A few words about lithium battery technology.
Lithium batteries appeared in common use in the 90s, that is over 100 years after lead-acid batteries. Initially, SONY used them in its portable equipment. They became popular quite quickly and today they are widely used in consumer electronics such as tablets, telephones, laptops, cameras, toys, etc. Today this technology is constantly developed and practically functioning without Lithium batteries is impossible. There are many types of lithium batteries, including: Li-ion, Li-poly, LiFePo4, LTO, etc.
Each of the above-mentioned batteries has its own advantages and disadvantages. The two important issues are:
Protection of cells / batteries against extreme situations - complete discharge, overcharging, short circuit. It is the basis of every Lithium battery. For this purpose, a protection system - BMS is used. Its task is to control the operation of the battery. It controls the voltage at individual cells of the battery, balances the cells to equal voltages, cuts the power supply in the event of too low / high voltage and short circuit. Thus, it makes the operation of the battery safe and maintains the battery parameters in the normal range.
Charging the battery - it is absolutely necessary to use chargers for a given type of battery, or charging regulators! You cannot use a regular car rectifier, alternator or charging from outboard engines for this purpose. It is caused by the charging process and different voltages of lithium cells. For example, a single LiFePo4 cell is charged to a voltage of 3.7V max, and the minimum value of work is 2.0V. For Li-ion, these values are 4.2V max and discharges to 2.75V.
Li-ion / Lipoly - the highest energy density W / kg, light, high discharge currents up to 30 times the capacity, high operating voltage of a single cell -3.7V.
Disadvantages: very unstable at critical moments. This means they can catch fire, explode when reloaded, discharged below the acceptable level, or mechanically damaged. The number of charge / discharge cycles is about 500. Up to this value, the cells maintain their capacity at a level not lower than 80% of the rated capacity.
LiFePO4 - (lithium iron phosphate battery)
The most stable type of Lithium battery, does not burn, does not explode. Number of charge / discharge cycles not less than 2000 !, service life 10 years. High energy density - but lower than in Li-ion W / kg. Discharge currents from 1C-10C (depending on the type of cells). They are more than half lighter than lead-acid batteries. 100Ah / 12V weighs about 12.5 kg. They have no memory effect - they can be easily recharged. Contrary to acid batteries, LiFePo4 does not experience a decrease in capacity with the load current. They can work in any position. Not all manufacturers indicate the battery capacity in relation to the load in the battery catalog cards.
LiFePo4 vs Liion 12V and electronics
Many sellers mislead customers by offering Li-ion 12V batteries as a replacement for acid or LiFePO4 batteries. Unfortunately, this solution is not very good. This is due to the usable operating voltage range of the Li-lion 3S (12V) battery. Such a package works in the range of 9-11.5V. During operation, the stable voltage will oscillate between 10.0-11V. When using electronics such as fishfinders, motors, etc., the operating voltage is 10.5-13V. Therefore, the 3S Li-ion package, after a slight discharge, will have a voltage below 11V (at 60-75% charge) and thus will prevent the devices from working! By adding another cell and creating a 4S - 14.4V package, the operating voltage may turn out to be too high for most devices. This situation ceases to occur for higher voltages 24/36 / 48V.
The principle of specifying the magic number C20 is generally accepted and used. In short, it means that a given battery is able to give back all the stored energy within 20 hours. This is where the problems begin, for example:
The Trojan Pb 12V / 100Ah battery, weight 31 kg (see the table below with the manufacturer's data), will give away the entire 102AH within 20H, in five hours only 85AH. Shorter times, e.g. 1 or 2 hours, were not specified. However, looking at the manufacturer's specifications, it will probably be around 60-70 Ah. Thus, at high currents, we lose even 1/3 of the capacity! It is worth noting that the battery taken as an example is a well-known and appreciated company. Where components and workmanship are at a very high level.
Another issue is the operation and purpose of the battery. First of all, batteries for high current, deep discharge operation - traction batteries are EXPENSIVE! Very often the price of such a 100Ah / 12V battery oscillates between PLN 1000-2000. Cheaper batteries are usually traction only in name ...
A brief comparison of acid batteries and LiFePo4
Weight: 12V / 100Ah Lifepo4 - 12.5kg vs acidic 12V / 100Ah 31kg
Capacity: LiFePo4 12V / 100Ah C1 - 100AH vs acidic around 60-70AH
Working position: LiFePo4 - any vs acid (defined working position)
Service life: LiFePo4 not less than 2000 COD vs acidic 800
Protection: LiFePo4 - BMS vs acid - NONE
Charging the battery - use chargers for a given type of battery, or charge regulators when working with a photovoltaic installation!
When you try to charge with rectifier / chargers / regulators that do not support LiFePO4 batteries, we will not recharge the battery to 100%, or the electronics inside (BMS) will disconnect the battery.
This is due to the charging process and different voltages of lithium cells / packages. For example, a single LiFePO4 cell is charged to a voltage of 3.7V max, and the minimum value of work is 2.0V. For Li-ion, these values are 4.2V max and we discharge to 2.75V.
The final charging voltage for a LiFePO4 battery in 4S configuration (12.8V) must be 14.6V. Meeting this condition and limiting the current in the last phase of charging ensures charging to 100% capacity.
OUR BATTERIES Lithium - LiFePo4:
We are an official importer and distributor of LiFePo4 batteries. All batteries we sell have:
Data sheets and instructions for use
BMS protections - protect against discharge, overcharging, short circuit
Each battery has a dedicated LiFePo4 CC / CV - 10A / 15A / 20A automatic charger (it is also possible to purchase a battery without a charger)
Hermetic enclosures with a voltmeter, and in some models also with a USB port
Intended for both traction and buffer work
Batteries are covered by a 24-month warranty for private users and a 12-month warranty for companies
Before sale, each piece is checked on high-quality measuring equipment