Suggestion:
There's an easy way to figure out if just the battery is at fault or it could be the alternator not charging the battery properly.
#1. Fill the battery cells with distilled water to the level of the plastic ring under the cap. Charge the battery with an inexpensive automatic self leveling battery charger @ 2 amps till the green light comes on telling you it's fully charged. 12 hours later after charging and not using it in the car test the voltage with an inexpensive hand held volt meter. A fully charged battery should test 12.85 volts. If the voltage has dropped below 12 volts in 12 hours the battery needs replacing.
#2.When the car has been started with the volt meter hooked to the battery you should see between 13.5 – 14.0 volts. This reading is the correct alternator voltage out-put voltage. If the voltage is not within this bracket, the alternator needs replacing.
{ 4 comments… read them below or add one }
Model & Year? How old is the Battery? Remove the Battery, Have it Fully Charged & "Load Tested" to see if it will take and Hold a Charge. Load Test it at 50% of CCA {Cold Cranking Amp.} Not dropping below 9 Volts during the Test.
Have your Alternator "Load Tested" to make sure you are getting the Listed Amperage, Low Amps means Bad Diode(s) that Will Drain Your Battery + not charging Properly.
Is are Fan Belt(s) at the proper Tension, Slipping or Cracked?
go to an auto electricians, hell test the car quickly with instruments possibly fan belt.alternator, or a duff battery.
it appears that u have either a battery fault or an alternator fault….. first ensure ur battery termanals r clean and fastened correctly….. then by using a multi metre on "volts" DC place one electrob on the positive and the other on neg, start the engine…. under cranking the reading on the multi metre should be no less than 10 volts…. if lower than this could indicate a defective cell in the battery.. if the voltage only goes around 11 volts it would indicate a "good battery " 2ndly when the engines running u should have a reading of between 13.5 and 14 volts… any lower than this and ur alternator is probably faulty
if you were driving and your battery died and car stalled. your problem is most likely your alternator. charge battery start car and disconnect battery if car stalls it your alternator. the car only uses battery to start the car once running it runs on power from your alternator if its bad then car will drain on battery as soon as its drained car will stall.
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