unknown problem

[cb3 vtec]

hai guys,need your help,my cb got an unknown issue,its about the battery,first i charge my old battery cause there are no power in it,so i start the car and its running but when nights comes the battery is flat again,the next day i bought a new battery,after 2 days that is yesterday,the battery is flat again,the alternator is good btw,what could be the problem?

[Fleetw00d]

so i start the car and its running but when nights comes the battery is flat again

So if you start it, it will run and continue to run, but if you shut it off and leave it for a while, the battery will be dead again? Are you sure the battery is dead? Or are you' not getting electical power to the starter? How do you know the alternator is good? (If it starts and runs for a while without loosing electical power, then the alternator probably is good).

If you have a multimeter, a fully charged battery should read right at about 12 volts. Voltage when the engine is running should be about 14 indicating the battery is being charged (alternator is working). If below 12 volts, it is not being charged.

Check the battery cable connections at both ends for corrosion and being tight. You might undo these connections, clean the mating metal surfaces and reconnect.

Is something draining the battery? With the battery charged and the engine shut off, disconnect the negative battery cable and measure the current between the cable and the battery post, there should only be a few milliamps of current. If there is a large current draw, you'll have to do some trouble shooting to determine what is draining the battery.

[cb3 vtec]

when the car is running,i took off the negative from the battery and the car still runs,after a few hours the battery is kinda weak to start the engine..i'll try to check the battery connection later..