Moshi moshi Otani-san,

Since these chemicals are electrical conductors, two terminals kept a short distance apart and placed at the base of the batteries so that the liquid from a leak would bridge the gap and close the circuit would do a good enough job of this. The terminals should be linked to an alarm system of some sort. This is something that a good electrician should be able to rig up at low cost. It goes without saying that the batteries should be located within a non-conducting chemical resistant tray (e.g. polypropylene) for this system to work.

After learning the previous post, a few new requirements have been added:

1. Battery type.

Nickel-Cadmium (NiCD whose ID color is green) rechargeable battery
Nickel metal hydride (Ni-MH whose ID color is orange) rechargeable battery
The electrolyte solution for both type is ionic liquid of potassium hydroxide KOH aq. and because of its manufacturing process some caustic potash K2CO3 might remain in it.

2. Early detection of vapor leak in addition to electrolyte liquid leak

Previous to liquid leak sympton, I guess vapor leak is detectable. I live close to Pacific coast, the rain storm of previous typhoon Malor (#18 of 2009) left a very thin layer of salt on window panes the next morning. The salt was carried by the rain from the atmosphere above the sea, I guess. Similarly, vapor from leaking battery will accumulate and condensation of potassium hydroxide will begin on the metal component surounding the battery. The color of the metal component changes and erosion begins, which is critical.

Perhaps, what I'm looking for is a high sensitive chemical detection method like the Llitmus paper, in addition to some detector of liquid leak.

Moshi moshi Otani-san,

If that is the case then you can use a pH sensor like those used in wastewater treatment plants. Those are normally used to regulate reagent dosing, but they can easily be used to trigger an alarm system as well. The only problem with them is that their sensor tips must be kept submerged at all times, so they can't be used in conjunction with the leak sensor system I suggested earlier, as your pH sensor must be immersed in shallow water sufficient to cover the tip. So in this case you could use a level sensor in conjunction with the pH sensor, so that any change in the water pH level or depth would trigger an alarm.

Hey do not use those awful batteries. LOL I am consulting on a job right now where a backup battery for RAM leaked all over the PCB. Ni Cads are known for this and are an old technology. Why not convert to Ni MH 1.2V? No memory effect and I have not seen one leak yet. Another thought is if you have some type of containment for the leaking Ni Cad you could just monitor the voltage and let if fail then the leak could be contained and not cause damage. You could use NASA technology and have a backup battery when the primary failed just trickle charge it less stress on the battery. Hope I gave you some ideas?

Avoid NiCad, definitely MiMH 1.2V, have no leak experience yet! Also your suggestion eliminates the Electrolite vapor detection discussion. Thanks.

Tell us details of the NASA technology of trickle charging. Trickle charge method is used in the computer backup battery equipment which usually employs sealed acid batteries. Trickle charging seems to place less stress on the battery cell, but it needs a special circuitry to control (one chip integrated circuit nowadays?). The charging control circuitry will also performs battery swapping? Let us know, how the switch of the battery takes place, what circuitry will be used - a solid state relay? A low voltage-drop switching design with 10Amp d.c. +/- capacity, please.

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