why is one charger quicker than the other?

On my phone, the wall charger is twice or 3 times faster than the one in my car. Why? (I'm looking for the technical details)

Thanks

Read the specs on the chargers.

I can only speculate

An ac charger uses a rectifier to convert ac to dc. Charging takes place only when the rectified waveform exceeds the voltage of the battery. This is a relatively small fraction of the time. The size of the transformer core is likely to be set by the output voltage.

Another possibility is that the car charger is a chopper supply unning at high frequency. That allows much more charging capacity in the charger than a conventional rectifier charger.

Bill

I will take issue with that. It used to be but is not like that anymore. Semiconductors are cheap while iron and copper are expensive. It is also a matter of size and weight. The bigger something is, the more likely it is to cost a lot. Many power supplies these days are forgoing the use of line voltage and frequency transformers in order to get lower cost.

It is not unusual for a power supply to rectify line output. Transistors are used to chop the rectified current at more than 100kHz. If transformers are used to get voltage change, the high frequency transformers are tiny compared to what was needed before. This kind of conversion is now used for supplies from those operating small computers to fairly large capacitor charging for lasers and rail guns.

Bill

Salmon Egg pretended :

What are you saying??

The bigger the output the bigger the box, wether it is old iron transformers or new switch mode power supplies. Just the SMPS is smaller per watt than old iron and generally better regulated and hopefully more efficient..

It's all about heat. A straight DC charge, such as from a vehicle, is a constant steady flow of current. While on the other hand, the wall charger has a ripple to it due to the AC. What happens with the DC is the battery become a load, as a load it absorbs power and heats up in the process. Since DC is constant, the battery has no cool down cycle. Now with the wall plug, the ripple output give you a high and low cycle, or more loosely put, it's on-off-on-off-on-off-etc. The off portion of the cycle give the battery a cool down period. This cool down period is what's allowing a higher current flow into the battery and the subsequent faster charge rate.

Perhaps the wall charger was designed for your battery and can thus charge the battery more agressively, whereas perhaps the car charger is a generic charger not designed explicitly for your battery, and thus is designed to charge more slowly to protect from overcharging.

d. young

It's all about heat. A straight DC charge, such as from a vehicle, is a constant steady flow of current. While on the other hand, the wall charger has a ripple to it due to the AC. What happens with the DC is the battery become a load, as a load it absorbs power and heats up in the process. Since DC is constant, the battery has no cool down cycle. Now with the wall plug, the ripple output give you a high and low cycle, or more loosely put, it's on-off-on-off-on-off-etc. The off portion of the cycle give the battery a cool down period. This cool down period is what's allowing a higher current flow into the battery and the subsequent faster charge rate.

A question is "how does the temperature affect the charging rate?" The battery resistance is not a major factor involved. So- any information. However,whatever the answer is:

a)While there is a ripple, the battery is still a load with AC. b)Sure the load occurs over part of the cycle only but the thermal time constants involved are considerably more than a cycle so cooling isn't the factor that favours an AC charger.

Don Kelly cross out to reply

Don Kelly wrote on 25/05/2011 :

Surly the main difference will be the different output from each charger and I am sure one could design either a mains charger or a car charger to charge faster or slower. There are car chrgers for Radio controlled model cars that charge relativly large 7.2 volt batteries in only minutes.

Is it a USB charger? Take a look at the USB spec as it relates to available power and negotiation between devices.

Its possible that your car adapter doesn't implement the high power mode, so your phone charges at a lower rate whereas the wall charger does support this.