I need to test many power tool batteries - how?

[sac02]

I've got a few dozen LXT 18V Makita battery packs that I need to test to figure out which ones are good, which are OK but acceptable, and which are no good.

Using them in a tool to test runtime or torque output does not seem like the best way to really objectively test the health of the battery, because it is time consuming, dependant on the tool itself, and potentially puts a fair amount of wear on the tool.

Has anyone had to figure out a decent way to test power tool batteries?

I test single-cell Li-Ion cells using a load, and measuring voltage (~3.7V) and amperage (under 5A) to find capacity and internal resistance. But the equipment I have is not heavy-duty enough to load test an 18V battery pack that could make dozens of Amps.

 

[JRC3]

Back when I ran RC cars with nimh battery packs I'd cycle them back in to shape with a car window defroster. I'd series two 7.2v packs and would hit about 15volts. Not sure what 18v would do though.

I'd maybe try a radiator fan for tool battery packs. Cheap and available, might be worth a little research.

 

[Advan]

The problem is that they aren't just simple batteries made from a few cells, but also have overdraw and temperature protection circuitry. Without cracking the cases and testing the cells themselves, you probably are better off using a high-draw tool and the diagnostic ability of the LXT charger to figure it out.

 

[sac02]

Yeah, I'm aware the batteries have IC's that are counting charges, and discharges, and full and partial discharges, and over amperage situations and etc etc. And I'm aware of how they are built from either 5S1P, 5S2P (or even 5S3P for new ultra capacity batteries), and I've even rebuilt several with Sony VTC6 cells (the best high-drain-high-capacity cell available at the moment). But I dont think the charger is going to tell me what I want to know - can this battery pack deliver full current, and does it still have decent capacity? I think the charger will only reject the battery if some significant issue has been detected.

I was just trying to pick everyone's brain on how might be a good way to load test power tool batteries.

The radiator fan might be a good one, it is a relatively high amp draw, and it would be trivial to measure the RPM at the same time I measure amp draw, so I would have two different indicators of battery output capability.