].

Personally I would try other methods. Most battery tests really take a whack out of the battery.

For your starter situation I would get a nice cheap little full cut-off battery charger and just keep the battery fully charged. Then you don't need to test it. It is always ready to go. I mean what happens when you are ready to test a starter, you test the battery and its low? Now you have stop charge and wait. It is rather a "reactive" situation instead of a "proactive" one.

Here's one of the best hook it up plug it in FORGET it!

http://batterytender.com/default.php?cPath=11_3

As for trouble shooting starters I use a DC clamp on ammeter probe that you plug into a DMM. Works really well because you instantly know the starter is pulling too many amps or too few amps. They aren't cheap though.

http://www.toolrage.com/prodView.asp?idproduct=2695

There are others, this is just an example. You need at least 1000Amps range though.


As for flashlight batteries. I really don't like testing them because you use an un-recoverable percentage of them with each test. If I want to test them I just turn them on. I know what you mean by them running down after a minute or two. If this is a concern I would just run the light for 1 minute.

I got sick of battery headaches and got one of these.

http://streamlight-flashlights.com/stinhpwitacc.html

http://streamlight-flashlights.com/stingerxp.html

We use it in the farm yard every night. It can run one hour. Has never gone dead. We have never changed batteries. We just screwed the charger to the wall by the door and keep it there.

As for the few batteries we test [zinc and alkali] we do open circuit voltage test. Anything over 1.4V is considered "full" anything 1.2 to 1.3 we consider serviceable preferably not in flashlights. Under 1.2 chuck it.

 

[VEBill]

"...use an un-recoverable percentage..."

I have a cheap Radio Shack battery tester that accepts all the common sized batteries from AAA to D, plus 9v. It was about $10 many years ago. A typical test takes only about a second or two and load current is just a few mA. The results (Green/Yellow/Red) are pretty reliable indication.

You're correct that the test consumes a percentage, but it is likely about 0.01% of the total life of the battery (a guess) so I don't stay up late worrying about it.

YMM certainly V.

For car batteries, once they reach a certain age (starting around 5 years), they're placed on an end-of-life watch (like being on probabtion). If they 'blink' even once (any imperfection, like slow cranking in winter), they get replaced. Not worth worrying about it. A new battery is probably cheaper than the total cost of even a single flat battery.

YMM certainly V.