Thought I would share (Black 3 BTW, New AGM Die Hard battery)

Bought a GAP tool a few months ago. When I first got it the temps outside were in the low 70's. Didn't play that much with it but would see voltage in the low 14's at start up. Then as I started to pay more attention and outside temps got higher I started seeing high 13's.

Week before road trip we had a "heat wave" with outside temps in the 80's-90's. I noticed voltages at mid 13's.

First thought is my alt is going. Bought a refurb unit and brought on my road trip through desert temps in the 100's. After first day of driving I saw 13 volts. Got paranoid and did a swap in the parking lot. At start up in the am I was showing 13.7 volts. After 6 hours of driving the newly replaced alt was showing 13 volts.

No Faults whatsoever. Did some consulting with bbyer and his thoughts were the computer was holding back on charging the battery due to temps.

Here are my findings:

- GAP tool measures aprox. .3 volts less than actual voltage reading at battery.

- In cooler temps I am showing higher voltage.

- My battery first thing in the AM was only charged to 58%!(Confirmed with expensive snap on tool for batteries). As bbyer and others have noted, all our batteries are not even close to fully charged by our systems.

I put the charger on trickle and charged to 100%. The next day in the am got a reading of 96%. Im sure as the days go on I will get lower percentage readings as time proceeds.

 

Yeah, that stinks. I ran a bunch of thick wire to the trunk to an aux fuse panel and then off to a bunch of accessories. One thing that comes off of this panel is a solar controller. The wire from the solar controller then runs out the rear taillight and down to the spare tire well/receiver hitch area. I did this because I went from having a hard mounted panel up on the roof rack to wanting to buy a foldable solar panel to deploy only when I am stopped.

Anyway, to make a long story short, I've been considering using these wires to hook my C-TEK charger up to every time I park for the night. Or at least a couple of times a week. Just hasn't been on my top priority list yet.

 

Part of the issue is likely that the regulator isn't optimized for an AGM battery. Back in the day, batteries were batteries, but these days every battery has it's own specific charging profile (available from the manufacturer) and to get the most out of them you need a custom charging profile. In the marine world chargers can be tailored to this need but I've never seen it done on an OEM regulator.

Also of note, the DieHard Platinums are made by Odyssey, and their group 31 in particular has proven to be troublesome to properly charge from an alternator/regulator. I (and many others over on ExPo) had one and got rid of it in under a year as it just never got to a proper full charge. That's also why Sears is no longer selling the DieHard Platinum as there were many people reporting issues. I'm currently running a group 31 Northstar which does better, though I generally still throw my Norco 260000 smart charger on it from time to time to properly top it off.

I haven't dug into the car config files with my GAP tool, but I seem to remember somebody saying you could change the battery profile there to AGM which would at least be a little closer even if not fully customized to the battery. I really should check on that one of these days.