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Parallel adapter for doubling battery capacity

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    Parallel adapter for doubling battery capacity

    Be careful with this one. Both batteries should have identical cells and charge level (mostly the same voltage). If voltage is very different the packs will equalize quickly, potentially damaging the pack.

    When you are ready to charge, do not charge while the packs are still in parallel. Parallel charging could be dangerous because if one BMS fails it will continue to charge. Packs MUST be unplugged from eachother before charging.

    For more info:
    Last edited by paxtana; 06-13-2016, 12:06 PM.

    Can't this adapter be fitted with a pair of diodes to prevent one pack from "charging" the other pack?

    A diode on each of the positive lines prevents current from flowing back to the pack and only allowing the packs to supply power to the motor system.

    Just a thought.


      Yes this is covered in the "more info" link above.


        I have 2 packs. One is the 11AH Shark and the other is the 13AH Shark. (Obviously both were purchased from Lunacycles.) Buying this adapter ready to go, makes a lot of sense for someone with the real estate I have on my trike. Both battery packs ready to go without the hassles of swapping them out. Just attach and ride. Since the Bafang BBS02 doesn't have regen, trying to charge through the discharge port is a non-issue for both packs. Preventing one from trying to charge the other is a major concern, since they have a different capacity.

        I guess the question was to ask why the diodes aren't already included in this adapter. The cost of the diodes themselves is a minor issue, adding a couple of bucks at most to the over-all costs of the adapter itself. From a safety standpoint it would seem a good idea. For those who use a regen type of motor the diodes would prevent any charging via regen. It blocks the current that would go on the discharge side. An adapter with a diode isn't something that someone with regen would want, I suppose. For the rest I expect anyone else with 2 or more packs would jump at it.

        From a marketing standpoint as well. "We have the only parallel adapter that prevents packs charging themselves. Buy this from us and protect your packs!"


          It is still a mostly theoretical design. We have not gotten enough feedback on it and I am not convinced that particular diode is the most ideal choice, it would involve cutting each diode with wire cutters before soldering. And which diode you want depends on how much peak current you use on your ebike, which will vary a lot. Plus I'm not sure we've seen enough demand, it's a lot more than a few dollars to have a factory do a production run.

          If using more than two batteries you would also be right back to needing to make it yourself, or there would need to be another production run for each number of packs in parallel, as well as another production run for each typical current level. It could easily end of costing many thousands of dollars to get a full production line going, with an uncertain level of demand.