CN205450222U - Test circuit of DC internal resistance - Google Patents

Abstract

The utility model discloses a test circuit for direct current internal resistance. The test circuit includes a voltage acquisition circuit, a battery pack, a current regulation circuit, a total positive relay and a total negative relay; Voltage, the total positive relay and the total negative relay are respectively connected to the two ends of the battery pack, the current regulation circuit is connected in parallel with the battery pack, and the current regulation circuit is connected between the total positive relay and the total negative relay. The discharge rate of the utility model can be controlled by controlling the number of resistors connected to the discharge circuit to control the size of the discharge rate. In addition, the circuit of the utility model does not need external charging piles and other equipment, and the BMS itself can accomplish.

Description

A test circuit for DC internal resistance

technical field

The utility model relates to the technical field of electric vehicles, in particular to a test circuit for direct current internal resistance.

Background technique

The power battery pack of an electric vehicle is composed of hundreds of strings of lithium-ion cells. The consistency between lithium-ion cells is crucial to the performance and life of an electric vehicle. The existing battery management system can sample the battery cell voltage, but cannot control the discharge current of the battery, so there is no standard reference for the calculated internal resistance. There are mainly two methods for measuring the internal resistance of electric vehicles:

The first is the DC discharge internal resistance measurement method, which has the advantage of high measurement accuracy, which can reach 0.1% if it is properly controlled. But its disadvantages are (1) only large-capacity batteries can be measured, and small-capacity batteries cannot provide 40-80A current within 3s; (2) large currents passing through the battery will damage the electrodes and shorten the battery life. It violates the original intention of measurement; (3) The measurement equipment is expensive and bulky.

The second is the AC excitation method, and its advantages are (1) it can measure all batteries, including small-capacity batteries; (2) the measurement process will not cause damage to the battery; (3) it is relatively low in cost and small in size. But its disadvantages are (1) the accuracy is lower than that of the DC method, but it can meet the application requirements; (2) the measurement accuracy of the AC method is likely to be affected by ripple current and harmonic current interference, which requires high anti-interference ability of the instrument circuit; ( 3) It is necessary to introduce an external AC excitation source, which increases the complexity and cost of the circuit.

Utility model content

The purpose of the utility model is to overcome the above-mentioned defects in the prior art, and provide a test circuit for DC internal resistance, which realizes controllable discharge rate and does not require external charging piles and other equipment.

In order to achieve the above object, the technical scheme provided by the utility model is as follows:

The utility model provides a test circuit for DC internal resistance, which comprises a voltage acquisition circuit, a battery pack, a current regulation circuit, a total positive relay and a total negative relay; Voltage, the total positive relay and the total negative relay are respectively connected to the two ends of the battery pack, the current regulation circuit is connected in parallel with the battery pack, and the current regulation circuit is connected between the total positive relay and the total negative relay.

As a preferred technical solution, the battery pack is composed of m _p single cells forming parallel branches, and then m _s parallel branches are connected in series, wherein m _p and m _s are both integers not less than 1.

As a preferred technical solution, the current regulating circuit includes multiple groups of resistor selection circuits connected in parallel, and the resistor selection circuit includes resistors and switches connected in series. When the switch is closed, the resistors connected in series with the switch are connected to the discharge circuit.

As a preferred technical solution, the resistor is a high-power aluminum shell resistor.

As a preferred technical solution, the voltage acquisition circuit is composed of a dedicated lithium-ion battery multi-string sampling chip, which samples the voltage value of the battery in real time.

Compared with the prior art, the utility model has the beneficial effects of:

1. The discharge rate of the utility model can be controlled by controlling the number of resistors connected to the discharge circuit to control the size of the discharge rate. In addition, the circuit of the utility model does not require external charging piles and other equipment. That can be achieved.

2. The resistance of the utility model has low cost, simple control method, and is easy to implement. High-power aluminum shell resistors can be selected (of course, other types of resistors also meet the technical solution of the utility model) to realize the test of DC internal resistance.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present utility model. Those skilled in the art can also obtain other drawings based on these drawings without any creative work.

Fig. 1 is a schematic circuit diagram of a test circuit for DC internal resistance provided by an embodiment of the present invention.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the utility model more clear, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the utility model. Obviously, the described The embodiments are some embodiments of the present utility model, but not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Example

The embodiment of the present utility model provides the test circuit of DC internal resistance, and Fig. 1 is the schematic diagram of the circuit of the embodiment of the present utility model, please refer to Fig. 1, the circuit of the embodiment of the present utility model comprises a voltage acquisition circuit, a battery pack, Current regulating circuit, total positive relay and total negative relay; the voltage acquisition circuit is connected with the battery pack to collect the voltage of the battery pack, the total positive relay and the total negative relay are respectively connected to the two ends of the battery pack, and the current regulation The circuit is connected in parallel with the battery pack, and the current regulation circuit is connected between the total positive relay and the total negative relay.

In this embodiment, the battery pack is composed of m _p single cells forming parallel branches, and then m _s parallel branches are connected in series, wherein m _p and m _s are both integers not less than 1. .

The current regulating circuit includes a plurality of resistor selection circuits connected in parallel, the resistor selection circuit includes resistors and switches connected in series, when the switch is closed, the resistors connected in series with the switch are connected to the discharge circuit, as shown in Figure 1, When K1 is closed, the current through R1 is 1C; when K2 is closed, the current through R2 is 2C; when K3 is closed, the current through R3 is 3C; when K4 is closed, the current through R4 is 4C, and the discharge current can be achieved through the combination of resistors. 1C-10C regulation.

The resistor is a high-power aluminum shell resistor, and the use of the high-power aluminum shell resistor can reduce manufacturing costs and is beneficial to large-scale industrial production.

The voltage acquisition circuit is composed of dedicated lithium-ion battery multi-string sampling chips, and samples the voltage value of the battery in real time.

The test circuit of this embodiment carries out the test of DC internal resistance through the following specific methods:

(1), before testing the DC internal resistance of the battery pack, the DC resistance to be detected is left to stand for a period of time; in this embodiment, the DC resistance to be tested is set aside for more than 1H to ensure that the battery pack is stable state;

(2) Assuming that the battery pack is composed of m _p single cells in parallel branch circuit, and then m _s parallel branch circuits are connected in series, where m _p and m _s are both integers not less than 1, and the first battery pack in the battery pack The operating voltage of n parallel branches m _n is expressed as follows:

v _n (t) = OCV (s _n (t)) - Ri _n (t);

Among them, v _n (t) represents the operating voltage of the nth parallel branch m _n in the battery pack;

s _n (t) represents the current SOC state of the nth parallel branch m _n in the battery pack;

OCV(s _n (t)) represents the open circuit voltage of the current SOC state of the nth parallel branch m _n in the battery pack;

i _n (t) represents the discharge current of the nth parallel branch m _n in the battery pack;

R represents the discharge DC internal resistance of the nth parallel branch m _n in the battery pack;

(3) To calculate the internal resistance of the DC discharge, the calculation formula is as follows:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$

After the above tests, the DC internal resistance is tested under the conditions of SOC of 10%, 20%...100%, respectively, and the DC internal resistance under different SOC conditions is tested.

In step (2), the actual values of the SOC, OCV (s _n (t)), in (t) and _{v n (} t) are provided by the BMS sampling circuit; The number of parallel connections is realized.

In step (2), the magnitude of the discharge current in (t) of the _nth parallel branch m _n in the battery pack is adjusted by controlling the number of parallel connections of the relay connection resistors.

In this embodiment, the change in internal resistance of the single battery is not very large in a short period, so the calculation period for the internal resistance of the battery can be controlled to be measured once every two weeks.

The above-mentioned embodiment is a preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the above-mentioned embodiment, and any other changes, modifications and substitutions made without departing from the spirit and principle of the present utility model , combination, and simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (5)

1. a test circuit of direct current internal resistance, it is characterized in that, this circuit comprises voltage acquisition circuit, battery pack, current regulation circuit, total positive relay and total negative relay; Described voltage acquisition circuit is connected with battery pack, collects battery pack The total positive relay and the total negative relay are respectively connected to the two ends of the battery pack, the current regulation circuit is connected in parallel with the battery pack, and the current regulation circuit is connected between the total positive relay and the total negative relay. 2. The test circuit of DC internal resistance according to claim 1, characterized in that, the battery pack consists of m _p single cells forming parallel branches, and then m _s parallel branches are connected in series, wherein Both m _p and m _s are integers not less than 1. 3. The test circuit of DC internal resistance according to claim 1, characterized in that, the current regulating circuit comprises multiple sets of resistance selection circuits connected in parallel, and the resistance selection circuit comprises resistances and switches connected in series, when the switch Closed, the resistor connected in series with the switch is connected to the discharge circuit. 4. The test circuit of DC internal resistance according to claim 3, wherein the resistor is a high-power aluminum shell resistor. 5. The test circuit of DC internal resistance according to claim 1, wherein the voltage acquisition circuit is composed of dedicated lithium-ion battery multi-string sampling chips, and samples the voltage value of the battery in real time.