THE CARE OF ACCUMULATORS.
Page 59
If you've noticed an error in this article please click here to report it so we can fix it.
A Timely Article Now that Electric Lighting is so Largely Employed on
Passenger-service Vehicles.
THE modern accumulator is a very reliable piece of apparatus If it be given the requisite amount of attention, but if neglected it will render the whole lighting system useless. The battery becomes doubly important if it also be called upon to supply current for ignition purposes, as although one could run without lights for a little while, the same cannot be said a the ignition.
The usual source of trouble starts long before it makes itself apparent ; that is, the dynamo ceases to charge and the system is running then entirely on the stock in the battery. It is not proposed to discuss the repair of dynamos in this article, hut it is of the greatest Importance for the driver of a vehicle to keep a watchful eye on the ammeter or other indicator and if it ceases to show charge an investigation should at once be undertaken, and not allowed to he deferred na1 the lights go out.
It is often desired to measure the amount of charge in an accumulator in order to learn whether the battery is in good condition or otherwise. The usual method is to measure the voltage across the terminals, a test, however, which, taken alone, is of no value whatever; yet it is often given in instruction books.
For example, one can take the case of a 6-volt starter-type battery, which, when almost charged, would show very little over 6 volts, and yet when almost discharged would still show about 5+ volts. The average small voltmeter which is usually employed for tasting such a battery is seldom accurate to half a volt, and so it is evident that the readings from the battery in question would be quite useless.
A. voltmeter will indicate when a battery is practically discharged, but there is then no need to make a test, because the lights will only give a red glow.
Unfortunately, there is no single method by which the charge in a battery can be Ascertained, but with the combination of one or two different tests a very good idea can be obtained, and the following are put forward as the best methods.
The hydrometer test is, in theory, an accurate indication of the state of the battery, but in practice may be somewhat misguiding owing to various irregularities.
It can be relied upon if it be known for certain that the acid in the battery is of the correct strength. There is only one way of ensuring this and that is to have the battery fully charged—not on the vehicle, but on a charging plant. By the expression "fully charged" is meant the state when all the cells are gassing freely with a charging rate of half the normal and the positive plates are a very deep brown (nearly black) colour. The hydrometer readings should then indicate a specific gravity of from 1.275 to 1.300. The exact figure will be found on the battery itself.
If the hydrometer shows more than these figures, the acid is too rich and should be diluted with distilled water. A word of warning here; when the distilled water is added another reading must not be taken immediately, but some minutes should be nllowed for the water and acid to mix, or it may appear too weak.
If the hydrometer shows less than the figures mentioned, the acid is too weak, and the best thing to do is to replace it with mixture of the correct strength. It is inadvisable to attempt to put neat acid into the cells in order to make weak mixture .up to strength, as heating wourd take place, which would not only give false hydrometer readings;but might damage the plates.
The electrolyte should be made up to the same level over the plates— say half an inch—which fact should be noted, as it will affect the snbsequent hydrometer readings if it differs materially from its first level.
The indications of a fully charged battery are :—(1) Hydrometer reading of 1.275 to 1.300; (2)\ positive plates of a dark chocolate or nearly black colour ; (3) voltage over each cell, 2+ volts to 2$ volts (this voltage will not be above 2 so soon as the battery is put into use) ; (4) all cells gassing; and this next Indication is almost infallible, that is, (5) the hydrometer reading ceases to_ rise, although the charging is continued beyond the gassing stage for several hours. If a battery shows all the
foregoing characteristics, it may be taken that it is fully charged.
When the battery is in use on the vehicle it should be inspected at least once a fortnight. It is often a nuisance to get trt the battery, as it means uprooting floorboards or crawling underneath, and that is one of the reasons why it is so often neglected.
If vehicle makers were wise in this respect they would house the battery in the really accessible position and, moreover, one that is well lighted, as nothing is more troublesome or dangerous than to work around with a naked light. However, the troubles hinted at and mentioned can be overcome by a conscientious driver, and the attention given will be well repaid by trouble-free lighting.
The inspection should include an observation of the level of the acid and its specific gravity. It is most imporf ant that the hydrometer reading should be taken before the addition of water, as a reading afterwards would suggest that it was run down, as the water would lie on top of the acid for a little time until it had been mixed by the movement of the vehicle.
The specific gravity readings to tell the precise charge in the battery are as follow :—Fully charged, 1.280 to 1300; three-quarter charged, 1.220; half-charged, 1.180; lowest advisable, 1,150.
The above figures are a general guide, but as individual makers recommend a certain strength of electrolyte, it is better to make certain from the instructions which are printed on the battery.
If a voltage reading be wanted, this should be taken across the battery terminals with all lights on. It Is useless to take a voltage reading while the battery is doing no work.
It is never necessary to add acid to the cells unless the electrolyte has been spilt. Water is all that is wanted, and the electrolyte should be made up to its original level, but brought no higher. In no circumstances should a "drop be put in for luck," as it decreases the efficiency of the battery, and renders useless otherwise valuable hydrometer readings.