Short answer: the core gain of a two-bay case over a single charger is parallelism — two FW50 batteries no longer queue, and total waiting time drops from roughly four hours to a little over two. That gain shrinks when the power supply is weak, because both bays split one 5V input. Whether the switch is worth it depends on how many batteries you own and how often both run flat at the same time. With a single battery, a dual case offers no charging advantage at all.
The FW50 is a small-capacity battery, and one of them already fills quickly, which makes parallel charging easy to undervalue. What separates the two setups is not the speed of a single battery but how long you wait before you are holding two usable ones.
How the two shapes differ
| Point of comparison | Single charger | DR-FW50 dual case |
|---|---|---|
| Batteries charging at once | 1 | 2 |
| Time to fill two batteries | About 3-4 hours, one after the other | About 2-3 hours in parallel, depending on supply power |
| Storage | None; batteries sit bare | Lid closes over both; dust and scuff protection |
| Packed size | Small, but the batteries travel separately | Slightly larger; batteries and charger in one unit |
| Best suited to | One battery, or a minimal kit | Two or more batteries, or centralized management |
The second row needs a caveat: the “4 hours” figure assumes about two hours per battery in sequence, and the real number moves with how depleted each one is. If your habit is to plug in one battery the moment it dies while the other keeps shooting, the queue is spread thin and the dual case stands out far less.
The time budget: what parallelism actually saves
Assume both batteries are empty and the supply is 5V/2A.
Single charger: the first battery runs about 1.5 hours from zero to full, then the second takes another 1.5 hours, for three hours total. For all of it you have one usable battery, and the second only arrives at the end.
Dual case: both bays start together. If the supply delivers 10W total, each bay gets about 5W, close to 5V/1A per side, so each battery fills in roughly 2 to 2.5 hours. Total time is still 2 to 2.5 hours — nearly an hour less than serial — and by hour two you already have two batteries ready.
The measure that matters is when a battery becomes usable, not the total duration. With a single charger you can walk out the moment the first one tops off. With a dual case both finish later but finish together. For anyone who needs to leave with two, the second shape is the right one.
With a 5V/3A supply and a case that splits power properly, each bay runs close to single-charger speed and the advantage grows. Run the same case off an old 5V/1A adapter and each bay gets 2.5W, stretching a full charge past three hours; at that point the only benefit left is not having to babysit the swap.
Why two bays matter more, not less, on small batteries
Intuition says a small battery charges quickly, so parallelism should count for less. In daily use the opposite holds, for three reasons.
- FW50 bodies run short and get swapped often. Two or three changes a day is routine on an A6400, A6500 or NEX body, and batteries tend to die in pairs — exactly the pattern two bays are built for.
- Short per-battery time means denser queuing. A large battery needs one charge a day; a small one needs two rounds, which magnifies the cost of serial waiting.
- Small batteries suit opportunistic charging. Dropping both into a case and connecting one cable beats remembering to swap at the two-hour mark. The real difference is management cost.
Put another way, a dual case does not sell charging speed. It sells not having to think about it, and that is worth most in high-swap, low-capacity shooting.
When a single charger is the better call
The reverse case deserves equal clarity. For these three users, a single charger is the better buy.
- You own one battery. The second bay stays empty forever, and you paid in size and price for nothing.
- You pack ultralight. A single charger plus one battery takes clearly less room than a case plus two. On hikes where every gram counts, the single charger is the practical choice.
- You already own direct-charge batteries. If the battery has its own USB-C port, one cable does the job and a separate charger matters less; adding a case on top is duplicate kit.
The third point is worth expanding. Direct-charge batteries like the TNP-FW50 put the charging input on the battery itself, so in principle no stand-alone charger is needed. The case then earns its place as storage and as a way to handle two batteries at once, not as the only way to charge. See the TNP-FW50 charging and compatibility guide.
How to choose, by battery count
One battery: a direct-charge pack plus a cable. No case needed.
Two batteries: the dual case fits best. Plug in once at night and both are full by morning. On a long trip, add a direct-charge battery as redundancy.
Three or more: dual case plus direct-charge batteries. The case handles the overnight batch, direct charging covers top-ups on location during the day, and the two paths do not compete.
If you are still unsure how the case itself works, the DR-FW50 category page covers the indicator lights and charging order in detail; the battery-side compatibility list sits on the NP-FW50 battery page.
FAQ
Does a dual case wear batteries faster than a single charger?
No. The bays are managed independently and each sets current from its own battery’s state. The real risk is heat: when charging with the lid closed in a hot room, open it and let air through.
Will a 5V/1A adapter leave both batteries short of full?
They will still reach full, just slowly. Shared power lowers current per bay and pushes the total past three hours, but charging will not stall halfway.
Can the case replace a dock charger for genuine batteries?
Yes. The bays are shaped for the FW50, so genuine and third-party batteries both fit. Mixing them works too; the two simply finish at different times because of their age.
On a business trip, can I bring only the case and no adapter?
It depends on whether a cable is included and whether you can find a 5V source. Most cases ship with a cable but no adapter; a hotel TV’s USB port or a phone adapter will do, though output varies. If time matters, bring your own 5V/2A adapter.