My beloved Nikon D40 has an issue where the battery drains ridiculously fast. New OEM batteries and changers don't help, so I think I need to replace the body. Since almost all non-DSLR cameras out there can recharge the battery inside the camera via USB, I'm hoping to find a DSLR that can do the same. Still impossible?
There are none. While there is an increasing minority of cameras that charge via USB, this is thankfully not the case for most cameras. Internal charging is annoying because you cannot use the camera and charge the battery at the same time, at least not further than a few feet away from a USB port. Many seriously high-end cameras even come with charger than can handle two batteries.
Most people like to charge one battery while they are out shooting with another. Sometimes even two. If you manage multiple batteries and charging them ties up your camera, you will miss a lot of photo time.
It is not nearly true that "almost all non-DSLR cameras can recharge the battery inside the camera via USB". In fact, I think it's the exception, rather than the rule.
In any case, I don't think you'll find that for a DSLR. For a compact camera that you might throw in a bag or keep in your pocket while traveling, it makes sense to not have to deal with an external thing. With a more "serious" camera, the balance tilts towards it being very inconvenient to have your camera out of commission while it's doing double-duty in the charger. Better to have two batteries -- one charged or in the charger, and one in the camera.
Ok, this isn't a DSLR exactly, but I guess the original poster is interested in interchangeable lens cameras (ILCs) and just used DSLR as a kind-of synonym for ILC, no matter whether they are DSLRs or mirrorless. It is clear by now that mirrorless will increase in market share and perhaps someday overtake DSLRs.
My Canon EOS RP does in fact support charging via USB. However, there are two peculiarities:
- It's USB-C and not micro USB, so you don't find the required charger that easily
- It requires USB power delivery (PD) support from the charger, meaning you 99% certainly will not find a charger while on a trip. Note USB-C quick charge adapters for phones don't work, it really must have standard USB power delivery (PD) support.
I understand the challenge is that most cameras unlike phones don't run from a 3.6 volt battery; they run from a 7.2 volt battery. USB provides 5 volts, perfect for charging 3.6 volt batteries. Charging a 7.2 volt battery from a 5 volt power supply would require slightly different charger design. Canon in EOS RP decided to use 9 volts which USB power delivery can support, but USB without PD cannot.