2005 Silverado battery light

[onebad65c10]

Have an 05 Z71 5.3. Replaced my alternator with in the past year do to charging issues and heat build up. With in the past couple of months the battery light has stayed on. Gauge reads about 14 volts at idle. Checked with a multimeter and it shows 13.76 at idle and 13.84 with throttle. Battery is a Optima Yellow top. Checked with our tester at work and after running said to replace battery. Truck has never failed to start even with the 20 degree mornings we've been having. Would the battery voltage being down cause the light to stay on? Possibly indicating a problem. I also checked the 2 wire plug on the alternator and both wires were reading ground, no voltage on either.

 

 

Do have an ongoing issue with my bose amp but I believe its a bad amp. The audio takes about 20 minutes of driving to come on, everything else on the radio works until it comes on. 

 

[Colossus]

I'm wondering if it's voltage regulator related..Even if it is built into/onto the new alternator..   Also, I have only seen a few posts in the many forums I scan but there has been some sort of connection I am seeing between Optima batteries and issues with alternators... however I have never experienced any optima issues in the few that I have owned.  They have been solid. 

[Jsdirt]

This would be a good job for a thermal imaging camera. Could be a hot spot somewhere in the wiring between the alternator and battery (high resistance, aka - bad connection).

 

That said, these systems were designed for regular lead acid batteries. Throw an AGM in there, and the alternator falls short in keeping them properly charged. AGM voltage is a touch higher at rest than a regular lead-acid battery, so the alternator on the newer units (don't think this applies to your '05) will stop charging prematurely, thinking the battery is fully charged, when it's only at 80-90%. Enough cycles of that, and the battery fails prematurely.

 

Another variable is, voltage is always lower in cold, and higher in heat. All fully charged specs are at 70°F.

 

Yet ANOTHER variable is, you could have got a bad, new alternator. These days, I'd put money on that one. Trying to get the place that sold it to you to cover it under warranty is yet another battle. "See, it's charging just fine" - can't tell you how many times I've heard that at chain auto parts stores on alternators with completely blown diodes in the rectifier ...

[carkhz316]

2 hours ago, Jsdirt said:

This would be a good job for a thermal imaging camera. Could be a hot spot somewhere in the wiring between the alternator and battery (high resistance, aka - bad connection).

 

That said, these systems were designed for regular lead acid batteries. Throw an AGM in there, and the alternator falls short in keeping them properly charged. AGM voltage is a touch higher at rest than a regular lead-acid battery, so the alternator on the newer units (don't think this applies to your '05) will stop charging prematurely, thinking the battery is fully charged, when it's only at 80-90%. Enough cycles of that, and the battery fails prematurely.

 

Another variable is, voltage is always lower in cold, and higher in heat. All fully charged specs are at 70°F.

 

Yet ANOTHER variable is, you could have got a bad, new alternator. These days, I'd put money on that one. Trying to get the place that sold it to you to cover it under warranty is yet another battle. "See, it's charging just fine" - can't tell you how many times I've heard that at chain auto parts stores on alternators with completely blown diodes in the rectifier ...

Haha, what? You don't need a thermal imaging camera to perform a voltage drop test. A $10 voltmeter will suffice. Also, dropping in a AGM battery in place of a standard lead-acid is perfectly acceptable, and won't suffer from diminished service life over the lead acid. AGM batteries are slightly more robust and can handle more rigorous charge/ discharge cycles compared to a standard battery too (think deep cycling/ running lights and radio without the engine running). I had a '03 Silverado that I installed an AGM in with no issue, and most of my smaller machines (lawn mower/ ATV/ snowmobile) have AGM batteries installed. Most modern vehicles now run AGM batteries from the factory as well, including my '12 Silverado and '14 SS sedan. However, AGM batteries can more easily be damaged by improper charging from standalone battery chargers that don't have dedicated AGM charging settings.

 

I agree with your statement about the bad alternator though. That does happen and I recommend OP to have a complete starting/ charging system done on his truck, complete with a load test of the battery and alternator.

[Jsdirt]

You don't need alot of tools, but they're sure nice to have. I figured a voltage drop test was understood in this situation - who wouldn't do one?

 

I'd agree with you about AGM on paper .. but from what I've seen of 5 years with an Odyssey battery, that is not the case. They've got plenty of power when fully charged, but run them months on end with nothing but the alternator charging it up, coupled with extended periods of sitting, they'll drop to a level I'm not comfortable with. I frequently have to charge mine on the 4-stage charger to keep it at 100%.

 

Next time I'll stick with the tried, true, and CHEAP lead-acid ...

[carkhz316]

I would love to have a thermal cam, though I probably wouldn't use it enough to warrant the cost, haha!

 

I'll give you that the added cost of AGM batteries is tough to swallow sometimes. In regards to my machines that sit seasonally with the AGMs installed, I have battery maintainers on all of them to keep them in check. I would attribute that as to the reason for them lasting longer for me. Anyway, I enjoy bouncing ideas and tech with you back and forth to help others out. More info the better!

[onebad65c10]

Thanks everyone for your input. I have load tested the truck at work and it does come up as battery discharged. Have set it on our battery tester a Gr8 unit. Charged the battery Under diagnosis and it has come up replace the battery. 

Voltage drop showed no draw. Not much installed on the truck. Only aftermarket accessories are led head lights, Cai and exhaust. Still have factory sound system. May just bite the bullet and swap out the optima for a regular battery. Truck is daily driven so no long time between being used. 

[Jsdirt]

Just making sure you understand what a voltage drop test accomplishes ... since you cannot measure "draw" via a voltage drop test - that would be an AMPERAGE test.

 

A voltage drop test can ONLY be done while current is flowing - no current flow = no voltage drop. You're measuring voltage differential through a wire - ONE wire. Positive lead of your meter on one end of the wire, and negative on the other end, wherever that "end" may be. Theoretically it should be zero, but it never is. To really test battery cables, the test should be done while cranking. You shouldn't see more than a volt drop on a high amp test like this. Any other wire, 200mV is what you'd want to see (or less). If you start seeing 5, 8 or 12 volts, that's all bad. If you're seeing a 12v drop, that means that nearly every volt being put out by the alternator and battery is being wasted, & turned into heat at the bad connection.

 

I'm sure Google will show plenty of examples of this. I'd recommend checking out ScannerDanner on YouTube for voltage drop basics.