sulphuric acid {water and potassium hydroxide in NiCads} - you should
be wearing protective clothing {gloves, goggles, etc.} when doing this.
Both types of battery give off an explosive gas when being charged - so
no smoking and no other naked flames in/near the battery compartment.
If the electrolyte level is low, top up with distilled/ de-ionised water - not
acid {it is the water that evaporates from the mix, not the acid}. For gel
type batteries and sealed low maintenance batteries the electrolyte-level
check is neither possible nor required. Check that your low maintenance
battery is not the type that does need occasional topping-up.
You should check the condition - internal and external - each
month, including:External
Security - are the batteries still held secure?
Cleanliness - are the tops clean and no metal tools left on the batteries?
Bulges - if battery cases are bulging then you are heading for trouble.
At some stage they will split and the electrolyte will leak out.
Contacts - should be tight and not corroded. You should check that
contacts are tight and that they are covered in the special compound
supplied for that job, avoiding petroleum-based products.
Internal
Condition can be checked using a load test. To do this you should:
Disconnect the batteries from the rectifier.
Switch radio equipment to an alternative supply {not the batteries
being checked}. In harbour, when the equipment is not reqUired, you
can switch it off altogether.
- Leave the batteries to settle-down for 30 minutes, if they have been
in use and/or on-charge, and then:
Measure the off-load voltage across the terminals and record that
voltage in a log.
Switch on all radio equipment and draw maximum current;
Measure the new on-load voltage reading and record in the log, e.g.
Jan Feb Mar Apr May Jun
off-load 26 ·0 26 ·0 26·0 26·0 26·0 26 ·0
on-load 24·6 24·6 24·6 24 ·6 24·4 24·0
The item of equipment that will draw most current {i.e. - prOVide
the biggest load - thereby prOViding the best test} is your SSB radio,
using H3E {SSB full-carrier}.
196 THE NAUTICAL INSTITUTE