"Frosting" on top of Ni-Cd batteries

Just wondering what this "frosting" on the Ni-Cd battery cap could be? How is it created? Is it dangerous? Should it be removed?

Check the pic below.

how long have they been in service?
are they filled to the correct level - not overfilled?
are they re-charged properly?
have they ever been overtemperature? (too hot?)
is the fluid level checked periodically?
is it the correct fluid?

Just wondering what this "frosting" on the Ni-Cd battery cap could be...

Click to expand...

These are NiCd batteries, right? The white powder suggests that the cell is leaking.

Test it to confirm: scrape a bit of the powder and put it on a clean glass plate. Add a drop of water; the powder should dissolve completely.

Next add a drop of vinegar and see if fine bubbles are produced. That confirms.

If the tests are positive; that means that the electrolyte has leaked (caustic liquid with a soapy touch) and formed pot carbonate (solid white power).

By the way it is not dangerous and can be safely removed with a damp (not dripping wet) cloth. It indicates that the battery is leaking.

how long have they been in service? - From Aug 2018.
are they filled to the correct level - not overfilled? - They are filled just below MAX level.
are they re-charged properly? Don't know, how to tell?
have they ever been overtemperature? (too hot?) Honestly, didn't check that. But, if they were, what would be the reason for them getting hot?
is the fluid level checked periodically? Yes.
is it the correct fluid? We just add distilled water if they need to be refilled.

how long have they been in service? - From Aug 2018. - so they are new

are they filled to the correct level - not overfilled? - They are filled just below MAX level. - ok

are they re-charged properly? Don't know, how to tell? - are they connected to a battery charger with temperature sensor other than the power connection and is there a temperature sensor, also connected to the battery charger, inplace?

have they ever been overtemperature? (too hot?) Honestly, didn't check that. But, if they were, what would be the reason for them getting hot? batteries overheat when charged too fast

is the fluid level checked periodically? Yes.

is it the correct fluid? We just add distilled water if they need to be refilled. this is good if and only if distilled water is the thing to add
distilled water is usually for lead acid batteries - i don;t remember what one adds to NiCads