How best to maintain driver/drill batteries?

[doggmann]

I did a quick search, as I imagined this would already be in the forums but didn't quite find what I needed...

There's controversy in my department about how best to keep the batteries for our driver/drills. They're mostly 14.4V dewalts with a couple 18v. I came in this year as the department's tech director, but the past tech director is still on staff and has trouble letting go of various duties.

Should the batteries be left in the chargers (sometimes weeks, when vacations roll around, coming up soon)?

Should batteries be left on the drill/driver when not in use?

My practice has always been to return drills to boxes, complete with battery, unless battery is low (like if it was just used for an hour or two). If it was just used for a quick fix - just put it away. Low and dead batteries go to the chargers and whenever I or anyone notices a battery is done charging, it's moved to the shelf below marked "CHARGED." Then, everyone knows where to find a charged battery, and everyone knows where to charge the dead ones.

Any advice out there?

T'hanks!!!

 

[TheaterEd]

My batteries suggest that they only have to charge for one hour, but once a month or so they should be charged for a full 8 hours to reset them. I personally leave them in their drill until they are dead. I have extras though. I have only had them for a month or so though, so I am interested to hear others responses.

 

[josh88]

Most manuals say whether or not you can/should leave batteries on after fully charged. My understanding is that most of the new lithium Ion batteries have smart chargers that don't keep giving full power to the battery after its done which makes leaving them on the charger fine. This isn't the case with older ni-cad batteries however.

I still take my Lithiums off out of habit.

A decent lifehacker article on the subject.
http://www.lifehacker.com.au/2011/06/ask-lh-can-i-keep-my-cordless-tools-charged-up-all-the-time/

 

[Bart53]

I'm with you on this one Doggmann; take the batteries off out of the charger after they are fully charged. Use them until they are nearly fully discharged, then charge to full. An old habit I learned with NiCads, but it still serves me well. I suspect the reason that the former director's policy was in place was to prevent finding a dead battery for the tools when it was needed.

 

[silicsound]

If they are Li-Ion, keep them it the chargers. There is a chip in the battery that monitors the batteries charge; and prevents you from charging it if the battery becomes to depleted, for safety reasons. Ironically, the same chip will drain all the power and prevent it from charging if left sitting for a few months.

 

[robartsd]

Modern batteries and/or their chargers have overcharge protection (for safety reasons as well as convienience). Some old battery chemistry (like Ni-Cad) suffered from "memory effect" when used with incomplete charge/discharge cycles, but batteries that suffer from "memory effect" are no longer common. For convienience of working most people want to have fully-charged batteries at the ready, so they keep them in the charger. How they age when not in use varies significantly with the battery technology.

Li-Ion is now the prevailing portable recharagable battery technology due to high energy density and light weight. They age the fastest when they are warm and fully charged. Fully depleted can cause premature death because the integrated monitoring circuits are not designed to be without power (the circuit will stop powering the device with some reserve left, but the battery should be returned to the charger fairly soon at that point). For long term dormancy, I've seen recommendations of refrigerating a Li-Lon battery with 30% charge (protect from freezing and check charge every few months). On the other hand, lead-acid batteries age most when stored in any state of discharge, so they should be maintained on a trickle charge as much as possible.