The paper describe design of battery powered drive unit intended for tree harvester application. Battery powered hybrid drive unit in working machine is currently quite common (1). The battery capacitance is not sufficient to realize harvester as an only battery powered machine. Nevertheless, the hybrid concept of electric drive is useful to cover short power peaks demands during the harvester standard operation. In harvester application there is typical high ratio between short power peak and average demanded power. The development in batteries increases of significance and possibility of electric drive utilization in three harvesters.
This paper deals with a measurement of alkaline and Li-ion battery impedances in wide-range frequency from about one Hz to a few hundred kHz. Measured battery admittances are used for the construction of battery transfer functions, i.e., the dependences of admittance on frequency. Comparison of transfer functions for different battery types is shown. It is shown that transfer functions for both types have the same form and this transfer function is only the third-order.
The main objective of this article is determination of the charging and discharging efficiency of the Li-ion battery depending on the value of the charging and discharging current. An automated workplace allows us to measure the capacity of cells, temperature and other parameters required for assessing the performance of batteries. A dependence of the energy storage efficiency on the charging and discharging current was found out. Consequently this measured dependence was approximated with an analytical expression. The obtained analytical result can be used e.g. in predictive models of EVs action radius etc.
This paper is focused on a design of a high-voltage (HV) generator, which is proposed for a high-frequency irreversible electroporation (H-FIRE). The generator produces bursts of bipolar symmetrical pulses. Most HV sources used for cell electroporation are based on a controlled discharge of a capacitor into a resistive load. This solution is very simple, but it is associated with a certain risk of an uncontrolled discharge of the capacitor. We present a different type of the generator, where a DC-AC inverter with pulse transformer is used and where the mentioned risk is eliminated. Our generator is able to deliver bursts with variable length from 50 to 150 μs and a gap between bursts can be set from 0.5 to 1.5 s. Pulse frequency can be varied from 65 to 470 kHz and the output voltage is controlled in two ranges from 0 to 1.3 kV or from 0 to 2.5 kV. Results are presented with resistive load and with tissue impedance load.
Deep discharging or over-charging of Li-ion cells must be avoided to ensure sufficient life-time and sometimes also the operation safety of these batteries. BMS circuits co-operating with the charger and forbidding deep discharging of the cells are necessarily present in battery packs. However, deep discharging can appear in a case of BMS failure or poor user care of the batteries. Then the battery can be discharged to zero voltage. Battery manufacturers do not allow such operation and battery behavior in this situation is not described in their datasheets. Experimental deep discharging was performed. After discharging, the battery was left in a fully discharged state (zero voltage) for various time intervals before it was fully recharged again. Consequently, capacity decrease or internal resistance increase was checked.
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