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batteries by automatic equipment. This method has a three-fold advantage; first, it properly tapers the charge and prevents over and under charging of the batteries, thus materially increas- ing their life; second, it provides the maximum efficiency and_ eliminates current losses so that the current bill is reduced; third, there is no need for an attendant during the charging, as each battery is cut off as charged and the motor generator set shut off when the last battery is fully charged. It is well at this point to speak about the proper ventilation of the battery box as the temperature of the battery should be kept as low as possible dur- ing both charge and discharge. Of equal importance is the mainte- nance of the electrolyte at the proper level and concentration. It should be remembered that the action of the bat- tery never weakens the solution as only water is passed off in “gassing” or by evaporation. With few ex- ceptions, therefore, it is only necessary to add enough water to bring the solu- tion up to the height specified by the manufacturers and the strength of the solution will be automatically cor- rected. If the level of the liquid is not maintained the effective area (and the capacity) of the plates is cut down and the exposed part is subject to slow deterioration. The continued use of anything but distilled water will eventually cause trouble as the water is evaporated and the impurities accu- mulate at the bottom of the cells until they rise to a level where there may be a short circuit. The above precautions may create the impression that a skilled staff of mechanics should be in constant at- tendance upon a few electric trucks. In order that this wrong impression may not be created actual instances of maintenance costs might well be given. In a steel mill employing 21 electric tractors which were in service for 20 hours per day the total labor charges for repairs and maintenance amounted to $3859. At $1 per hour for mechanics this amounted to 184 hours per truck per year or 74 hours per truck per year if based on the ordinary 8-hour day—a little less than 14% hours per week for trucks which averaged 5 to 6 years in service. Give Low Maintenance Cost At a marine terminal in the South, the average maintenance and repair cost per truck per year was $234.35. For one month the tonnage handled by these trucks and the savings gained thereby were as follows: Truck No. Tonnage handled Savings Mie gin cansts aesaekekuavaiioas subousvuewv enue $ 448.00 Decree cues saa issdewssssncees suedascacs 8,240 4 681.00 Diccccaheiceascidhsabankssdadatares esstehnns 4,142 392.00 he scedaved once cveuoctine in casuneasadaasesaie 3,208 413.00 Bass vai cian scassisatebasasdnsessasiuaoveaasis 5.520 720.00 Gis sadecsteseurseosn sonecsesensteh ip nsttuss 8,212 380.00 3,539 582.00 485 43.00 2,767 219.00 36,887 $3878.00 At a Brooklyn pier rolls of paper weighing 1300 pounds each are han- dled by electric trucks with an inge- nious crane attachment which permits tiering the rolls to a height of 9 feet. The rolls are moved an average of 300 feet down the vier and yet each truck stacks 43 rolls per hour. At an operating cost of 50 cents per hour for the truck plus 85 cents per hour for the driver the cost for this han- dling and stocking operation is less than $0.048 per ton. At another location 12 tractors were employed and a monthly report shows the following costs: Total days Of Operation....i......cccccsscsccscssees 338 Total hours of operation...........00 pees: 2,496 Maintenance labor 3icicisesvicleveteisectasece $303.68 Maintenance material .........c.cccesecscssscsseees 17.90 Power (4734 k.w.h. at 5¢ per k.w.h.).... 2380.95 Total: cost of: oper st? On: (icc Asses sidieccscceue $552.53 Cost per truck per month.................. 42.50 Cost per truck per day © i...c.cc..cccssescscveee 1.63 Keep Accurate Records of Cost A large concern in the middle west has kept accurate cost records on its industrial truck equipment for the past three years. The cost figures in the accompanying table are for the second year. The company (a _ sub- sidiary of the United States Steel Corp.) operates 20 hours per day in most difficult service, the conditions in the plant are not above the average as to floors and ramps but a most ex- cellent repair and maintenance service is supplied and all equipment is regu- larly inspected. The operating and maintenance expenses are determined per hour of operation, as these costs will increase in proportion to the hours of use, the costs are taken directly from the records of the plant. The fixed charges have been figured on an hourly basis, assuming 20 hour serv- ice for 300 days per year. Deprecia- tion, interest in investment, power, battery repairs and maintenance are figured on the 42 sets of batteries for the 21 electric tractors. It is believed that the figures given in the table provide an excellent ex- ample of a well-kept set of records and at the same time are factual evi- dence that low operating costs are the result of proper maintenance. MARINE REVIEW—July, 1929 iain LATEST TYPE OF MULTICIRCUIT AUTOMATIC BATTERY CHARGING SET 39