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I purchased a GPS tracker from Amazon and instead of wiring it to the car battery I would like to simply attach my own power battery pack.

I am a complete noob when it comes to electronics and I attempted using a 9V battery. It worked but the GPS tracker stayed on for about two hours. It consumes at 300 mAh, I've been told.

I then attached 8, 1.5V rechargeable batteries with 2300 mAh. How long should it last? Is it simply (8 * 2300) / 300? 61 hours?

What other batteries would you recommend to get the GPS tracker to last as long as possible. No car battery or acid batteries please!

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  • \$\begingroup\$ "consumes at 300mAh" is nonsense. If it consumes 300mA (which is quite a high current) you can expect the batteries to last 2300/300 = almost 8 hours. ( 8 batteries in series gives 12V but still only 2300mAh. 8 batteries in parallel - not recommended - would give 18.4Ah but only 1.5V...) \$\endgroup\$ – Brian Drummond May 6 '16 at 10:55
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Do the math. You say the thing you want to power takes 300 mA at 12 V. You are powering it from a 12 V 2.3 Ah battery.

  (2.3 Ah)/(300 mA) = 7.7 hours

That's of course the theoretical answer. There are a number of things that conspire to make batteries much less predictable than a simple amp-hour rating. The amp-hour rating the manufacturer quotes is usually under the most favorable conditions, so you'll likely get less. At low temperature you can get a lot less. You're probably fairly likely to get at least 6 hours run time at room temperature with fully charged batteries in good condition.

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  • \$\begingroup\$ Thank you for the help! What battery type would allow me to keep this running for longer? \$\endgroup\$ – Abs May 6 '16 at 12:33
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    \$\begingroup\$ @Abs: A bigger one. \$\endgroup\$ – Olin Lathrop May 6 '16 at 14:31
  • \$\begingroup\$ @OlinLathrop I liked your note about battery conspiracies :) They are a more complex beast than most people give them credit! \$\endgroup\$ – crowie May 6 '16 at 14:36

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