The battery – it’s not enough to replace it, it needs to be programmed – part 1.


The battery – it’s not enough to replace it, it needs to be programmed – part 1.

In this article, for a change, we’ll touch on the topic of managing… battery charging. To be able to optimize this process, it is moribund to have the right data.
This is what has happened with the charging of lead-acid batteries used in cars as starter batteries. The appearance on the market of vehicles equipped with a start-stop system has forced the development of systems that allow the idea of stopping with the engine off. Travelling in city traffic means that the smoothness of driving is highly dependent on traffic control lights. Waiting for a ride can last from a few seconds to several minutes. Standing in traffic can generate not only impatience in drivers but also pollution, emitted by a running engine that could simply be turned off during this time. So do we have a solution to offset this effect?

Changes are needed…

In order to put the start-stop system into practice, the smooth operation of many systems is needed, which can be grouped into two main areas: the mechanical and electrical parts. Both require specific changes to make the start-stop system work properly. In the mechanical part, at least an increase in the strength of the starter is required

Driving from point A to B years ago required only one engine start. Now there will be many more such cycles when passing through a congested city. In addition, the engine design itself has to withstand so many starts. The mechanical changes were an adaptation of what was already in place to the new requirements. In the electrical part, on the other hand, much had to be created from scratch. This has resulted in the fact that today replacing a battery is not just a mechanical operation. A new battery increasingly requires “checking in” to the car during replacement. And batteries also have their own requirements.

Battery requirements.

Start-stop systems have forced the development of batteries that can withstand multiple starts while driving. It is estimated that a typical battery lasts approx. 3000 startup cycles. The number of starts for a start-stop system is typically about. 2000 in the year. If one were to base such a system on ordinary batteries, they would last 1.5 years (and in practice less due to other limitations). With the required annual replacement of the battery, such a situation would be unacceptable.

Here the AGM battery has found its application. This battery works well in a car with a start-stop system due to its faster charge absorption. In addition, its greater resistance to vibration and safer design is something that has become a requirement for new construction today.
Trapping the electrolyte in a fiberglass mat increases the freedom of battery placement in the vehicle. It allows it to be placed in different locations, such as under the seat or in the trunk. All this makes AGM batteries the preferred choice for start-stop systems. In addition to AGM technology, a tweaked traditional car battery, or so-called: EFB, has also found application. The polyester coatings on the positive plates used in this type of battery increase the stability of cyclic operation. The EFB battery is an alternative choice for vehicles with start-stop systems.
The latest approach to the subject is the use of Li-ion batteries, already forming almost a “black box” – with protection, condition monitoring and diagnostics in a single housing.

Each start-up is a consumption of energy drawn from the battery. And this cavity needs to be replenished on an ongoing basis. In order to have an idea of the battery’s state of charge, it was necessary to create circuits to make such measurements. And this need has prompted the development of battery management systems (BMS). To be able to influence the charging process of the battery, alternators with a configurable voltage regulator have been developed. All of this has made it possible to introduce diagnostics and inform on the on-board computer display when the battery is not working or needs to be replaced. The topic of BMS seems to be quite complex, so we will delve a little deeper into how it works….

How does the battery energy management system – BMS – even work?

The initial circuits for determining the state of the battery were relatively simple. This was due to the gradual evolution of the system and its expansion to include more needed functionality.
The first step in implementing the BMS in vehicles was to add a sensor that measures the direction and current flowing to the battery. Data from this sensor is routed to the BCM (Body Control Module). This module, in turn, collects information from a number of other sensors and on the status of active circuits, such as lights on and rear window heating. This processed information on charge/discharge and attached loads is routed to the engine ECU (Electronic Control Unit). In the stage, this controller communicates with the alternator and can change its parameters. Such a strategy was used in the Opel Insignia, for example. So let’s move on to the section on current and its measurements.

Current sensors – on the left the smart clamp (5QA915181), on the right the current sensor (13502261) flowing through the cable leading to the battery.

Current and its measurements.

Cars mostly have batteries to start and power the vehicle’s systems when the engine is not running. This makes it imperative that the state of the battery be monitored not only while driving. The battery in a car is discharged when the engine is turned off and does not drive the alternator. This happens, for example, during a momentary stop when the start-stop system is triggered. Similarly, when the car is parked and at rest – the current although much smaller – is still drawn from the battery. Also, when the engine is running, many of the devices in the car draw current, which can add up to a lot. This can result in a situation where the amount of current generated by the alternator does not fully cover the demand in the system. The loss is, of course, replenished from the battery, deepening its discharge. Therefore, it is important to monitor the current. Gradually, the measurement capabilities of BMS systems began to be expanded to better monitor the condition of the battery, especially for types of cells that are sensitive to overload or overcharging. This led to the battery becoming a module with its own communication connector. We will tell you what this means for the users of the car, as well as the service technicians who operate it, in the second part of the article.

The modern Li-ion battery used in cars already has an integrated BMS and requires communication with the controller.


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