25 Watt Panel with 100Ah battery

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  • bouree
    Junior Member
    • Jun 2021
    • 4

    25 Watt Panel with 100Ah battery

    From the sticky named "12 Volt Design and Safety Considerations" it would seem that using a 25 watt panel to charge a 100Ah (10hr) AGM battery is a no no. The post mentions that the charge rate should be a minimum of C/12. In my case I am yet to pull the trigger on purchasing my 100W panel(s), but I bought the battery and MPPT 20A controller and am planning to give it a change with my existing 25W panel - understanding that it will take a while.
    I am mostly tinkering with the aim of learning and with the final goal to have backup power for small outages and also have something for overlanding.
    What is the downside of charging with a smaller panel other than time?
    Thanks!
  • SunEagle
    Super Moderator
    • Oct 2012
    • 15123

    #2
    Originally posted by bouree
    From the sticky named "12 Volt Design and Safety Considerations" it would seem that using a 25 watt panel to charge a 100Ah (10hr) AGM battery is a no no. The post mentions that the charge rate should be a minimum of C/12. In my case I am yet to pull the trigger on purchasing my 100W panel(s), but I bought the battery and MPPT 20A controller and am planning to give it a change with my existing 25W panel - understanding that it will take a while.
    I am mostly tinkering with the aim of learning and with the final goal to have backup power for small outages and also have something for overlanding.
    What is the downside of charging with a smaller panel other than time?
    Thanks!
    The downside is not giving the battery enough charging amps so it then sulfates and slowly dies.

    A trickle charge (via small panel or charger) is ok once the battery is full but not good if you try to recharge a battery that is less than 95% SOC.

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    • bouree
      Junior Member
      • Jun 2021
      • 4

      #3
      Originally posted by SunEagle

      The downside is not giving the battery enough charging amps so it then sulfates and slowly dies.

      A trickle charge (via small panel or charger) is ok once the battery is full but not good if you try to recharge a battery that is less than 95% SOC.
      Good to know - Thanks!!

      Comment

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