AGM won't fully charge from alternator?

[gathermewool]

With BMS enabled, my ford charges at higher voltage (14.0 - 14.8) during downhills and deceleration, and around 12.6 and 12.4 at cruise, temperature dependent. The oem setting targets 80% state of charge, as set by the factory.

I played with it for a while and eventually defeated it for a standard float voltage of 14.0-14.4.

So, 80% SOC is not unheard of.

Note - I’ve lost somewhere between 0.6-1 mpg since disabling BMS.

That change in MPG doesn’t seem realistic, though I could obviously be wrong. Once the battery is fully charged the amp draw is almost nothing.

Now, if you’re short-tripping a lot, causing a frequently depleted SoC, then there are many others more likely factors for such a degradation in mileage.

 

[GMBoy]

I've had the longest lasting batteries in a lead acid charging vehicle using AGM battery. Probably worse for lead acid battery in AGM charging system though.

That actually makes some sense too.

 

[SubLGT]

Can you explain this to me?

This is what I did. Battery was around 55F-60F for the procedure, and never warmed up more than 3F. SOC never fell below 60-65%.

Day 1: With a carbon pile, apply 250A load to battery for 3 sec. Charge battery at 14.4V with 6A charger.
Day 2: Apply 250A load twice, with a 10-15 minute rest between discharges. Charge battery at 14.4V with 6A charger
Day 3: Apply 250A load 4 times, with a 10-15 minute rest between discharges. Charge battery at 14.4V with 10A charger.
Day 4: Apply 250A load 7 times, with a 10-15 minute rest between discharges. Charge battery at 14.4V with 20A charger.