Car Battery Voltage Fluctuation While Running

During that time the alternator of your vehicle is busy charging the battery. These days cars use smart charging technology where the cars PCM computer decides how much output the alternator will put out at.

Battery Voltage Sag During Engine Cranking

Posted on Apr 28 2013.

. If I cold start the car the voltage seems perfect. To move instantaneously from 12 to close to zero would mean an instantaneous short on the battery or an open connection. As an instantaneous short would cause the battery to explode then you must have a bad connection.

Ive never had one that would read over 125 fully charged. Wli98122 When testing the voltages for batteryalternator test directly on clean battery terminals when possible. Light was off for one day then back on.

137 V is OK when engine running and alternator putting out charge. Answer 1 of 5. When the engine of your vehicle is running the voltage of your car battery should be between 135 and 147 volts.

The jeep lights dim and the car stalls the battery voltage at idle is 117 and goes up to 149 when running at 2k rpms i changed the two batteries and the alternator still have the same problem the car now stalls or wont start at times. Generally the voltage was fluctuating between 132 and 138 Volts. Also I disconnected the voltage regulator while this problem was occurring and saw no change in the voltage at the battery or stator wire 114-119 volts but as soon as I plugged it back in.

When the Car Is Running. Why does my car battery voltage drop. First I had the battery light flash in message center and voltage was at 147 and took to AutoZone and replaced battery.

If no voltage is measured either the fusible link wire is blown as a fuse without any signs of burning or the connection to the alternator twisted the terminal post and damagedbroke the internal wire connection between the exterior post and internal wiring. My bet would be the regulator in the alternator is getting ready to take a. Back of belt should be level with the pulley edges if V belt.

With the engine off you should get a reading of 126 volts. After it was warmed up and idling i measured the voltage again. The battery condition is not related to the voltage guage unless it is really shot and we can see this is not the case.

A simple problem of loose wires and connections can cause your battery voltage to fluctuate. So looks like when the enginealternator are cold I get some voltage variation. Its easy to check whether the alternator is not working or the battery is at fault.

Battery voltage fluctuates while in idle. Then next day voltage was at 147 and stopped and started back up and I noticed the volt meter went to 11 and stayed there. So Ive driven the car for a few miles to warm it up.

36 L V 6 gas engine. Voltage on a good battery cannot fluctuate between 01 and 12 volts. If its in the ballpark the voltage is a bit low.

The ideal car battery voltage with the engine running is between 137 and 147V. Check condition and belt tension for alternator. If I shut the car off while at operating temperature and turn it back on again the voltage is low.

Its around 100mv fluctuation on what appears to be a 25 meter. You will need to connect a voltmeter to the battery when the car is running and idle. Therefore a voltage appears that is higher than usual.

This time it was almost steady between 137 and 139 Volts. If I look at the gauges on my car with the engine running the charging voltage varies. An excessive resistance of your high amperage circuit is an overlooked problem that can cause your volts to drop in your batteries.

If you have a battery that has 14 volts without the engine running you have an exceptional battery. Any known issues or any tip thank you in advance. You say the battery is good and charged if you measure voltage at the batterycold it should be 124-126 to be goodmaybe have load tested.

Or even a bad battery. In an ideal situation the voltage will read somewhere close to 144 volts but it will stay at this number and wont continually fluctuate. If serpentine belt check for cracks on the inside of the belt-- Replace if hard and cracked.

If you have voltage fluctuations while the engine is running it is an indicator of a problem with the charging circuit or a major short. Consequently the vehicle owner may observe a fluctuation in the voltage meter from 12 to 14 volts while starting the car. The jeep has 68k miles.

You may push the system into Charge Mode by putting the car into towhaul mode or by simply turning on the vehicles headlights if equipped. If the battery isnt fully charged it will diminish to 124V at 75 12V when its only operating at 25 and down to 119V when its completely discharged. It is not necessary to change any components of the charging system.

I personally wouldnt trust any meter that isnt made by Fluke. In the old days reading 12V when the car was running meant a bad alternator regulator or slipping belt. You may think it is flat charge it and afterwards voltage can go as high as 15V or 16V.

Either you have something kicking in and causing a major draw or a bad voltage regulator. It should measure as battery voltage.

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