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I understand that AED (defibrillators) use a 200 V capacitor with a small amperage. I am wondering if it is possible to fill this 200 V capacitor using a 12 V car battery? If you could, you could create the rest of the AED in a box and use any car's battery to power it. Every car on the road would be a source for an AED.

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    \$\begingroup\$ AEDs have a battery, and generate the high voltage from it. \$\endgroup\$ – JRE Sep 7 '17 at 5:43
  • \$\begingroup\$ I would go as far as saying your average AED battery on the market is using 12 V battery internally. Given their long shelf life, non rechargeable lithium should be the only option but stacking then to a 12 V configuration should be realistic. \$\endgroup\$ – winny Sep 7 '17 at 5:50
  • \$\begingroup\$ really, no one makes a 12v AED already? \$\endgroup\$ – user3528438 Sep 7 '17 at 17:53
  • \$\begingroup\$ really, engineering is simple in this case compared regulatory. before you try to design/make/try/use your own make sure it's legal and safe first. \$\endgroup\$ – user3528438 Sep 7 '17 at 17:54
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a 200 V capacitor with a small amperage

Capacitors do not have "amperage", they have "capacity".

Good capacitors (low ESR) are capable of delivering a high current (until it is discharged). How much current and how long depends on that capacity and ESR.

Sure, an AED could be built into every car. But having the 12 V available is not a sufficient reason. All houses have mains voltage, it can also be used to power an AED. The reason why we would not want to have an AED in every car is cost. The cost is not the power source, not the electronics to make 200 V from some battery voltage and also not the 200 V capacitor but the electronics needed to safely revive the patient !

Also, when you need an AED you want it right next to the patient. So an AED which can operate stand alone, I mean, no wires, uses its own power source, is much more useful. So AEDs almost without exception use non-rechargable Lithium batteries. These have a long shelf-life (hold their charge for a long time) so they will work when they're needed. You want that when people's lives depend on this. With a Lithium battery it would only need to be replaced every 5 years or so.

An AED is very rarely used so that 5 years is needed to guarantee that that battery is OK, not to power a 200 V capacitor. Charging a capacitor takes less than a minute. Do you have a camera with a flash ? Do you sometimes need to wait for the flash to charge ? There's also a 200-300 V capacitor in the camera which needs to be charged. Keeping it at 200 V all the time is not energy efficient and not needed.

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  • \$\begingroup\$ Safety Note in addition to your comments... a Defibrillator does NOT "Restart" the heart. It stops it. Using a defibrillator actually causes a flatline, and manual (and proper) CPR is required to re-establish a heart rhythm. Just using a defibrillator will kill someone. They aren't toys, magical or for the untrained. \$\endgroup\$ – R Drast Sep 7 '17 at 10:13
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    \$\begingroup\$ According to en.wikipedia.org/wiki/Automated_external_defibrillator modern AEDs tell you what to do (no training required) and indeed stop the heart so that it can "find it's own rhythm" again. So that would mean no CPR is required. Maybe you're thinking of the Defibrillators used in ambulances, hospitals etc. I see AEDs in supermarkets these days but only shop personnel is allowed to use them. There are however models anyone should be able to use (according to the manufacturer). \$\endgroup\$ – Bimpelrekkie Sep 7 '17 at 10:18
  • \$\begingroup\$ AED's only detect the defect in rhythm, and determine if they can safely provide a corrective shock to stop the defective rhythm. CPR is still required in more than 85% of the cases. The chances of the heart restarting from CNS oxygen starvation is between 0 and 10%, but granted, it is possible. \$\endgroup\$ – R Drast Sep 7 '17 at 10:23
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You just need a boost regulator capable of supplying 200V or a flyback converter capable of the same.

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