Hearing Aid Battery Sizes Explained: 10, 312, 13 and 675

Hearing aid batteries are the smallest part of the whole purchase and the one that generates the most phone calls: which size, how long should it last, why did it die in two days, and is it safe to buy the cheap pack from the market.

Here is the practical version.

The four sizes

There are four button-cell sizes in use, all 1.45 volt zinc-air. The size is a code, not a brand, so a 312 from any manufacturer fits any aid that takes a 312.

Size	Colour code	Typical use	Typical life
10 (blue)	Blue	The smallest in-canal aids (CIC/IIC)	3–5 days
312 (brown)	Brown	Most RIC and small BTE aids	5–10 days
13 (orange)	Orange	Larger BTE aids, more power	10–20 days
675 (blue, larger)	Blue	High-power BTE, severe to profound loss	2–4 weeks

Blue appears twice because 10 and 675 both use blue packaging. Read the number, not the colour.

Your aid takes exactly one size and it is printed inside the battery door or in the manual. Do not force a larger cell in; the door will crack, and that is a repair, not a battery problem.

What changes how long they last

Manufacturer figures are optimistic. Real life involves streaming, heat, and humidity:

• Streaming. Bluetooth audio is the biggest drain. Two hours of calls a day can cut runtime by a fifth or more.
• Power output. A 13 in a high-power fitting does more work than a 13 in a mild-loss fitting, and dies sooner.
• Heat and humidity. Acidic sweat and monsoon air corrode contacts and shorten life.
• Age on the shelf. Zinc-air cells start discharging once the tab is removed; old stock loses capacity. Buy from a shop that turns stock over.
• Leaving them in the aid. A cell left in a device that is switched off still drains slowly. Take it out, or switch the aid off properly, if you are storing it for weeks.

Zinc-air needs air

The sticker on the back is not packing material. Removing it lets air in, which activates the cell. Two consequences people do not know:

1. Wait a minute. After pulling the tab, wait 60 seconds before inserting the battery. It gives the cell time to reach full voltage, and it can add a day of life.
2. Do not remove the tab early. A cell with its tab intact keeps for years. Once opened, it starts dying whether you use it or not.

Cost per year in Pakistan

Battery prices move, but as of 2026 you are looking at roughly:

	Typical price	Packs per year (both ears)	Approximate yearly cost
10	PKR 150–300 per pack of 6	~40 packs	PKR 8,000–12,000
312	PKR 150–300 per pack of 6	~26 packs	PKR 5,000–9,000
13	PKR 200–350 per pack of 6	~15 packs	PKR 3,500–6,000
675	PKR 250–400 per pack of 6	~8 packs	PKR 2,500–4,000

Two things follow from that table. Smaller aids are more expensive to run, not less. And over five years, batteries can add up to more than the price gap between a mid-range and premium device — which is worth factoring in when you buy, as our hearing aid price guide sets out.

Rechargeable models avoid this cost entirely and I compared the two properly in rechargeable vs battery hearing aids.

Buying them in Pakistan

• Buy brands you recognise. The cheap unbranded packs often have less capacity and inconsistent voltage, which makes the aid behave strangely.
• Check the expiry date. Zinc-air cells have one printed on the pack. Short-dated stock is a false economy.
• Buy a month at a time, not a year. Batteries store better in the shop than in a Karachi or Lahore summer.
• Keep them out of the fridge. It causes condensation, which is worse than heat for a button cell.
• Carry spares. A dead battery mid-conversation is the most common reason people stop wearing aids in the first month.

Battery care in three rules

1. Let the tab off for a minute before use.
2. Wipe the contacts and the battery door with a dry cloth when you change a cell.
3. Store packs in a cool, dry drawer, away from direct sun.

If a battery dies in a fraction of the usual time, the cell is usually not the problem. Corroded contacts, a failing receiver, or an aid that was left switched on will all look the same. Our maintenance guide covers the checks, and if it keeps happening, send us the model on WhatsApp and we will tell you whether it is the aid or the battery.