Announcement

Collapse
No announcement yet.

Amp hours

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Amp hours

    Do they rate amp hours in a lithium ion battery the same as they do in a lead acid battery

  • #2
    Originally posted by Outdoors View Post
    Do they rate amp hours in a lithium ion battery the same as they do in a lead acid battery
    Yes. It's a basic unit of measurement - one amp for one hour.

    The details under which that is measured, and whether it's good for the battery or not (and how many times you can draw it etc etc) differs from chemistry to chemistry. But an amp hour is always an amp hour. It's like a volt, or a mile per hour.

    Comment


    • #3
      Originally posted by Outdoors View Post
      Do they rate amp hours in a lithium ion battery the same as they do in a lead acid battery
      Now for the correct answer, No they do not rate them the same.

      Lithium Ion battery AH are rated at 1C discharge rate, consumer grade Pb are rated at C/20, and industrial Pb batteries are rated at C/8 to C/4 discharge rates.

      On paper an Amp Hour is an Amp Hour, but how it is expressed and measured is different.

      Example if you took say a [B][I][U]Rolls S-140 batter[/U][/I][/B]y is rated @ 105 AH at the 20 hours discharge rate. What that is telling you is if you applied a 5 amp load on the battery, it can supply 5 amps for 20 hours until discharged. Take a 100 AH lithium and you apply the same 5 amps would last 20 hours.

      But what happens if we apply a 1-hour discharge rate of 100 amps. Well the lithium battery would last 1 hours. The Rolls would be discharged in less than 23 minutes because the same Pb battery at 100 AH at the 20 hour rate is only 38 AH at the 1 hour rate.

      It is called Peukert Law. FWIW that same Rolls S-104 discharged at 100 hour rate (1.4 amps) would be a 140 AH battery and the Lithium would still be a 100 AH at the 100 hour discharge rate of 1 amp.

      Look at th espec sheet I just provided you. It list the AH capacities at various discharge rates.

      100 Hour Rate = 140 AH @ 1.4 Amps
      20 Hour Rate = 105 AH @ 5.25 Amps
      1 Hour Rate = 38 AH @ 38 Amps

      That is [B][I][U]Peukert Law[/U][/I][/B] the thief in action in the real world.

      Lithium batteries are not as affected by Peukert Law as Pb until the discharge rate goes faster than 1 hour aka 1C rate. A 100 AH Lithium will have

      100 AH if discharge at 1 amp for 100 hours
      100 AH if discharged at 5 amps for 20 hours
      100 AH if discharge at 100 amps for 1 hour
      Last edited by Sunking; 04-26-2018, 05:16 PM.
      MSEE, PE

      Comment

      Working...
      X