The Trainer #56 - Battery and Charging System Testing Tips

The battery residing under the hood (or back seat or trunk) is still essentially the same as it has been for decades. The vehicle to which it is attached, however, shares very little in common with its older predecessors. In the name of increasing fuel economy (mandated by Federal CAFE standard to reach 54.5 MPG by 2025), many of the traditionally mechanical systems on the car have been recreated to operate electronically. But that presents a “Catch 22” of sorts - adding electrical demand requires more from the battery and charging system which, in turn, robs more from the engine (something has to turn the alternator) and reduces fuel economy.
The solution has been a variety of charging system strategies that tailors charging system output to specific need. Some strategies are becoming so precise that installing a battery that is not approved can result in reductions in fuel economy and unexplainable Diagnostic Trouble Codes (DTCs). Other OEMs actually require you to use a scan tool to update the Engine Control Module (ECM) when you replace the battery, even if it is the exact replacement called for.
The good news is that testing these systems still starts with the fundamental techniques of checking open circuit voltage, battery loaded voltage and system charging voltage. The interpretation of these results depends on the vehicle specifics, but you already know I’m going to tell you to read up on those system specifics before you start any kind of testing, don’t you?
More and more, techs are reporting they are finding a variety of concerns related to a bad or incorrect battery. So don’t let this simple component be the cause of your diagnostic frustration. Watch the August Trainer!
#battery_service #battery_testing #howtotestabattery
Due to factors beyond the control of Motor Age, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. Motor Age magazine (UBM Americas - Automotive Group) assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Motor Age recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of Motor Age, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not Motor Age magazine or its corporate parent, UBM Americas.

[@nickayivor8432]

Very KNOWLEDGEABLE Pete Meier Motor Age Take care and have a great day Pete Meier Motor Age Thank you 👍 From Nick Ayivor from London England UK 🇬🇧

[@pedrolriveranegron5178]

GREAT Pete!! Practice..Practice and Practice DIY!!!

[@robertmullen2480]

Thank you very good Pete

[@mmcjocciano]

Thank you sir pete

[@mesalazar3303]

thanks

[@mr.technician2638]

Thank you sir for the valuable information😊 sir can I ask a question hope you will reply...what happens when a lead acid battery vehicle originally equipped with, will be replace or installed a AGM battery as per customer request so that higher CCA will be and longer life span of a battery customer vehicle as he state?....thank you and god bless sir, always watching your new knowledgeable videos uploads😊

[@josephquattrocchi5620]

thanks Pete I appreciate your thorough help with diagnostics. I watched your TST seminar on everyday scope usage. I wasn't sure of the bad values for your scope batt/charging system test. Battery is good if voltage trace drops to a min of 8.5 volts while starting the vehicle. If the battery is charged at least to 12.4 volts open circuit voltage prior to testing; and the cranking voltage falls below 8.5v. We may have a faulty battery. The current trace should show a max of 3 amps of current flowing into the battery. If the battery is weak this value will be higher.

[@MotorAgeMagazine]

Just to clarify - that's 3 amps NET current, or the positive current used to keep the battery maintained. If you don't have all the ground cables looped into the clamp, you'll get a false reading.

[@josephquattrocchi5620]

Thanks for the tip ! Your the man !!!

[@rickwulfe2399]

Why is using a larger cca rating battery bad when extra equipment has been added, extra lighting, and changing h/lights from std bulbs to hei bulbs with ballast and a 800 and 200 watt amps and a powered sub woofer ? My car calls for 700 cca and I put in a 1000 cca gel cell, and after 3 optima batteries in 3.4 years, I went back to lead/acid, but remained with 1000 cca.

[@kasapis6]

Great Info thanks but you forgot to tell us how we can tell the engine speed with the info we have on the scope ! you have enough info to work this out just blow up the volts line and you should see the humps and we know this is a 4 stroke motor so just pick the two events this will make up the 4 stroke motor the scope your using will do the math's for you but we need to have 200 RPM we can use this info to make sure the motor is spinning fast enough to start the engine but you might have to give your scope more Sample rate to do this I see you only have 100ks you need to give your scope more the 2m sample rate then you see the humps on the volts line so then you can zoom in and work out the engine speed

[@MotorAgeMagazine]

I don't worry about calculating engine speed. A tech's greatest resources are his senses, right? I can hear the engine and know the difference between a healthy spin and one that's not so much...:-)

[@kasapis6]

yes your 100% right and if your like me 40 years of working on cars its very easy for us to know just by using our senses what's good and bad . but what about someone that's only been working on cars for a few years ? .and I just like to say thanks for all the great info you give us and a big thank you for the motor age magazine that I get all the way from Australia your one off the best Pete thank you and all the best

[@stephenweston4487]

I get frustrated when training info implies that I as a technician should perform work that is not authorized or there is just not time for. If I as a technician performed these tests on every car I would not be profitable. These tests would end up taking several hours out of my day. It would be nice to see training videos that were a little more real world.

[@MotorAgeMagazine]

Somewhat valid point Stephen. Many states will not allow you to open the hood unless the work you were hired to do required it, or you had permission to do a preventative maintenance inspection. The PMI is a valuable way to generate additional business - legitimate business if it uncovers real service needs. When I was fulltime, I always performed a brief visual check for safety related issues and always checked all 4 tires (and the spare if it was readily accessible). It doesn't take that long...but ultimately it's up to you and your shop owner.

[@stephenweston4487]

Thank you for your answer. Yes I do agree that inspections are good thing for both customer and shop but if it goes beyond a visual inspection it should have customer approval and should be paid for by the customer. There are too many shops out there that give away this and that and then try to make up for all the money they lost on selling unneeded service. I try to give the customer as much info as I can but I am not going to diagnose his car for free.