When to charge Li-ion batteries

[Muse]

15 months ago I bought a factory refurbished Porter-Cable PCL212IDC-2 12-Volt Max Compact Lithium-Ion 2-Tool Kit off an Ebay volume seller who specializes in Porter-Cable refurbs (if I'm not mistaken). This kit includes a drill and drill driver. I was so sick of my 2 Dewalt 9 volt drills and their Ni-Cad batteries. Most every time I'd reach for one of the Dewalts, the battery was close to dead (if I was lucky, it wasn't dead).

This Porter-kit has two Li-ion batteries, which are pretty small. I have yet to use the drill-driver (I've never used one!) but the drill has worked great for me every single time. However, I've never charged it. Never! I only use it once in a while, maybe once a month on average. The drill is running on the charge with which it was shipped. The other battery hasn't been touched (by me).

I'm wondering when I should charge the batteries. Should I just keep using the drill with the only battery I've used it with until I notice a loss of power and then charge it according to the manual's instructions? Should I have charged the batteries to begin with? Should I charge both of the batteries now? How would I know how much charge each of the batteries has (and therefore when to stop charging)? I know that Li-ion batteries age better when stored something less than full charged but not deeply discharged. The optimal state is ~40%, if not being used for a while, is my understanding.

What do you think/recommend for dealing with the batteries at this point?

 

[Red Squirrel]

It's not good to deep cycle batteries too much or store them in a state of discharge, but in your case they are not really discharged so you're probably fine. I'd probably charge them anyway once in a while for good measure. Like when you're done using it maybe put it on the charger for like 10-15 minutes. The nice thing about lithium ion, unlike ni-mh or lead acid is that they have a really low self discharge rate. Nickel cadminium was pretty good for that too, but you don't really see those around much.

 

[Muse]

It's not good to deep cycle batteries too much or store them in a state of discharge, but in your case they are not really discharged so you're probably fine. I'd probably charge them anyway once in a while for good measure. Like when you're done using it maybe put it on the charger for like 10-15 minutes. The nice thing about lithium ion, unlike ni-mh or lead acid is that they have a really low self discharge rate. Nickel cadminium was pretty good for that too, but you don't really see those around much.

I think you mean Nickel Cadmium? Those (I heard) self discharged at a rate of about 20%/month, whereas typical NiMH are at about 30%/month. Eneloop and maybe some other slow SD batteries (which are, IIRC NiMH) SD only around 15%/year. I don't remember seeing figures for Li-ion. I have the vaguest idea of how to handle Li-ion charging other than to be sure to use the proper charger and not let them run all the way down except once in a great while and then charge them immediately.

 

[Rubycon]

Long term storage charge to about 50% is what's recommended.
As long as the cells remain open terminal. If integrated into a pack with conditioning they will discharge faster.
Especially lipo batteries. They really aren't supposed to be stored fully charged and most packs will self discharge them at a higher rate than if they were just to sit not connected to anything.

 

[Muse]

Long term storage charge to about 50% is what's recommended.
As long as the cells remain open terminal. If integrated into a pack with conditioning they will discharge faster.
Especially lipo batteries. They really aren't supposed to be stored fully charged and most packs will self discharge them at a higher rate than if they were just to sit not connected to anything.

Never heard of Lipo batteries before. Just did a quick Google search, guess they're a kind of Lithium battery. I have no idea if the batteries that ship with this tool are those or "standard" Li-ion" batteries.

Just what the internal configuration is, I can't guess. Of course, the batteries are 12v. I think the manual says they are that but on load are 10.8v. I had a look and there's a complex set of conductive terminals and I don't have any idea where to put the probes of a multimeter to get some idea of what charge these batteries have. There's a set of 3 terminals that are chrome in color (like polished steel), and two others that look like copper. Complicated!

Would there be conditioning going on in the battery when it's attached to the drill or drill-driver and not in use? I can't guess. Never heard of that either.

Yesterday, I did as Red Squirrel suggested and charged the one battery that I have been using (and which I'd never charged) for 15 minutes. I had no way of knowing what charge state it was in before or after doing it. I hadn't noticed any dropoff in performance.

The manual says to fully charge a battery after using the tool and even suggests leaving the battery in the powered charger! It warns against leaving a battery in a fully discharged state (or, I suppose, close to that), saying it will severely impact battery longevity. It really says nothing more in terms of clues how to extend the life of the batteries.

I figure this: Absent any way of determining the charge on a battery other than noticing loss of power in use I can fully charge it BEFORE a usage where I think I'll actually use significant juice. Otherwise, ignore the charging advice in the manual. Thing is, I pretty seldom use the thing(s). Usually it's just a quick use that won't significantly reduce the battery's charge. However, I suppose that once in a while I will have a project that's more taxing and I can fully charge BEFORE doing that and otherwise forget about charging it and just have that as my charge strategy.

 

[Rubycon]

Lithium ion battery conditioning as a phrase could be categorized as mythological.
Individual unprotected cells were never really meant to be in consumer hands for a good reason!
The packs in series/parallel configurations will have circuitry on both the pack and the charger to assure balance charging across cells, over discharge protection, over current protection (both directions) and that cell surface temperature does not exceed safe limits.

Most power tools will use common 18650 cells. Laptops were using them for the most part but have switched over to lithium polymer (lipo) due to size constraints.
Packs that have charge indicators built in (push a button and a series of LEDs indicate charge level) make it easy to determine whether the pack should be charged or not.