Battery maintenance

[Not]

My camera uses LI rechargeable batteries. I ordered a couple of new ones, and in a moment of weakness read the instructions that came with them. In a nutshell, they say they ship them uncharged, and for best results I should fully charge them, then discharge them, and then fully charge them. These instructions are consistent with other small rechargeable batteries that have come into my life.

Charging them is no problem, as the camera has a built in charger. Discharging them is not explained anywhere that I have found, other than that they say don't short them out. I used to discharge them by taking a lot of pictures, but recently the batteries have greater capacity, and to discharge these, for example, I would have to take about 1000 pictures, and that would take a while.

So my question is how to safely but rapidly discharge these batteries, especially as this initial conditioning will be more and more frequent as devices move to the more modern battery technology? One article I found said they will discharge themselves over a month or two, and suggests setting a schedule to recharge them, but also warns against recharging before the battery is substantially discharged (not for LI but for other types of rechargeables) to avoid creating a memory in the battery, so there must be some way to discharge these batteries other than using them, or just letting them sit around.

[David Nebenzahl]

On 2/14/2009 11:54 AM Not@home spake thus:

Not sure what physical shape those batteries are, but if they're of a type that will fit in some kind of standard battery holder (e.g., AA, etc.), then you could build a simple discharger; all you'd need would be a small resistor, say a couple K ohms, across the battery terminals. This should safely discharge the battery slowly enough to not harm it. (The resistor would need to be able to dissipate the full power of the battery, so would probably need to be 1/2 watt or 1 watt. If it gets hot, so what?)

[Ed Pawlowski]

How many with the flash? Probably 25 to 50?

[ransley]

You wont get much more power the second charge, easiest is use them in the camera, use the flash to quickly drain them, then put in playback mode, your camera should have slide show mode that shows your photos, leave it on. If you manualy discharge past the safe design volts you could ruin the cell, some can reverse polarity.

[Van Chocstraw]

Nicad are the only ones that have bad memory. Li batteries can be recharged no matter what charge is left. You do not need to discharge them.

[David Nebenzahl]

On 2/14/2009 1:58 PM Van Chocstraw spake thus:

That's true, and I don't know why they're telling you to discharge them at all.

Read all about lithium batteries here:

They say "There is no memory and no scheduled cycling is required to prolong the battery's life.".

[salty]

Although that SOUNDS like a couple of good ideas, they have a fatal flaw that makes them VERY bad. You NEVER want to drain a rechargeable battery completely flat. It immediately ruins them.

[salty]

No, but NEW LI batteries need to be deep cycled a few times before they will attain full capacity.

[Jim Elbrecht]

Poppycock. I drain my NiMH batteries regularly and they keep recharging for several years. By then the new batteries available have much higher capacities so I get a couple new sets.

Jim

[salty]

You either don't understandf the meaning of "drained completely flat", or you are making up stories.

[Not]

I had read that a complete discharge is to be avoided, and that LI batteries don't develop the memory, and their instructs are consistent with your advice to deep cycle them a few times. While it was the camera batteries that prompted my question, there are actually a number of batteries (such as in my laptop) that are all in strange shapes and lack an easy way to fasten a lead to them (I read somewhere that this is a safety feature, as they can explode if accidentally shorted, which is what apparently led to TSA limiting the number you can take on a plane, and requiring that they be guarded against shorting).

I had tried taking pictures with the flash, and even taking movies, but (and I shouldn't complain) these batteries have a very large capacity. I will try the idea of running a slide show; at least then I can let it go on its own and it should stop when the battery is weakened, but not absolutely discharged. Thanks for the information.

[salty]

You are correct in assuming that the camera has circuitry that will prevent total discharge. Most battery operated equipment beyond the very primitive will have circuitry that includes a voltage threshold below which, the device will not operate. In fact, that circuitry is sometimes why a particular device will specify which types of rechargeable batteries are NOT compatible. I have a handheld VHF radio on my sailboat that can use either regular alkaline batteries or NiCads, but not NiMH batteries. The reason is that the initial voltage of the NiMH batteries is too low and the radio detects them as "Low Batt" and sounds a beep alarm even when they are fully charged.

If I silence the alarm, the radio then works just fine for the next many hours, as the NIMH discharge curve is much shallower than the NiCads.