DOES THIS SOUND LIKE BATTERY OR ALTERNATOR PROB?

Excuse my spelling if it offends. ive a 99 ford taurus problem is lately my car wont start! once the lights on the dash came on when i turned the key on and thats about it!we guessed ok someone left door opened and flattened the battery. so we chargebatteryup and take it to the mechanics where
they take a reading and say battery is ok.
we put batt into car,car goes we take her for a bit of a drive on the straights and she goes fine everythings fine ;).We even come home park car up for few hours then take car for a second shorter trip to the shop which yep no worries. come home thinking awesome thank goodness all is well now.park car up overnight get up to take kids to school jump in the car and what do you know its happened again! now remember car batt had been charged up the previous night so theres our dillema :( only this time no lights on the dash are showing up at all its completely flat! shit man now what! ive had this problem before on an entirely different car and yep it was definately time for a new batt purred away after that no probs but mechanics took a reading of mine and the numbers read reasonably high! yea we think somethings draining the car so we made sure check lights in doors were shut properly so that wasnt it.we dont know !maybe you could help shed light on the prob lol before i have to fork out to the all expensive mechanic

what about glovebox light or boot light!

Recheck the battery connections, and next time you get it going run it past your local garage and get them to check the charging rate.

How was the battery tested!
It may of looked good because you had just charged it, but, it may not hold its charge.
How old is the battery!

Did they just use one of those useless electric gizmo's to test it or do a proper carbon load test, check acid levels etc as well!

probably the battery is draining back thru a faulty alternator, ( buggered diode in rectifier )BUT i could be wrong. just disconnect battery terminal overnight and replace in morningtill u get to a auto sparkie

Yep they used one of those electric gizmo things i saw it with me own eyes we charged battery up and it shouldve read 550 but it read 520 we had it charging four or five hours prior it getting checked by that gizmo! yep a few people have said might be alternator problem but the man thinks time for a new battery i dont know how old battery is to be honest it came with the car lol

If it read 520 directly after charging I'd say its a bit sour. It should be equal or above its CCA Reading after being charged!

I'd get the battery tested properly with a load tester, battery cell levels etc checked.

Can be the alternator, easiest way to check is there is a charging voltage, above around 13.6V when engine running. Other things like a Diode could go as well, but you would be better off getting a sparky to check those.

Try it with the battery out of wifey's car.

Simple things first, When you turn key on does the battery lamp illuminate!
If so when you get the engine started does the same lamp go out!
If so alternator is 99% OK.
Is the fan belt tight not slipping (No screeching when engine first fires)!
Are battery terminals tight without any white corrosion/ If so tighten and boil jug / pour over terminals / rinse off with cold water.
If all the above is 100% then battery is either faulty or something is draining it. You really need volt meter to easily diagnose charging faults. Bear in mind when you put a voltmeter across the battery that is failing or half flat the voltage will not read the ideal 13.8v until the battery is fully charged. Ideally to accurately assess the charging system it must be done with a fully charged battery.