Testing Dewalt's 20V/60V Batterys

sam am I

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Joined
Jun 26, 2013
Messages
2,169
Since I see myself using these (20V and perhaps the Flex 20/60V's) battery's for sometime well into the future as I have almost every 20V tool DeWalt makes, and since I have a growing mix of older and newer, I'd like a quick capacity tester as the integrated 3 LED bar graph "state of charge" tells me nothing about the battery's capacity.

That said, I'd like to NOT necessarily use a/the running power tool/s test method to tell me my battery's capacity is low due to my tool/s are crapping out earlier then normal (what's normal with what size battery and for what tool? Hmmmmm, a pickle), and although this method is definitely one way to know, sorta....I'd like a little more qualitative way to know where my battery's capacity's are. New or old,.....

A side note...Nothing bugs me more (well, one of many) than getting an out of box shelf, perhaps date coded and aged battery that has a "somewhat" lower capacity then it should!! Or is it not as advertised at all? Perhaps the source (Sanyo, Panasonic) of the battery's are just not up to snuff and the manu (Dewalt) hasn't tested a particular lot......

What is needed (for me anyway) is THIS [a] quick and easy tester that would in a snap allow me to have a battery pack back to the store (or not even leave the parking lot) in a heart beat if it was any less then 1% of advertised capacity, especially beings these are so damn $$$$ as well as becoming all to common with tons of tools for them.

To me, buying a battery with somewhat a unknown/subjective capacity level hanging over it is analogous to perhaps buying meat that's sealed in blister packs, that isn't shelf dated per-se and is covered over in such a way we have no way of knowing tell we open it!!, Cept one thing, bad meat stinks and is green, usually!! Battery's don't stink and change color and can be 20%-30%, XX% down, how do we know our battery is 20% less than it should be??

In this above case of the "new" battery, my drill (Non-XR) runs fine, my jig saw (XR) runs sorta fine just not quite as long as my sander(XR) but, longer than the fan on high but, not as long but twice as long then the propane heater and the leaf blower(Non-XR), yada yada yada......This is the issue, for me anyway, how do I know I got what I paid for when I have no idea what a normal run time is for this particular tool with this particular battery?

I envision the tester to be battery powered and fit nicely in tool bag i.e., it uses the battery under test to power the tester......I also envision it to use the/a similar slide in seating method as current charger cradles do. In fact, it looks just like and uses the same charge cradle cept, it's a capacity tester.

My desire is to not only be able to test out of box but, purge/recycle any current and future batteries who's capacity's are say 50% - 60% gone with a 99% confidence level.

I will build this using a converted/extra Dewalt charge cradle gutted/modified as such, It will have a selector switch to set it at the advertised battery capacity size and will test with a few selectable constant current discharge rates, it will use a micro controller that is per-programed with the appropriate algorithms to calculate and display, in real time the instantaneously (perhaps no more than 1 minute) the charge capacity's in amp hours of Dewalt's 20V/60V lithium-ion battery's.

Soon........

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gm280

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Jun 26, 2011
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14,604
Back in my R/C days, I built a battery cycler setup that not only told you the capacity but also cycled them to bring them back up to near new. It was pretty easy to design and build, but those were NiCads.

You could build the same type setup for whatever type battery you have, but it wasn't something that was battery powdered being portable (although I guess it could have been). It took time to drain them and recharge them back. Not something you could simply attach and get any type capacity. And that is because the REAL capacity isn't a one quick test result. It has to drain the battery to a preset level using an absolute known load to calculate the capacity.

Then it switched out the load and recharged them again. So one cycle period allowed you to see the capacity and recharge for another cycle if desired. And usually three cycle periods made them near new again with more capacity then when you started the cycling. JMHO
 
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