Short answer: for a trip of two days or less, where you get back to a socket every evening, two spare packs are the better deal — lighter, smaller, one less cable. For three days or more, for back-to-back location days, or when several people share one set of batteries, the DR-FZ100 wins, because it turns charging two packs from a hunt for two sockets into a single connection. The deciding factor is not how many packs you own but whether you can guarantee a stable charging window each night.
This looks like a weight comparison, but it is really a comparison of charging capacity. Spare packs only answer whether you have enough power; a charging case also answers when that power becomes available. What goes wrong on a trip is rarely a shortage of batteries — it is arriving at the second evening with only one pack charged.
First, the weight
An NP-FZ100 pack usually sits in the 80–85 gram range, so two come to 160–170 grams. An empty DR-FZ100 weighs about as much as a pack, or a little more; with two packs inside, the whole set lands around 260–320 grams. In other words, the case option costs you roughly one extra pack’s worth of weight over two bare batteries.
A hundred-odd grams in a camera bag is imperceptible. On a lightweight hike where you carry it for a dozen hours a day, that margin adds to everything else and stops being negligible.
Do not forget the cable
Carrying the case usually means also carrying a power cable and a charger. With two bare packs, the camera’s own USB cable is enough — often you do not need it at all, since hotel rooms generally have sockets and USB ports. At packing time this item is often more noticeable than the batteries themselves.
Then the volume
| Option | Weight | Space taken | Charging capacity | Best for |
|---|---|---|---|---|
| Two bare packs | About 160–170 g | Two thin slabs, fits any compartment | Two sockets needed; one in camera, one in a dock | 1–2 day trips with a reliable socket each night |
| DR-FZ100 plus two packs | About 260–320 g | One rigid box, needs its own compartment | One connection charges both; closes into storage | 3 days and up, continuous location work, shared kits |
| Two TNP-FZ100 direct-charge packs | About 160–170 g | Two pack-sized items plus a short cable | Each runs off a power bank or charger, in parallel | Light travel, uncertain charging conditions |
Volume is the part people underestimate. Bare packs are flat, slip into gaps in a bag and can even roll up with clothing; a rigid case demands a full compartment. If the bag is already tight, one more box may mean one less lens.
The third option deserves its own paragraph: packs with a USB-C port built in, such as the TNP-FZ100, weigh the same as bare packs but each can charge independently from a power bank. It is effectively the case’s capability broken up and distributed into the batteries, at the cost of needing two USB ports and two cables while charging. For light travel this is often the best answer.
The real dividing line: the charging window
Put the three options side by side and the weight difference is at most a couple of hundred grams, the volume difference at most one compartment. What actually decides the experience is this: how many usable sockets you have at night, and how much time the packs can stay there.
- Hotel room, same place every night: sockets are a non-issue and two bare packs alternating is plenty. The case is a convenience, not a requirement.
- Guesthouses, hostels, camping, campervans: socket count and position are both uncertain, and a case that charges two packs from one connection immediately earns its place.
- Continuous location work with no time to return to the hotel: you need to charge while shooting, and the case becomes a daytime staging post — part of the workflow, not just a charger.
- Several people sharing one set of packs: numbering and slot discipline prevents the usual confusion about whose battery is on charge, which bare packs cannot do.
So: if you can reliably lay two packs out on a desk for four or five hours every evening, the case’s marginal value is low. If the window is tight or uncertain, what it saves you is getting up at midnight to swap batteries.
Variables that get overlooked
Cold weather
In winter the usable capacity of a pack drops, so you need more spares than you would in summer. That raises the value of charging two at once, because you may be rotating three or four packs with only a few evening hours available. The cold-weather article covers how the packs behave.
Security checks
Lithium batteries are generally required to travel in the cabin, not in checked baggage. Kept together in one case they are quicker to count at security; scattered across several bags, an inspection takes longer. The rules are set out in this article — how you pack does not change compliance, but it does change how quickly you get through.
In-body charging
Many bodies support USB-C charging directly, so one cable to the camera is enough and no separate charger is needed. That further weakens the case’s case: if your body supports it and the schedule is not tight, two bare packs and a cable will do.
Three criteria
- Trip length. Two days or less, bare packs; three days or more, the case starts to pull ahead.
- Charging conditions. Fixed accommodation with plenty of sockets, bare packs; moving between places with uncertain sockets, the case.
- Shooting load. Two or three hundred frames a day with the occasional clip, bare packs; a thousand frames a day or long recording sessions, the case.
If two of the three point to the case, take it; if only one does, save the weight. The judgement does not need to be precise — a couple of hundred grams and one compartment will not ruin a trip, but the wrong call will keep nagging at you.
If you cannot decide, there is a middle path: bring the case but only one pack in it, with the second in your bag. You pay the weight, keep the charging capability and use a little less space. The DR-FZ100 works fine with a single slot loaded; operating notes and indicator meanings are in the category page, and the trade-offs for direct-charge packs are covered here.
FAQ
Is a charging case alone enough, with no spare packs?
No. The case is charging equipment, not a power source — it cannot run the camera and it adds no usable energy to what you carry. The real combinations are case plus at least two packs, or case plus one pack plus in-body charging.
Are two packs really enough for a two-day trip?
At three to five hundred frames a day plus a few short clips, two usually suffice, provided you can charge them fully each night. If you record long takes during the day or shoot in cold conditions, plan for three, since usable capacity drops in the cold.
Can the case go in checked baggage?
Without batteries inside it can be checked. With packs installed it falls under lithium battery rules and generally has to travel in the cabin. The safe habit is batteries with you, case wherever you like — do not stuff a loaded case into checked luggage for convenience.
Does the case add much bulk to my luggage?
A dual-slot case is roughly the size of a small lens case. If your bag already has a compartment for a lens, it will usually fit; if the bag is full, it will displace something. In that situation a direct-charge pack is the more space-efficient alternative.