by Jack Searle, reprinted from the January 1994 DX Times
It has become evident that many DXers going to remote places on DXpeditions are using lead acid batteries as a power source for their lights and radios. It is also evident that many are not fully conversant with the proper use and care of these quite expensive units. That battery benefit from proper care and maintenance is amply demonstrated by the fact that the writer has in some 50 years of motoring never had a battery fail in under 6 years while most of his acquaintances struggle to get 2 or 3 years from theirs.
I have known well cared for batteries to last almost 10 years. Nowadays most motor vehicles are equipped with “SEALED” or “MAINTENANCE FREE” batteries , they are not the most desirable type for use by DXers. They are designed for use in voltage controlled circuits where they will be held in a fully charged state during their life and almost never require to be charged as will the type used for powering radios on DX trips.
Try to buy the type intended for Caravans and Invalid scooters or some other type that has cell caps that unscrew or pull off to expose the batteries internal parts. You will note that the battery is filled to about 10mm above the plate with
a liquid that is technically referred to as ELECTROLYTE, it is an extremely corrosive mixture of water and SULPHURIC ACID that needs to be treated with respect for it will burn holes in almost anything that it comes into contact with such as clothes, upholstery etc., not to mention the result should you let it splash into eyes !!
In the event of accidental spillage douse it with a solution of washing soda and water if possible (or baking soda) followed by copious quantities of water to neutralise the acid. Splashes on the skin or eyes should be immediately treated with plenty of water.
Occasionally you may need to top up the electrolyte to maintain the desired level as evaporation takes place and the water is lost, the acid remains. Add only water, NEVER ACID, using distilled water for preference though in an emergency it is quite OK to use clean tap water. Perhaps the best source of suitable water is to melt a slab of ice from the walls of your deep freeze unit, melt it in a clean plastic container and store in a clean bottle with a plastic or rubber bung. Don’t bring battery water into contact with ferrous metals if this can be avoided.
Now we come to charging the battery…. You will need a charger unit, these are freely avaible and one that will put out 4 or maybe 6 anps will be quite adequate, preferably it will be equipped with a meter to indicate the actual rate of charge during the operation. You’ll also need a battery type hydrometer to monitor the omspecific gravity of the electrolyte as charging proceeds. (No, the hydrometer you got with your home brew kit will not be satisfactory ! )
CHARGING THE BATTERY The procedure. . .
(1) Attach the charger leads to the battery posts (terminals) ensuring that poisitive lead marked + goes to the positive or simalarly marked post on the battery. (It is normal for batteries to have a positive terminal post bigger than the negative one and another indicator is that due to electrolytic action the positive terminal takes on a black scaled appearance.) Negative lead marked with a minus sign goes to negative on the battery.
(2) Ensure the cell caps are removed and that they remain OFF during the charging to ensure adequate ventilation. Room ventilation needs to be good too.
(3) Switch on the charger and if a meter is provided note the charging rate which will reduce as the batteries state of charge rises, this may take several hours if the battery was near flat.
(4) Draw sufficient electrolyte up into the hydrometer to allow the internal float to rise clear of the base and note the reading on the scale at the water level, the float will rise as the charge of the battery increases. (Of course you put the water back into the cell you sampled after each check.)
Continue charging until the reading on the hydrometer reaches somewhere between 1.260 and 1.280 and ceases increasing. Once the level has stopped rising continue charging for a further 3 hours to complete the charging procedure.
As the charging nears the maximum you will notice that the electrolyte is bubbling and giving off a strong smell of sulphurous gas, the battery case will probably be quite warm to the touch. This is quite normal. while the battery is charging DO NOT smoke over it or bring any matches or naked lights near for the gas being given off is highly explosive and many batteries have been shattered by a careless spark while removing or attaching leads, BE CAREFUL.
STORING YOUR BATTERY. before storing your battery fully charge it then hose it down out in the garden to remove acid splashes. If it will not be used for some time a top-up charge is advisable every four to six months. Unlike Ni-cads which should always be stored in a discharged condition lead acid batteries should be kept fully charged. (and you might get five minutes warning about exotic DX and you won’t have 48 hours to charge the battery.
Note that the charging time will depend on the state of the battery at the start and could take up to 48 hours, before setting out for that important DXpedition ensure that you have your battery well topped up, fully charged it will supply your radio for 50 hours at least.
Occasionally corrosion is evident on the terminal posts, though this is more likely to be a problem with your car battery, the treatment is the sane. Neutralize the area with the soda solution mentioned above and when dry coat the posts with VASELINE from your medical cabinet. Another good anti corrosion medium is SAVLON ointment again from the medical kit.
The hard black scale which forms on the Positive terminal is non conducting and
can be a problem, especially with cars where a heavy drain of up to 400 Amps is needed to move a cold motor at starting. Simply scrape off the scale to expose the clear lead beneath and coat with one of the medical items mentioned above. Care should be taken to avoid severe knocks or thumps to the battery, such treatment can easily result in a cracked case, especially with the old hard rubber cases, In any case severe shocks shake the filling in the plates loose and it is ultimately the disintegration of the plate that cause the battery to fail, it is no use speeding up the inevitable end by careless tee.