Short answer: the DR-FW50 is a two-bay charging case, not a battery. It charges two NP-FW50 series batteries at once and doubles as storage with the lid closed. The five most common misuses are mixing old and new batteries, leaving it plugged in overnight, closing the lid on a battery that sits proud, charging in high heat, and never cleaning an unused bay. None of these is immediately damaging, but all of them affect battery condition slowly — and most people only think back to them once a battery starts misbehaving.
The positioning first: it stores no energy and stops working the moment power is removed; it also does not assess batteries for you, it simply charges whatever it is given. So whether it is used well depends entirely on the batteries you load and the environment you load them in.
The five at a glance
| Misuse | Typical scene | Immediate result | Advice |
|---|---|---|---|
| Mixing | An old and a new battery side by side | You lose track of which is full and get caught mid-shoot | Number the batteries and pair them by group |
| Overnight | Plugged in at bedtime, unplugged at noon | Long spells at full charge accelerate capacity loss | Unplug when full, or use a timer socket |
| Forcing the lid | Closing the lid on a battery sitting above the bay rim | Shell deformation, stress at the contact roots | Confirm it is fully seated before closing |
| Heat | Charging in a car, by a radiator, in direct sun | Current derates or pauses; long-term aging speeds up | A ventilated table at room temperature |
| Dusty bay | Only one battery, the other bay left open | Dust collects on the spring contacts | Clean periodically with a dry swab |
Item by item: why each one bites
Mixing: old and new in the same case
The bays are controlled independently and each judges its own battery, so there is no electrical problem. The problem is in your head: an old battery that has served two years and a new one charging side by side finish at different times, their lights go out at different times, and after a few rounds you cannot tell them apart.
The more practical risk is what follows the confusion. You believe you left with two full, healthy batteries when one is down to sixty percent of its original capacity, and you find out halfway through the shoot. The fix is plain: number the batteries on the back with a label, pair adjacent numbers together, and keep the pairs intact.
Overnight: never unplugging after the charge finishes
A well-made case stops output once the battery is full, so an occasional night plugged in does no immediate harm. But “occasional” and “every night” are different things. Staying connected keeps the battery at full charge for long stretches, and full-charge storage is one of the main accelerators of capacity loss.
In a lithium battery held near full, the cathode material is more reactive and side reactions run faster. The common industry statement is that a battery stored full loses capacity noticeably faster over a year than one stored at half charge. You will not notice the difference the same day, but in two or three years it becomes the gap between “still good for two hundred frames” and “still good for three hundred.”
The recommendation is to unplug once the indicator goes out, or to use a socket with a timer. If you leave early the next morning, charging at bedtime and unplugging on waking is already enough. If you own a battery with a USB-C port, such as the YO TNP-FW50, you can top it up from an adapter instead of leaving the case on standby all night.
Forcing the lid: physical pressure
The DR-FW50 doubles as storage with the lid closed, but the lid is there to keep dust out and hold batteries still, not to compress anything. If a battery sits above the bay rim, it is not seated; forcing the lid puts the load on the battery shell and the contact roots.
Do that repeatedly and the shell deforms slightly and the latch loosens. A deformed shell can make poor contact in the camera, and stress at the contact roots can crack a solder joint — showing up as “no light in the case” or “works intermittently in the body.”
Heat: the most direct consequence
Charging generates heat on its own. Add a hot room and battery temperature climbs toward the protection threshold, where the case will typically derate or pause. You see an indicator that never goes out and a charge that takes twice as long, with no idea why.
The classic hot spots: a car dashboard in summer, next to a radiator, a windowsill in direct sun, beside a laptop’s exhaust. In use, these run ten degrees or more above room temperature.
The test is simple: feel the battery after charging. If it is clearly hot and uncomfortable to hold, ventilation was inadequate — move it and charge again. A properly finished charge leaves it slightly warm, close to body temperature.
Cold deserves the same attention. Coming in from sub-zero outdoors, a battery may have condensation on it; charging immediately carries risk, so leave it an hour to reach room temperature first.
An open bay: dust on the contacts
Carrying a single battery is normal, which leaves the other bay empty. Left open, it collects lint, sand and crumbs from the bag, all of which end up on the spring contacts. Dirty contacts show up as charging that cuts in and out, or as no detection at all.
Cleaning needs no tools: with power off, brush the contacts with a dry cotton swab or blow them out. Do not scrape with a metal pin. The contacts are plated, and scratching the plating makes oxidation worse.
If you only ever use one battery, close the lid over the empty side too, or treat the case purely as storage and open only the side you need while charging.
A routine that avoids most of this
- Back at the hotel, label the batteries first, pairing them A1/A2 and B1/B2, two to a group.
- Put the two spent batteries into the DR-FW50, connect power, and place it on a ventilated table rather than a bed or carpet.
- Unplug once every indicator has gone out, leave the batteries in with the lid closed, and take the case with you the next day.
- Every three months, clean the contacts with a dry swab and check the shells for swelling or deformation.
- For long spells of disuse, store at half charge and top up every three months.
It is not a complicated routine, but it avoids most of the five items above. More on using both bays is on the DR-FW50 category page, and the battery specifications are on the NP-FW50 series page.
FAQ
Can the DR-FW50 charge a phone like a power bank?
No. It is a charging case: the input charges batteries, and the only output is the battery contacts. There is no USB output and no ability to power other devices.
Can it charge two FW50 batteries from different brands at once?
Yes. The bays are controlled independently, and anything to the NP-FW50 specification will charge. It is still unwise to pair a very old battery with a new one over the long term.
Is it normal for the case to get warm while charging?
Slightly warm is normal. If it is hot to the touch, or smells of plastic, disconnect power immediately and check whether a battery has swollen.
Can a battery stay in the case after it is full?
Short term, yes. For longer storage, take it out or leave it at half charge; extended full-charge storage accelerates capacity loss.