Electronics > Beginners

Newbie questions on batteries

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Trinity:
I have two simple newbie questions about batteries...

1.  How do you measure how much life is left on a battery?  Either in amp-hours, or rough percentage of it's normal capacity?

2.  If you have a rechargable battery, but are unable to find any spec sheets on it, how can you determine the correct voltage and current to charge it with?

Kiriakos-GR:
Before you get in there , electrical specs etc etc ..

First you must identify the type :  chemistry type

If you say the type , we have the first starting point ,
so to find and the rest answers.

tyblu:
For #2, you can't, not without characterizing it. What I would do if I absolutely had to charge it would be to guess a capacity based on chemicals and size, then charge at 0.1C and monitor temperature. If temperature rise changes dramatically, stop charging. If cell voltage peaks, (drops 10mV-20mV or more), stop charging. Discharge and characterize, identify, then recharge properly.

Mechatrommer:
i'm no expert at this but let me try and be corrected:

Q1: How do you measure how much life is left on a battery?
A1: it depends on what device you are putting it into. some device will shut down at say 1V (for 1.5V alkaline), and some at much lower V, so... it varies.

Q2: If you have a rechargable battery, but are unable to find any spec sheets on it, how can you determine the correct voltage and current to charge it with?
A2: first you need to know whats the battery normal operating voltage, without it i cannot answer. but if you do, i suggest charging at a little bit higher than normal volt, say 0.01-0.1C current (i stand to be corrected on this), but still, as Kiri and tyblu stated, you need to know what battery's type,volt and capacity.

Trinity:
Okay, so your replies would suggest that if you know the chemicals and amp-hour capacity, you can both measure how much life is left, as well as determine the correct voltage and current to charge it with.  Am I interpreting that correctly?

If I am, then I would guess the recharge specs would largely be a matter of looking up some baseline reference, or finding a spec sheet for a battery of similar specs, figuring that would be close enough?

But then, I would still like to know how you would properly determine how much charge is remaining.  Pick any type of battery you want - standard alkaline AA, or lithium coin cell, and give me an example?