DE29620628U1 - Self-learning device for determining the state of charge of accumulators - Google Patents

Description

Utility model application: Self-learning'Vo'fricftturtg for
Determination of the charge level of batteries

Applicant: Helix Solarelektronik GmbH
Description Page 1
general description

The invention is a device with the help of which the charge level of accumulators (in particular lead accumulators) can be determined. The prerequisite for successful use of the device is that the charge level of the accumulator can be derived from its voltage in the idle state. The device is able to adapt itself automatically to the accumulator.

Technical description (see also Fig.l)

For many accumulators (particularly lead accumulators), the charge level of the accumulator can be determined precisely by determining the voltage in the rest state (Uo). However, this is no longer possible as soon as the accumulator is charged or discharged. When charging or discharging, a voltage drops across the internal resistance of the accumulator, so that only the rest voltage (terminal voltage Uk) distorted by this voltage drop can be measured at the accumulator terminals. By using an appropriate characteristic model, conclusions can be drawn about the rest voltage and the charge level. The characteristic model can also take non-linearities of the internal resistance into account. The acid concentration gradient between the inside of the accumulator plate and the acid surrounding the plate can be seen as a component of the internal resistance. Since the build-up of this acid concentration gradient takes some time, the characteristic model must include an appropriate time delay in order to avoid high errors in dynamic operation.

However, such a characteristic model has the disadvantage that the internal resistance underlying the model (including its non-linearities) depends on the battery capacity, the design of the battery and the age of the battery. Therefore, the characteristic model described here has been supplemented by a calibration device that makes it possible to adapt the internal resistance (including all non-linearities) underlying the characteristic model to the actual internal battery resistance.

Utility model application: Self-learning device for
Determination of the charge level of batteries

Applicant: Helix Solarelektronik GmbH

Description Page 2

Continuation of technical description

The calibration device includes a calibration detection. As already described, the rest voltage can be used to determine exactly what state of charge the battery has. Since the rest voltage at the terminals only appears with sufficient accuracy after a waiting period (since the falsifying acid concentration gradient only decreases over time), a rest detection is required which starts a timer. If the rest state exceeds the timer's own waiting period, calibration is released. If the rest state is interrupted before the waiting period has elapsed, the timer is reset. The rest detection not only ensures that the timer starts, but also freezes the current display value that was determined by the characteristic model. This is logically justified by the fact that the state of charge should not actually change in the rest state (self-discharge is neglected in this case, since the rest state occurs in a few hours, while self-discharge leads to a significant change at most within a week).

As soon as the calibration process is released, the charge level is determined based on the battery terminal voltage. This newly determined charge level is compared with the previously frozen charge level. If the comparison results in an error, this information is used to adjust the internal resistance in the characteristic model accordingly.

As an alternative to the rest voltage, the full charge state (calibration criterion: high voltage despite low charging current) or the state of complete discharge (calibration criterion: low voltage despite low discharging current) can also be used as a calibration criterion. However, this is only possible if the time delay following the characteristic curve model corresponds approximately (slightly less than or equal to) the actual time behavior of the charge state. In this case, the calibration detection does not require a timer.

Utility model application: Self-learning device for
Determination of the charge level of batteries

Applicant: Helix Solarelektronik GmbH
Description Page 3
Advantages of the invention

The device described has the advantage that a relatively precise determination of the charge level of the accumulator is possible without this device having to be adapted to the accumulator actually used. Even with age, the use of this device leads to an automatic adaptation to the accumulator and thus avoids major display errors.

Application of the invention

The device described can be used as a component of protective devices against overcharging and deep discharging of batteries. It can also be used as a display instrument.

Claims (3)

Utility model application: Self-learning device for determining the charge level of accumulators Applicant: Helix Solarelektronik GmbH Claims Page 1 Claims 1. Device for determining the state of charge of accumulators, characterized by that a calibration detection is used to correct the characteristic model, which identifies the battery voltage as the rest voltage using a timer. 2. Device according to claim 1, characterized in that that a calibration device is used to correct the characteristic curve model, which detects the full charge state by means of high voltage and simultaneously low charging current. 3. Device according to claim 1, characterized in that that a calibration device is used to correct the characteristic model, which detects complete discharge by means of low voltage and simultaneously low discharge current.