Electrical Dry Suit Heating

[Joaquin]

To be able to stand the cold during deco after 2 hour plus cave dives in 40F degree water I was looking for some sort of electrical heating system.

I was thinking of buying components (13.5 amp canister + batteries) with wet conectors from Amphibico to perforate the drysuit (or modify a pee valve system to get the two electrical pins through the suit) and stripping an electrical car seat heating or blanket to wire my dry suit underware for a good 75 watt heating.
Alternatively there is an off the shelf solution from FaMi which does not seem convincing to me as it giving only 35 Watts.

Is there anyone out there that has an off the shelf solution or experience with home made heating systems?
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Fate is the hunter