I’ve got to get this off of my chest. USB is not a very good charging scheme.
Yeah, it might be okay for your phone, and there are reasons they use it there, but still, not really good.
But, more and more bicycle accessories are using a USB source to charge them. Lights and computer/GPS accessories alike are now using this method to charge internal rechargeable batteries.
Here’s why I don’t like it.
1. Most USB connectors are not waterproof. The Knog light, shown here. claims theirs are, but for most of the accessories out there, you are lucky if they have a little rubber (soft plastic, nothing is rubber anymore, except your tires) plug that you need to pop in and out to use the connection. It’s invariably in the way and on a little flap that keeps pushing it back in the way when you try to plug in the charging cable.
2. They never give you a charger. They assume that because you bought a USB device, you must have at least a laptop computer to plug a cable into. Guess what, I’m not going to drag an expensive laptop out to the bike to charge my light. And I may not want to take the accessory off the bike to carry it into the house. Sure, you can get AC adapters with a USB fitting. So, if that’s the case, why not package one with the device, so you have one? They will tell you that you can charge it from the cigarette lighter socket in your car with the common adapters available as well. True, but why not include a cord with a lighter plug, then?
And there is the issue of charging these items while you are away from AC power. I like to go on multi-day camping trips from my bike. (bikepacking) There is no guarantee that you will find a place to plug in, and if you do, your cell phone is probably going to take top priority. I’ve been in campgrounds where a group of 10 riders were all lined up to use two outlets. That’s why I like things that can always drop back to AA/AAA batteries that I can buy out on the road, if I need, especially low priority things like lights that I only use part of the time.
3. USB supplies only about 5 volts. Most devices that run off of a USB supply charge up Lithium-ion batteries that keep about 3.7-4.2 volts. So the 5V is just enough to charge them. The circuitry inside the devices must then be designed to run off of 3.7V. Most use 3.0-3.3V, so that is adequate. That’s fine for things like LED lights or cyclecomputers. But anything that needs a bit more power or is designed for a 12V automotive environment ends up with boost circuits that generate the higher voltage at an extreme loss of efficiency.
4. What do you do when those Lithium-ion batteries die? They have a lifespan. A certain number of charge cycles that they endure before losing their capacity. Even sitting unused, there is a shelf-life. Normal batteries, either disposable alkalines or rechargeable Ni-Cd, Ni-MH, or variants of them, all die too, but you can just replace them. The Li-ion batteries are not easily replaced unless you are an electronics technician and are not readily available. Besides, they are sealed inside. You either throw it (the whole device) away, or send it back to the manufacturer.
Li-ion batteries are great. They pack more capacity into a given space than almost any other kind of battery and can save a whole lot of weight. They are the battery of choice for e-bikes, although you won’t be charging them off a USB port! I have little doubt that the next devices I buy for my bike will be powered by Li-ion batteries and will have the annoying USB connection to charge them. I’ll end up using wall-wart style chargers just as I do now, but with devices with better connectors. I’ll charge them on the bike, in the garage, just like I do now. I already have Li-ion powered headlights on both my bikes, but they have bigger packs that probably wouldn’t be practical to charge from the limited current of a USB supply, and come with a dedicated AC adapter.
The real reason for USB-charged devices was to combine power and data into one cable. It allowed a device that communicated with a PC to work and not need a separate power source. It’s great for cell phones or MP3 players where you might also want to work with them using the computer and charge at the same time, but it was really intended for devices like keyboards and mice, external data storage, and even audio and video devices.
The last problem is the variety of connectors in use. There’s the USB-B, the old full-sized connector. You don’t see them much anymore other than on printers. When you get to the smaller devices, you have to choose between mini-B and micro-B. The mini came first and is slightly larger than the micro-B which has pretty much become standard for smartphones – other than Apple products, because Apple just knows you want to pay extra for a special connector that you can’t get anywhere else. But you don’t see them on anything but Apple products.
And as connectors, they aren’t very good either. The Micro-B male connector that plugs into my phone, tablet, bluetooth speaker, and everything else from soup-to-nuts nowdays, is flattish with one side slightly wider so that it only goes in one way. You’d think I’d have a 50-50 chance of it fitting when I try to plug it in. No. I usually take three of four tries to get it to work. There is absolutely no self-guiding taper on them at all. You must do all the line up even if it means standing on your head in the dark to do it.
So, suppose I want to order a new bike light, for instance the one pictured above. If I want to also order a cable and power cube to go with it, which connection do I need? I can’t tell. No photos show the connection. Nothing in the specifications tell me what connector it uses. They go on and on about the special steps they’ve taken to make it water-resistant, but don’t show or tell. They even show some kind of extension cable that is supposed to make it easy to plug in while on the bike, but the ends on the extension don’t make sense – they’re the male and female USB-A ends that should be at the other end of the cable.
So there’s my frustration. USB charging – bad. Li-ion batteries – good. Just give me a decent charger with an appropriate connector.