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Building a true parallel charger

Discussion in 'Pro/Adv Discussion' started by Lovelight, Aug 3, 2015.

  1. Lovelight

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    Hi All-

    I've searched the previous posts for this and can't seem to find any information on building a true parallel battery charging rig. Does anyone know what kind of connector DJI uses for their batteries? It doesn't look like any other I've seen used in RC. My intent is to solder up some adapters to connect the batteries to a parallel charging board like this one http://www.hobbyking.com/hobbyking/...ging_Board_for_6_packs_2_6S_T_Connector_.html and apply 17v DC with the amperage appropriate for however many batteries I'll be charging at once. That should get me multiple batteries charged during the same time it takes to do one.

    It seems pretty clear that the DJI batteries themselves have the balancer and LiPO charging logic built in them instead of in the charger itself. The label describes it as an AC power adapter and nothing else.

    If there are no pre-made connector form factors, I can just build some but it would be ideal if some existed that were polarity protected due to their shape.

    Thanks!

    P.S. Not doing anything crazy here. I've flown collective pitch RC helicopters for years and am very familiar with doing this for other LiPO batteries. Totally get the precautions and necessary steps to be safe doing this. Those parallel boards all over eBay are kind of pointless since you have to split up the current across all the batteries you are charging so it just takes longer. And I'm not interested in dropping the $500 on the pre-built charger that one company has. This is completely doable with gear I already have except the connectors.
     
  2. SteveMann

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    What's wrong with a parallel charger as long as your power supply can provide the total current draw? You could put a 20 Amp supply on it since the Phantom battery has its own regulator and cell monitoring.
     
  3. dedstik

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    The Phantom P3 batteries have their own in internal parallel charging circuit !

    A standard parallel charging board is of no use and will serve no benefit.

    You only need to supply power to the mains input with the appropriate DC voltage and current capability.

    I have seen some posts that say that the Traxxas female connector will fit the P3 battery mains but I can not verify this.

    Have you seen this post:

    http://www.phantompilots.com/threads/phantom-3-3-port-battery-remote-charger.49741/#post-469185

    :harry
     
  4. Lovelight

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    I thought of taking that approach as well but since I would need to build a connector to attach my DC power source, I may as well use the parallel board I already have. I would also need to see what amperage that kind of connector is rated for since I expect to be charging up to 4 batteries at once. I know my current set up will take 23 amps safely.
     
  5. Lovelight

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    I won't be using my charger in LiPO mode. I would be using it in Pb mode which just applies a load of whatever voltage and amperage I configure it for. From the batteries perspective it will look the same as the DJI charger.
     
  6. III% Streve

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    The above linked charger seems to be exactly what you are trying to build yourself. Is it not?
     
  7. timz5011

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    If you're going to Macgyver the thing, why not salvage the connectors off of an inexpensive set up from china that is already being sold on eBay.
     
    Joao Carlos likes this.
  8. Lovelight

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    Looks like the Traxxas connector is close but not an exact fit. It might work so I'll give that a shot. Thanks for the input. Just thought it might be some sort of standard connector I hadn't seen yet.
     
  9. Stephan

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    Why buy a parallel charger, your P3 is going down soon, so wait till you get your next one :)
     
    Joao Carlos likes this.
  10. Lovelight

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    Found this helpful video on YouTube.

    The main take aways are that the "intelligence" on the DJI batteries effectively apply current limiting. The Meind power supply can provide 500W of power which is many times higher than the default Inspire power source. It should be perfectly safe to apply a power source to a parallel charging board which is 6 amps x N at 17 volts where N equals the number of batteries in parallel that need to charge.This isn't surprising considering it is effectively a LiPO charger on the battery.

    Although I would not tempt fate by plugging in a 75% charged battery and a 10% charged battery into the parallel board, the circuitry on the batteries will prevent a flood of current from the fuller battery to the drained battery. The battery doesn't distinguish where the power is coming from (another battery or an AC rectifier). It just senses a current source and starts charging the LiPO cells as needed. The fuller battery will charge the emptier battery until you turn on your power source at which point that will take over both batteries become load.

    As previously noted, you do *not* want to use LiPO charge mode from your power source. This will apply current in the on/off mode that LiPOs need to be charged up. The batteries do this for themselves. Your charger just needs to be configured to provide a consistent DC source of around 17 volts and the appropriate amperage for the number of batteries you want to charge. Based on the video, you can technically set it much higher since the batteries protect themselves from over current draw but keeping a lid on it will be an extra layer of safety.

    My charger has a lead acid battery setting that can be used along with motor break in and hot wire foam cutter mode which are just configurable DC power source modes. This looks promising and should be an easy way to charge multiple batteries in the same time it takes to charge one.
     
  11. N017RW

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    There is no tempting fate with a proper understanding. You seem very knowledgeable.

    So long as you follow your 5-6amp x N rule there is no problem with connecting batteries at different levels of charge or discharge.
     
  12. Jeff48920

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    Lol. You take the cake dude.