COMANCHE TECH TALK
BATTERY BOX DRAIN CLAMP
by Omri Talmon
The battery box has three openings with tubes connected to them: Two at the top, for ventilating the box (air inlet and outlet) and one at the bottom, for draining it.
Here is the point: The drain tube should be clamped, and opened only on the ground, if necessary, during maintenance, and inspections.
Here is an excerpt from the Piper manual:
"The battery is enclosed in a stainless steel box with a vent system and a drain. The vents allow fresh air to enter the box and draw off fumes that may accumulate due to the charging process of the battery. The drain is clamped off from the bottom of the fuselage and should be opened occasionally to drain any accumulation of liquid and during cleaning of the box." (bold and underline – mine).
The reason is quite simple: If the battery starts to leak during a flight and the drain is not clamped, a stream of acid will start to flow along the bottom of the fuselage. The pilot and passengers will have the opportunity to look at the landscape right underneath. Not a very appealing prospect.
The three battery tubes, from right: Air intake, drain, air outlet