Spidergears
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- #16
I get the decline in charging, I just didn’t expect it to be so low for my given state of charge.An exponential decline in charging current is how batteries work. I have begun to wonder about Ford's programming. Some detailed homework surfaced that 12.69VDC is the theoretical fully charged voltage. As it appears to me Ford has programmed 12.7VDC as the 80% charged point. Well, why would they do this? I believe that Ford has assessed th lifetime of AGM batteries and concluded that going above that 12.7VDC point will, in the long term, overcharge the batteries. My homework also revealed that AGM batteries are more susceptible to damage from overcharging than a typical flooded cell battery. I have begun taking a voltage reading, with a handheld Digital Voltmeter, every morning. I leave the hood unlatched so that I don't have to trigger modules. I find that the battery, after sitting overnight will have a rest voltage of around 12.8VDC. It then declines about 0.05VDC day by day. recall that lead acid batteries will have a self-discharge rate of about 1% or 2% per week. You can't change this, it's a fact of how these batteries work. So what's up? Well first I finally figured out that the truck is "Always on." It has to be so that when you approach it with your key FOB, it'll recognize it and unlock the doors. So, engine on or engine off, the computer is active. Admittedly, its active at a very low current draw, but it's there. Combine that with a self discharge rate and no matter what you'll see battery voltage slowly declining... Now do you have some modules that aren't turning off when they should have been commanded? Go take a look.
As far as modules go, nothing obvious is on. Any suggestions on how to do a deeper diagnosis of this? Ive recently started leaving my obdlink mx plugged in, but it shuts off pretty quickly after the key is off, likely due to the truck cutting power to the port.
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