How to Load Test a 12v Car Battery

4DIYers
4DIYers
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Published 2014-04-25
Video tutorial on how to determine if the battery in your vehicle is still good by doing a load test. In order to do a load test, you will need to purchase a 12V load tester which can be found at your local auto or tool supply store. The one that is used in the video was purchase at Princess Auto on sale for $25. The original price was $50. I do recommend doing a battery load test yourself, because I have found in the past that some auto parts stores and automotive repair shops do have faulty equipment. Therefore you will be spending extra on purchasing a battery you don't need. This particular tutorial was done on a 1997 BMW 540i.

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Tools/Supplies Needed:
-12V battery load tester
-socket set
-ratchet set

Procedure:
-make sure the needle on the gauge reads 0
-adjust accordingly if needed
-adjustment procedures will vary between models of load testers
-ensure that the battery is or exceeds 12.4V (fully charged battery is over 12.6V)
-remove the battery from the vehicle
-determine what the cold cranking amperage is of your vehicle's battery
-ensure that the posts are clean before testing
-put the battery tester clamps on the battery posts and ensure they are secure
-push the test switch, not holding it longer than 10 seconds
-when the needle stops moving, take the reading
-if the battery reading is under 9.6V, it needs to be replaced
-depending on your vehicle's cold cranking amperage will depend where it falls on the graph of the load tester
-so this will determine what the appropriate specs are for a good battery

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All Comments (20)
  • @frankmontez6853
    There's three tests I could do with this and did the first two checking first the charge which was good at least 13 volts right ? Also the load test which was just under 11 volts putting it in slightly in the yellow range. Do you recommend the starter test and what reading would be good ? Should I replace battery and don't need to further check starter ? Been having trouble with starting it first time . Need to crank it a couple of times to start ..
  • @jerrychen9167
    One question, how do I test 12v electronic on the car battery? Which goes first? Thanks!
  • @johnson7228
    Do I.use the same tools for testing a deep cycle marine battery? Batteries are on and electric powered boat. CCA not important in this case. Thank you!
  • @frankmontez6853
    I'm thinking just getting a battery. The first one in the car was holding a charge but did the second test which was load test came up totally dead like I was testing a piece of wood. The needle fell to zero. So got the other battery from car I don't use much thinking it was pretty good but load test came out to just under 11 volts slightly into yellow weak zone . And yes charge test came out to 13 volts . Replace?
  • @zzhughesd
    Will this test the starter motor as well as load. ? Thanks
  • @MasterKief-fo20
    Thanks, got my exams today and I think this is going to help.
  • @dannychuqui4797
    Hi, I just watched you video......Question? So really work that item? So what I am saying is I can check the battery life if is weak like you said UNDER 9.6 I have to replace the battery? So I don't have to go anymore to the auto parts near me to check right......... Because one time I did w/ the multimeter, the VOLTAGE it was okay..... and I took to the auto parts to check for me......you know they have a big tester in there.....SO W/ THIS BATTERY TESTER I CAN CHECK THE BATTERY LIFE RIGHT? and what's the bad number and good battery life number...... thanks again.!!
  • @johnson7228
    Can you also test the battery using the digital meter by plugging the red input lead into the plug to.the left of the black COM plug?
  • @dannychuqui4797
    Thank you very much for you information..... So like you said if the battery is more cranking amp's than the smallers battery 9.6v So will be a little more higher.....yes make sense, depends of the cranking of the battery I guess my car maybe is 700cranking amps.....But the really important is good w/ this item to check also the BATTERY LIFE......thanks again!!!
  • @TheKeks808
    great video. better than all the others i watched
  • @404notfound.....
    The only problem with this is the machine doesn't have enough load to put on the battery your testing. You have to put a load on it to the equivalent of the starter draw of the engine.
  • @dannychuqui4797
    Thanks again for helping me...... (I will try to get a battery charger)
  • @Dennis-et9vq
    Aren't those testers only good for 100 amps test? If a car needs 500 to 700 amps won't that mean its not really good to tell if a battery is really a good one?
  • @cjmacq-vg8um
    so, does the battery have to be fully charged for an accurate load test? i just went to get my tires rotated and ford service claimed to do a load test without my request. they said the battery is bad but i've never had any indication of a bad battery. also, wouldn't they have to CHARGE my battery before the test? and why would they charge my battery for free just to do a load test a never requested? i'm suspicious of a scam. should i be? also, where's the date of installation on batteries? if i knew the date of installation it might give a clearer idea of whether the battery might be in need of replacement.