Direct answer: no. The A6400 runs on an NP-FW50 and physically cannot take an NP-FZ100 — different size, contacts, and capacity, with no adapter or workaround. It is hands down the most common battery purchase error in Sony-land, and the cause is easy to see: the A6400 and A6600 sit one generation apart and share a name, while the A6600 is the model that moved to NP-FZ100. The assumption “Sony mirrorless batteries are interchangeable” does the rest. Below: a table of commonly mis-bought bodies, each myth dismantled, and a three-step check before checkout. The deeper model differences are in NP-FZ100 vs NP-FW50 explained.
Bodies people buy the wrong battery for
| Camera | Correct battery | NP-FZ100 usable? | Why it’s confusing |
|---|---|---|---|
| A6400 | NP-FW50 | No | Name is close to the A6600, same 6000-series |
| A6300 / A6500 / A6000 | NP-FW50 | No | Every early 6000-series body uses FW50 |
| A6600 | NP-FZ100 | Yes | The only 6000-series body that switched |
| A6700 | NP-FZ100 | Yes | Current APS-C generation stays on FZ100 |
| A7 / A7 II / A7R II / A7S II | NP-FW50 | No | All full-frame, so people assume A7 III sharing |
| A7 III / A7R III / A7R IV / A7R V / A7 IV / A7S III | NP-FZ100 | Yes | The full switch happened at the third generation |
| A7C / A7C II / A7CR | NP-FZ100 | Yes | Small body, big battery — frequently misjudged |
| A9 / A9 II / A9 III / A1 | NP-FZ100 | Yes | Flagships draw heavy power |
| FX3 / FX30 / ZV-E1 | NP-FZ100 | Yes | Video bodies belong to the FZ100 camp |
| RX100 series | NP-BX1 | No | Compact cameras use their own standard |
The two lines worth committing to memory: A6400 takes FW50, A6600 takes FZ100, and A7 II takes FW50, A7 III takes FZ100. Sony happened to change battery families right at those generational seams.
Six myths, taken apart
Myth 1: Sony mirrorless batteries all fit each other
They don’t. Sony runs at least three incompatible standards — NP-FZ100, NP-FW50, and NP-BX1 — differing in size, contacts, and voltage. Full breakdown in every Sony mirrorless battery model explained.
Myth 2: If the capacity is bigger, it must fit somehow
The NP-FZ100 is clearly bulkier than an NP-FW50 and physically won’t go into the A6400’s bay. Any sanding or bodging introduces short-circuit and body-damage risk. Don’t.
Myth 3: Upgrading from A7 II to A7 III lets you keep your old packs
It doesn’t. FW50 in one, FZ100 in the other — a new body means new batteries. Going the other way onto an A7 II backup body requires separate, clearly separated packs too.
Myth 4: Third-party packs get rejected by the body
Most shoot fine. Some Sony bodies display a notice that remaining charge may be shown inaccurately; keep shooting, it’s normal behavior. A “cannot be used” style warning is a different matter — then work through the contacts and the stated compatibility list.
Myth 5: Buy the cheap kit, sort the model later
The wrong model is worthless at any price. Confirm the part number, then decide between a bare battery, one with a charger, or two with a charger.
Myth 6: The small A7C must use a small battery
Backwards. The A7C, A7C II, and A7CR are compact but run NP-FZ100 — one reason their stamina reviews read so well.
Three checks before you order
- Read the pack you own. Whatever is printed there is the final word: NP-FW50 or NP-FZ100.
- Check the manual’s spec page. The power or specifications section lists the supplied battery. Do this especially on used bodies, where sellers sometimes substitute cheaper cells.
- Match the product listing. Your exact model should appear in the compatibility list, not a vague “fits Sony mirrorless.”
For used bodies, add one more: pull the battery, read the label, and confirm it agrees with the manual. Also confirm the body runs cleanly on a known-good pack.
Already bought the wrong one?
- Sealed: ask the seller for an exchange, quoting your camera model and the correct battery part number.
- Opened, unused: most sellers accept returns in that condition if you contact them quickly.
- Used: negotiate with the seller, or keep it as a spare for another body. Never modify it or force it in.
- Then buy the right one. A6400 owners should re-order in FW50; FZ100 owners can use the suggestions below.
FAQ
The A6400’s runtime is weak. Now what?
Carry two more FW50 packs and trim the camera’s draw — lower screen brightness, fewer reviews, unnecessary features off. That’s more realistic than chasing a different battery. Lower screen brightness and review fewer frames between takes.
Can A6600 and A6400 share batteries on a shoot?
No. FZ100 for one, FW50 for the other. Store them in separate pouches, labeled, or you will grab the wrong one on set.
Why doesn’t Sony standardize one battery?
Battery size follows power draw and physical design. Early bodies were lower-power and smaller, so FW50 suited them. By the third generation, draw had jumped enough to justify the larger FZ100.
Can I trust a third-party compatibility list?
Trust lists that name camera models explicitly, and compare your body against them word for word. Phrases like “universal for Sony” are a red flag.
Will my current packs survive my next upgrade?
Depends on the destination. Moving to an A7 III or later, an A6600/A6700, or the A7C series keeps FZ100 relevant. Landing on an A6400 or A7 II means switching to FW50.
Bottom line and buying notes
Everything here reduces to one sentence: the A6400 cannot use an NP-FZ100 — it needs NP-FW50; only the A6600 and A6700 belong to the FZ100 family. Shooting an A7 III/IV, A7R III/IV/V, A7S III, A9 series, A1, A7C series, FX3, FX30, or ZV-E1? YO’s NP-FZ100 compatible battery (2280mAh / 7.2V / about 16.4Wh) fits directly, at around $17.89, with kits at about $22.93 and $36.74. The TNP-FZ100 (2400mAh / about 17.3Wh) adds headroom at around $19.66, or about $39.92 for the two-battery kit. Sony’s own pack sells for $70 and up. A fuller model cross-reference is in the complete list of NP-FZ100 compatible cameras. Studios, rental houses, and resellers buying 100 or more should go through the wholesale inquiry page.