When to replace the aux batt and how to know?

[Gros Ventre]

Battery terminal voltage without current in or out tells you state of charge. AGM batteries are susceptible to overcharging more so than flooded cell batteries. Ford has then programmed the charging strategy to take it to 80% ~12.8 ~ 12.9 VDC.

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[Davexxxx]

Battery terminal voltage without current in or out tells you state of charge. AGM batteries are susceptible to overcharging more so than flooded cell batteries. Ford has then programmed the charging strategy to take it to 80% ~12.8 ~ 12.9 VDC.

I'd like to find a definitive on that.

Renogy says 12.7V = 100% and 11.7 is 50%

https://www.renogy.com/blogs/general-solar/agm-battery-voltage

For this one, the same range is 13V - 12.05.

https://learnmetrics.com/agm-battery-voltage-charts-12v-24v-deep-cycle-battery-voltage/

Batteries Plus, puts it from 12.6V - 12.1.

https://www.batteriesplus.com/blog/power/find-voltage-of-car-battery

 

[Gros Ventre]

I'd like to find a definitive on that.

Renogy says 12.7V = 100% and 11.7 is 50%

https://www.renogy.com/blogs/general-solar/agm-battery-voltage

For this one, the same range is 13V - 12.05.

https://learnmetrics.com/agm-battery-voltage-charts-12v-24v-deep-cycle-battery-voltage/

Batteries Plus, puts it from 12.6V - 12.1.

https://www.batteriesplus.com/blog/power/find-voltage-of-car-battery

The electrochemistry for a lead acid battery (regardless of construction) will yield a float 100% voltage of 13.2 VDC. Note there is a temperature dependency. Those numbers you cite are system design connected to a charging controller's programming. Go look up the chemistry involved. Charging system voltages for a home system will be lower since these do not want to get to the point of evolving significant hydrogen (which is explosive), so they keep the programmed 100% voltage below the chemistry 100% value.

 

[Davexxxx]

Charging system voltages for a home system will be lower since these do not want to get to the point of evolving significant hydrogen (which is explosive), so they keep the 100% voltage below the chemistry 100% value.

The Batteries Plus link, is specially for car batteries. Nothing to do with home systems.

It would be helpful, if we used the same metrics re SOC.

 

[Gros Ventre]

The Batteries Plus link, is specially for car batteries. Nothing to do with home systems.

It would be helpful, if we used the same metrics re SOC.

So look up the electrochemistry.That's the definitive measure for float voltage. Also I advertised the home system without trying to attach it to a vehicle system.

 

[Davexxxx]

The charger is still flashing red, which according to the unit's instructions is <75% SOC. Voltage reading at the bat with charger on = 12.64

 

[Ricksc]

Try disconnecting charger see what battery reads after 30 min

 

[Davexxxx]

Try disconnecting charger see what battery reads after 30 min

I'll try to do that after it reaches full charge, if I can keep it parked long enough. But it'll be an hr. vs. 30 mins.

 

[Davexxxx]

I'm gonna let this run a bit more to see if it can finish but I'm getting tempted to revert to my old strategy, that served well twice, for near a yr. each.

 

[Ricksc]

I ran my charger till green let it maintain for another 8 hours. Said 100% on charger. Unplugged it and it dropped to 79%. I finally just gave up

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