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Charger outputs don't match battery/controller volts?

Discussion in 'Pro/Adv Discussion' started by Beanz, Jul 6, 2016.

  1. Beanz

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    So I've got these 2 different DJI chargers, one with an output of 17.4 V/3.3 A and a bigger one with an output of 17.5 V/5.7 A. Having quite a string of bad luck with Phantoms, I'm trying to be cautious, and am trying to decide which one to use, and I'm thinking the smaller one may have been from a 4k and I'm trying to use a Pro. And as I've recently found out, trying to swap parts between the two models can really cause problems. So I check my batteries and they all say 15.2 V/4480 mAh (which is milliamps per hour, which further confuses me as I'm not sure how that relates to just "regular" amps). So neither charger actually fits the batteries, or the controller for that matter (7.4 V/6000 mAh). I understand that you don't want an adapter with a voltage that's too high or a current that's too low, as either may cause the device it's charging to overheat. Both chargers have too high of a voltage, so I guess that doesn't matter? However the smaller one has a current that's too low while the bigger one doesn't (assuming that 4480 mAh is 4.48 A?). But then again, neither one has a current high enough for the controller.

    Since this is all official DJI stuff, I'd like to think it'll just be fine either way, but as I subtly brought up earlier, I'm a little bitter and paranoid with this company. Do you think I should use one over the other? Do you think I can use them both just fine and be able to charge two batteries at the same time?
     
  2. GadgetGuy

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    Both do exactly the same job. The P3P charger just does it quite a bit faster than the P3A charger. Both will shut off when the charge is complete. You won't gain much by using both chargers simultaneously, as the P3P charger would charge both batteries sequentially in the same time as the P3A charger would charge one. However, having two chargers allows you to charge 3 batteries in the the time it takes to charge 2 batteries on the P3P charger, or you can charge the transmitter on the P3A charger, while charging the batteries on the P3P charger, as using both outputs simultaneously (battery and transmitter) from one charger is not recommended.
     
  3. Beanz

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    Thanks for the confidence boost!
     
    GadgetGuy likes this.
  4. Vertigo

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    AH or mAH is a measure of capacity, its how many (milli) amps the battery can output for an hour. Or if you factor in the voltage, how many watts for an hour.

    A=amps, is a measure of current. In your case, the amp rating of the charger is a measure of how fast it can charge the battery. An amp rating of the battery would indicate how much current it can deliver. But we rarely use amps for that, we use C ratings, which is amps/capacity. So for instance, a 4500mAH 20C battery can deliver 4.5x20=90A peak current. You can also solve that formula for time, if you do that, you find that a 20C battery can -in theory-, deliver its full capacity in 1/20th of an hour.

    As for charging; 1A charger can charge a 5000mAH (5AH) battery, it will just take ~5 hours (assuming perfect efficiency). More isnt always better though, a lipo is typically charged at a maximum of 1C, that means 1x its capacity. Or in 1 hour. In reality, it will take longer, because the charge rate has to be lowered when the battery is nearly full. So its not because the charger can deliver, in this case, 5.7A, that it will charge at that rate. It will most likely charge at 1C maximum, just has some headroom for charger inefficiency, to charge the remote or whatever. A 3.3A charger will take more than an hour to charge an empty phantom battery though.

    As for voltages; dont worry about that. The charger will supply what the battery needs. 15.2 is the nominal voltage of the battery, but the actual voltage will vary between 17.4V full and ~13.2 depleted.