A rechargeable car battery is a fundamental component of every single modern car. Its most important job is to power the starter motor, as well as the alarm and central locking and the vehicle’s low-voltage bus and ECU memory.
Of course, a battery forms an integral part of a car’s electrical system. It’s mainly discharging when the engine is off, and the alternator should recharge it when the engine’s running.
But will it ever stop holding a full charge? The answer there is yes. This article explains why, and how to know when it’s time to get a new one.
What causes capacity loss over time?
It would be simpler if a battery had an on/off switch, and only charged or recharged when it decided. Unfortunately, that’s not quite how electricity works.
In simple terms, the battery discharges – slightly or significantly – whenever a component in the electrical system demands current. That could be anything, from the starter motor cranking to the interior lights, or a short-circuit or parasitic drain in a particular item or application.
It also recharges – that is, its chemical reactions are reversed – whenever the alternator’s regulated output isn’t demanded by the auxiliary system.
Now, every time the cells inside the battery charge and discharge, a tiny bit of active material breaks away. It takes some time, but eventually the battery will hold noticeably less energy than before.
There’s also sulphation to consider. When a battery sits undercharged for a period of time, lead sulphate crystals form on the plates. These harden and reduce the surface area. That means there’s less potential for the chemical reactions that generate current to take place.
No amount of standard recharging can fix advanced-stage sulphation.
And to cap it all off, high heat and vibrations exacerbate the problem. Once the chemistry has degraded in ways mentioned above, you will have lower available capacity and faster self-discharge.
How charging habits affect battery degradation
When it comes to charging your rechargeable car batteries, the most important principle is to charge them to the optimal amount. Overcharging evaporates the electrolyte (so the ions can’t flow as effectively) and warps the plates.
On the other hand, undercharging means sulphation problems build up.
Then there’s fast charging. Sometimes, in emergency situations, you need to get as much charge back into the battery as possible, for example, when you need to jump-start the vehicle.
However, what you’re really doing in these cases is reversing the chemical reactions. Doing this with too much power generates excessive heat, which leads to increased chemical breakdown.
While fast charging is acceptable on rare occasions and in emergencies, it’s bad for long-term battery health.
There’s one last habit we’d like to mention here, and that’s how frequently the vehicle is used. In some fleets, some vehicles might be parked for weeks at a time. In that period, a parasitic drain could pull charge from their batteries.
And an undercharged battery means sulphation. Without maintenance charging, the rechargeable batteries in your parked cars will see a decrease in available capacity over time.
The rate of sulphation depends on the depth of discharge, the time at a low state of charge (SoC), temperature and the battery type.
Use a modern smart charger to ensure you neither undercharge nor overcharge your car’s rechargeable battery.
When does it make sense to replace instead of recharge?
Nothing lasts forever, and that includes batteries. However, good maintenance is far cheaper in the long term than emergency repairs and all the associated fallout.
But how do you know when you really should replace your rechargeable car battery instead of just recharging it?
The answer is to perform a temperature-controlled load test after you finish reconditioning. This is one of the most crucial battery tests in your arsenal. If voltage recovery is slow or current delivery is weak, it’s probably time for a new one.
It can be very difficult to keep track of ‘slow’ voltage recovery or ‘weak’ current delivery without having the data from all your past tests. That’s where a battery management system like ROBIS can help.
Our cloud-based platform stores and saves the results of your technicians’ previous tests for each battery. Over time, you’ll be able to identify trends, especially in certain vehicles, on certain routes or in certain batteries.
The more data you can collect, the better decisions you can make about when to replace your car batteries.
Extend your car batteries’ lifespans with Rotronics
As every technician knows, no battery lasts forever. In busy fleets, you’re doing well if you get three to five years out of one.
However, careful charging routines and data-driven maintenance can extend the lifespans of your rechargeable car batteries. It also helps them stay in optimal condition, resulting in fewer problems with your fleet on the road.
Rotronics is your go-to partner for battery testing and charging solutions. We’ve helped fleets and other automotive and marine businesses across the country. Our equipment, especially when combined with ROBIS, reveals what’s really happening inside your batteries, before their performance starts to decline.
Explore our full range of diagnostic tools online, or get in touch with us for a no-obligation chat about your business. We’d love to hear more about you and suggest areas we can help.
