All About Deep-Cycle-Marine-Batteries
All About Deep-Cycle-Marine-Batteries More useful information on deep cycle marine batteries What is a Load Calculation Table? A Load Calculation Table is used to list and carry out calculations. To calculate the total boat electrical system loading, multiply the total current values by the number of operating hours to get the amp-hour rating. If equipment uses a current of 1 amp over 8 hour period, then it consumes 8 Amp-hours (Ah). The table shows many typical power consumptions. There is space for insertion and calculation of your own boat electrical load current data.
How should intermittent loads be calculated? On small boats there are few loads that come on and off periodically such as water pumps, using battery power for short periods. It is difficult to quantify actual real current demands with intermittent loads. I use a baseline of 6 minutes per hour, which is 0.1 of an hour. A water pump can be classified as an intermittent load. All About Deep-Cycle-Marine-Batteries How to perform a Load Calculation. All equipment on the boat must be listed along with the power consumption ratings into a worksheet or table. Ratings are found on the equipment nameplates and in equipment manuals. Insert your own values into the Current column, typical values are in brackets. To convert power in watts, to the current in amps, divide the power value by the system voltage. Add up all the current figures relevant to your boat and multiply by hours to determine the average amp-hour consumption rate. Most equipment will be on when drifting and fishing. Depending on the frequency between charging periods select the column that suits your boat activity. Can all the battery capacity be used? Nominally it can, however in practise this is rarely possible. For example if our calculation comes to 10 amps for 6 hours we have a requirement for 60 Ah. For a deep cycle battery the discharge capacity should be kept at 50% of nominal battery capacity to maximize life, so we double the required rating to 120 Ah. In an ideal world, this would be a minimum requirement, but certain frightening realities must now be introduced into the equation. Factors can vary by 10 – 30%. Lost capacity is where an older battery no longer has full capacity availability, and the percentage increases with age. In many cases the battery is not fully charged and this also decreases capacity: Nominal Battery Capacity = 120 Ah Max Cycling Level (50%) Deduct 60 Ah Lost Capacity (10%) Deduct 12 Ah Actual Charge Level (90%) Deduct 10% = 12 Ah Available Battery Capacity = 36 Ah What is battery load matching? The nominal required battery capacity of 120 Ah has been calculated as that required to supply 10 amps per hour over 6 hours to 50% of battery capacity. What is required is a battery bank with similar discharge rates as the boats electrical current consumption rate. This will maximise the capacity of the battery bank. All About Deep-Cycle-Marine-Batteries B What happens if the battery is discharged faster than the nominal rate? OAT BATTERIES The faster a battery is discharged over the nominal rating, which is either the 10 or 20 hour rate, the less the real amp-hour capacity the battery has. This effect is defined by Peukerts Equation, which has a logarithmic characteristic. This equation is based on the high and low discharge rates and discharge times for each to derive the Peukert coefficient 'n'. Average values are around 1.10 to 1.20. If we discharge a 250 amp-hour battery bank, which has nominal battery discharge rates for each identical battery of 12 amps per hour at a rate of 16 amps, we will actually have approximately 10-15% less capacity. Smart battery discharge meters such as the E-Meter incorporate this coefficient into the monitoring and calculation process. What happens when the battery is slowly discharged? The slower the battery is discharged over the nominal rate the greater the real battery capacity. If we discharge our 240 amp-hour battery bank at 6 amps per hour we will actually have approximately 10-15% more capacity. The disadvantage here is that slowly discharged batteries are harder to charge if deep cycled below 50%. Does a deep cycle suffer from memory effect? These batteries do not suffer memory effect and the practice of running them right down and then recharging actually shortens the life of the battery. Keep discharge to a maximum of 50%. All About Deep-Cycle-Marine-Batteries What is internal impedance or resistance? The battery internal circuit has resistance or impedance. This includes the plates, the electrolyte, internal connections etc. This affects both the rate of discharge and rate of charge possible. The lower the impedance the greater the charge and discharge rates and the less heat generated and power lost. AllAbout Deep-Cycle-Marine-Batteries
Click on this link to find out more about Yachting and Sailboats All About Marine Batteries and all you need to know. All about the deep-cycle-marine-batteries and more |