Short answer: most of the time a dead indicator points to the supply chain rather than the battery. Work through cable, then adapter, then bay, then battery, then contacts, and you will usually localize it within ten minutes. The order matters: outside in, cheap to expensive, so you do not condemn a healthy battery before you have established the cause.
The DR-FW50 is a two-bay charging case with no battery and no storage of its own; it only starts working once power is connected. That is the key to diagnosis. A dark case may be getting no power at all, or it may be powered but not detecting a battery — and the two look almost identical.
First, confirm when the light should be on
Normally, with power connected and a battery loaded, that bay’s indicator lights up and shows charging by staying steady or pulsing, then changes color or goes out when full. An empty bay usually stays dark or shows only a power indicator.
So the first false alarm to rule out is an empty bay, or a battery that never seated. An FW50 has to be pressed to the bottom of the bay with full contact before the detection spring moves. Plenty of people leave the battery riding high; the lid closes and it looks installed, but no current flows.
The second is the supply itself. The case’s input is typically USB-C and needs 5V. Some older adapters, computer USB ports and car chargers cannot deliver enough, and the case drops into a protection state that looks like no response at all.
The five-step method
- Swap the cable. Substitute a cable you know charges a phone reliably. USB-C cable quality varies widely, and cheap charge-only cables sometimes cannot even deliver stable power.
- Swap the adapter. Use a known-good 5V adapter straight into a wall socket — no power strip, no extension cord, no USB splitter. This rules out an inadequate supply.
- Swap the bay. Move the battery from the left bay to the right. If it lights up in the other bay, the original bay’s spring or circuit is faulty, which is a case defect.
- Swap the battery. Try a battery you know works. If the light comes on with a different battery, the problem is the original one — over-discharged, protection board latched, or oxidized contacts.
- Clean the contacts. With power disconnected, wipe the contacts in the case and on the battery with a dry cotton swab, then blow out loose dust. Do not scrape with a metal pin; once the plating is broken, oxidation accelerates.
After those five steps you will usually know which link failed. None of it requires opening the case, and opening it is not advisable — the charging circuit is inside, and under non-professional conditions the risk outweighs any chance of repair.
What each result tells you
| Recovers after swapping | Where the fault is | What to do |
|---|---|---|
| Lights after a cable swap | Original cable cannot deliver enough, or has a broken conductor | Replace the cable; demote the old one to low-demand devices |
| Lights after an adapter swap | Original adapter output too low or incompatible | Use a standard 5V adapter; avoid cheap car chargers |
| Lights after a bay swap | Original bay’s spring deformed or contacts dirty | Clean the contacts; if it still fails, contact support |
| Lights after a battery swap | Original battery over-discharged, protection tripped, or contacts oxidized | Clean contacts first; a deeply discharged battery may recover on a slow charge |
| Lights after cleaning contacts | Contact resistance too high for detection | Make cleaning a routine |
| No light after all of the above | Fault inside the case | Stop using it and contact support |
Only the last row needs service. The first five are yours to fix, and contacts in particular are the most common cause of a dark two-bay case.
Three dark-light situations that are normal
The battery is already full. Some designs stop showing a charging indication once a full battery is detected, or give only a brief signal. If you put a freshly charged battery in, no light is expected. Test by trying a battery you know is empty.
The battery voltage is very low and pre-charging has begun. A battery left unused for a long time can drift down, and the case will first trickle a small current into it; the indicator may come on late, only once voltage passes the threshold and normal charging starts. Give it fifteen minutes and look again.
Temperature protection. A battery that has been in a hot car, or one that is still warm from shooting, can cause the case to pause charging on temperature, with no light. Let it return to room temperature and try again; it usually recovers.
None of these is a fault, and returning a perfectly good unit over them wastes both time and shipping.
There is also a way to test around the case: if you own a battery with a USB-C port, such as the YO TNP-FW50, charge it directly from an adapter and see whether it takes power. If it does, the battery is fine and the case is the problem; if it does not, go back and inspect the battery.
When to stop. If the case produces a smell while powered, the shell becomes noticeably hot, or the indicator blinks abnormally rather than holding a steady or pulsing pattern, disconnect power at once. Those point to an internal circuit fault, and continuing to use it carries risk.
Also, never put a swollen battery into the case. Pressure from the closing lid worsens the swelling, and this is one of the few scenarios with a genuine safety hazard — not something to try “just to see.”
Day-to-day maintenance is simple: wipe the contacts after each use, keep the case in a ventilated spot, and do not leave it plugged in permanently. Those three habits make a dark indicator much less likely. More on using both bays is on the DR-FW50 category page, and battery specifications are on the NP-FW50 series page.
FAQ
The light is off, but the battery works in the camera. What does that mean?
It means the battery is healthy and the fault is on the case side, so focus on the cable, the adapter and the bay contacts. If the camera recognizes the battery, its protection board and contacts are working.
Only one of the two bays lights. Is the case broken?
Not necessarily. Swap the two batteries once: if the problem follows the battery, it is the battery; if it stays with the same bay, it is the case.
Can I use a fast charger to power the DR-FW50?
Yes, but the case only draws what it needs. A fast charger negotiates down to the 5V level and will not force a higher voltage in. The real thing to avoid is a poor-quality adapter that cannot deliver enough current.
The indicator stays on and never goes out. Is that normal?
No. It should change color or go out when charging finishes. Staying lit for a long time usually means the battery cannot be judged full, which may point to an aged battery or poor contact.