Superior Technology Integration Knowledge

Valve-regulated lead-acid (VRLA) batteries will not leak if inverted, pierced, or otherwise compromised. These batteries will continue to operate even underwater.

In general, lithium-ion batteries are known for their higher performance, but also for their volatility and reactivity, which makes them subject to greater control and inspection. Among the lithium battery chemistries, LiFePO4 is unique in that it is significantly safer.

There are several regulatory organizations that have jurisdiction over the construction, use, and safety protocols for lithium batteries. The United Nations (UN) sets many of the basic standards used for testing, construction, and transport, but many individual nations will also set their own standards, which may differ from the UN’s policies.

For example, the United States Department of Transportation (DOT) recognizes the UN guidelines as a foundation for its policies and procedures, but also puts forth its own standard operating procedures for organizations subject to its jurisdiction that must handle lithium batteries. The International Civil Aviation Organization (ICAO) and the International Air Transport Association (IATA) provide additional regulatory guidelines for international and domestic air transport. The International Maritime Organization (IMO) regulates all transport by sea-going vessels. Regulations governing the transportation of lithium batteries are strictly enforced and are revised frequently. Please consult all relevant agencies and documentation prior to shipping.

Testing Lithium-ion Batteries” by Argonne is licensed under CC BY 2.0

Safety of lithium-ion batteries is greatly enhanced when the use of a battery is limited to a single role, such as supporting a specific electronic device like a handheld radio. Additionally, the power management required for “maximum protection” and “optimal operation” can be custom tailored if the battery is being limited to performing a single function.


Gassing occurs when you attempt to charge a battery faster than it can absorb the energy. This excess energy is turned into heat, which then causes the electrolyte to boil and evaporate.

Solar Stik Expander Paks and Power Paks contain AGM lead-acid batteries, which for the most part are very reliable and inert. There are, however, a few situations at the end of their useful life in which they have the potential to produce two quite volatile gases, H2 as well as O2. In a open area, these gases tend to dissipate before they reach a concentration level—4% by volume—that is explosive. When these dilapidated batteries are in a closed container such as an Expander Pak, the probability of an explosion is of much greater concern. As the cells begin to lose capacity and reach the end of their life cycle, the other cells must absorb the extra voltage. For example, a normal battery of six cells at 2 VDC per cell requires that a damaged battery with three functioning cells would be at 4 VDC per cell.

As the voltage potential increases between cells, some reactions begin happening in the battery. The one in concern here is electrolysis. Electrolysis is a common occurrence with batteries throughout their life, and production of these two gases is very minimal with a healthy battery. It is only at the end of their life when the cells begin to degrade and short that the production of these gases increases. This effect is also amplified due to the fact that the batteries no longer hold a charge and require more frequent charging, which again brings the voltage up and produces more gas.

Gassing of Different Battery Types


Lead-acid Gassing
Evaporated electrolyte can be replenished in batteries with removable caps, which are present on most flooded deep-cycle batteries. However, most car batteries are sealed and need to be replaced when their electrolyte evaporates.

It is very important to ensure VRLA batteries are not overcharged. The only way to ensure this is to use a temperature-compensated charging system. Such chargers use a temperature probe on the battery to ensure that it does not overheat. If a charger has temperature compensation, it will detect and react to the battery temperature accordingly. As the battery heats up due to a fast (high-current) recharge, the charging current is reduced to prevent thermal runaway.


LiFePO4 Gassing
Gassing is not usually a problem with lithium batteries, but if they are overheated, the case may deform and bulge, which can damage or destroy the battery. If any battery of any type starts to bulge or warp, it should be taken out of use immediately to prevent the possibility of bursting or explosion.

Early cell phones required large bulky batteries to operate. If you are old enough to remember the 1970s, then you may remember that a portable communications radio often required a battery that weighed more than the radio itself. With lithium batteries, cell phones and radios today are much lighter in weight with much more power.

Thermal Runaway

Thermal runaway is a very dangerous condition that can occur if batteries are charged too fast and become too hot. The increased heat accelerates the chemical reactions in the battery, which in turn generates even more heat. It is a snowball effect.

Thermal Runaway of Different Battery Types


Lead-acid Thermal Runaway
If the heat gets out of control, the electrolyte boils and releases large amounts of hydrogen and oxygen gas, both of which are highly explosive. The battery case can bulge and explode as the battery melts from the inside out.

The danger posed by local accumulation of hydrogen gas is so serious that many regulatory agencies require that batteries are installed in well-ventilated areas.

If you have purchased an automotive jump-starting kit in recent years, you may have noticed that many of them include safety goggles. This is because some ten thousand battery explosions are reported each year due to improper jump starting and the resulting explosions.


LiFePO4 Thermal Runaway
Lithium batteries can absorb current at a much higher rate, and LiFePO4 batteries do not produce the same explosive gas mixture as conventional batteries. However, some types of lithium batteries can still catch fire from thermal runaway.


Equalization is a process that is sometimes used to decrease sulfation on the plates of a lead-acid battery. Because sulfation acts as a barrier on the lead plates, it inhibits their ability to store and dispense energy. To help reverse sulfation, an equalizing charge is applied to raise the battery voltage above its rated voltage for several hours. This process reduces sulfation, reversing the aging process of the battery.

“Sulfation” is what ultimately ends the operational life of a lead-acid battery. It is the normal buildup of sulfate from the electrolyte that sticks to the lead plates in a battery during the charge and discharge process. This condition can be reversed under normal cycling conditions, but it can be exacerbated if the battery is abused (stored in a discharged condition) causing irreversible sulfation and battery failure.

Although beneficial in reversing sulfation, the side effects of equalization are elevated temperature, gassing, and loss of electrolyte if the equalizing charge is not administered correctly. The equalization step should be a last resort to break up the sulfate layers. Because the process will likely cause the battery electrolyte to boil and produce potentially explosive gas, it should only be done with strict supervision of the battery and with the proper precautions.

Equalization of Different Battery Types


Lead-acid Equalization
Equalization should be done with a flooded lead-acid battery only. A VRLA battery should not be equalized.


LifePO4 Equalization
Our LiFePO4 battery systems are never factory configured for equalization. If you are mixing and matching batteries and chargers, make sure that your charger does not do periodic equalization charging, as this will ruin a lithium battery. Equalization should never be done with lithium batteries.

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Explorer’s Log

  • The battery is the heart of a high-efficiency electrical circuit.
  • The two main battery chemistries used by Solar Stik are AGM lead-acid and LiFePO4.
  • Selecting the best battery for an application requires knowing the load requirements and operating conditions.
  • Lithium batteries are used for high-performance applications where it is critical to keep weight down and to maximize energy density, while lead-acid batteries provide low-risk solutions needed by many users.
  • No rechargeable battery should ever be stored in a discharged state.
  • The primary safety concerns with batteries are gassing, thermal runaway, and equalization.

Energy Storage
Battery Care—Lithium-ion

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