Electrical issue

My truck has seemed like it has been a little sluggish starting the last week or two. Today I ran some errands and when I started it, it was slow, but then my tach and other gauges were acting up for a second or two then they worked fine. Got home and with key on but not running it read 9 volts with truck running its just under 14 volts. Took my battery in and they said the battery was fine, but it needed to be charged. Started the truck and disconnected the negative and everything ran fine, gauge is still just below 14 volts. Turned on everything, 700 watt amp, headlights on bright, 400 watt light bar and everything worked fine with negative disconnected so I assume my alternator is working. Gauge did drop to about 12 with everything on but negative disconnected. The bolt on top of the positive battery cable was loose. Could that prevent my battery from getting a full charge? Or is my alternator weak?

 

Clean up your terminals and keep em tight. Sounds like a poor electrical connection was preventing a proper charge.

 

Do you have an AGM in-lieu of a standard battery?

 

Yes, had it for about a year and a half.

 

Awesome, they are stellar batteries...however the factory system cannot "properly" charge the AGMs without tricking the ECU using an expensive fuse-like chip...your alternator needs to charge the AGM at 14.5v and that half volt makes a huge difference in how long and how well the battery will be...I'm digging in my archives for the name of the fuse...but you need this said fuse to not deal with what you're dealing with anymore....

 

Did some research on them before ai bought it last year. Seemed like a good idea at the time due to amp and lights etc drawing power. After buying it, I did read some issues with charging, but I didn't have an issue with it for the first year and a half. Did I slowly damage the battery?

 

I'd say you're okay on the battery and yes,it would take about a year to start noticing what you're experiencing...just get that alternator fuse and throw it in and you're good to go...I am still.dogging looking for the name of what I bought...mine came from Aus and was like $50 but they are found elsewhere for much cheaper...

 

I run agm without the fuse, just give it a good top off charge every couple of weeks.

 

Unless you increased your running voltage, you haven’t been charging your battery properly. You may read 14v at startup, but voltage is regulated on these trucks to below 13.7. This is typically not adequate to charge an AGM battery. If you haven’t been topping off your battery every month or so with a trickle charger, you undoubtedly have been draining the battery lower than what it is designed to be drained too, which is typically less than 50%.

 

That IS the best work-around! Thanks for stating that!

 

Damn guess I should've done more reading before buying it. I thought I was just buying a better battery didn't realize it really isn't compatible with our trucks.

 

I'm wondering if the loose nut on my battery cable may have been the tipping point. It may have lessened the charging just enough to cause a problem. I charged it up and will keep an eye on it and see what happens. If I continue to have issues with it, I'm just gonna go buy a normal flooded battery.