Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm sorry if this is a horrible place to ask such a question. I just stumbled upon here from google.

So I have this battery charger that DOES NOT indicate when a battery is fully charged (stupid right?)

It simply says:

input: d.c.5v
output d.c.1.4v
aa 2 160mA
aaa 2 160mA

Additionally, I see that my batteries say Voltage: 1.2V. Does that mean using a charger that says 1.4v is BAD, or totally fine?

I figure someone here would know.

share|improve this question

Using the 1.4V is fine - the batteries need to be charged at a slightly higher voltage than their "nominal" voltage marked on the case.
The 160mA is probably the rate it charges at - if there is no end of charge indication, then don't leave them in there too long (more than 12 hours or so if they are fully discharged)
It may change over to trickle charge mode when the battery is fully charged (hopefully if it's not a really nasty charger) but without knowing more about it (do you have model number?) it's best to be safe.

If you read the Wikipedia page on Ni-Mh batteries (I'm assuming yours are of this type) you can see the recommended charging voltage is between 1.4V-1.6V per cell. Also reading further on that page, some seem to think that trickle charging at C/10 (0.1C) for extended periods is not so bad (although others disagree, and it will shorten the life of your batteries anyway)
C/10 for your batteries is 1800/10 = 180mA, so your charger is supplying slightly less than 0.1C.

So I wouldn't worry about anything really bad happening, although I'd get a better charger when you can (unless you can confirm the charger switches to a much lower trickle when the battery is charged)

The time it takes to charge can be roughly calculated by your battery capacity / charge rate, so in your case:

1800mAh / 160mA = ~11.25 hours

share|improve this answer
I do not have a model number. It was just something cheap. Is there some way to determine how long it takes to charge batteries of a certain capacity, based on its voltage and 160mA? – Derek Jan 13 '13 at 6:32
Okay, I added a bit on charging time at the end of my answer. – Oli Glaser Jan 13 '13 at 6:39
Ah, thank you very much. You've been most helpful! – Derek Jan 13 '13 at 7:06
I would assume that charging is never going to be 100% efficient, and allow another 10% time on top. So about 12 to 13 hours to charge from flat. At less than 0.1C, leaving it a bit too long isn't going to wreck the battery. – Simon B Jan 1 at 19:30

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.