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  • AMP effects?

    How does Amp rating on batteries effect tool performance? I can guess that higher Amp ratings means better but I was wondering the difference between say-2.0 Amps and 3.0 Amps in comparable voltage batteries.

    Make any sense?

    J.C.

  • #2
    Re: AMP effects?

    j.c. amps are nothing more than watts divided by volts.

    then you have amp hours.

    most rechargeable batteries are rated by milliamp hours.

    the higher the milliamp rating, the longer the battery run for.

    think of a aaa cell battery and a d cell battery. both are the same voltage, but the d will out last the aaa.

    i'm sure there are more technical answers, but this is the basics.

    rick.
    phoebe it is

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    • #3
      Re: AMP effects?

      The 'amp' rating on batteries is actually amp hours. An amp hour is defined as the ability to provide one amp for 1 hour (2.5 Ah would be 2.5 A for 1 hr or 5 A for 30 min etc. up to the max draw design point)
      So the difference between 2 Ah and 3 Ah in the same tool at the same load would be about 50% longer run time

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      • #4
        Re: AMP effects?

        Even though this doesn't affect something like a power tool that is somewhat regulated in voltage output, but higher amp ratings in rechargeable packs is usually desired because it allows the pack to discharge at a faster rate. Meaning more power output per minute. This is really useful in something like R/C racing, where runtime isn't as important. Later!

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        • #5
          Re: AMP effects?

          Originally posted by JCsPlumbing View Post
          How does Amp rating on batteries effect tool performance? I can guess that higher Amp ratings means better but I was wondering the difference between say-2.0 Amps and 3.0 Amps in comparable voltage batteries.

          Make any sense?

          J.C.
          For NiCd batteries current output would be the about the same regardless of capacity (Ah rating). For NiMH and Li-Ion, the higher the capacity the lower the current the battery can produce. For example 1.3 Ah NiMH is more powerful than 3 Ah NiMH. This has to do with internal battery resistance and active material granularity and density. Li-Ion is also formula specific.

          For example Makita uses 1.5 Ah cells which can produce 14-20 A max. They use them in 2x parallel in "fat" batteries to gain 40 A. Bosch uses 1.3 Ah cells with the same chemistry as Makita, but they can produce up to 25 A per cell (50 A per battery). Dewalt uses 1.1 or 2.3 Ah cells that are different from Bosch and Makita, they can produce up to 100 A (that's a hundred).

          Milwaukee V28/v18 uses yet another formula that can produce up to 30 A per cell.

          Makita uses 1.3 Ah cells in their 10.8v stuff for that reason - there are 3 cells in series, so they sacrifice capacity for power.

          Higher energy density cells also behave differently at high loads - they discharge FASTER than lower density cells. So if you compare a 1.1 Ah battery with a 1.3 Ah battery - at high loads 1.1 will give you the same or LONGER runtime than 1.3.

          To overcome this problem, companies "tweak" the chemistry to achieve the best ratio capacity/discharge current. They also stack cells in parallel thus killing 2 birds with one stone: double the capacity and half the load per cell.

          I have datasheets and test charts for all major manufacturer batteries, if you want I can email them to you.

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          • #6
            Re: AMP effects?

            see, i told you there would be more technical answers

            thanks guys

            rick.
            phoebe it is

            Comment


            • #7
              Re: AMP effects?

              The same applies to laptop computers when looking at battery capacity. NEVER believe what the manufacturer of the laptop claims what the battery life is in hours. It's pretty much only accurate if you plan on using your laptop as a night light with no sound and the contrast at minimum. Find out how many cells are in the battery pack, and what it is rated at (in mAh). My older laptop draws about 30 watts of power when idle and only basic power saving features on. Probably uses almost twice that at full load. After doing the math, I think it's close to the 2.5-3 hours I get on battery power.

              As anyone familiar with power tools will know, ambient temperature also affects battery life. If you're operating a laptop in temperature extremes, performance will suffer.

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              • #8
                Re: AMP effects?

                Originally posted by wathman View Post
                As anyone familiar with power tools will know, ambient temperature also affects battery life. If you're operating a laptop in temperature extremes, performance will suffer.
                In most cases yes, however Dewalt's batteries have higher discharge current when hot.

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