This is important to limit the voltage that is provided to the battery as a whole and keeping the individual series connected cells to a maximum of 3.65V. LiFePO4 chargers in pretty much all the major and reputable brands will limit the charge voltage to 14.6V. Even at 25% state of charge it will still be at approx 12.8V whereas a lead acid battery at 25% state of charge is around 11.7V with a range of over 1.1V. LiFePO4 batteries operate in a very narrow voltage range with only 0.5V from full all the way down to 20% state of charge. A lead acid battery typically will be fully charged at rest at 12.6-12.8V where as a LiFePO4 battery will be 13.3-13.4V. There is a lot more to it than just outline above, but it does get into a very technical discussion which is outline below if you want more info.įirstly it's important to understand the voltage range that each battery type operates in. No matter what they say in their marketing (which is really all it is - a made up marketing spiel) about their supposedly magic batteries that you can use any charger on, it is just totally wrong and demonstrates a total lack of understanding of LiFePO4 chemistry, the narrow voltage range that it operates in and the effects of using a multi-stage Lead acid charger to charge LiFePO4 cells. For those that do, you then get an on/off/on/off scenario for many hours leading to poor charge performance and sometimes never getting out of those stages for many hours. For those that don't, the battery is open circuit and turned off till you realised and take action to reset it. When these stages kick in, they will cause pretty much every good quality LiFePO4 battery on the market with an internal BMS to go into high voltage disconnect protection mode at around 15.0V - the battery goes open circuit and the charger and all loads disconnect before starting all over again once it resets (if it auto resets - not all BMS will do this automatically). Many lead acid chargers have equalization as an automatic stage that cannot be turned off. It can heavily reduce the life of the cells due to regular over voltage charging or cause irreversible damage to the battery. This is really important to correctly charge and to maintain lead acid batteries, to avoid stratification of the electrolyte and ensure proper voltage equalisation of the cells, but are definitely not suitable for LiFePO4 batteries. Many lead acid chargers have desulphation and equalisation stages built in, which will pulse high voltages of 15.3-15.8V into the battery. The battery impedance characteristics were also examined by using non-destructive techniques, such as electrochemical impedance spectroscopy, and it was determined that the ambient temperature at which the battery was charged had the most effect on the battery impedance parameters.Lithium batteries require a Constant current/Constant voltage (CC/CV) charge type with simple Bulk, Absorption, Float stages. It is also determined that the duty cycle of the pulse charge current has the most impact on the cycle life of the battery. The results are compared with the benchmark constant current-constant voltage (CC-CV) charging algorithm and it is observed that by using a pulse charger at optimal parameters, the cycle life of a LiPo battery can be increased by as much as 100 cycles. This paper seeks to evaluate the impact of pulse charge current factors, such as frequency and duty cycle, on the life cycle and impedance parameters of lithium-ion polymer batteries (LiPo) while using a design of experiments approach, Taguchi orthogonal arrays. The impact of pulse charge current factors on the life cycle and battery characteristics are seldom investigated. However, to get the benefits of pulse charging, the pulse charge current parameters have to be chosen carefully to ensure optimal battery performance and also extend the life cycle of the battery. The pulse charging algorithm is seen as a promising battery charging technique to satisfy the needs of electronic device consumers to have fast charging and increased battery charge and energy efficiencies.
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