how to charge a 12V battery?

Hi, Brian. Most AA batteries aren't rechargeable. What kind do you have?

Chris

You need a power supply with a slightly higher voltage than the battery to b e charged, and something (possibly just a resistor) to limit the charging current to an acceptable level.

For a 12 volt car battery, the charging source should be about 14.4 volts, reducing to 13.6 as the battery approaches full charge.

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Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  

Peter Bennett wrote in news: snipped-for-privacy@news.supernews.com:

*snip*

That looks like 20% of the battery voltage dropped to 10%. Just out of curiousity, are you posting from experience, or according to that ratio?

Puckdropper

--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm

Experience, and a knowledge of lead-acid battery characteristics.

A fully charged "12 volt" lead-acid battery (as used in cars) will be about 12.6 volts at rest, some time after the charger is disconnected.

13.6 volts is the "float voltage", at which the battery may be left on the charger indefinitely, and will be maintained at full charge. With the engine running, a car's electrical system will be somewhere in the 13.4 - 13.8 volt range, depending on engine speed.

Further information is available from the battery manufacturers, and from "alternate energy" web sites.

--
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  

How about changes in the weather? Does temperature have any effect on the "rest" and "float" voltages for a lead acid battery?

-Bill

How about changes in the weather? Does temperature have any effect on the "rest" and "float" voltages for a lead acid battery?

-Bill

Yes. Temperature Compensation

To obtain optimum life from the battery, it is recommended that, if the battery is to be operated continuously above or below +20°C, the charger should be fitted with temperature compensation to prevent over and under charging. With an increase of temperature the charge voltage should be reduced and, conversely, with a decrease of temperature the charge voltage should be increased. The temperature coefficient is:

(1) For cycle use ? 5m V / °C / cell

(2) For standby use (trickle charge of float charge) ? 3.3m V / °C / cell

For short-term temperature changes of between 5°C and 35°C it is not essential to apply temperature compensation, although it is recommended. For temperature fluctuations below 5°C or above 35°C, temperature compensation is necessary. Refer to Figure 5 for further details with regard to charge voltage set points in relation to temperature. Two curves are shown: one for cyclic applications and the other for stand-by use.

Hi Chris,

I have the 1.5 AA battery from Duracell, they are rechargable but I don't have a charger. I like electronics so I like to build a charger to charge my 1.5v AA. It's 2500mAh

Brian

Chris wrote:

Buy their charger.