Now that mine has gone through it's teethng issues including a near thermonucleur meltdown I am only planning to open it once a year or after each season. Rebuild it, install new batteries, close it up and be done with it. I use the cheap 12V 18/20 AH batteries, work good and are cost effective, often well under 40 dollars each. I have a charger that lets me keep it on trickle but I don't do that, I put it on the charger about once a month when not being used.
It is my opinion the Tekna should be charged and connected to the charger while sitting on it's shroud and ONLY after the plug has been open for at least an hour. Do not close the plug until several hours after charging is complete. This allows any hydrogen to vent off.
N