LinsyRC 2-Pack XT90 Parallel Battery Connector Plug 1-Female to 2-Male Parallel Adapter Splitter for RC Quadcopters Multirotors LiPo Battery

I am using this to combine two batteries on my Ebike. Doesn't overheat. Well built, good quality.

However, I did need a short T90 cable between them, as there is not enough space to gang them and allow another cable to plug into the first. But not a big deal.BTW, for my application, I'll be using high amp switches and a manual procedure to ensure the batteries don't interfere with each other - only one can be active at a time. (I didn't want to run them at the same time, but I could by using an appropriate device to balance the load.)

車の屋根の太陽光パネルからポタ電に接続する用途で使用していたが、環境的に劣悪でもあるのを割り引いても、半年持たずに接続部が溶けて破断してしまった。最低2〜3年程度は使えると良いですね。

Had to slit the two plugs open a little for my two connections and once I did that, this baby works perfect.