The most obvious sign of a flat battery is when your car won’t start. Modern motor vehicles can show symptoms like the idle stop-start not working or the cars air conditioning not working to full capacity.
Other signs include cracked, dirty or leaky batteries, a rotten egg smell under the hood of your car or regularly needing a jump start or recharge. Learn more about car batteries here.
The short answer is no - you should only use a battery that is specially designed for your vehicle type and usage.