Deep-discharge lead-acid type batteries, when properly used and maintained, can last 150-600 charge-discharge cycles. Most often they are used on boats and boats to power pumps, electric motors, winches, echo sounders and other marine equipment.
Deep cycle battery design
Twelve-volt deep-cycle batteries for outboard motors consist of six cells, each with a voltage of 2.1 volts. Serial connection of cells is carried out by connecting the positive terminal to the negative. The positive and negative cell plates are separated by thin sheets of electrically insulating material which prevents short circuits. The plates are arranged in a cell in alternating order.
The plates themselves arefrom a metal mesh acting as a supporting frame for a porous active material pressed into it.
The plates are placed in the cells only after hardening. The body of deep-discharge batteries is made of high-strength polypropylene material. The cells placed in the housing are connected to the terminals, after which the housing is closed with a lid and the electrolyte is poured.
Deep discharge battery test
Battery performance is checked in several ways:
- Visual inspection.
- Charging.
- Removal of surface charge.
- Electrolyte density measurement.
- Check under load and recharge.
The density of the electrolyte is checked using a hydrometer, which is most often used for non-sealed batteries. A load tester is used for daily use of the battery.
The battery is inspected for obvious defects - bulging or corroded cables, low electrolyte levels, fouled cover, corroded or loose terminal clamps, damaged or leaking case.
The low electrolyte level is raised to the required level by topping up with distilled water. The plates should always be under the electrolyte layer, but overflow should be avoided.
The 100Ah deep cycle battery is charged to full capacity. If there is a difference between the cells, charging is carried out at an increasedvoltage.
As a result of charge or discharge, a surface charge is formed near the surface of the plate, which is an uneven mixture of water and sulfuric acid. Eliminate the surface charge in one of the following ways:
- The battery is left for four to twelve hours to remove the surface charge.
- A load equal to 30% of the battery capacity is connected for five minutes, after which it waits for five to ten minutes.
- Battery load is set to half CCA battery for 15 seconds.
Changing the charge level
The charge level of the battery is determined at the density of the electrolyte of a fully charged lead-acid or deep-cycle lithium battery of 1, 265. Voltage and density at other electrolyte temperatures are determined using special temperature compensation tables. Gel and AGM batteries have a different voltage than wet batteries.
Using a hydrometer, density is checked in each cell of non-sealed batteries, after which an average is displayed. For sealed batteries, the terminal voltage is measured with a digital voltmeter.
Deka deep-cycle batteries, for example, are equipped with a built-in hydrometer that measures the voltage level in one of the cells. The minimum electrolyte level is indicated by a transparent or light yellow indicator. Recharging the battery is carried out if the levelbattery drops below 75%.
Battery replacement is required in the following cases:
- The difference between the density in the cells exceeds 0.5, which indicates damage or discharge of one of them. This can only be fixed by equalizing charging.
- The built-in hydrometer does not work or the battery charge does not rise above 75%.
- Digital voltmeter shows zero voltage and damaged cells.
- One of the cells had a short circuit or the battery was completely discharged.
Load test
The capacity of a fully charged deep cycle battery is measured by connecting a specific load and measuring the time it takes for the battery to charge up to 20%. In most cases, a load is used that allows the battery to be discharged for 20 hours.
Deep-cycle traction batteries with liquid electrolyte reach their nominal capacity only after 50-100 charge/discharge cycles. The operating capacity of gel and AGM analogues is achieved in less than 10 cycles.
Selection of batteries
When choosing deep-cycle batteries for phones, boats or other equipment, you need to pay attention to several basic parameters that affect battery life.
Capacity and reserve capacity
Characteristics that provide maximum information about the battery and determine the weight and battery life. Checking the batteries fordischarge is carried out by manufacturers within 100, 20 or 8 hours. The internal resistance of the battery and the Peukert effect affect the battery capacity: the higher the discharge current, the lower it is.
Reserve capacity refers to the time during which a fully charged battery is discharged to a terminal voltage of 10.5 volts at a temperature of 26.7 degrees and a current of 25 amps.
The higher the capacity and reserve capacity, the longer the life of the battery and the higher its weight due to the increased thickness of the lead plates.
To increase the capacity, several 12-volt batteries of the same capacity and type are connected in parallel. Connecting batteries of different ages and types may result in one of them being either overcharged or not charged.
When properly connected, deep cycle batteries charge and discharge the same way. For connection, short thick cables are used to avoid surges and voltage drops - it should be 200 millivolts, no more.
Variety
During the first 5-15 seconds, the starter battery generates a current of 500 to 1000 amps to start the engine, which leads to its discharge of no more than 5% of its capacity. The starter battery can withstand from 50 to 80 charge-discharge cycles, which is enough for 80,000 engine starts.
Marine deep cycle batteries work a little differently and are designed to discharge 5-50 amps forlong time. Can withstand many hours of discharge and discharge to 80% capacity.
Deep cycle batteries for outboard motors are mostly dual-use and represent a compromise between starter models and deep cycle batteries. They have a high starting current and work more cycles than starter batteries. AGM batteries are considered the best dual-use models.
Deep-cycle wet batteries are divided into two categories - serviced and low-maintenance. The plates of the former are made of an alloy of lead and antimony, the plates of the latter are made of a lead-calcium alloy. Low-maintenance batteries do not require the regular addition of distilled water, unlike serviced ones. The frequency of topping up depends on the operating conditions, but it is advisable to check the electrolyte level once every two weeks.
VRLA, or sealed, batteries are divided into two types - AGM and gel. They do not require maintenance during the entire operational life.
AGM batteries
- The space between the plates is filled with a porous material impregnated with an electrolyte, not a liquid electrolyte.
- Long working life and deep discharge are provided by thick plates.
- Can be used to power devices that have high power consumption and require high current.
- Reliable.
- More efficient operation is possible at low temperatures.
- Stand averagecharge-discharge cycles.
GEL deep cycle batteries
- The plates are filled with a jelly-like electrolyte resembling a gel in consistency.
- Maintenance and water-free.
- When working with highly loaded devices, they can withstand a large number of discharge / charge cycles. They work effectively in conditions that require a deeper discharge than AGM batteries can provide. Differ in constant productivity throughout the entire operational period.
- High reliability.
- Work more efficiently when the ambient temperature is high.
There is no loss of water in both types of VRLA batteries due to the recovery of the electrolyte from oxygen and hydrogen during the charging process. In the event of a short circuit or overcharging, a slight gas leak may occur due to the internal pressure of the battery.
VRLA type deep-cycle batteries are charged according to a special mode that limits the charge voltage to avoid electrolyte drying out and overcharging.
Production date
You should not buy batteries with liquid electrolyte that were released more than three months ago: if it has not been charged during this time, its capacity decreases and the plates begin to sulfate.
