Have you ever looked at a battery data sheet and wondered what all the terminology and specifications mean? Let's take a deep dive into lithium deep cycle battery data sheets.
Electrical Specifications
Starting with electrical specifications, we'll take a look at nominal voltage. LiFePO4 batteries have an operating range between 2.5-3.65 volts per cell. However, 3.2 volts per cell is the nominal voltage for LiFePO4 batteries. Because it's the midpoint or average operating voltage. The RB100 is composed of four banks of three two-volt cells connected in series, making the total nominal voltage of 12.8 volts.
Nominal capacity is one way of stating the approximate amount of specific energy a battery contains measured in amp hours. Drawing a one amp current for one hour equals one amp hour. The RB100 is a 100 amp hour battery, which means its approximate runtime to 100%. Depth of discharge can be estimated by dividing the amp load of the DC devices you plan to power by a 100 amp hour capacity. So if you're running a five amp load, the 100 amp power capacity will last roughly 20 hours, ten amps, 10 hours, and so on. Like nominal capacity, the capacity at 25 amps, also known as reserve capacity, is the amount in minutes. The battery can operate at 25 amps. For the RB100, we arrive at 240 minutes by dividing the capacity by the load and multiplying by 6100 amp hours divided by 25 amps equals 4 hours, times 60 minutes equals 240 minutes.
In the product description on the top, we also reference energy in watt-hours. Watt hours are another way of measuring the specific amount of energy a battery holds. Watt hours are the nominal voltage multiplied by the capacity. Most electronic devices are rated in watt-hours. So similar to a nominal capacity method, you can divide battery energy in watt-hours by the sum of all devices.
What are our ratings? So if the devices you power sum to 200 watts, you could run them from this RB100 for about six 4 hours. Resistance measured in milli-ohms is the measured amount of restrictions the battery encounters. Delivering power to its intended application to simplify low internal resistance ensures all of the available energy within the battery is delivered. As the next cell describes, RELiON LiFePO4 batteries are 99% efficient, meaning almost all available energy is put to work.
RELiON LiFePO4 batteries, when disconnected from all current draws, will self-discharge at less than 3% per month. This means that you can place batteries in storage for long periods without worrying about capacity diminishing. If you do put your batteries in storage, we recommend disconnecting from all devices and cycling the battery once every six months. The maximum number of modules in series is the total number of batteries that may be connected in series, so for the RB100, up to 6 may be placed in series to make a 76.8-volt system. Parallel connections are also allowed, but we recommend no more than ten without consulting with us first. Please check the user manual for further guidance on connecting batteries in series in parallel.
Discharge Specifications
The maximum continuous discharge is the maximum current. The battery should be discharged continuously. At the least, running above this current will shorten the life of your battery, so it's very important to understand the demands of your application to remain under the maximum continuous rating. Doing so will prevent damage to your battery or loss of power to your application. The peak discharge current is the maximum amount of current the battery can handle in short bursts. Many larger devices like motors and compressors have a higher startup current that drops off once the device is operating. The RB100 peak current is 200 amps for five to 10 seconds.
BMS Discharge Current Cutoff is When the BMS detects a current at or above this amount, it will open the circuit and go into protection mode. When the load is removed, the BMS will recover and return to normal operation. Recommended low-voltage Disconnect is the voltage we recommend disconnecting at to ensure the BMS does not go into protection mode and your device remains powered. BMS Discharge Voltage Cutoff and Reconnect Voltage is the low voltage point that the battery will enter protection mode. If the BMS detects the entire battery is less than 8 volts or any individual cells below 2 volts, it opens the circuit to protect the health of the battery. To recover from this condition, charge the battery and the BMS will reconnect when the voltage reaches nine 2 volts. A short circuit is an unintended bridging of the positive and negative terminals that allow current to travel at a high rate with very little impedance, which could damage the battery. Simply stated, shortcircuit protection safeguards the battery cells from damage if a short circuit occurs. Although shorts are measured in microseconds which are millions of a second, and cells are protected by the BMS, a spark may still be produced that is hazardous to your health. The battery cables and bolts, so shorts are best avoided. Always wear appropriate safety gear that includes insulated tools, high protection, and gloves.
Temperature Specifications
These are the temperature ranges RELiON LiFePO4 batteries may operate in. Although LiFePO4 batteries are capable of being discharged in temps as low as negative four degrees, they are much less tolerant of charging and freezing conditions. Be sure to refer to charge specifications for capabilities below 32 degrees Fahrenheit.Mechanical Specifications The mechanical specifications cover all the physical characteristics of the battery and will help you determine if a model fits your dimensional requirements.In addition, the group size of the battery is listed in the product description at the top of the datasheet. Many rely on batteries that meet BCI group size guidelines, so they're dropping replacements for lead-acid batteries charge Specifications The Charge Specifications section covers charge voltage and currents RELiON LiFePO4 batteries can accept, along with BMS voltage, cutoff, reconnect voltage, and balancing voltage. Please take special note that LiFePO4 batteries do not tolerate charging in low temperatures. Charging at full rate even once in freezing temps can cause irreparable damage to the cells. The charge current must be reduced to less than or equal to 10% of the maximum between 14 and 32 degrees Fahrenheit, and less than or equal to 5% of the maximum from negative four to 14 degrees Fahrenheit. We hope this review of the datasheets has been informative. In part two of this video, we'll take a look at the performance charts of lithium batteries and what they mean, and real-world use.
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