A used electric lift truck with an unknown background may require some attention to ensure that it will operate reliably in normal use. Luckily, because an electric lift truck is a very low maintenance vehicle, this attention to detail is less than would be required by an engine-powered truck. For the purposes of this column, we will concentrate on the power pack.
Start by investigating the connectors and cables. Are the connectors, truck, battery and charger properly matched and in good condition? Replace any melted, cracked, or burned components. If connector heating seems to have been a chronic problem with the system, cut cables back a few inches to a bright copper (unoxidized) portion of the cable and install new connector tips and housings. Cables should be free of cuts that could cause short circuits and dangerous arcing. A battery cable should show no signs of swelling or separation of the insulation at the point it attaches to the top of the battery. Defective cables are more than a cosmetic problem, they can be a safety hazard. Replace them. Is the battery properly matched to the truck? Is it the recommended voltage for the truck? (Many 48 volt lift trucks will operate with a 36 volt battery, but the manufacturer may not recommend it). Is the battery large enough to provide the recommended counterweight to allow the lift truck to lift its rated capacity? If the battery installed in the truck does not fill the battery compartment, verify that its weight is within the manufacture’s recommended limits. Is the charger properly matched to the battery? The nameplate voltage and ampere hour rating should match that of the battery. Avoid using small chargers with large batteries. A small charger’s low finish rate current can cause problems for the battery. Trade up to the charger designed for your battery. Observe the behavior of the charger during its eight hr. charging cycle. On a discharged battery, the charger panel meter should indicate a charging rate approximately that of its nameplate rating. By the time the battery is 2/3 of the way through the charging cycle, when the battery is at its gassing voltage (2.35 volts/cell), the charge rate should “taper” or drop off to a “finish rate”: approximately 4 amps per 100 ampere hour of battery capacity. If the behavior of the charger is unusual, you will need to have both the battery and charger checked out. Battery problems can cause variations in charger output, as well as prevent control circuits from shutting the charger off. Battery heating is an indication that such a condition exists.
Checklist
The following symptoms are indications that your newly acquired electric truck needs professional battery and charger attention:
- The truck does not have enough run time to do its job without a “boost charge” during the day.
- The battery gets hot on charge or in service.
- Strong odors, smoke or steam are emitted by the battery.
- Fully charged battery acid density (measured by hydrometer) varies from 1.275 (or a higher value specified by the manufacturer) by more than 20 points (plus or minus 0.20). Check all cells for variation. Do not try to add acid to the battery unless you are experienced in battery service.
- Severe corrosion, cracks or acid seepage are present.
Before you Buy
When simply looking at a used electric forklift battery, it is difficult to tell anything about its performance in service. Checking each cell with a voltmeter (an “open voltage” reading) will tell you if any of the cells are “dead,” but will not provide otherwise reliable information. Dead cells, or any cells that are jumpered out of the circuit, must be replaced before the battery can resume normal service. Cracked cell covers and eroded or damaged intercell connectors on top of the battery will need to be replaced also. These costs must be figured into any battery transaction. Be sure to find out if the battery has been in storage for a long period of time. If a battery sits idle without periodic charging for more than a few months, a disabling condition called sulfation may make charging the battery difficult. If the battery is still an attractive purchase after considering the above points, it is wise to obtain a complete capacity discharge test and evaluation. This test is the only reliable measure of a battery’s performance under its rated load. You should purchase used batteries from an experienced electric truck or battery shop that can provide a test sheet detailing performance and percentage of remaining battery capacity. Few people would buy an engine-powered truck without listening to the engine run, but many take just that sort of risk with an electric truck transaction by neglecting to check out the battery.
For more information, contact Arcon Equipment Inc. (440) 232-1422.
