Is my ‘14 going to fully charge an AGM battery?

[mr_dave]

I put an 850CCA AGM battery in my 2013 Exp exactly 2 years ago. I didn't do anything other than take the old lead acid battery out and put the AGM in. It has been working perfectly since then.

 

[jmden]

Update: NAPA warantied the Odessey ODX-AGM65M because their testing showed it was bad. Got it replaced with the ODX-AGM65, the two terminal version instead of the 4 terminal marine version. It’s actually a bit stronger battery at 950CCA and 74Ah vs the 930CCA and 65Ah of the marine battery. Since then, I’m showing significantly higher voltage at the battery terminals—14.6 instead of 14.2 or 14.3. Does that make sense? Could a ‘bad’ battery cause the lower voltage reading? Also, if that 14.6 voltage stays steady, I think that’s enuf to charge the AGM battery without adding a diode, right?

 

[DieselMonk]

So while driving around with a voltage monitor/USB port adapter in the 12V power outlet, I’m seeing 13.9 -14.1 and it seems when we are driving in warmer weather (mid to upper 80s) that voltage is dropping to 13.6-13.7V. Does this make sense? Or, do I have an alternator going bad? It’s a OEM alternator that was replaced by dealership about 100k ago, at about 25k miles. I occasionally run a 50amp DC to DC charger off the battery and am already wondering if I’m asking too much of the stock 175amp alternator.

Makes sense and it is normal.

 

[DieselMonk]

Update: NAPA warantied the Odessey ODX-AGM65M because their testing showed it was bad. Got it replaced with the ODX-AGM65, the two terminal version instead of the 4 terminal marine version. It’s actually a bit stronger battery at 950CCA and 74Ah vs the 930CCA and 65Ah of the marine battery. Since then, I’m showing significantly higher voltage at the battery terminals—14.6 instead of 14.2 or 14.3. Does that make sense? Could a ‘bad’ battery cause the lower voltage reading? Also, if that 14.6 voltage stays steady, I think that’s enuf to charge the AGM battery without adding a diode, right?

Now this does NOT make any sense, unless the battery is almost dead. The older style dumb alternators does not know what kind of battery is on there and frankly gives a sh.t what you put on it, so they do NOT correct any voltage between a flooded and AGM. The regulator gives about 13.8V to a fully charged battery and 14.5V right after start or an empty one.A bad battery makes the engine consuming more fuel and ruining the fuel mileage, specifically on a lot of short trips.

Clean the battery posts and the cables, do not use silicon lube or any thing around the posts. Just clean and reinstall the hardware. Take a charger and fully charge the battery, then do your test again.

 

[jmden]

Now this does NOT make any sense, unless the battery is almost dead. The older style dumb alternators does not know what kind of battery is on there and frankly gives a sh.t what you put on it, so they do NOT correct any voltage between a flooded and AGM. The regulator gives about 13.8V to a fully charged battery and 14.5V right after start or an empty one.A bad battery makes the engine consuming more fuel and ruining the fuel mileage, specifically on a lot of short trips.

Clean the battery posts and the cables, do not use silicon lube or any thing around the posts. Just clean and reinstall the hardware. Take a charger and fully charge the battery, then do your test again.

Yup, cleaned the posts and terminals as standard procedure once I got home from NAPA. Then—after charging with 10 amp charger on AGM profile—since then the voltage has been back down to 14.2. So, maybe the alternator was just putting out a bit more on a brand new installed battery that just needed to get more charged? IDK. But it was weird to see the 14.6V on way home with new battery install was weird.

 

[DieselMonk]

brand new battery does not mean it is fully charged. In fact, most of them are not. If I buy a battery, I'll take it home and charge it first. Then the install.

 

[jmden]

brand new battery does not mean it is fully charged. In fact, most of them are not. If I buy a battery, I'll take it home and charge it first. Then the install.

Yes, of course. That’s what I wanted to do but NAPA was going to have to charge me for the new battery and refund me for the old battery when I brought it back if I took the new one home and charged it. Rather than deal with all that, I swapped batts in the parking lot, monitored system voltage on the 1 mile drive home and put it on a 10 amp NOCO Genius charger in AGM mode once home.

 

[DieselMonk]

Very good charger! I got the same one.

 

[jmden]

Very good charger! I got the same one.

I guess I could use that periodically (monthly…?) to top off the battery in lieu of installing a diode. I have all I need to install a diode in the alternator sensing wire using bullet connectors, which allows the diode to be taken out easily and the sense wire put back together.

 

[DieselMonk]

That all depends. I do a lot of short trips. All my older cars with factory AGM batteries were not able to keep up with the charging, specifically not in the winter. Now with my new 24, or my wifeys 22 I don't have that problem anymore.
Basically short distance driving and opening and closing the doors all the time will kill the battery fast. My 24, will only turn on the dash and the splash screen once. Next time I am opening the truck those screens stay dark.

 

[jmden]

That all depends. I do a lot of short trips. All my older cars with factory AGM batteries were not able to keep up with the charging, specifically not in the winter. Now with my new 24, or my wifeys 22 I don't have that problem anymore.
Basically short distance driving and opening and closing the doors all the time will kill the battery fast. My 24, will only turn on the dash and the splash screen once. Next time I am opening the truck those screens stay dark.

Why do you think the newer cars are keeping up? My wife has a ‘20 Subaru with smart alternator and although the battery tests good at NAPA, I still have some concern the battery isn’t getting fully charged.

 

[DieselMonk]

Like I said, driving short distances will drain down the battery. All depends on the BMS and the programming of the modules. My 18 would drain a Group H8 battery in 2 days if you camp and OPEN / CLOSE the doors all the time. Each time the door opens most of the modules come online. My 24 doesn’t do that. After the second time opening the door, the screens and crap do not come on any more, unless I start the car again.

Try it. Park the car, open the door and all the screens come on. Close the door and try in 30mins again. I do a lot of short trips, like 10km to work (5km of that is highway), open up and close the doors a few times for tools, then go home 10km. I am better off, skipping the highway and just go slow on the backroads. Then I got a fuller battery and use less gas.
Same reason why I use mostly 87 octane gas, because the car / truck dumps the fuel into the cylinders when started cold anyway (open loop) for 90% of the 10km trip. Fuel efficiency only comes in when the engine is in closed loop and all the oils, coolant etc is hot.