road an workshop
Page 53
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by Handyman
Auto-electrics for the mechanic (17)
BEFORE I deal with the ignition and auxiliary sides to auto-electrics, I must take a look at another method of storage, the alkaline battery. This battery, although not in common use in cars and the lighter vehicle, does play a big part on electric forklift trucks, etc, and can be met oh the passenger vehicle and the more special commercial vehicle such as the tanker, where auxiliary electric motors are needed.
The advantage of the alkaline battery is in its ability to give both a long, heavy discharge and accept more than a generous recharge; also it can stand up to quite severe boosting without damage, should the occasion arise. Its particular advantage is, however, its long life and durability.
This battery, unlike the lead acid type, has a cell voltage of 1.5, calling for more cells to make up 24V. Several points have to be borne in mind in connection with the care and welfare of the alkaline battery. For instance, it is of all-steel construction, and this means that the cell containers are live, and metal items or tools must not be placed on top of the cells or between them, as this can cause short circuits that will do considerable damage.
Maintenance is reasonably simple — the main feature is cleanliness, if the full long life is to be obtained. Cleanliness means what it says; it must be clean and dry at all times; and any collection of dirt or dust around the bottom of the cells and between them must be avoided, as any water gaining entry will cause current leakage and cell damage.
Any incrustation seen to be developing is easily removed with hot water, but after washing down the cells should be thoroughly dried off, and then the terminals connections, and cell lids smeared with pure petroleum jelly. Do not on any account use grease or other lubricants.
To remove dust between cells, use dry compressed air; by dry air I mean air that has been obtained from a regularly drained compressor, or has passed through a water trap filter such as used on paint spray air lines. If dry air is not available, use a thin sliver of wood in conjunction with a dry absorbent cloth.
Alkaline batteries are heavy and the battery carrier needs to be specially robust to hold them firmly, as vibration must be avoided. Where the cells are somewhat undersize to the carrier, suitable wood packings should be made and fitted; avoid
using narrow strips that register just at one point. If there is a gap to fill between cells or the carrier side or rear, fit a piece of wood that will cover the whole area. If the cells need packing up for any reason, again completely floor the battery carrier bottom, but do not use battens only or permit a cell to rock about.
Topping up is if anything more critical than with the lead-acid battery, as with alkaline batteries a regular inspection and top up programme should be adhered too, as the level of the electrolyte should not be allowed to drop below fin. or 6mm above the top of the plates.
To check the level it is not wise to rely on dipping a rod or stick into the electrolyte, as apart from the risk of depositing some foreign substance in the cell, dipping is unreliable. A far cleaner and accurate method is to obtain a length of clear glass tube around 6mm bore; lower this into each
cell until it touches the top of the plates, then place the finger firmly over the top of the tube and lift the tube out. The height of the electrolyte above the plates will be clearly indicated by the amount in the tube.
Where topping up is necessary, care must be taken that the distilled water is absolutely pure; only distilled water must be added — on no account add electrolyte, Take care not to overfill, about lin. or 25.4mm is normal above plate level, and also watch that spillage is dried out between cells.
Particular attention should be paid to the storage of distilled water for these batteries, as carboys may have previously contained liquids that are unsuitable. Mark the carboys clearly and ensure that the alkaline supply cannot become contaminated with other battery water.
I will deal with a few more pointers on alkaline batteries and their welfare in my next article... .