A battery, when charged, is really just an electrical storage tank. In other words, the alternator’s rating should be equal to 25 percent (lead acid) 30 percent (gel) or 45 percent (AGM) of your total battery capacity. Reconnect the negative lead to the battery if no interruptions or issues are noted. Check all the fuses and reconnect the battery if there is an interruption in the vehicle running. An alternator field disconnect is used to protect the diodes in an alternator when the battery switch is inadvertently turned to the "OFF" position. Disconnecting a battery cable while the engine is running causes the alternator to spike a 25-125-volt surge within 40 milliseconds after cable removal. If you get less than 12. Disconnect the battery if arc welding is to be done on the vehicle. For all of these cases, the answer is to test the battery frequently with a hydrometer. Disconnecting the battery while the engine is running isn’t a valid test for alternator function and may damage sensitive electronic parts. Another way to check is with a voltmeter. That is how I saw Dad test to see if it was the alternator or battery so that is what I did. If disconnecting the battery interferes with the voltage regulator's control voltage input, it's possible for the alternator voltage to go way over the top (I've heard some say hundreds of volts), frying everything. Begin by parking and turning off the car with the charged battery next to the dead one. I have been checking the internet, but I get both answers. Many new car batteries are of the sealed 'maintenance' free variety. Too small a wire will restrict the flow of electricity. If it lights up, you're good, if it doesn't, follow that circuit to the battery and find the break. Locate your alternator and check to be sure the alternator belt isn’t. If you need help having the problem scoped out, a certified professional from YourMechanic can come to your car’s location to diagnose the loss of power. Watch the ammeter while disconnecting the battery (fully charged battery) to determine if a slight discharge is indicated. As far as the 1 2 switch going thru the off could make a surge. But that will cause you to lose the radio code and, on an MG/Rover, you might lose the security code as well. Neg wire from battery to some point on the engine. circuirty, the risk is greatly reduced. 5 milliamps. If you disconnect the D+ wire from your alternator, your charging system will and will not charge dependingon a few variables and circuit situations. If you get less than 12. Battery disconnect switches give you the ability to cut power to your ride before storing your hot rod battery during routine maintenance or after an on-track accident. Most racing organizations and sanctioning bodies require these for an emergency cut-off switch. Your new alternator is up and running! Featured Video: How to Replace Alternator in Civic. Still, using a few simple tests at home that show you how to test an alternator, how to inspect a battery, if necessary, and check a drive belt will help you pinpoint the cause of the problem. My battery bank will not charge above 12. Use a battery saver, 12-volt power supply or battery charger to maintain voltage to the vehicle's electrical system when disconnecting the battery or when replacing a battery. A healthy alternator will allow the vehicle to run. Check the system by turning the fan on with the engine running. 6 when I charged it for 3. This voltage test result tells you that the alternator is working (charging the battery). A healthy alternator will allow the vehicle to run. Disconnect the regulator plug, then jumper the A terminal to the F terminal. I have studied up on this issue (on another site) and believe my van passes the smell test: power steering pump leaking Very dirty alternator (sand, dirt,mud) Believe ALT is OEM and never replaced Battery has charge, but cannot start engine without a jump start. once all is disconnected and. Then test after an overnight rest. Disconnect the jumper-cables or whatever it was that you used to start the vehicle. The battery disconnect switch. circuirty, the risk is greatly reduced. It’s always a good practice to check for any voltage drop when testing an alternator circuit before rushing in there and changing parts. ) Test your new alternator by using your voltmeter and touching the positive voltmeter wire to the positive terminal on the back of the alternator; touch the negative voltmeter wire to the negative battery terminal in the engine compartment. Normal charging system voltage is between 14. Continuity checks okay and no shorts to ground. Connect a multimeter to it and start your car. The test showed my batter was a little low and out of specification for the battery and it showed the alternator as being good. The main reasons to remove the battery are to change or charge it. 8L Engine See Figures 15 and 16 Disconnect the negative battery cable. As noted in the schematic, the output should be 26 volts AC. The Alternator's Voltage started dropping over a couple of days and would not produce full voltage under full load at low RPM. This varies by the model, but when the alternator starts to let go, it can light up a “Check Engine," “ALT," or a battery icon indicator. Alternator Removal and Installation Instructions Removal Make sure that the rest of your charging system is in good working order. Basically, your battery gets the engine going, but once it's on, the alternator takes over and can, in theory, continue running the car without the battery's help. It could be quite high - my SR500 amazed me with open voltages of over 90 VAC! If all three voltages are about equal, reconnect the alternator output wires and do a voltage check at the output of the regulator/rectifier unit. Measure the voltage across the battery terminals - red lead of the voltmeter on the positive terminal, black on the negative (ground in most cars). Still, using a few simple tests at home that show you how to test an alternator, how to inspect a battery, if necessary, and check a drive belt will help you pinpoint the cause of the problem. For a 24-V or 36-V rechargeable battery, check the label on the battery to determine its voltage, and set the meter to at least one. If the lights dim, it points to the alternator as the cause of the vehicle's issues. If the alternator is ever disconnected from the battery when it is charging, you get something called a load dump and that’s a bad thing. Any easy way to test the output (in amps) of the alternator. BTW, if it's the alternator, don't buy a new one. 3) If overvoltage still exists, disconnect regulator wiring plug and repeat NO LOAD. However, if you turn off the truck and the battery is at 12. (If the needle does not move to the right, you may need to replace the meter's battery or fuse). volts above battery voltage), connect a jumper wire between regulator base and alternator frame. If your alternator is putting out less voltage than required, another quick test you can do is to measure AC voltage at the battery. For what it's worth, I have essentially zero faith in autozone/advance/etc battery and alternator testing stations. get a new battery. Check for open circuit in White/Green wire between PGM-FI ECM and alternator. If it lights up, you're good, if it doesn't, follow that circuit to the battery and find the break. Here is a simple test that can tell you a lot about what is going on inside a battery, and whether it is good or not. Using the Alternator Check Function. When three successive readings are alike, the battery is as charged as it will get. Once the engine runs, the alternator takes over the electrical delivery, supplying voltage to the spark plug and sending extra current to the battery for recharging. it on the charger. Don’t assume everything is working OK just because you bolted in a new alternator. So that's the normal operating range of system voltage. How to Test the Alternator in Your Car: An alternator helps power all of a car's electrical systems, including the starter motor, speaker system, and lights. Learn how to give them new life with our step by step battery reconditioning guide. Alternator should not really be spun up with output disconnected as it's output voltage can go considerably higher than 20V and cause internal damage. A good battery should read 12. If it's been a while, or it has been a rough season for your battery, now is the time to test it yourself or bring your car into Pep Boys for a free battery test. page 1: battery charger vec1093cbd 4/10/20/40 amp 12 volt smart battery charger with 110 amp engine start, alternator voltage check and battery recondition functions user’s manual & warranty information important safety information, save these instructions to reduce the risk of injury, user must read and understand this instructional manual. How can I test my alternator to see if its working? I disconnected it from the wiring harness which connects to the starter solenoid, and systematically tested (while the car was running) all 3 terminals (connected to battery gnd) and found no voltage at ANY of them. > I agree with Curly; the risks of disconnecting the battery with the engine running are terrible. If the battery is working properly and nothing is wrong with it, then it's the alternator that will more likely cause a problem. Too small a wire will restrict the flow of electricity. Disconnecting a battery cable while the engine is running causes the alternator to spike a 25-125-volt surge within 40 milliseconds after cable removal. 5, or 500mV AC. The charging source knows it is supposed to maintain 13. You should NEVER disconnect the battery in ANY modern car. give or take a bit. You'll go through 2 or 3 batteries in 100k miles, and then one alternator. The alternator has to produce enough current to keep the car’s battery recharged and to supply all the other electrical components with power. When below 13, car is running off the battery only. I pulled the negative battery cable off and measured the voltage between the cable and the negative battery terminal and got 12. There is an external diode that can be placed on an alternator, ZAP STOP, I believe that also will protect the diodes should the battery switch disconnect the battery from the alternator. To charge the battery, higher voltage (about 13V to 15V) is required. I drove it 250 miles and it failed the smog check again. Disconnect the battery cables. Many will be familiar with that stomach-churning feeling when your car fails. Check SG again. If the battery is faulty, your alternator tests will not be accurate. The charge wire is the wire that carries power from the alternator to the battery and the electrical system. Challenges when charging lithium with an alternator. CHECK BATTERY TERMINALS, FUSIBLE LINKS AND FUSES (a) Check that the battery terminals are not loose or corroded. Alternator Check Disconnect Battery: Batteries lose charge over time and replacing them can be expensive. How to determine Battery Isolator Size: Your battery isolator will depend on the size of your alternator. Curiously, they suggest not using analog multimeters in favor of digital multimeters. Check the ground wiring. If they weren't working, and the engine needed power from the battery to run the spark plugs, the engine would die. With a voltmeter connected to the battery, simply disconnect the voltage regulator, then start the engine. A battery that’s kept clean lasts longer than a cruddy one. However, this is not a good idea because it could damage the electrical system of your vehicle and cause greater problems. What you are gonna do now is check to see if one of the windings in the alternator is broken, or if something external to it has grounded it out. That’s nonsense. So I bought a new battery and put it in. In other words, a bad alternator can get your attention by killing your car's battery,. First check drive belt tension, then the battery condition. A car battery, by definition, has a finite life and will not last forever. The serpentine belt could have stretched with age and may not be spinning the alternator pulley effectively, leading to a lack of charge. The battery must be kept in parallel with the alternator with solid connections. e) The alternator is turned by the engine drivebelt which could cause serious injury if your hands or clothes become entangled in it with the engine running. Negative (black) first and positive (red) second. My Alternator Light came on and I went to the auto part store where I had bought the alternator and it was tested on the car and wasn't charging so we thought the voltage regulator had gone bad within 24 hours so I took it off right there i the parking lot and they took it in and did a bench test on the Alternator and it passed the bench test. This is usually an indication that the battery may be flat. Voltage removed from the battery is restored by the alternator on a proper charging system. If the engine revs up a little, the alternator in ok. That’s nonsense. Replace a battery if it fails a load test. How to test to see if you have a bad battery or bad alternator 3 Answers. you should start by cleaning the battery post. How to Disconnect a Car Battery If you are looking for guidelines explaining how to disconnect a car battery, you've landed on the right page. • Connect the red clamp to the positive (+) terminal and the black clamp to the negative (–) terminal. If the lights dim, it points to the alternator as the cause of the vehicle's issues. A battery, when charged, is really just an electrical storage tank. swap it into some other vehicle and see if it goes flat there, this would indicate the battery is bad, and lastly you can take it back to the supplier and have them do a load. Find out why Close. In the case of the 3-wire alternator, you want to see the same voltage from all 3 possible combinations of output wires. Test the alternator to make sure that it can start up the battery. Do NOT forget, you must ALWAYS disconnect the cables from the battery first. People often think that a dead battery should be discarded and pay huge bucks to buy a brand new one. Finally, start the car to test the alternator. Need help deciding how you’re going to power your beer fridge? This is a design guide for 12V systems or dual battery systems used in vehicle setups for touring and camping. How to Disconnect a Car Battery. It could be quite high - my SR500 amazed me with open voltages of over 90 VAC! If all three voltages are about equal, reconnect the alternator output wires and do a voltage check at the output of the regulator/rectifier unit. Do not disconnect the battery cable while the engine is running to test the health of your alternator. As for the battery, if the car has done this to other batteries in the past, I would investigate the alternator. A bad or failing alternator can discharge your battery, cause issues with your car's electrical systems, or leave you stranded wh. If the engine will not run without the jumper cables on, then shut off the engine on the car you are jumping from. Step 1: Know What Kind of Charger You Have. The alternator's job is to charge up your battery--and if the alternator isn't providing voltage, then your battery simply cannot hold the power sent to it. With the availability of affordable silicon diode rectifiers, alternators were used instead. Disconnect the positive battery terminal. Disconnect the negative battery cable. There's two schools of thought either wire the output of the alternator directly to the battery bank using a diode splitter to allow you to charge the banks. The trick is putting a load onto the alt. Today I found out how to test a car alternator. High conductivity studs are long enough to handle more than 1 cable and strong enough for torque needed for secure connections. I have been checking the internet, but I get both answers. Battery chemistry. Summit Racing carries a large selection so you can find the battery kill switch you want. As has already been said here, disconnecting the battery cable with the engine running can cause serious damage to the electrical system. The battery light may come on the dashboard to alert you. However, if you turn off the truck and the battery is at 12. When an alternator fails not only will the battery light come on but it can cause the check engine or service engine soon warning lights to come on. If you regularly use engine off loads, you should use a high CCA rated deep cycle battery such as an Optima Yellow Top for your main battery. it's just a possibility. Computerized battery and charging system tester. Use 5/8 socket and remove alternator bottom bolt. Also, if the battery itself is bad, an alternator in working order won't be able to charge it. SMART AUTOMATIC BATTERY CHARGER 12 VOLT 2/10/20 AMPERE CHARGE RATES WITH ALTERNATOR VOLTAGE CHECK AND BATTERY RECONDITION FUNCTIONS. After three years I would test the battery by connecting a lamp that consumes one or two amps to discharge, measure amps and time. How to determine Battery Isolator Size: Your battery isolator will depend on the size of your alternator. Disconnect the alternator lead And start the engine. Replacing an alternator on a P2 chassis Volvo is a moderate level repair which usually takes no longer than 3 hours to replace. Start the bike and check the reading. Before taking parts out of your car, you should try to diagnosis the problem by: 1. 2 volts, then start your car and rev the engine to 2,000 RPM. If this does not locate the problem, check the alternator and voltage regulator as described in Chapter Thirteen. What to clean/check if voltage drop too high: Check the motor grounding. How to Test a Car Battery with Battery Load Tester Driver can use this tool to check the disconnection. Before ordering your alternator from FCP Euro, be sure to check the amperage rating which is listed on a tag on the back of the alternator. Changed the Car Battery and Failed Smog Check. When re-attaching the alternator, make sure the belt is still out of the way before the alternator is slid 'home'. There are two simple tests you can perform to determine if your car's alternator is going bad: a headlight test and a battery test. When disconnecting charger, disconnect AC cord, remove clamp from vehicle chassis, and then remove clamp from battery terminal. If the alternator was bad, then driving to autozone and then back could be enough to drain the battery - particularly since it sat for a few days after that. If you have the patience you culd disconnect one side of the battery after coming in. Use the Basic Wiring Primer and Troubleshooting Guide for simple procedures for testing the alternator and regulator. Disconnect the other end of the Positive (+) cable from the Positive (+) post of the dead battery. You cant disconnect an alternator's output while it is running because with nowhere for the power to go its internal voltage would soar and destroy the diodes. Because all. To test your alternator, follow these simple steps. does your engine cranks slowly the matter seem weak rather strange noises coming from under the hood please are all signs that you might be having a problem with your alternator but how can you tell for sure the truth is there are number of possible causes so it's important check under the hood to make sure that the alternator is really the issue in this video will go over the basic steps. View and Download Vector VEC1090 A owner's manual & warranty information online. Get garage to check the battery and charging system. When your car won't start the first place to check is the battery. Once your car engine is running, and if the battery is still good, the alternator will recharge it. You need to check all the main fuses in the engine fuse box. last updated 30/08/2018. A good battery should read 12. I thought my battery was bad so I had it. The two key issues demonstrated in the video are:. I've used disconnecting a battery while the engine is running as a quick and dirty way to see if the alternator is working (at least enough to run the engine electronics). High Voltage - DO NOT use a high voltage source to test diodes. Autozone is the one nearest me. A faulty charging system or a bad battery that is unable to maintain a charge can leave you stranded and feeling helpless. 8-Sep-2019-AM : Alternator Check Disconnect Battery @ Alternator Check Disconnect Battery EZ Battery Reconditioning Get Access Now Best Alternator Check Disconnect Battery. From the alternator output to the ground should be at least 13. Reconnect the negative lead to the battery if no interruptions or issues are noted. Resistance should be 0. Next, perform a battery test. How To Test Alternator By Disconnecting Battery: Batteries lose charge over time and replacing them can be expensive. Watch these videos and learn alternator diagnosis as well as how to disconnect the battery on your car; and how to locate the alternator; how to remove the alternator by disassembling the intake, removing the throttle linkage and radiator hose; learn how to unplug the vehicle. A battery will last three or four years. All of the local BigName shops now test stuff for free. Remote Sense utilizes a second wire that reads the actual voltage at the battery and signals the alternator to increase its voltage output to compensate for the voltage drop, ensuring a constant 14 volts at the battery. With the Alternator connector disconnected check the resistance of the alternator at the connector blades. Check the alternator amperage Disconnect the voltmeter and connect an amperage meter (if you aren't using a multi-meter) to your battery the same way as you connected the voltmeter. Made Easy Free Download PDF Recondition Your Dead Battery Best Free A Step-By-Step Guide Battery Reconditioning, Battery Desulfator. All you need is a socket set and spanners plus a brush and regulator replacement kit for your model of alternator. If the voltage reading at the battery is higher than 13. Shopsarahmac sells a wide range of items, from dress, electronic, accessories to all another products. Not sure where else to look. Remove the jack stands and lower the car back. Equipment needed: multi-meter With the engine on: Step 1: Open your hood and so you have clear access to the car battery. If your battery is putting out less than 12 volts, it's time to replace it. " Test the alternator by disconnecting the battery with the engine running. 5 volts, the alternator is trying to charge it and the battery needs to be tested further. If voltage is then correct, replace the oil level sensor. Disconnect the battery cables. Hello, thanks for writing in. To repair my charging problem, I took apart the marine style battery cable (positive) and replaced the old 12 gage ground with a new piece and replaced the skinny 16 gage wire I had crimped onto the new negative cable with the 12 gage also. Warning: Never disconnect a battery cable while the engine is running to "test" your alternator. Lights work, radio plays, car runs, and so on. How to test car battery for dead cells. Step 2: Loosen the two bolts that hold the alternator in. With a voltmeter connected to the battery, simply disconnect the voltage regulator, then start the engine. Recharge battery. How to test to see if you have a bad battery or bad alternator 3 Answers. you should start by cleaning the battery post. circuirty, the risk is greatly reduced. Charging System The alternator supplies power for the vehicle when the engine is running and engine speed is above idle. This is because the alternator can produce more electricity and it can also charge the battery better even at low engine speeds. page 1: battery charger vec1093cbd 4/10/20/40 amp 12 volt smart battery charger with 110 amp engine start, alternator voltage check and battery recondition functions user’s manual & warranty information important safety information, save these instructions to reduce the risk of injury, user must read and understand this instructional manual. systems which isn't any good. Most alternators require a battery to prevent blowing up the diodes. Hook the multimeter leads into the two (or two of the three) yellow leads from the alternator with meter set to AC and read the voltage. This is so that you can check how much capacity the battery still has. The headlight test is quick and easy, and should be performed outdoors to ensure that you don't have a carbon monoxide buildup inside your garage. But if you need to do some checks in the car, here are some tips. To make sure you know what you’re doing when you use a car battery charger, read these step-by-step instructions. With the engine not running and the ignition in the off position, disconnect the ground (negative) battery terminal and connect a test light in line with the ground cable and the battery negative terminal. And the natural variance from 1 Alternator to another ,both good. If you disconnect the battery, there will be a spike in the voltage from the alternator which will then send more that 14 volts to all the electronics in the car. If the battery is in good condition the voltage should not fall below 9 volts. How to test your alternator. 8-Sep-2019-AM : Alternator Check Disconnect Battery @ Alternator Check Disconnect Battery EZ Battery Reconditioning Get Access Now Best Alternator Check Disconnect Battery. While this is one option to retrieve. The Below chart, shows how the charging system behaves at different temperatures. 1) Check to make sure the battery is charged to 12. Use the PennTex Four-Step Charging System Test Form & Full Field Test Form to check the system condition. With a voltmeter connected to the battery, simply disconnect the voltage regulator, then start the engine. Disconnect the battery terminals and clean them with some sandpaper or a small file. This varies by the model, but when the alternator starts to let go, it can light up a "Check Engine," "ALT," or a battery icon indicator. Connects full battery voltage to alternator field, leaving regulator out of circuit. If you need help having the problem scoped out, a certified professional from YourMechanic can come to your car’s location to diagnose the loss of power. Looks better already, doesn't it? Test fit the battery in the new Moroso box. Check out the denso brand at rockauto. If the battery is bad, at least you can drive to an auto parts store to buy a replacement battery. I spoke to a mechanic who could not explain to me why is that you need a battery to make the motorcycle run. Corrosion is usually heavier on the alternator side but you should also examine the voltage regulator plug including the wiring that leads to the indicator light on the dash. DuraLast with no know history---- theres not much Dura or Last in those batteries. With the availability of affordable silicon diode rectifiers, alternators were used instead. Disconnecting the battery for this job is a must, not just a precaution or a suggestion but a must. Do NOT disconnect the battery with the engine running. People often think that a dead battery should be discarded and pay huge bucks to buy a brand new one. Posted: Sun Sep 22, 2013 4:43 am Post subject: Unhooking Battery to Test Alternator Down below is a discusion about unhooking batteries in order to test alternators. Richpin demonstrates how to test an alternator with a standard multimeter. Do I disconnect the negative or positive charge on my battery to check if my alternator is going out?? I know that I need to disconnect one of those then start the car, if it doesn't start it's the alternator. 5 volts when your Cooper is running. Positive output on your alternator and your positive battery terminal and also with other connections. 8L Engine See Figures 15 and 16 Disconnect the negative battery cable. If the alternator isn't generating enough current, your battery will not properly charge. Measure the output voltage at alternator terminal B. I have been checking the internet, but I get both answers. While the alternator is providing current, you can also do a voltage drop test across the battery positive terminal of the battery and the battery lead wire on the back of the alternator (heavy gauge wire. If you suspect your battery isn't charging properly it's likely either to be the battery, or the alternator that's at fault. Two of the easiest methods to determine if your alternator is dying are the headlight test and the battery test. It may be connected by a bolt/screw hole to the body of the alternator or vehicle. Place the metal tip on the end of the multimeter's red wire on the positive ("+") battery terminal. Basically, your battery gets the engine going, but once it's on, the alternator takes over and can, in theory, continue running the car without the battery's help. 5 volts when your Cooper is running. but no reason to switch because you are charging the low battery. When the discharged battery reaches 10. Never disconnect the battery while the engine is running to check the charging system. Wiring a Lucas alternator is a fairly straightforward process, but some car manufacturers do position alternators in hard to access places. This is so that you can check how much capacity the battery still has. If they didn't connect the alt lead to the starter there would be a loose wire that they would need to leave hanging off at an undetermined length for each boat the motor would go in. Turn on the battery voltage on the cluster menu. Then test after an overnight rest. The amperage battery drain test requires disconnecting one of the battery cables. Learn how to give them new life with our step by step battery reconditioning guide. It failed the smog check because there is no data; the tech said no monitors. Then shut off the lights, start the engine and test the battery voltage again. The charging system for the Briggs and Stratton engine begins with the battery, which supplies voltage to the starter. As a quick check, I want to see something well above 12 volts when idling to assume everything is peachy. If it's from autozone then I wouldn't doubt they're bad. Odd noises. If the vehicle stayed running after disconnecting whatever it was. 5 ohm with just the meter probes crossed, so it was about 1 ohm for the battery cable through the fuses etc when I did the cable measurement. Connect the meter leads to the battery terminals and look for 13. A battery and charging system test (AVR test) can cost from $30 to $50. The Below chart, shows how the charging system behaves at different temperatures. In some cars, especially those made before the mid-1990s, you can reset the check engine light by disconnecting the battery. Drill a hole through the car to the area where the switch is to be mounted. Be sure they check the grounds for the battery, engine block and the power wire from the alternator to the battery (the "Big Three"). The regulator is pre-set at 14. alternator relay. Prior to the test, check the following items and correct as necessary. If previous Steps 1 through 6 check satisfactorily, check alternator as follows: Disconnect battery ground cable. Switches isolated battery banks to all loads or combines battery banks to all loads; Includes AFD (Alternator Field Disconnect) Make-before-break contact design allows switching between battery banks without power interruption; Ignition protected—safe for installation on gasoline powered trucks and buggies. How to load test a car battery. I drove it 250 miles and it failed the smog check again. Any easy way to test the output (in amps) of the alternator. First, check the voltage at the battery terminals with the engine running and the headlights, blower motor, and wipers on. 81v is good for the battery, but the alternator should be putting out 13. If all of the fuses are fine, take your vehicle to an auto shop to have your alternator professionally tested. How to test your alternator. If you disconnect the relay disconnects and you only take power from the AGM supply battery. and no components of the charging circuit have been replaced with the exception of the battery cables. Starter/alternator short to ground? My 80 911 SC has developed a short which is draining the battery in a few hours. Pop both car’s hoods and get the jumper cables out. 2 volts or my run time between charges is not what it used to be. If this voltage is at the battery, check the voltage at the alternator. After you remove the battery charger, turn on the headlights (engine off) for four minutes. How to Test a Car Battery with Battery Load Tester Driver can use this tool to check the disconnection.