Brand new battery,drove car about two days and the lights got very dim,stereo turned off,no accellaration,and now dead.(1994 mitsubishi mirage 1.8 liter)

It sounds like the battery has gone dead and will need to be replaced due to a bad Alternator. Once you get the car started, check the voltage on the battery, there should be 13.5 to 14.5 Volts. A fully charges battery should have 12 volts with the engine not running and once the engine is running there should be 13.5 Volts with the head lights on and heater on too. If there is less then 12 volts reading on the battery with the engine running, then replace the Alternator. You can pick up a Alternator at Auto Zone and they can give you the step by step instructions to replacing it with common tools and they can also check the Alternator in your car to before you buy the new one. Good luck and hope this helps and insect the wire harness from the battery to the Alternator, look for any sighs of damaged like corrosion and repair any damages to the wire harness.

I have the same problem, the battery its new and the alternator its new, how can I check the wiring

You probably should have replaced the alternator (or voltage regulator) instead of the battery. Place the new battery on slow charge (4-6 amps) overnight, then drive the car to your favorite auto parts supplier who (for free) should be able to check the operation (and sell you a new/rebuilt part if needed) of the alternator and the VR. When the engine is running, the battery voltage should 13.5 to 14.5 volts DC showing that it is being charged properly. If it reads 12.6 volts, the alternator or VR is not doing it's job. Hope this helps!

You must have the alternator checked ,mybe the battery is not charging