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Home › Batteries › R40
Regular battery

R40 is the same as No. 6

1What it is2Other names3Facts4Buy it
  1. 1

    What it is

    No. 6

    R40 is just another name for No. 6. Same battery, different label, so you can buy either one.

    Search Amazon for R40As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases.

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  2. 2

    Names you might see in the store

    All of these are the same battery. Any of them will work.

    No. 6905FLAGIgnition Cell
  3. 3

    Quick facts

    Size
    Much bigger than an AA
    Power
    1.5 volts
    Keeps in a drawer for
    About 5 years
    Rechargeable?
    No, use once
    Found in things like
    Vintage transistor radiosIndustrial metersVintage cameras
  4. 4

    Where to buy it

    As an Amazon Associate, KnowYourBatteries.com earns from qualifying purchases.

    Amazon searchEnergizer listings, any pack sizeSearch Amazon for Energizer No. 6
    See results on Amazon →
    Amazon searchMulti-packs from any brandSearch Amazon for R40 (No. 6) multi-packs
    See results on Amazon →
    Amazon searchDuracell listings, the same batterySearch Amazon for Duracell No. 6
    See results on Amazon →

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See it at real size

No. 6 next to a US quarter and an AA battery. “Real size” matches your hand once your screen is set up in Measure it.

No. 6US quarterAA

What do the letters mean?

Battery names are a code. Here’s how to read R40:

RRound cylindrical form factor
40Carbon-zinc size number, not a dimension. Actual size 67.0 × 172.0 mm

The same battery from each brand

BrandTheir name for it
Official nameR40
Shop nameNo. 6

Exact measurements

Width
67.0 mm (2.638 in)
Length
172.0 mm
Voltage
1.5V (empty at 0.9V)
Energy stored
35000 mAh
Weight
—
Made with
Carbon-zinc
Works between
-10 … 60 °C
Official code
R40 · ANSI 905

Questions people ask

Is R40 the same as No. 6?

Yes. They’re the same battery with different names. You might also see No. 6, 905, FLAG, Ignition Cell.

How long will a spare keep in a drawer?

About 5 years if it stays cool and dry.

Can I recharge it?

No. Never try to recharge it.

No. 6
No. 6Regular battery
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1What it is2Other names3Facts4Buy it