I was born and raised in some anglophone Asian country where people use the word "flat" to describe a battery when no electrical current can be generated by it. Some would even use the word "flat" to describe their phone when its battery is dead (although their phones are three dimensional). So one day I looked up OED and realised


British (of a battery) having exhausted its charge.

but I couldn't find this definition of flat in the New Oxford American Dictionary.

So here are my questions:

If I go to the States will people understand me when I say "My battery is flat"?

How about "my phone is flat"? Is this usage of flat even common in the UK?

  • 6
    “My battery is flat” is perfectly understandable in American English as well, though it is listed in American dictionaries as being ‘chiefly British’. Nobody will misunderstand you or have trouble understanding what you mean, even if they might not use the phrase themselves. “My phone is flat” is less obvious. In the right context, you will probably be understood, but you might also get funny looks and people wondering what phones aren’t flat (spherical phones?). Commented Oct 14, 2013 at 10:31
  • 1
    I think "My phone is flat" would be perfectly comprehensible in BrEn, but isn't common among native speakers IME. A more interesting question would be the etymology.
    – Chris H
    Commented Oct 14, 2013 at 10:54
  • 4
    Even I, British, and veteran of many a flat battery would be slightly puzzled if someone told me their phone was flat. 'Aren't they all'? might have been my reply. I would take care to point out that your phone 'needs charging'. Though I must add that my father, in his nineties, thought that that meant it needed money putting on it.
    – WS2
    Commented Oct 14, 2013 at 10:54
  • 7
    Yes, Americans would say a battery is dead. Commented Oct 14, 2013 at 15:29
  • 4
    I live in the States, and I would assume you were not from around here if you said your battery is flat. You're more likely to be understood if you said your battery is out of juice, but I'll be damned if I know why people stick to that expression. Better if you just said it is dead. Commented Oct 14, 2013 at 16:44

2 Answers 2


My battery is flat is perfectly fine in British English, but from the comments, it might not be understood in American English, depending on the context.

My phone is flat is sometimes used according to a quick Google search, but it isn't particularly common in British English and may be misunderstood. It might be more common to say my phone is dead.

This use of flat for an electric battery was first used in 1951 according to the OED (sense 9c). The others related senses are: 9a) wanting in energy and spirit (1604); 9b) depressed, dull or inactive trade (1831); and 9d) a drink that has lost its flavour or sharpness (1617).

I found three 1941 antedatings in Starters and Generators (Edward Molloy, ‎Ernest Walter Knott). Page 85:

If the clutch is not slipping, the trouble may be insufficient volts reaching the motor, due to a flat battery or a bad connection or switch introducing resistance in the circuit, an electrical fault in the starter, or, very rarely, a mechanical fault in the starter.

Page 86:

A flat battery should be replaced, but the reason for the battery being discharged should be investigated.

Page 98:

Under this no-gap condition, the plunger will remain home on a very reduced voltage (which may occur with a flat battery) and will be less susceptible to vibration, and the contact pressure is a fixed and known amount, being the force of the spring (11), and does not vary with voltage.

  • And those antedatings make it sound like the term was in common use at the time of writing.
    – Chris H
    Commented Oct 14, 2013 at 12:05
  • @Hugo So how do Americans describe a flat battery?
    – WS2
    Commented Oct 14, 2013 at 16:39
  • 1
    @WS2 It is a dead battery, as it has ceased to function. If you say your battery-powered device is dead (I need to hang up; my phone is dying; I was going to email you but my laptop died), it usually means the battery has discharged, but appliances and vehicles and whatnot can die for reasons other than their power supply.
    – choster
    Commented Oct 14, 2013 at 17:25
  • 4
    @WS2 Like going flat, it's a figurative usage, as with dead air, dead silence, dead ball, dead stop, etc.— it shows no signs of life. Besides, even in the literal sense, being dead isn't necessarily a permanent or absolute condition. Ask Lazarus. Or Karen Cooper.
    – choster
    Commented Oct 14, 2013 at 22:34
  • 1
    @choster, I think what WS2 is getting at is that (in British English) “the battery is dead” is likely to be understood in the same way as “my laptop is dead”—i.e., that it can no longer be recharged, it has ceased to function, it is ready to be chucked in the bin. In AmE, “my phone just died” is not ambiguous, but “my phone is dead” is: it can either mean that the battery is flat, or that the phone is fubar and I need a new one. In BrE, the latter wording would be so heavily skewed to the latter meaning that it is almost unambiguous. Commented Oct 14, 2013 at 23:18

Years ago I had to call a tow truck for a flat battery, the dispatchers huffily said "you can have a flat tire, or a dead battery, which is it?"

So, yes, you may be misunderstood, it's not common American English. But you can always elaborate when you see the look of confusion.

I am trying to remember, I think in the UK flat means no charge, and dead means cannot accept a charge. I've been in the US too long now and get my languages confused.

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