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AGM Battery (Renogy 100Ah) Maximum Depth of Discharge

jbajor
jbajor Member Posts: 233
in Battery/Electrical & Solar
I am setting up my new Victron Smart Shunt  (IP65, 300 amp) and, in my research, seen MANY references to setting max discharge to 50% as well as 80% discharge (50% remaining charge and 20% remaining charge).  Clearly this makes a significant difference to the calculated time remaining on the battery for a given load. Are there any real world uses that you have had with respect to how far you allow your AGM battery to discharge without ill effect?  Where 50% is considered 'safe, I do not want to short change my capacity but I also do not want to prematurely damage my battery. What say you oh wise ones?  Cheers!  Jordan
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Comments

  • pthomas745
    pthomas745 Administrator, Moderator Posts: 4,527
    There have been several interesting discussions on this subject in this group in the past. This thread is one of them, with some data on the various "depths of discharge" and life of the battery.
    A lot of this sort of info depends on the relative health of the battery, its age, how well it has been treated, etc.  All batteries will fade in amp hour capacity over time, and lead acid batteries, no matter how well they have been treated, are getting sketchy when over 5 years old. 
    The batteries mentioned in this thread (Trojan, Odyssey, Concorde, etc) were considered the "high end" AGM batteries of their time.  See if this thread helps, or simply adds to the "analysis".  

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  • Marceline
    Marceline Member Posts: 1,745
    edited December 2025
    jbajor said:
    I am setting up my new Victron Smart Shunt  (IP65, 300 amp) and, in my research, seen MANY references to setting max discharge to 50% as well as 80% discharge (50% remaining charge and 20% remaining charge).  Clearly this makes a significant difference to the calculated time remaining on the battery for a given load. Are there any real world uses that you have had with respect to how far you allow your AGM battery to discharge without ill effect?  Where 50% is considered 'safe, I do not want to short change my capacity but I also do not want to prematurely damage my battery. What say you oh wise ones?  Cheers!  
    I hardly ever look at the "calculated time remaining on the battery." I think that data is a lot more useful when the controller is connected to a system where there is some kind of regular-ish load. I just don't think it's very useful when you have the compressor from a fridge (or the fan for a furnace) kicking on/off at irregular intervals. I mostly focus on the SOC (voltage) and the net amps consumed. Just my two cents.
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  • jbajor
    jbajor Member Posts: 233
    I completely agree with you, however, how far will you allow your battery to discharge (lowest state of charge) for an AGM...  I currently am planning on not exceeding a SOC of 40% (less than 50% but sill more remaining than at an 80% discharge (20% SOV).  Sigh...  certainly MANY additional variable rendering it no trivial...  Just curious what other AGM owners have set there Victron Smart Shunt to..  btw, pthomas, that is a great thread!!  (albeit still not definitive but excellent food for thought!  Thanks all

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