After some further research, I've discovered that I have made a mistake. It doesn't really change the way most people use the phone, but it is important to know. Since this forum has no strikethrough option & I want to be transparent about my corrections, I will put incorrect information into quotes. I know a fair bit about batteries because I have been selling them for 15 years, but I am not a scientist, or battery engineer or whatever the battery makers are called, so some of my information may be a little inaccurate, but I doubt it. Before I start, let me tell you that the following information does not apply to all batteries, only the kind that we are specifically concerned with, the one in our Desire. Many, many devices use the same kind of batteries though, & this information will also apply to them (portable laptop computers for example). I will explain what the kinds of batteries are, & how to tell them apart, at the bottom. This turns out to be not quite right. The best way to treat a rechargeable lithium battery is to discharge about 40-60% of the battery before recharging it, and about once a month deep cycle the battery by letting it drain until the phone turns off. Clearly, it will not always be practical to wait for the battery to get within a certain range before recharging it, so the best option is still to charge it more frequently. The most damaging thing you can do to your battery is to completely drain it so that it is totally flat. Thus ends the simple instructions on how to best care for your battery. But there is still a lot more to know about them, so read on if you're interested. I have no idea whether this is true of this particular phone or not (because I have not had a flat battery yet), but as far as I know, all of these high tech devices that run on lithium batteries have a battery protection built into them that prevents the battery from completely draining. In other words, when the battery level gets critically low, the phone will shut itself down (note that critical in this case does not refer to when the battery indicator turns red. Critical in this case refers to a point far beyond that). (Yes, the phone does indeed have a critical shutdown, and the battery has a 2nd safety cutout, but if the battery one ever trips, then the battery wont charge again without professional equipment) So you don't need to panic if the battery gets low & you can't charge it, however, you might want to worry a little if the phone has shut itself off and you wont be able to charge it for several days. Even when a battery is not being used, it's still discharging a little. That's why you don't have a full charge on the battery when you take it out of the box for the first time. Rechargeable lithium batteries do not like heat, so if possible, try to avoid using the phone in hot environments. If possible, you should only do one of the 3 things below at a time: ~High drain use (like playing a game that pushes the limits of the phone's abilities) ~Charging the phone ~having the phone in a hot environment (more than 40c/104f) The batteries will last longer the cooler they are, but they don't like to be frozen, so never freeze the battery. Note also that you can check the battery temp in the settings or many battery monitor apps. Try to keep it under 40c. One final note about the Desire in particular before I go on to more general battery information: There is no good explanation for why the battery seems to get better after a week or two of use. The only explanation is that people are simply using the phone more than they realise because it's a new toy. The only other possible explanation is that HTC have a software bug that is not accurately representing the battery life at the start of the phones use. Deep cycling the battery: This refers to intentionally using the battery until it is critically low before recharging it again. It's probably worthwhile doing this a few times when you first get the battery, but the benefits are not really that great. Doing this for every charge cycle is not good for the life of these types of batteries. Deep cycling the battery is not good for the life of the battery, the more often you do it, the fewer times the battery will be able to be recharged. These batteries do not suffer from the typical memory effect which is explained below, but the battery will probably suffer from what's referred to as the digital memory effect. So, a deep cycle is recommended about every 30 cycles or once a month. I only recommend deep cycling once when you first get the battery. The memory affect: This refers to batteries behaving like they have a smaller capacity than they actually have. This does not happen on lithium batteries, so I will go into further detail on this later. The digital memory effect: This refers to the electronic battery meter no longer accurately indicating the battery life. A single deep cycle charge is enough to fix this, and performed monthly will prevent it from occurring on the device. Doing this once when you first get the battery is definitely a good idea. Cell Vs Battery: A cell is basically a single container with all the chemicals needed to produce electricity whereas a battery is a bunch of cells all joined together. Disambiguation: some parts of the world, most notably, North America refer to mobile phones as Cell phones, this refers to the service range of a wireless tower or some such thing. I dunno much about this, ask an American It's important to note that these terms get mixed up all the time, and it's usually regional, North Americans tend to call both kinds cells & Australians tend to call both kinds batteries. Go figure. In the end though, it doesn't really matter whether you call them a battery or a cell, the difference is really only academic. Battery Types: Note that this is by no means an exhaustive list of the kinds of batteries that are available, only the most common ones, ranked from best to worst. For example, a citrus fruit with a couple of nails in it is a cell, but it's not useful to know for the purpose of this post. Nor is it very useful to know that button (or coin) batteries come in a type called silver oxide. Battery kinds: I need another term for explanation purposes, but it's not really accurate, just an easy way to tell the 2 apart. Lets call the 2 terms common & specialised. Common refers to batteries that you find in things like kids toys and torches. They have codes that everybody recognises, like the following: AA, C, D, 9v, UM-1, UM-2, UM-3 or UM-4. Specialised refers to the kind of battery included with the Desire. The are not universal batteries and [usually] only fit in the one device they are designed for. Memory effect continued: The so called memory affect would be better described with the name Burn In, but memory effect is what it's called. Burn In would be better because it describes the effect better, especially since most of us are probably familiar with this term with regards to display screens. In the case of batteries, it basically occurs when you repeatedly recharge a battery before it has completely discharged. Essentially if you recharge it at 50% all the time, the battery will burn 50% into it's "memory" and eventually will only work at 50% capacity all the time. there are ways to reverse this in a very limited way, but the results are usually not very good, and will only partially repair the damage, and the problem will re-occur. The ways that you can kind of "fix" a memory affect are: Deep cycling the battery several times in a row. High current discharging &/or charging. Basically overworking the battery, putting more strain on it than it's designed for. This is probably the most effective, but don't do it, the chance of things like explosion is too high. freezing the battery. Rechargeable Lithum (Li) Nickel-Metal Hydride (Nimh) Nickel Cadmium (Nicad) Im not sure where lead acid batteries fit into this list, probably second, but since they are used in far different situations (like car batteries) they are not really relevant to this crazily long post. Disposable Lithium Alkaline Carbon zinc I didn't include the abbreviations for these because they are not referred to by that, at least not in Australia. Lithium These batteries, confusingly, come in rechargeable & disposable versions, but it's generally pretty obvious which kind of one you have. I mean if it comes with a rechargeable mobile phone, then it's rechargeable (specialised), but if it comes with a smoke detector, which has no charger, then it's disposable (common). There is a more accurate way to tell though, a rechargeable lithium cell (cell, not battery) is 3 volts (actually, they vary from 2.8-3.2, but let's just say 3 for simplicity). Whereas a disposable is 1.5 volts. So if you have a battery, like those common square ones with the 2 connectors at one end (9v batteries in Australia) they are obviously 9 volts which can be divided by 1.5 volts 6 times evenly. Which means that 9v batteries actually have 6 cells inside them. If you pull them apart, they often contain button batteries inside them, but I do not recommend opening a battery if you are not a professional battery repairer who has had training (they contain acid & can explode or create toxic smoke). This btw, is why you can not get rechargeable lithium pencil cells (like AA or UM-3), because they have not figured out how to make a 1.5v version. Disposable ones are common cell & battery types Rechargeable ones are specialised cell & battery types, they don't suffer from the memory effect. Nickel-Metal Hydride These cells are 1.2 volts They come in both common & specialised. These batteries can suffer from memory effect, but it's not as common or pronounced as the next battery type. It should be noted that in common form, these are interchangeable with disposables, even though disposables are 1.5 volts. Nickel Cadmium These cells are 1.2 volts They pretty much only come in common, but there are a few specialized. These cells also come in battery types. These cells do suffer from the memory effect. Frankly, these batteries are so outdated that they really should not be making or selling them anymore. & they are finally started to disappear. It should be noted that in common form, these are interchangeable with disposables, even though disposables are 1.5 volts. Alkaline These are the most common of the common batteries & cells. I can't think of a single specialised alkaline battery, but one probably exists somewhere for some obscure device. Disposable batteries don't suffer from the memory effect. These batteries come in 1.5 volts Carbon Zinc These cells and batteries only come in common form, but like the Nickel Cadmium cells, these cells are so outdated that they really should not be making or selling them anymore. & they are finally started to disappear. However, they do still have limited use in things like TV remotes & clocks. Even then though, you're better off putting alkalines in your remotes. These batteries come in 1.5 volts. TELLING THEM APART ~It's usually written on them or their packet what kind they are. The most common exceptions are alkaline and carbon zinc. Rechargeables usually have their abbreviation on them. ~The price. for example, the cheapest rechargeables are Nickel Cadmiums and the cheapest disposables are Carbon Zincs. ~Their use. The devices they are used in & whether that device has a charger. It should be noted that some devices that charge common batteries often support disposables. Look for a switch to turn the charging function on & off, if the device has a charger. ~Their voltage. 1.5 volts for Alkaline, Carbon Zinc and disposable Lithium. 1.2 volts for Nickel-Metal Hydride and Nickel Cadmium. 3 volts for rechargeable Lithium. Some final notes on safety. As I mentioned earlier, all kinds of batteries have the potential to leak acid or other toxic substances, emit toxic gas clouds, or explode and some care should be taken when handling them. - Do not short out the contacts/connectors, this includes touching more than one connector at a time, & especially don't touch them with your tongue. - Do not mix batteries. This includes chemical types, brands, fresh with used, or any other way you can think of to mix them together. - Do not get them wet - Do not charge disposable batteries - Do not attempt to charge a battery with a charger designed for a different kind of battery. - Do not impact a battery. Batteries never need a hammer. - Do not expose a battery to extreme heat, like a fire or oven, or a microwave for that matter. - Do not leave them in the sun. - Do not attempt to open a battery. - Do not leave them in an unused device for an extended period of time. - Do not use them if they show any signs of leakage or changing shape. - Do not dispose of them with general waste. Many electronics stores, recycling centres, and garbage dumps can arrange to have them recycled. They also contain toxic chemicals that are not good for the environment. These chemicals can kill people if they, for example, get into the drinking water when their containers/shells start to break down. Questions?