When Guide 2 and Guide 3 are not enough
CR / LR / SR explain most coin and button cells. AA / AAA explain everyday cylinders. This guide covers the remaining codes on this site: zinc-air hearing sizes, legacy photographic PX cells, multi-cell photo stacks, and specialty lithium packs.
Always match the device page or empty pack. Same outer size can still be the wrong chemistry.
ZA / PR — zinc-air hearing aid sizes
ZA10, ZA312, ZA13 and ZA675 are the four common zinc-air sizes (retail 10 / 312 / 13 / 675) with colour tabs (yellow / brown / orange / blue).
ZA5 (IEC PR63, red tab) is a rarer size-5 cell for some older CIC aids — same zinc-air family, not interchangeable with size 10.
IEC often prints PR70 / PR41 / PR48 / PR44 for the four common sizes (PR63 for size 5). ZA and PR are size-family labels for zinc-air — not the CR/LR/SR chemistry+shape pattern.
Peel the tab when ready to use. Sealed rechargeable hearing aids do not take these cells. This is a size guide, not clinical fitting advice — see the hearing-aid size hub.
PX — legacy photographic / meter cells
PX names are older photo and meter designations. Many original chemistries were mercury oxide and are obsolete — do not seek genuine mercury as new stock.
PX625 (also PX13 / MR9) — legacy ~1.35V meter cell. Modern paths are usually Wein MRB625 zinc-air or an MR-9 adapter with silver oxide. Alkaline lookalikes can fit and still meter wrongly.
PX675 / V76PX — related 1.35V mercury lineage; Wein MRB675 is a common zinc-air path. Not PX625’s chamber and not ZA675 hearing zinc-air without checking the device.
PX400 — smaller 1.35V mercury cell; Wein MRB400 is the usual zinc-air trade path.
PX28 / 4SR44 / PX28-S — silver-oxide ~6.2V photo cell in the ~13 × 25 mm tray. Not the same as alkaline 4LR44 or lithium PX28L.
PX28L / 2CR1/3N / L544 — lithium 6V in that same outer size. 2CR1/3N is a dual 1/3N stack — not a single CR13N (3V).
Discontinued mercury PX28 / 4MR44 / HM-4C names are historical; modern silver / alkaline / lithium packs replace the form factor, not mercury chemistry.
PX32 (HM-N / E164) — legacy ~5.6V mercury photo cell. Modern alkaline A32PX / PX32A are common Electro 35 replacements — not a PX625 and not an automatic 4LR44 swap.
PX27 / V27PX and PX23 / S23PX — specialist mercury photo cells; use device-specific adapter/voltage guidance — do not assume PX28/4LR44. See classic PX mercury replacements.
4LR44 — alkaline photo stack
4LR44 means four LR44-class alkaline cells stacked as one 6V photo battery (packs may say A544 / PX28A).
The “4” is a count/stack prefix; L = alkaline; R = round in the IEC sense for the element cells. It is not a single LR44 button cell and not a 1.35V PX625.
Same tray as silver-oxide PX28 / 4SR44 and lithium PX28L — see PX28 vs 4LR44 vs PX28L.
Specialty lithium packs and cylinders
2CR5 — 6V lithium dual-cell pack used in many mid-era Canon Sure Shot / Prima bodies. Not AA and not CR123A.
CRP2 (IEC CR-P2, also DL223A / EL223AP) — different 6V lithium photo pack used in many late-1980s/1990s AF compacts. Not CR2 and not 2CR5 — see CRP2 vs CR2 vs 2CR5.
CR123A (also labelled CR123) — 3V lithium cylinder for sensors and some compact cameras. Rechargeable RCR123A / 3.7V cells are not automatic substitutes.
CR2 — shorter 3V lithium cylinder than CR123A; confirm the tray. Not a drop-in for CR123A by voltage alone, and not a CRP2 pack.
CR13N (trade label CR1/3N / 2L76) — 3V lithium about as tall as two stacked LR44 cells. Some film SLRs allow it instead of 2× LR44/SR44 only when the manual says so. Not a CR123A.
CR-V3 (CRV3) — 3V lithium primary camera cell that can share a compartment with approved AA options on some Kodak EasyShare bodies. Not a proprietary Li-ion pack and not CR123A.
Quick takeaway
Read the full code: ZA/PR = zinc-air hearing size; PX = legacy photo/meter family; 4LR44 / 2CR5 / CRP2 = multi-cell packs; CR123A / CR2 / CR13N / CR-V3 = specialty lithium shapes. Then open the battery or device page — do not flatten them into “camera battery” or “hearing battery” generics.