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  1. #1
    Seasoned Camper
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    Battery Questions

    Help, please. We’re relatively new to RV’ing, and I need a little help understanding battery specs and capabilities.
    Here’s the scenario (even numbers for the sake of simplicity: SLA battery has a 20aH rating of 100 hours.
    Question: does this mean that the battery will, theoretically, supply 20 amps for 100 hours? Or does it mean that it will supply 20 amps for 5 hours.
    I realize the battery shouldn’t be discharged more than 50%, but I’m just trying to wrap my head around the math. We’re planning an extended trip that may require boondocking for a night or two, and we’ve never boondocked before.
    Thank you for any information or insight you can share.
    Mike 🏌️⛳️
    2017 Ram 2500 CC, 6.7L Cummins Diesel 🐏
    2022 Solitude S-Class 2930RL-R
    Full-time since 8/9/21

  2. #2
    Site Team Second Chance's Avatar
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    If a battery has a 100AH rating, that means 1 amp for 100 hours. As you said, lead-acid batteries are toast if discharged below 50%. A a specific gravity of about 1.200 or a voltage of 12.25 to 12.3 means the battery is about 50% discharged.

    Rob
    U.S. Army Retired
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    (Previously in a Reflection 337RLS)
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  3. #3
    Long Hauler huntindog's Avatar
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    Quote Originally Posted by Longshhm View Post
    Help, please. We’re relatively new to RV’ing, and I need a little help understanding battery specs and capabilities.
    Here’s the scenario (even numbers for the sake of simplicity: SLA battery has a 20aH rating of 100 hours.
    Question: does this mean that the battery will, theoretically, supply 20 amps for 100 hours? Or does it mean that it will supply 20 amps for 5 hours.
    I realize the battery shouldn’t be discharged more than 50%, but I’m just trying to wrap my head around the math. We’re planning an extended trip that may require boondocking for a night or two, and we’ve never boondocked before.
    Thank you for any information or insight you can share.
    If a battery has a 100AH rating, that means 1 amp for 100 hours. As you said, lead-acid batteries are toast if discharged below 50%. A a specific gravity of about 1.200 or a voltage of 12.25 to 12.3 means the battery is about 50% discharged.
    This is two different ways of measuring AH.
    Some generally cheaper brands will achieve 100AH via the 1 amp for 100 hours method. The 20 AH rating uses the 20 amps for 5 hours method. This is the more stringent method. Generally (as I have not seen the data on all batteries) a battery that is rated by the 20 amp method will have no problem meeting the 1 amp standard, and the battery rated by the 1 amp standard probably will fall short when under the 20 amp standard. IOW, the higher the draw, the harder it is on the battery.

    As noted, withdrawing FLA batteries down below 50% shortens their life.... Some have reported getting away with it using 6 volt golf cart batteries,,,, though it seems that those that can do it are very regimented in their battery care practices.
    2021 398M Full Body Paint 8k axles. LRH tires. Disc brakes.
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  4. #4
    Rolling Along jleonard's Avatar
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    Quote Originally Posted by Second Chance View Post
    If a battery has a 100AH rating, that means 1 amp for 100 hours. As you said, lead-acid batteries are toast if discharged below 50%. A a specific gravity of about 1.200 or a voltage of 12.25 to 12.3 means the battery is about 50% discharged.

    Rob
    Click image for larger version. 

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    This is a chart I used for years on my boat to monitor battery state. I used to take them down to 12.1 many times and still got excellent life out of them. Last set lasted 8 seasons and they were still serviceable although getting tired.
    Jay Leonard
    New Port Richey, Fl
    2022 Imagine 2600 RB, 2021 Ram 2500 CC Bighorn 6.7L Cummins

  5. #5
    Big Traveler dryfly's Avatar
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    Quote Originally Posted by Second Chance View Post
    If a battery has a 100AH rating, that means 1 amp for 100 hours. As you said, lead-acid batteries are toast if discharged below 50%. A a specific gravity of about 1.200 or a voltage of 12.25 to 12.3 means the battery is about 50% discharged.

    Rob
    After doing some research I was under the impression that discharging a deep cycle lead acid battery below 50% would only shorten the life span, not completely ruin the battery. This is unlike regular vehicle batteries where on a couple of deep discharges will fry the battery.

    Some articles I have read state that deep cycle batteries have as much as 150 deep cycles (below 50% discharge) available before the battery is considered useless. Am I misunderstanding?
    2020 Reflection 273MK

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    Site Team Second Chance's Avatar
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    Quote Originally Posted by dryfly View Post
    After doing some research I was under the impression that discharging a deep cycle lead acid battery below 50% would only shorten the life span, not completely ruin the battery. This is unlike regular vehicle batteries where on a couple of deep discharges will fry the battery.

    Some articles I have read state that deep cycle batteries have as much as 150 deep cycles (below 50% discharge) available before the battery is considered useless. Am I misunderstanding?
    You are correct. I should have been more specific and quoted numbers for lead-acid batteries in general.

    Rob
    U.S. Army Retired
    2012 F350 DRW CC LB Lariat PS 6.7
    2020 Solitude 310GK-R, MORryde IS, disc brakes,
    Sailun LRG tires, solar, DP windows, W/D
    (Previously in a Reflection 337RLS)
    Full time since 08/2015

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