|Many people are tempted to buy cheap laptop chargers because the genuine ones you can buy from the laptop manufacturer are considerably more expensive. There is a good reason for this - quality & safety - but unfortunately many people just think they are a "rip-off".|
Had you bought one from the laptop manufacturer, you would have had some degree of consumer protection & the right to claim through them if it didn't work or if it damaged your laptop.
As it is, you've no guarantees at all with a third-party one. I doubt that any damage is limited to the battery alone. You may have damaged the laptop itself since the charger also supplies power directly to the laptop, not just to the battery.