"topping off" batteries

<p>I will stick my batteries (Nikon DSLR's) in the charger to bring the charge up to full even if I haven't taken a single picture because they slowly drain just sitting in the bag for a few weeks unused. Is this a problem, does it count against the life cycle of the battery?</p>

<p>maybe you are an RC enthusiast :-) i top off batteries in my RC helicopter before each flight. "topping off" is not as bad on the batteries as "peaking". anyway, both are not necessary and they will just shorten the life of your batteries.<br>

a good habit to develop in dslr (also for flash units) is to just check the batteries before any shoot. replace them with fresh ones, not topped off, if you worry about batteries dying in the middle of the shoot; and put the partially used ones in the charger on site or in your car. carry spares and chargers for both camera and flash.</p>

<p>It's my understanding that lithium-ion batteries don't mind being topped off. I'd be interested in other viewpoints, though.</p>

<p>Scot</p>

<p>I have read some articles that indicate "topping off" is not a bad practice at all. In fact that it is a good practice when using lithium-ion batteries. Better to top off than let them go completely uncharged.<br>

Just my 2 cents worth of info.<br>

phil b<br>

benton,ky</p>

<p>I have no idea how accurate this information is, but here is a site that talks about all things battery:</p>

<p>www.batteryuniversity.com</p>

<p>LiOn batteries last longest if stored at a partial charge (40-60%, if I recall correctly) and a low temperature. So, topping them off but not using them (and, therefore, keeping them fully charged most of the time) can shorten battery life, particularly if the batteries are stored in a warm environment. On the other hand, leaving batteries partially charged means they'll take a while to top off when you want to use them. Perhaps the best compromise between convenience and battery life would be to top them off just prior to a shoot, then recharge when you get home, then top off again just prior to a shoot.</p>

<p>Topping off a battery is an old habit from the rechargeable Nickel Cadmium (NiCad) and Nickel Metal Hyrdride (NiMH) days. The reason for topping off was because NiCad and NiMH has a fairly high self discharge rate. For NiCad, topping off was actually a bad idea because it forms crystals in the battery and the capacity of the battery will be lowered over time. We still did it. NiHM has a worse self discharge rate so topping off was almost mandatory. A NiMH pack can self discharge by 1/3 the capacity over night.<br>

However with most "modern" DSLR and the Lithium Ion batteries there is really no reason to top off a battery anymore. Lithium Ion batteries have very low self discharge rate.<br>

That said the Lithium Ion batteries are very sensitive to low battery voltage. Once a battery cell is reduced to a specific voltage the battery will become irreversible. So it is definitely a good idea to take the battery out of the camera and recharge the Lithium Ion battery once every three to six months. The reason is that the camera has a slow drain on the battery also.</p>

<p>ni-cads had a " memory" and would get in a mode where a smaller capapicty was the limit. and only a very long charge 2-3 days would "fix them" and would reverse when charg3ed in series and the weak one needed to be charged individually.<br>

most of these problem are minimized with newer batteries<br>

still they often gradually lose their charge after several weeks rest.<br>

since I don't think the newer chargers have a discharge // charge cycle, the only thing you can do is recharge them<br>

and let the electronics in that charger do their best.<br>

keep a few sets of alkaline handy as they tend to be stable for a year or so. Just for bakup.</p>

<p>at least the newer batteries don't have a terrible memory problem like the old ni-cads.</p>

<p>That battery university site has generally accurate information on Li+ batteries. I work in the aerospace industry and consider myself as fairly knowledgeable about this type of cell, as my work depends on it. (The batteries we use on satellites are not the same as the ones we use on the ground, but the concepts are the same. Good thing too, since a set of flight batteries are close to $1M or more.)</p>

<p>There are two ways that Li+ batteries lose capacity: from cycling, and from storage (also known as "calendar" loss). Both types of loss are typically treated as though they follow a square root law in terms of degradation. Calendar loss would be proportional to the square root of time at a given condition, while cycling would be to the square root of the number of cycles to a given depth of discharge (DoD). Combinations of conditions are combined in a RSS fashion to give the total degradation after a period of use, since damage coefficients vary for DoD for the cycling damage, and for both temperature and state of charge (SOC). Generally speaking the temperature effect follows Arrhenius law, with an exponential increase versus absolute temperature increases. It also increases as the storage SOC is increased. Finally, it is generally true that taking the same amount of total energy out of these batteries in many small cycles results in less degradation than by doing so in fewer deep cycles.</p>

<p>Finally, discharging Li+ at cold temperatures will usually result in getting less capacity out, but doesn't harm them. Charging them while cold, especially at high rates, however will prematurely degrade them due to a plating out of metallic Lithium onto one of the electrodes - not a good thing.</p>

<p>So, store them cold and at the lowest SOC you can.<br>

Warm them up before charging them.<br>

Charge them after using if you are going to use them again, but otherwise leave them sit partially discharged.<br>

I hope that helps.</p>

<p>I read that all rechargeable batteries even if specified as "having no memory", still have a limited number of recharges, so "topping off" in theory will shorten the life of your battery. In practice that might not matter if you don't keep a camera for 5-10 years, and your new camera uses a different battery.<br>

I have 4-5 batteries for D200/D300 and 1 of them is from a year ago, the others date from different times since Nov 2006. They still show "0" for health in D300 menu, so no "aging" on it, and it has been near 200,000 shutter actuations since Nov 2006, across those 4-5 batteries. I try to circulate them so that each has about the same number of recharges on them. I have seen one as low as 80% or so when it was "fresh", it must have sat in the bag for a month or more perhaps [since its last recharge, no usage for photos].<br>

I think it's a good practice to use a battery until all empty and thereby minimizing number of recharges over its lifetime.</p>

<p>>>I think it's a good practice to use a battery until all empty and thereby minimizing number of recharges over its lifetime.<<<br>

That practice in itself can cause a premature death for rechargeable batteries. NiCad and NiMH will easily reverse polarity when the nominal voltage is dropped too low. Lithium Ion will simply self destruct when discharged to a certain voltage. That is the reason why most warning label suggest storing battery half charged.<br>

That said most rechargeable battery and definitely all rechargeable Lithium battery has a protective circuit on the battery pack to protect the battery from catastrophic failure.</p>

<p>Batteries are so inexpensive and long lasting now that it hardly makes sense to spend brainpower or time fretting about how to squeeze an extra month of life out of them. Most important: 1) Make sure you have well charged batteries when you need to press the shutter release. 2) Keep a spare charged battery (less important now on bodies like the D300 where you can take about 1,000 pictures on a single charge). 3) Buy a new battery when needed (about $30).</p>

<p>I like David's answer - keep doing what I'm doing and don't worry about it. Thanks all.</p>