2013 5.0-Alternator for AGM Battery
 

Hello all. Here's the TL;DR: Need recommendations for new alternator on 2013 F150 5.0 with a new AGM Battery.
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I have a 2013 FX4 5.0, and I just replaced my battery with an AGM. A Duralast Platinum (part: #65-AGM, SKU: #319465), 750 cold cranking amps, 935 cranking amps. My previous battery may have died, but it seems more like excess corrosion on my battery terminals was more likely the issue (although it was leaking badly). The lights/accessories would turn on fine and remain on for a lengthy time. But when you tried to start it, it would just tick. Not even like it was trying to start but didn't have the juice, it was just a single click/tick sound and nothing happening. Jump starting made no difference. I cleaned and wire-brushed the terminals that morning to get to work and it did manage to start, but it ceased starting again at the end of the day and wouldn't ever start again until I replaced the battery/terminals.
I've had all kinds of problems with my previous flooded batteries. I admittedly don't check them as often as I should, but they always end up leaking, and my terminals get crazy amounts of corrosion. I've had to replace the positive battery terminal twice. I didn't replace the cables, since Ford makes you buy the whole assembly, so I crimped on factory replacement terminals. I am running two aftermarket amplifiers, a 400RMS speaker amp and 300RMS subwoofer amp. I'm not sure if those have had any impact on the excess corrosion or power issues, but the "professional" installation leaves a lot to be desired. They ran two separate 4ga power wires all the way from battery to amps, alongside speaker wires in many spots. And their grounding points don't look ideal. One amp is currently dead, which coincided with my previous battery/terminals dying. I plan on replacing the full power run to the amps once I sort this out (my speaker amp is the dead one so I don't have speakers anyway at the moment), and I'll run 1/0 to a distribution block at the amps.
I know power requirements are higher for AGMs, and likely with my amps too. So is there a recommended replacement alternator I could install? I have 200,000 miles on it, and it's run two amps most of its life. I previously had an alternator die on a Mustang with only 1 amp and half the miles, so I'm willing to eat the cost. Just looking for a good recommendation.
I'll also eventually have questions about FORSCAN (I have a device and the software) and if I need to tell the battery management system that it is now an AGM, or "reset" the system. But one issue at a time
Thanks for any help!

I would unplug the BMS sensor on the negative battery cable to start. And put protectant on the battery terminals.
I don't have the extra audio amps, but I've been running an AGM for years, still on the OE alt.

I do believe there is an ambulance high output alt. But I don't think it'll be neccessary. I've run a yellow top for well over a year now with Rigid lights all over my truck, ive had no issues. Do as the man said tho and disconnnect that battery minder and also reset your truck, 8 hrs sleep I think. It's all in
​​​​​​ your book

If you're really looking for a quality, high-output alternator, I've been using Mechman alternators in my fleet and personal trucks. Put a couple on for customers as well. They are pretty pricey, but they are well engineered, well built, and their customer service is top-notch.

Thanks for the suggestions so far. I've disconnected the BMS sensor, did that this morning so we'll see how that pans out. The truck has sat locked for well over 8 hours multiple times, so the reset should taken car of. I've even tried the high-beam/brake pedal method, even though I'm 99% sure that is for the 2015+ gens.
It's exhibited some odd behavior still, coming up to a red light as my speed dropped just before I came to a stop the RPMs suddenly dipped down to I'd say 400ish or less, and my A/C (was on at 50% fan speed) noticeably had the power to it cut down. This happened for just a second and then the RPMs jumped back up along with the A/C. Looking back, I do remember things like this happening with my last battery swap. Not as aggressive as they were yesterday or when I first changed the battery, but todays behavior seemed more in line with what i previously experienced. And eventually they stopped happening, just a lengthy "relearn" process I guess.

Are you sure this isn't just the A/C compressor cycling during idle? My 5.0 idles right around 500rpm, and will drop a bit lower momentarily when the A/C compressor is cycled. I'd turn the A/C completely off and see if you have the same issue. I'm just not seeing how your idling issue could be tied to the alternator, especially if you unplugged the BMS.

Edit: you could also log voltage with FORSCAN and look for anything odd. You could also log battery current if you plug the BMS back in. Given that you unplugged the BMS, you shouldn't see any sudden spikes/drops in voltage.

The truck wasn't idle yet, I was still moving and the RPMs were still dropping, and then this rapid drop below the normal idle RPMs happened. It definitely wasn't normal behavior. I have taken recorded some logs on my OBD2 reader (it's an OBLink MX+), but I can't figure out how to export anything that's usable. There's an export CSV option, but then the only data on there is latitude, longitude, and vehicle speed. I do have a graph I'll attach pictures of below, though it's hard to decipher and I had some useless variables being graphed as well. You can see in the graph the first time the rpms dipped almost to 400, and the control module voltage dipped as well down to 12.7V, and then the other dip where RPMs dipped down to 500, but the voltage stayed up closer to 14V. I'm not sure if control module voltage is the best variable to graph (there's 1000 options for battery or electricity related PIDs). I had Battery Positive Voltage tracked in a graph below it, but it showed no strange drastic dips or peaks. I have a dashboard screen with about 20 different variables tracked, that also saves the min/max/mean, and a lot of them seemed to be roughly consistent with control module voltage in terms of dipping/peaking at similar times. But that data is lost once the engine is powered off and I forgot to take notes.
Last week a day after changing the battery I was sitting at idle, I let my foot off the brake and just barely kissed the gas with my foot before having to let off because a Tesla didn't let me merge. The RPM dropped way below idle once I initially let off the gas and the truck actually died. That's only happened once, but there's been plenty of moments where the RPMs drop way too low and it almost dies. If I let off the brake and didn't give it more than 5-10% throttle continuously it would dip way down. The first couple of days if it was in park and idling and you gave it a short blip of throttle, as the RPMs dropped back down they would once again dip way below idle, act like it was going to die, and then the rpms would slowly ramp up way above idle, like 2000+ rpm, and then usually settle down back at idle. A couple times though it would get to idle, dip again, and then quickly jump out, and then repeat. It honestly sounded like I had a ghost cam tune. This extremely weird behavior I'm thinking could be down to the "relearn" process (it had already sat long enough for a reset) because it hasn't done anything that drastic since.
https://cimg5.ibsrv.net/gimg/www.f15...59c0b0091e.jpg
https://cimg6.ibsrv.net/gimg/www.f15...b1dbe35270.jpg

Ya I might plug BMS back in tonight so I can get more detailed logs. May also open my laptop up and drive around with FORSCAN to log like you said. I haven't actually used it yet, just used the OBLink mobile app since I've been too busy to dive in.

The voltage drop is stumping me. If it wasn't for that, everything else you describe is nearly identical to what I experienced when my A/C compressor failed. I would try and log the command for A/C if you can. FORSCAN has the option.

Ya that's a good idea, I'll do that.
Here's the other 2 variables graphed, just for kicks. Not sure if they're any use. Interestingly, the only time the Generator Command Percentage wasn't at ~56% was during the big voltage drop, where it was commanded to only 52%. Probably means nothing, but interesting that those two events coincide with each other.
https://cimg1.ibsrv.net/gimg/www.f15...be14ed7469.png
https://cimg3.ibsrv.net/gimg/www.f15...2a7b431dd1.jpg