Not every battery is the same, and we carry a large range of battery chargers for a reason. Below we outline different kinds of chargers and their typical applications. This is our first entry in our series about battery chargers and types of batteries.
1. Simple chargers
A simple charger works by supplying a constant DC or pulsed DC power source to a battery being charged. A simple charger typically does not alter its output based on charging time or the charge on the battery. This simplicity means that a simple charger is inexpensive, but there are tradeoffs.
Typically, a carefully designed simple charger takes longer to charge a battery because it is set to use a lower charging rate to prevent damage. Even so, many batteries left on a simple charger for too long will be weakened or destroyed due to over-charging. These chargers also vary in that they can supply either a constant voltage or a constant current, to the battery. Simple AC-powered battery chargers usually have much higher ripple current and ripple voltage than other kinds of battery chargers because they are inexpensively designed and built.
Generally, when the ripple current is within a battery’s manufacturer recommended level, the ripple voltage will also be well within the recommended level. The maximum ripple current for a typical 12 V 100 Ah VRLA lead-acid battery is 5 amps. As long as the ripple current is not excessive (more than 3 to 4 times the battery manufacturer-recommended level), the expected life of a ripple-charged VRLA battery will be within 3% of the life of a constant DC-charged battery.
2. Intelligent chargers
A “smart charger” should not be confused with a “smart battery”. A smart battery is generally defined as one containing some sort of electronic device or “chip” that can communicate with a smart charger about battery characteristics and condition. A smart battery generally requires a smart charger it can communicate with (see Smart Battery Data). A smart charger is defined as a charger that can respond to the condition of a battery, and modify its charging actions accordingly.
Some smart chargers are designed to charge:
- “smart” batteries.
- “dumb” batteries, which lack any internal electronic circuitry.
The output current of a smart charger depends upon the battery’s state. An intelligent charger may monitor the battery’s voltage, temperature or time under charge to determine the optimum charge current and to terminate charging.
For Ni-Cd and NiMH batteries, the voltage across the battery increases slowly during the charging process, until the battery is fully charged. After that, the voltage decreases, which indicates to an intelligent charger that the battery is fully charged. Such chargers are often labeled as a ΔV, “delta-V,” or sometimes “delta peak”, charger, indicating that they monitor the voltage change.
The problem is, the magnitude of “delta-V” can become very small or even non-existent if (very) high[quantify] capacity rechargeable batteries are recharged. This can cause even an intelligent battery charger to not sense that the batteries are actually already fully charged, and continue charging. Overcharging of the batteries will result in some cases. However, many so-called intelligent chargers employ a combination of cut off systems, which are intended to prevent overcharging in the vast majority of cases.
A typical intelligent charger fast-charges a battery up to about 85% of its maximum capacity in less than an hour, then switches to trickle charging, which takes several hours to top off the battery to its full capacity.
3. Pulse chargers
Some chargers use pulse technology in which a series of voltage or current pulses are fed to the battery. The DC pulses have a strictly controlled rise time, pulse width, pulse repetition rate (frequency) and amplitude. This technology is said to work with any size, voltage, capacity or chemistry of batteries, including automotive and valve-regulated batteries. With pulse charging, high instantaneous voltages can be applied without overheating the battery. In a Lead–acid battery, this breaks down lead-sulfate crystals, thus greatly extending the battery service life.
Some chargers use pulses to check the current battery state when the charger is first connected, then use constant current charging during fast charging, then use pulse charging as a kind of trickle charging to maintain the charge.
Some chargers use “negative pulse charging”, also called “reflex charging” or “burp charging”. Such chargers use both positive and brief negative current pulses. There is no significant evidence, however, that negative pulse charging is more effective than ordinary pulse charging.
Thank you for reading our introduction to types of battery chargers we will follow up on more information on all the various kinds of batteries you may encounter. We also discuss how these above chargers are to be used correctly and safely. Feel free to share on facebook and interact with us either here in the comments or on our facebook page.