After this, I promise, I won't mention "potting" again in this thread. I'll use "some other term".
Depending on which one of these groups you fit into, potting is good or bad for you.
1. For OEMs and parts sellers, potting is brilliant. They know the electronic device can't be repaired so they get to sell a new widget.
2. For the end user such as a DIY EV builder, they have to buy that new widget when the old one may be repairable IF it wasn't buried in potting. For you, it's BAD.
I'm talking to end users...NOT OEM's or resellers.
Potting makes your electronic device very difficult if not impossible to repair WHEN it breaks. 100% of all electronics devices will eventually fail. Some fail sooner than others. High amperage electronics (motor controllers) are FAR more prone to failing than low power electronics. Operating electronics at a few milliamps versus several hundred amps has it's advantages. Same for voltage...5 volts vs 100 volts is a BIG difference. Both of these things together make low power electronics tend to last far longer than high power electronics. I have several 30 year old digital watches that still work. I don't have any 30 year old high power electronic devices that still work.
Some percentage of electronics devices will FAIL soon AFTER the warranty runs out. Some percentage will last many years before they fail. In either case, you won't be able to get your expensive controller repaired. If it had no potting inside, that may be easily done. Blown mosfets are super common and easy to replace. Thanks to potting, you won't have that option and will be buying a new controller instead of replacing $30 worth of parts in a $600 controller.
2 nights ago I blew 2 mosfets in a brand new controller. No big deal, I have spare mosfets and that controller only had conformal on it. Replacing the blown parts was cheap, quick and easy. I spent an hour and it cost me $10. IF it was potted, I would have been unable to repair it. I didn't even need the warranty!
This is potting. It's poured in as a thick liquid that flows down into everything. I agree that it does protect from water and chemical incursion and that does have it's place. BUT, protection from incursion can be done other ways too. Conformal is a great solution and so are silicon seals on the controller shell. Potting cures into a soft epoxy that generally has a rubbery feel to it. Once it is used to cover electronics, it's a safe bet that those electronics wont ever be repairable when they fail. It's a giant PITA to remove when you need to repair said electronics. Depending on the formula of the potting, some get soft and crumbly when heated. Others do not. Quite often potting chemistry is designed to be chemical and heat resistant. This also means that common solvents don't remove the potting and that heating won't make it break down. AKA...the electronic device is NOT repairable since you can't get past the potting easily.
EDIT:
I forgot to mention what conformal is. Most people won't know what this is.
Conformal is a thin, clear coating. It's sort of like clear fingernail polish or spray on enamel. Coating electronics with it protects them from water and chemical incursion. It also doesn't get in the way of soldering or desoldering. If you need to do some form of work on a circuit coated in conformal, go for it! At worst your soldering iron tip will get dirty quicker. I buy it in a bottle and brush it on the exposed electronics I want to protect. When cured it usually creates a glossy, clear protective layer over the electronic parts that does not impact repairability at all.
The BIG difference here is conformal protects just like potting does, but leaves the electronics accessible so they can be repaired or accessed later.
Conformal since it is a thin layer, does not thermally isolate parts. If I needed to add a heat sink on top of these parts or blow air on them or whatever the cooling method, that is still possible. It's a much more flexible protective product than is potting and provides the same kinds of protection from water and chemical incursion.
These close-ups are from a 20S BMS that has conformal on the small electronics. Notice how everything looks glossy and a bit bluury. That's not a camera or photo issue, that's the conformal coating. I think on this BMS, they dribbled it over the electronics or brushed it on since in several of the images you can see where the edge of the conformal is and where bare circuit board is. It can also be sprayed on to coat everything.