SAFETY HAZARD WARNINGS FOR LITHIUM ION BATTERIES
Rechargeable Lithium Ion batteries are potentially hazardous and can present a serious FIRE HAZARD if damaged, defective or improperly used. Larger Lithium batteries and those used for industrial use involving high discharge current and frequent full discharge cycles require special precautions.
A FIRE IS MOST LIKELY TO OCCUR DURING THE CHARGING PROCESS UNDER THE FOLLOWING CIRCUMSTANCES:
- THE BATTERY HAS BEEN FULLY DISCHARGED AND IS NOT RECHARGED SHORTLY AFTERWARD. This potential is aggravated if batteries are damaged, contain an undetected factory defect, are used or stored at temperature extremes, or are approaching the end of their useful life. (See useful life) Ideally, batteries should be recharged within 24 hours of a full discharge.
- CHARGING IS ATTEMPTED AT TEMPERATURES BELOW 40°F (4°C). Charging below 40°F (4°C), causes a chemical reaction in the battery cells that can cause permanent damage and the possibility of fire or explosion during charging.
- THE BATTERY HAS BEEN EXPOSED TO LIQUIDS, ESPECIALLY SALTWATER. Exposure to liquids can cause internal corrosion or damage to the cells or to the Battery Management System (BMS). The BMS protects the battery from overcharging, high self- discharge or imbalanced charging of the cells, any of which can present the possibility of fire during recharging.
- OPERATING OR CHARGING A BATTERY THAT HAS BEEN DAMAGED FROM DROPPING OR FROM SHIPPING DAMAGE.
- USING A CHARGER OTHER THAN SPECIFICALLY DESIGNATED FOR THE PARTICULAR BATTERY. Lithium Ion battery chargers provide a specific charging voltage and microprocessor current and voltage control. They are fundamentally different than chargers for SLA, NiCd, NiMH, or other rechargeable batteries. Chargers for LiNiMnCoO2 (NMC) batteries (VML) and LiFePO4 batteries (VLX) are not interchangeable, and require different charging voltages.
The following recommendations, in addition to those precautions above
, should be followed when charging Lithium Ion batteries to ensure the avoidance of potentially catastrophic fire or explosion.
- Charging should be performed in a fire-safe area, away from children or pets. For maximum safety, a metal trashcan with lid placed on a non-flammable surface is suggested. Never charge batteries unattended, or where objects such as carpet, furniture, wood or vinyl floors, curtains or other flammable objects are present.
- Charging should be performed at a temperature between 40°F and 110°F (4°C and 43°C). Never charge below 40°F (4°C).
- Do not attempt to charge a battery that is swollen or bulging. Use only supplied charging cables and connections. Make sure connections are in good condition. Do not allow the charging polarity to be reversed or short-circuited. If equipment is connected during charging, equipment should be switched off. As a delayed chemical reaction can occur if a fault is present, observe the battery in a safe place for at least 15 minutes after charging is complete.
- A healthy battery should only get slightly warm during charging. If the battery becomes hot, smokes, swells, or gives off an odor during charging, terminate charging immediately and contact the manufacturer. Note – the charger itself may get quite warm to the touch when charging a deeply discharged battery.
OPERATING AND STORAGE CONSIDERATIONS
- Batteries may be safely discharged at temperatures between 4°F and 140°F (-20°C and 60°C). Note this is the safe battery temperature rather than ambient temperature. Heavy use (frequent flashing) will cause the battery to develop internal heat beyond the ambient temperature. It is recommended that the discharge duty cycle be limited to 50% or less for long-term continuous use (more than 5-10 minutes). Example: If recycle time is, say 4 seconds, allow 8 seconds between shots. If shooting is in ambient temperatures above 105°F (41°C), lower duty cycles are recommended. Typically, in Vagabond units, the inverter will temporarily shut down if overheated from excess duty cycle. Note that battery capacity is lower at cold temperatures.
- Batteries should be stored at temperatures between 40°F and 80°F (4°C and 27°C) for maximum life and safety. Higher storage temperatures increase the self-discharge rate from the nominal 1-2% per month to as high as 35% per month, and can reduce battery life and increase the possibility of catastrophic failure with long term high temperature storage. Never store batteries at temperatures higher than 170°F (76°C) as this can potentially result in self-combustion, particularly in LiNiMnCoO2 (NMC) batteries. LiFePO4 batteries are intrinsically safer, more tolerant and robust than LiNiMnCoO2 (NMC) batteries.
- Batteries may be stored at 100% charge if used frequently. However, for maximum life, batteries infrequently used should be stored at 40% to 70% charge. An easy way to bring a discharged battery into the proper long-term storage charge is to charge for about 60 minutes with the supplied charger. An easy way to reduce a fully charged Vagabond VML or VLX battery down to the recommended long-term storage charge is to connect and operate the Vagabond into a 100-watt table lamp for about 30 minutes. Batteries in long-term storage at room temperature should receive a refresh charge every three months or so. If you are unsure of the state of charge of Vagabond batteries, turn the Vagabond ON and observe the battery gauge LEDs. Ideal long-term charge is present if the center LED (>50% charge) is lit.
USEFUL BATTERY LIFE FOR LiNiMnCoO2 (NMC) batteries (VML)
LiNiMnCoO2 (NMC) batteries used in cell phones, camera and laptops have a typical useful storage life of three to four years, and about 500 charge/discharge cycles – (about two to three years useful life in typical usage). The same type of batteries generally have a much shorter useful life in applications such as Vagabond VML and other power supplies used to drive flash units.
The reason for this is that batteries driving flash units are subjected to very high intermittent discharge currents during operation and frequent deep discharge conditions, which dramatically reduce the number of charge cycles. A lithium battery can be considered near its end-of-life when its capacity falls to 60% to 70% of its initial capacity. Capacity loss accelerates beyond this range.
The number of charge cycles in flash usage depends on the ratio
of battery size (power capacity) to the peak power drawn during flash recycle. Some portable flash applications use a rather small capacity battery to achieve fast flash recycle times at relatively high Ws ratings (low ratio)
. This reduces the number of full discharge/recharge cycles to as few as 100. Thus, with every day heavy use, the batteries can potentially be depleted in as little as four months
VML units use a high capacity battery for a fairly high ratio, and typically achieve around 250 full discharge/recharge cycles
. This varies according to storage conditions and depth of discharge. For example, if discharged to 50% to 60% every day and recharged daily, around 2 years of useable life is typical. In lighter use, a VML battery can be expected to last for about three years, depending on storage conditions.
USEFUL BATTERY LIFE FOR LiFePO4 BATTERIES (VLX)
LiFePO4 batteries are the latest widely used battery chemistry, developed for high current applications such as electric vehicles, power tools, and other high power applications. They are somewhat larger and heavier than common LiNiMnCoO2 batteries, but are capable of about ten times the discharge current vs capacity and vastly lower flammability and high resistance to abuse. They are the safest and most robust Lithium batteries available, and offer the lowest long-term operating cost.
LiFePO4 batteries have a typical storage life in excess of 10 years and are capable of over 3000 charge/discharge cycles. At the ratios used in the Vagabond VLX, approximately 1200 to 1500 full discharge/recharge cycles are anticipated.
If fully discharged and recharged almost daily, the VLX battery can be expected to last for about four to five years. In lighter use, the VLX battery should last for around ten years. Thus the operating costs range from 1/3 to less than 1/20 of the LiNiMnCoO2 (NMC) batteries used in other systems.
It’s important to note that the LiNiMnCoO2 (NMC) batteries typically used in popular portable flash systems have around a 45 watt-hour capacity and cost up to $250 for replacements. The VLX LiFePO4 battery has a 158.75 watt-hour rating (offering almost 4 times the number of flash Ws per charge) and cost $159.95. The cost difference has no reflection on battery quality, but is a result of Paul C. Buff’s customer-direct marketing and high volume/low markup pricing policies.
SAFE DISPOSAL OF LITHIUM ION BATTERIES
Lithium Ion batteries contain elements that may pose health risks to individuals if they are allowed to leach into the ground water supply. In some countries, it may be illegal to dispose of these batteries in standard household waste. Fortunately, many recycling facilities exist that process lithium ion batteries, in part due to the value of the materials contained within the individual cells. In the United States and Canada, a large network of over 30,000 battery drop-off locations may be found at www.call2recycle.org
To render the battery safe, apply tape over any exposed connectors to prevent the accidental shorting of the positive and negative terminals of the battery during transport. Place each battery into its own plastic bag, seal the bag, and deposit the battery into the recycling container. NEVER dispose of the battery in a fire or incinerator, as the battery may catch fire and explode.