Can I use a different size?

No. The battery compartment is sized for one cell and a different size will not seat correctly, if it fits at all. Sizes 312 and 13 share a diameter and differ only in height, which is the one pair that occasionally gets confused, but a 13 will not close into a 312 compartment and forcing a door damages it.

Why does this style need changing so often?

Because battery life is capacity divided by draw, and a smaller shell holds a smaller cell. A size 10 holds roughly a sixth of what a 675 holds while the device draws a broadly similar current, which is why the smallest and least visible devices need attention most frequently. It is a direct trade against visibility.

Would a rechargeable version of this style be better?

If handling the cell is the difficult part, yes, and that is the most common reason people switch. A rechargeable device replaces a fiddly few-day task with dropping the aids into a charger each night. The trade is that it cannot be revived late in the evening with a spare from a drawer, and the built-in battery eventually needs a service replacement.

How many batteries will I get through in a year?

For a pair of devices taking size 312 cells at 3 to 10 days each, roughly 73 to 243 cells. Buying in larger packs brings the cost per cell down sharply, and zinc-air cells carry a stated shelf life of several years, so bulk buying is sensible.

Battery size for a in the ear hearing aid

Quick answer

A in the ear hearing aid most commonly takes a size 312 battery, the brown one, IEC PR41, measuring 7.9 by 3.6 millimetres. This is the size usually fitted to that form rather than a rule, and the tab colour on the packet you use now is the reliable identifier.

What battery does a in the ear hearing aid take?

A custom or stock shell filling part of the outer ear. Larger than a completely in canal device and correspondingly easier to handle, with room for a longer lasting cell.

The relationship between device style and battery size is simple and it is really a relationship between size and endurance: a smaller shell has room only for a smaller cell, and a smaller cell runs down sooner. That is the whole trade behind the four sizes.

Trade convention Taught everywhere in the clinic and the trade, and published as a standard by nobody. Useful, and not a standard.

A in the ear device most commonly takes a size 312 cell.

Battery size by device style
Device style	Usual battery	Tab colour	Typical life (days)
Completely in canal	Size 10	Yellow	3 to 7
In the ear	Size 312	Brown	3 to 10
Receiver in canal	Size 312	Brown	3 to 10
Behind the ear	Size 13	Orange	6 to 14
High power behind the ear	Size 675	Blue	9 to 20

This mapping is a trade convention rather than a rule, and manufacturers differ. The reliable identifier is the tab colour on the packet you are currently using, because size number, colour and IEC designation are a universal published standard.

The size 312 in detail

Published figure From a named standards body, regulator or professional classification. Reproduced here, not derived by us.

Size 312 is the brown one, IEC PR41, 7.9 by 3.6 mm.

The four hearing aid battery sizes
Size	Tab colour	IEC	Diameter (mm)	Height (mm)	Typical life (days)
Size 10	Yellow	PR70	5.8	3.6	3 to 7
Size 312	Brown	PR41	7.9	3.6	3 to 10
Size 13	Orange	PR48	7.9	5.4	6 to 14
Size 675	Blue	PR44	11.6	5.4	9 to 20

Size number, tab colour and IEC designation are a universal standard: every maker uses the same colour for the same size, which is why the colour is the fastest way to identify a battery. Zinc-air cells are activated by air, so the tab should be left on until the battery is needed and then given about a minute before the door is closed.

Making a zinc-air cell last

Zinc-air cells are activated by air reaching them through holes under the tab, and two consequences of that account for most complaints about battery life.

Leave the tab on until you need the cell. Once it comes off the cell starts discharging whether or not it is in a device, and putting the tab back does not stop it. Then wait about a minute after removing it before closing the battery door: a cell that has not fully activated reads as weak or dead, and a great many good batteries are discarded for exactly this reason.

Store cells at room temperature. The old advice to refrigerate them does not help zinc-air chemistry and the condensation can hurt.

Common questions

What size battery does a in the ear hearing aid use?: Most commonly a size 312, which has a brown tab and is IEC PR41. That is the size usually fitted to this form rather than a rule, and manufacturers differ. The reliable check is the tab colour on the packet you are currently using, since colour and size are a universal standard.
Can I use a different size?: No. The battery compartment is sized for one cell and a different size will not seat correctly, if it fits at all. Sizes 312 and 13 share a diameter and differ only in height, which is the one pair that occasionally gets confused, but a 13 will not close into a 312 compartment and forcing a door damages it.
Why does this style need changing so often?: Because battery life is capacity divided by draw, and a smaller shell holds a smaller cell. A size 10 holds roughly a sixth of what a 675 holds while the device draws a broadly similar current, which is why the smallest and least visible devices need attention most frequently. It is a direct trade against visibility.
Would a rechargeable version of this style be better?: If handling the cell is the difficult part, yes, and that is the most common reason people switch. A rechargeable device replaces a fiddly few-day task with dropping the aids into a charger each night. The trade is that it cannot be revived late in the evening with a spare from a drawer, and the built-in battery eventually needs a service replacement.
How many batteries will I get through in a year?: For a pair of devices taking size 312 cells at 3 to 10 days each, roughly 73 to 243 cells. Buying in larger packs brings the cost per cell down sharply, and zinc-air cells carry a stated shelf life of several years, so bulk buying is sensible.

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Last updated 2026-09-17.