Alternator, battery, or amp meter?

[Doubeleive]

historically speaking my own personal experience with "flickering lights" has been "weak battery" with the one exception of a poor headlight ground one time which was remedied pretty easily by grounding the headlight ground right to the frame

 

[dwinters14]

Two very interesting and insightful posts. Thank you for them. Currently the headlights AND my interior lights dim, so it's definitely through the entire system. I am going to unplug the RVC and go for a drive and see what happens. This is why you don't buy crap parts because I have a lot of question marks and not a lot of answers! I will report back with my findings.

 

[dwinters14]

Alright here's my report on a ~20 minute drive after unplugging the RVC.

Volts were steady between 14.4 - 14.7. Headlights flickered heavily for the first 5 minutes, then almost completely went away for the rest of the drive. Overall about 70% better but still not eradicated entirely. Volts would drop about .4 with the bass. Had the music cranked. The lower the volume, the less the flickering. So the amp draw is 100% causing it, but I'm still unsure of the problem being the battery or the alternator.

 

[Joseph Garcia]

One item to note is that the alternator does not increase amp output for increased truck amp demand instantaneously. When a pulse current draw request comes from the truck (in this case, a bass note that generates an amp surge to move the subwoofer), that pulse is handled by the battery (assuming that correct size power cables are used everywhere). If the battery cannot handle the current request, the lights dim, as the instantaneous voltage of the system drops, due to the current demand. You won't see that voltage drop with a multimeter, since it is a pulse of very short duration, but you would see it on an oscilloscope.

So, if there is a light dimming with bass notes, there is an issue either with the battery itself or some greater-than-zero Ohm resistance electrical connection, such as a ground point. Your opening statement says that the battery was replaced. Have you subsequently removed the battery and taken it to an auto shop and have it bench load tested? If not, I suggest the you do so first, in order to eliminate the battery as a source of your issue. As @Doubeleive stated, a battery issue is not always readily apparent, unless it is bench load tested.

If bench load testing eliminates the battery as a source of your issue, the next steps would be a re-inspection of all of your electrical connections and ground points.

 

[Doubeleive]

Alright here's my report on a ~20 minute drive after unplugging the RVC.

Volts were steady between 14.4 - 14.7. Headlights flickered heavily for the first 5 minutes, then almost completely went away for the rest of the drive. Overall about 70% better but still not eradicated entirely. Volts would drop about .4 with the bass. Had the music cranked. The lower the volume, the less the flickering. So the amp draw is 100% causing it, but I'm still unsure of the problem being the battery or the alternator.

the battery should be able to keep the voltage fairly steady, presuming power and ground are good with very little to no restriction.
if you feel everything is good and the amp is not very efficient you could try going with adding a cap and see if that resolves the dimming.
you can find used ones pretty cheap

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The product is a Tsunami 1.2 Farad 20VDC car audio speaker capacitor with a digital readout. It is used for enhancing the audio performance in a car entertainment system. The capacitor helps in providing a steady power supply to the speakers for improved sound quality.

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[Doubeleive]

One item to note is that the alternator does not increase amp output for increased truck amp demand instantaneously. When a pulse current draw request comes from the truck (in this case, a bass note that generates an amp surge to move the subwoofer), that pulse is handled by the battery (assuming that correct size power cables are used everywhere). If the battery cannot handle the current request, the lights dim, as the instantaneous voltage of the system drops, due to the current demand. You won't see that voltage drop with a multimeter, since it is a pulse of very short duration, but you would see it on an oscilloscope.

So, if there is a light dimming with bass notes, there is an issue either with the battery itself or some greater-than-zero Ohm resistance electrical connection, such as a ground point. Your opening statement says that the battery was replaced. Have you subsequently removed the battery and taken it to an auto shop and have it bench load tested? If not, I suggest the you do so first, in order to eliminate the battery as a source of your issue. As @Doubeleive stated, a battery issue is not always readily apparent, unless it is bench load tested.

If bench load testing eliminates the battery as a source of your issue, the next steps would be a re-inspection of all of your electrical connections and ground points.

you sort of can see the voltage dipping if you have it turned up and have the meter on the amp, that's why I stated to check at the battery post's and then compare that to the amp connections. this would tell you if there is a significant voltage drop in between. i.e. poor ground, poor power
if the power is dipping much more at the amp that's your sign

 

[dwinters14]

One item to note is that the alternator does not increase amp output for increased truck amp demand instantaneously. When a pulse current draw request comes from the truck (in this case, a bass note that generates an amp surge to move the subwoofer), that pulse is handled by the battery (assuming that correct size power cables are used everywhere). If the battery cannot handle the current request, the lights dim, as the instantaneous voltage of the system drops, due to the current demand. You won't see that voltage drop with a multimeter, since it is a pulse of very short duration, but you would see it on an oscilloscope.

So, if there is a light dimming with bass notes, there is an issue either with the battery itself or some greater-than-zero Ohm resistance electrical connection, such as a ground point. Your opening statement says that the battery was replaced. Have you subsequently removed the battery and taken it to an auto shop and have it bench load tested? If not, I suggest the you do so first, in order to eliminate the battery as a source of your issue. As @Doubeleive stated, a battery issue is not always readily apparent, unless it is bench load tested.

If bench load testing eliminates the battery as a source of your issue, the next steps would be a re-inspection of all of your electrical connections and ground points.

The battery is about 2 years old right now, and I have had to clean corrosion off of it at least 3 times. The first 2 times was pretty bad and what prompted me to upgrade my ground wires and terminal.

I purchased a foxwell battery tester that can test the battery under multiple conditions as well as the alternator. I will hook that up and see what it says. If it's inconclusive I will physically inspect the cells in the battery and test the acid to see what's going on before I move on to wiring and then the alternator.

 

[Joseph Garcia]

The battery is about 2 years old right now, and I have had to clean corrosion off of it at least 3 times. The first 2 times was pretty bad and what prompted me to upgrade my ground wires and terminal.

I purchased a foxwell battery tester that can test the battery under multiple conditions as well as the alternator. I will hook that up and see what it says. If it's inconclusive I will physically inspect the cells in the battery and test the acid to see what's going on before I move on to wiring and then the alternator.

IMO, the only true test for a battery is the bench load test. I don't believe that your Foxwell battery tester can perform this load test, as a HUGE high wattage resistor is used in the bench load test, which is larger than your entire Foxwell battery tester case. Just my 2 cents worth for battery testing, particularly in troubleshooting your specific issue.

 

[dwinters14]

After an exhaustive couple of days I think I have detangled the mess of my electrical system. It all started when I did my system initially. I did my big 3 the old fashioned way, NOT properly incorporating the RVC unit. I also didn't use a smaller serpentine belt. As a result I think I fried the ebay alternator I bought and in the process have stressed the battery really hard. Although it still seems to be good.

What I am going to do is run a ground wire from the alternator through the RVC as well as the headlight ground while keeping all the OEM ground connections (battery to chasis, battery to engine and battery to lights) I am also going to remove the alternator to chassis ground that I put in. I hear this can cause alt wine, and it also splits the amps away from the RVC.

We'll see how that performs, but I anticipate needing to purchase another high output alternator and if so, JS as mechman is just out of my price range. Next will be an AGM battery, and a complete re-wire (just for cleanliness and future upgradeability's sake) of my amps. I plan on replacing them anyway as I would like to expand my system. I will report back with my findings once I properly incorporate the RVC just to see what changes.

 

[j91z28d1]

just my experience load testing batteries fairly often at work with one of those new style Snap-on testers. They usually read much higher than the factory rating on brand new batteries. so say an 800 cold cranking battery will show a thousand on there when new. so if you see say 600 cca test from a 800cca battery, it's pretty weak compared to new. now that's just our testers, yours might do a better job. load test a brand new one out curiosity if you can.


back when I added electric fans to my 96 Tahoe, it would drag the smaller stock alt down to battery voltage at hot idle max ac type of rush hour traffic. at killed batteries every 2 years and went thru a few alts. once I found the large case diesel version fit in the bracket and was still 99$. all that was fixed and batteries lasted 5 plus years again and the alt was still on the truck 15 years later when I sold it. so I think you're right under driving it at high load wasn't good for either one.