Stray electrons strike again

[chl]

The 50% Rule: Maximizing AGM Lifespan

The most critical takeaway from the SoC chart is the 50% mark (12.2V to 12.3V).


Deep-cycle AGM batteries are designed to deliver optimal lifespan when their Depth of Discharge (DoD) is limited. Repeatedly discharging the battery below 50% significantly reduces its overall cycle life.

• Goal: Keep your AGM battery above 50% SoC 12.2V as often as possible. This ensures the battery can reliably deliver power when needed and helps prevent capacity loss.
• Avoid: Never discharge an AGM battery below 11.8V (0% SoC), as this results in severe, permanent damage due to hard sulfation.

For optimal performance and longevity, AGM batteries should be charged using a smart charger specifically designed for AGM batteries. A three-stage charging approach is generally recommended for AGM batteries. For a typical 12V AGM battery, the recommended charging voltages are 14.4V–14.8V during the bulk/absorption phase and 13.2V–13.8V during the float phase. Improper charging practices, such as overcharging, can accelerate degradation and shorten the lifespan of AGM batteries.


For long-term storage, an AGM battery should be kept as close to 100% SoC (12.8V) as possible and maintained with a proper float charge 13.4V to 13.8V.

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[chl]

BTW, not sure if our AGM batteries are truly considered 'deep cycle' so even more critical to keep them charged as much and as often as possible.

 

[MaintGrl]

1. Wait for Resting Voltage

To get an accurate reading, the battery must not be actively charging or discharging. This waiting period allows the surface charge (a temporary, artificially high voltage caused by charging) to dissipate and the chemical reaction inside the battery to stabilize. Deep cycle batteries are designed to discharge slowly, providing consistent power over extended periods. The discharge current—the rate at which the battery is used—affects how long you should wait before taking a resting voltage reading; higher discharge currents may require a longer waiting period for the voltage to stabilize.

• After Charging: Wait at least 12 to 24 hours after the charger has been disconnected.
• After Discharging/Use: Wait at least 1 to 4 hours after the load (lights, inverter, fridge, etc.) has been removed.

Measuring the voltage immediately after charging will always give you a reading close to the charger’s absorption voltage (e.g. 13.5V to 14.8V, which is not the battery’s true SoC.

Truck had been sitting for several days w/o use...

 

[chl]

Truck had been sitting for several days w/o use...

Sometimes that is enough, the truck uses some energy even when OFF running things in the back ground.

That's why I use a maintainer, I don't drive every day so the battery could get deeply discharged just from the background energy use if I didn't.

 

[MaintGrl]

Sometimes that is enough, the truck uses some energy even when OFF running things in the back ground.

That's why I use a maintainer, I don't drive every day so the battery could get deeply discharged just from the background energy use if I didn't.

Yes, I have been reluctant to having to resort to, having an umbilical cord attached to my truck when at home. Heck occasionally I unhook the charger and attempt to drive away when I get the charge port door open alert . . .duh!

 

[chl]

Yes, I have been reluctant to having to resort to, having an umbilical cord attached to my truck when at home. Heck occasionally I unhook the charger and attempt to drive away when I get the charge port door open alert . . .duh!

I agree that it's a shame we have to resort to this to avoid the hassle of the warning messages, the getting stranded because it won't start, and the final premature death of the 12v battery, because Ford didn't program the truck to effectively maintain the 12v battery for maximum longevity.

But such is life.

I put a small hole in my charge port area under the door so I wouldn't have to leave the frunk open to maintain the battery, several of us on the forum have done that as well. You could probably find a local service station mechanic who would do that for you if you don;t want to DIY?

See this thread:

https://www.f150lightningforum.com/forum/threads/charging-12v-battery.16979/


My truck:

And with the etsy made weather cover on:

Good luck!

 

[chl]

If you still have the bumper to bumper warranty in effect, Ford will be responsible for giving you a new battery after they test it and you describe the issue.

 

[Jim Lewis]

For long-term storage, an AGM battery should be kept as close to 100% SoC (12.8V) as possible and maintained with a proper float charge 13.4V to 13.8V.

It's worth noting that the proper float voltage depends on temperature, and good trickle chargers like the NOCO Genius2 reduce the float charge to allow for ambient temperature. If you go as high as 90°F, as my garage sometimes does, the float voltage should be reduced by about 0.1 volt. IIRC, I've read 13.2 to 13.2V across the jump point terminals with my NOCO in operation. When the temperature drops significantly, the voltage correction is applied in the positive direction. The voltage is only applied in pulses as needed, too, and not continuously, IIRC.

 

[chl]

It's worth noting that the proper float voltage depends on temperature, and good trickle chargers like the NOCO Genius2 reduce the float charge to allow for ambient temperature. If you go as high as 90°F, as my garage sometimes does, the float voltage should be reduced by about 0.1 volt. IIRC, I've read 13.2 to 13.2V across the jump point terminals with my NOCO in operation. When the temperature drops significantly, the voltage correction is applied in the positive direction. The voltage is only applied in pulses as needed, too, and not continuously, IIRC.

Another thing the Lightning probably does not take into account with it's 12v battery regime, good point.

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