それから私は別の充電器で試してみました、そしてそれは大丈夫でした。 注：最初の充電器はラップトップに接続されているスマイリーデータ充電ケーブルです。 この充電器私は絶対に使用していた、この問題を早くしていました。これは大丈夫ですか？
I have samsung s duos. Suddently one day, when i was charging .. though the indicator shows charging, the battery level keep going down. I restarted mobile... still same issue.
Then i tried with another charger, and there it was ok. Note: The first charger is a smiley data charging cable connected to Laptop. This charger i was using never, had this problem earlier. Is this OK ?
The charger will show as connected because the cable is making contact with the charging port, regardless of actually charging.
Yes chargers do go bad, usually at inopportune moments and there is a long list of reasons why. Sometimes from being plugged into long, getting dropped, getting too hot, used with wrong devices, being improperly pulled out from the wall, the charge connector getting bent in the charging port, etc.
When acquiring another charger, check a few things.
It sounds like your laptop can't supply enough current to charge the phone. Most USB devices only want a fraction of an amp of current (e.g. a mouse might draw 0.1 A), so the USB ports on laptops can only supply a little current. Generally a phone or tablet wants 1 A or more to charge efficiently, which most USB ports can't supply.
The cable isn't really the issue. As HasH_BrowN states, cables can be damaged, so it's good to check with another, but in this case the problem is what the cable is plugged into. Ideally, you should use the wall charger that came with the phone.
When you do have to plug it into a lower-current supply like a PC, you can get best results by turning the phone off to charge, so that the phone's not using more power than it's getting from the charger.
For more explanation of why chargers don't always charge, you might like to look at the related questions such as What causes battery to drain faster than it can charge?
I know how frustrating this can be. Mine did the same thing. At first any micro-usd could charge my phone, then some would not work, then all of a sudden, none of them worked. Everyone told me it is the charger, the outlet, the cable, etc. Luckily, I was in the Philippines and I took it to the repair shop. It was a defective port. They replaced it and it works fine now. It took about 45 minutes and cost 300 pesos = $7 USD.
I hope that helps.