Lead-acid deep-discharge batteries with proper operation and maintenance 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 Discharge Battery Design
Deep-discharge twelve-volt batteries for outboard motors consist of six cells, each of which has a voltage of 2.1 volts. Serial connection of the cells is carried out by connecting the positive output to the negative. The positive and negative plates of the cells are separated by thin sheets of electrical insulating material, which prevents a short circuit. The plates are arranged in a cell in alternating order.
The plates themselves consist of a metal mesh that acts as a supporting frame for the porous active material pressed into it.
The plates are placed in the cells only after hardening. The case of deep-discharge batteries is made of polypropylene high-strength material. The cells placed in the housing are connected to the terminals, after which the housing is closed by a lid and the electrolyte is filled.
Deep Battery Test
Battery performance is checked in several ways:
- Visual inspection
- Charging.
- Surface charge removal.
- Electrolyte density measurement.
- Check under load and recharge.
The electrolyte density is checked using a hydrometer, which is most often used for non-sealed batteries. For daily battery use, a load tester is used.
The battery is inspected for obvious defects - cable swelling or corrosion, lowering the electrolyte level, clogging of the cover, corrosion or lowering of the terminal clamp density, damage or leakage of the housing.
A low electrolyte level rises to the required level by adding distilled water. The plates should always be under the electrolyte layer, but overflow must be avoided.
A 100 Ah deep-discharge battery charges to its full capacity. If there is a difference between the cells, charging is carried out at an increased voltage.
As a result of a charge or discharge, a surface charge is formed at the plate surface, which is an uneven mixture of water and sulfuric acid. Eliminate surface charge in one of the following ways:
- The battery is left for four to twelve hours to remove surface charge.
- For five minutes, a load equal to 30% of the battery capacity is connected, after which it waits five to ten minutes.
- The battery load is set at half the CCA battery for 15 seconds.
Charge level change
The battery charge level is determined when the electrolyte density of a fully charged lead-acid or lithium deep-discharge battery is 1.265. Voltage and density at other electrolyte temperatures are determined using special temperature compensation tables. Gel and AGM batteries have a voltage different from liquid electrolyte batteries.
Using a hydrometer in each cell of unsealed batteries, the density is checked, after which the average value is displayed. In the case of sealed batteries, the voltage at the terminals is measured with a digital voltmeter.
Deka deep-discharge batteries, for example, are equipped with a built-in hydrometer, which measures the voltage level in one of the cells. The minimum electrolyte level is indicated by a transparent or light yellow indicator. The battery is recharged if the charge level 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 corrected by leveling exercises.
- The built-in hydrometer does not work or the battery charge does not rise above 75%.
- Digital voltmeter shows zero voltage and damaged cells.
- A short circuit has occurred in one of the cells or the battery has been completely discharged.
Load test
The capacity of a fully charged deep-discharge 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 you to discharge the battery for 20 hours.
Deep traction batteries with liquid electrolyte reach their rated capacity only after 50-100 charge / discharge cycles. The working capacity of gel and AGM analogues is achieved in less than 10 cycles.
Battery Choice
When choosing deep-discharge batteries for a telephone, boat, or other equipment, it is necessary to pay attention to several basic parameters, on which the battery life depends.
Capacity and reserve capacity
Features that provide maximum information about the battery and determine the weight and battery life. Checking the batteries for discharge is carried out by manufacturers within 100, 20 or 8 hours. The internal resistance of the battery and the Pakert effect affect the battery capacity: the higher the discharge current, the lower it is.
By reserve capacity is meant 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 amperes.
The higher the capacity and the reserve capacity, the greater the service 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 cause one of them to either be recharged or not charged.
When properly connected, deep-discharge batteries charge and discharge equally. For connection, short cables of large thickness are used to avoid surges and voltage drops - it should be 200 millivolts, not more.
Variety
During the first 5-15 seconds, the starting battery generates a current of 500 to 1000 amperes to start the engine, which leads to its discharge not more than 5% of capacity. The starter battery can withstand 50 to 80 discharge-charge cycles, which is enough for 80 thousand engine starts.
Marine models of deep-discharge batteries work somewhat differently and are designed to discharge with a current of 5-50 amperes for a long time. They can withstand hours of discharge and discharge up to 80% of capacity.
Deep discharge batteries for outboard motors are in most cases dual-use and represent a compromise between starting models and deep-discharge batteries. They are distinguished by a high starting current and operate a larger number of cycles, unlike starting batteries. The best dual-use models are considered AGM batteries.
Deep discharge batteries with liquid electrolyte are divided into two categories - serviced and low-maintenance. The plates of the first are made of an alloy of lead and antimony, the plates of the second are made of lead-calcium alloy. Low-maintenance batteries do not require regular addition of distilled water, unlike service batteries. The frequency of adding water depends on the operating conditions, but it is advisable to check the electrolyte level every two weeks.
VRLA, or sealed, batteries are divided into two types - AGM and gel. They do not require maintenance during the entire operational period.
AGM batteries
- The free 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 plates of large thickness.
- They can be used to power devices with high power consumption and requiring high current strength.
- Reliable.
- More efficient operation is possible at low temperatures.
- Withstand the average number of charge-discharge cycles.
Deep Discharge Gel Batteries
- The plates are filled with a jelly-like electrolyte resembling a gel in consistency.
- Do not require maintenance and topping up water.
- When working with highly loaded devices capable of withstanding a large number of discharge / charge cycles. Effectively operate in conditions requiring a deeper discharge than AGM batteries can provide. They are characterized by constant performance throughout the entire operational period.
- High reliability.
- More efficient operation is ensured at high ambient temperatures.
Water loss in both types of VRLA batteries does not occur due to the reduction of the electrolyte from oxygen and hydrogen during charging. In the event of a short circuit or overcharging, a slight gas leak may occur due to the pressure inside the battery.
VRLA type deep-discharge batteries are charged in accordance with a special mode in which the charge voltage is limited, taking into account the avoidance of electrolyte drying and overcharging.
date of manufacture
Acquiring batteries with liquid electrolyte, released more than three months ago, is not worth it: if during this time it has not been charged, its capacity decreases and sulfation of the plates begins.