PatR,
What are these "simple modifications to their aircraft" you speak of?
Before going into that we need to first accept some inconvenient truths;
1) Lithium ion batteries have a finite lifespan, used or unused.
2) Yuneec batteries are not as good as they could be.
3) The new batteries currently being provided by Yuneec for the H have for the most part have started to degrade because, although unused they are two or more years old.
4) The batteries bought by the early buyers of the Typhoon H have started to degrade because of both age and use cycles.
5) Unless noted, we don't know the age of after market batteries being sold for the Typhoon H.
6) Proprietary batteries are a brilliant means to assure product model obsolescence.
Those flying a Q-500, Chroma, Typhoon 500 4K, H-920, and H-920 Plus started experiencing the same problems somewhat earlier and have the same issues that Typhoon H owners are soon to face, which is a continued source for reliable power supplies. Anyone obtaining a new battery that has individual cells providing double digit IR values new out of the box needs to understand those new batteries are not as healthy as a new battery should be.
If we accept the above as factual we will recognize that if we desire to continue to use aircraft models that are in all ways except power supply fully capable of continued use we'll have to come up with alternative power sources. In and of itself that should not be a problem but what does become a problem (for some) is battery configuration. If Yuneec ceases manufacturing of any given model it will not be long afterwards that after market manufacturers will cease the manufacture of proprietary case after market batteries, so supply will soon be depleted. Where do we go for batteries or how can we make use of what will be available?
Despite using a proprietary battery shell which limits the type of battery that can be used Yuneec either accidentally or deliberately did us all a favor, they didn't tie the battery and shell to a "smart" battery design. That means that any battery of the correct cell count with an adequate C rating, milliamp capacity, and reasonable weight that can fit in the battery compartment can be effectively used as the power source. But they won't have a "Yuneec" shell you say. This is where we come to the simple modifications part.
Every Yuneec proprietary shell battery comes with the parts we need to make adaptive changes so there's no problem finding parts. Something that may be an issue to some people is accepting that modifications to enable use of different batteries will alter the external appearance of their aircraft. If this of significant concern those people should stop here, but they will end up hanging their H on the wall long before it's worn out and buying another aircraft.
Those that don't have issues with minor cosmetics and are good with small tools could separate the top and bottom shells of an H (or Chroma, Q-500, or Typhoon 4K) to make a hole large enough to pass power wires through in the bottom shell just below or to the side of the power plug on the main board. They could disassemble an old and worn out H battery and remove the power plug from the battery and PC boards. They would save the main power wires at the outside ends of the plug remove the balance tap wires from the center as they are not used in flight and will not be necessary for any reason moving forward.
Use the power plug and main power wires to create an Yuneec to XT-60 or other connector type (your preference) adapter. Make it long enough that when plugged into the main board and route out through the hole in the bottom shell to reach about 3/4 of the distance between the main board and the aft battery bay opening. Plug the adapter into the main board and leave it there forever. There will be no need to ever remove it again.
While the shells are separated, take a look at the small plastic "divider" that's built into the lower shell jut aft of the power plug location. That divider is just about the perfect distance from the board to help prevent a battery from being slammed into the main board and damaging the electrical contacts or solder joints. It's not quite tall enough to be perfect but the addition of a piece of foam that is slightly wider than the space between the divider and the power plug will assist prevention of motion. From this point all we need to do is peruse battery manufacturers that manufacture batteries of a size that will fit inside the battery well.
I've found quite a few of different capacities that easily fit fully within the well. Thus far the highest capacity found has been a 5500mA 4S pack but I have not even come close to exhausting my research. Perhaps the largest issue with those batteries that fit in the well is that they are usually shorter than a Yuneec battery and will need the addition of a piece of foam at the back of the battery to prevent aft movement. The batteries should be inserted in the battery well with the battery's main power leads facing the back of the aircraft. Those leads will be connected with the adapter plug you made and routed out the bottom of the aircraft.
Securing the battery is easy. Velcro or similar straps have functioned perfectly since the dawn of multirotors. All you need to de is decide how you want to attach the straps to the outside of the shell in a manner that assures they will not fall off of the shell. Run the straps tightly across the battery well and you're good to go.
