Forum Discussion

mooky_stinks's avatar
mooky_stinks
Explorer
Apr 08, 2022

Walmart 27DC….80 or 109AH?

I ordered 2 27DCs from the Walmart website yesterday. The description stated an amp/hr rating of 109. When I picked the batteries up they had hold stickers on top with my name etc. When I got them home and peeled the stickers off they had a rating of 80 amp hours @ 20hr on the label. They do weigh what the description states @ 50.2lbs each. I’m pretty sure Johnson Controls were making batteries for them and they have been bought out by Clarios? I’m not familiar with this 20hr style of rating either. There is some mention of this in some of the reviews but nothing more than someone returning the batteries for this reason. Did I get what I wanted or is there something more to this?
  • valhalla360's avatar
    valhalla360
    Navigator
    Apr 09, 2022
    KD4UPL wrote:
    it's called the Peukert effect


    This is the answer.

    Basically, the higher the amp draw, the lower the amp-hr you can expect. Therefore, they need to define the amp-hrs in terms of the draw. 20hr rate is basically 5% of amp-hr rating which is fairly reasonable for a house battery.
  • Skibane's avatar
    Skibane
    Explorer II
    Apr 08, 2022
    KD4UPL wrote:
    Basically their marketing guys used a non standard number to make the advertising look better. It's not wrong, just a little sneaky.


    If they used a 0.001 amp load, they could probably get 150 AH out of it! :B
  • KD4UPL's avatar
    KD4UPL
    Explorer
    Apr 08, 2022
    Just about all Group 27 batteries are, give or take, about 75 amp hours. Yours are 80 so that's on the upper end. Rating them with a 20 hour draw is the industry standard.
    A manufacturer can rate them at any draw they want for marketing purposes. Apparently yours are about 109 AH at what is roughly a 100 hour rate. I suspect if you tested them at an 80 amp draw you might only get 1/2 hour making them 40 AH at that rate.
    All the numbers are correct, it's called the Peukert effect if you want to read all about it.
    Basically their marketing guys used a non standard number to make the advertising look better. It's not wrong, just a little sneaky.
  • Skibane's avatar
    Skibane
    Explorer II
    Apr 08, 2022
    mooky stinks wrote:
    I did just look at the website photo of the battery and it shows on the label: 109 amp hrs @ 1 amp
    VS what I received which states 80 amp hrs @ 20hrs. I can’t find anything that states if these two ratings are just a number game or they truly are different.


    It's the same battery, just being tested with two different loads.

    At higher loads (i.e., more amps), the battery has less effective capacity, because higher loads cause more of the battery's power to be wasted as heat. With more power wasted as heat, less power is available for whatever you're powering.
  • 2oldman's avatar
    2oldman
    Explorer II
    Apr 08, 2022
    All deep-cycle batteries I've seen are rated nominally at 20 hours.
  • red31's avatar
    red31
    Explorer
    Apr 08, 2022
    from a JCI 2003 spreadsheet showing amp hours vs constant draw down load

  • BFL13's avatar
    BFL13
    Explorer II
    Apr 08, 2022
    20 hr rate is 4 amps If you draw it down at 1 amp it lasts longer Not a scam, but a sales trick to use the 1 amp rate
  • mooky_stinks's avatar
    mooky_stinks
    Explorer
    Apr 08, 2022
    I did just look at the website photo of the battery and it shows on the label: 109 amp hrs @ 1 amp
    VS what I received which states 80 amp hrs @ 20hrs. I can’t find anything that states if these two ratings are just a number game or they truly are different.
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Apr 08, 2022
    Twenty-nine amps is significant when talking about totals of 218 vs. 160. I’d return them and ask for what was advertised. Take your written proof.

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