Implementation and robustness of an analytically based battery state of power

Today it is common practice to use simplified equivalent circuit models for predicting the short term behaviour of the voltage and current during charging and discharging battery cells. If the circuit parameters are assumed to be unchanged the response for a given open circuit voltage (OCV) will be the solution to a linear ordinary differential equation. This means that for given voltage limits the maximum charge and discharge powers can be analytically derived. In advanced battery management units, such as those used for hybrid electric vehicles, it is central to know how much that can be charged or discharged within a certain range of time, which is one definition of state of power (SoP). Using the linearizing assumption we derive a method for an adaptive estimation of the state of power based on incremental analysis. The method is easy to implement and have two tuning parameters that are straightforward to relate to. Using frequency analysis the method is analytically proven to have very strong robustness properties. The risk of exceeding voltage limits by effectively applying the maximum charge or discharge currents is marginal in spite of large circuit parameter errors, unmodelled hysteresis, unknown OCV and static nonlinearities

Estimating power capability of aged lithium-ion batteries in presence of communication delays

Efficient control of electrified powertrains requires accurate estimation of the power capability of the battery for the next few seconds into the future. When implemented in a vehicle, the power estimation is part of a control loop that may contain several networked controllers which introduces time delays that may jeopardize stability. In this article, we present and evaluate an adaptive power estimation method that robustly can handle uncertain health status and time delays. A theoretical analysis shows that stability of the closed loop system can be lost if the resistance of the model is under-estimated. Stability can, however, be restored by filtering the estimated power at the expense of slightly reduced bandwidth of the signal. The adaptive algorithm is experimentally validated in lab tests using an aged lithium-ion cell subject to a high power load profile in temperatures from −20 to +25 \ub0C. The upper voltage limit was set to 4.15 V and the lower voltage limit to 2.6 V, where significant non-linearities are occurring and the validity of the model is limited. After an initial transient when the model parameters are adapted, the prediction accuracy is within \ub12% of the actually available power

Telomerase activity is required for the telomere G-overhang structure in Trypanosoma brucei

Abstract Trypanosoma brucei causes fatal human African trypanosomiasis and evades the host immune response by regularly switching its major surface antigen, VSG, which is expressed exclusively from subtelomeric loci. Telomere length and telomere proteins play important roles in regulating VSG silencing and switching. T. brucei telomerase plays a key role in maintaining telomere length, and T. brucei telomeres terminate in a single-stranded 3′ G-rich overhang. Understanding the detailed structure of the telomere G-overhang and its maintenance will contribute greatly to better understanding telomere maintenance mechanisms. Using an optimized adaptor ligation assay, we found that most T. brucei telomere G-overhangs end in 5′ TTAGGG 3′, while a small portion of G-overhangs end in 5′ TAGGGT 3′. Additionally, the protein and the RNA components of the telomerase (TbTERT and TbTR) and TbKu are required for telomere G-overhangs that end in 5′ TTAGGG 3′ but do not significantly affect the 5′ TAGGGT 3′-ending overhangs, indicating that telomerase-mediated telomere synthesis is important for the telomere G-overhang structure. Furthermore, using telomere oligo ligation-mediated PCR, we showed for the first time that the T. brucei telomere 5′ end sequence – an important feature of the telomere terminal structure – is not random but preferentially 5′ CCTAAC 3′