Most EV drivers and operations are used to thinking about battery health, at least on some level. Many people spend a lot of time (even subconsciously) thinking about the range and when and where they’ll need to charge up.
But most people don’t think too much about battery management, which is the most effective way to keep an EV’s battery as healthy as possible.
The truth is, battery management is essential for electric vehicles. On this page, our team at Rotronics explains why.
Why does battery management matter more in EVs?
EVs have two separate battery systems, each with very different and very specific jobs.
- The high-voltage propulsion pack is what actually drives the EV. It also receives charge from external charging and regenerative braking.
- The 12-volt auxiliary battery handles the lights, relays, actuators and all the usual ‘auxiliary’ system components. This also includes control modules, locks, wake-up sequences and so on.
A failed 12-volt system often prevents ‘wake-up’ and contactor closure, and a failed traction system stops propulsion. In other words, in either case, the driver is unlikely to be going anywhere.
Now, just like a ‘normal’ internal combustion engine (ICE) car, the car charges the 12-volt system as it runs. In an EV, this is handled by a DC-DC converter rather than an alternator. And in the same way as ICE cars, EVs draw from that 12-volt battery even when you’re parked up (from central locking, alarms, dashcams, etc).
Battery management is crucial for any 12-volt battery. Even when a 12-volt battery shows a ‘healthy’ voltage at rest, it might still fail during a start sequence. With all the electronics in EVs, this becomes even more important. EVs rightly demand stable voltage during module checks and contactor closure, because a voltage dip at the wrong moment could trigger undervoltage faults and prevent contactor closure.
And on the high-voltage propulsion battery side, an onboard battery management system tracks how the cells are performing, including cell voltage imbalance and charge acceptance behaviour. A good built-in battery management system helps your battery last as long as possible. But manual, plug-in battery management, as part of a carefully implemented routine workflow, enables you to gain a more in-depth understanding of the battery’s current condition and to know when to rebalance the modules.
What actually goes wrong without proper management?
So, why is it that battery management for EVs is important? What is it that actually goes wrong?
Well, cell imbalances in the high-voltage pack limit how much capacity the battery has available. All EV manufacturers design battery assemblies differently, either in series (strings) or parallel (modules). But this general principle is the same: a propulsion battery can work only as well as its weakest component. The system actively protects its weakest member. That means the cells don’t fully charge, and the discharge cycle ends early, both of which mean reduced range and performance.
And for the 12-volt battery, undercharging remains one of the most common causes of failure. First of all, no battery is expected to last forever, and 12-volt batteries need to be replaced every few years, just like in ICE vehicles. Secondly, the DC-DC converter typically charges the auxiliary battery based on system conditions, not necessarily the 12-volt battery’s health. If it reaches voltage thresholds early, the charging tapers off (although vehicle-specific systems vary), sulphation builds up on the plates, and internal resistance rises, but the battery will still read fine on a voltage meter.
And with EVs, you get a lot of electrical ‘noise’, which complicates things. All vehicles carry minor active loads even when they’re ‘off’, but EVs, in particular, power things like control modules, pumps, and network traffic. You need a battery management system that measures load response and charge acceptance, not just whether a number ticks the box or not.
How does battery management protect electric vehicles?
Battery management is all about taking a proactive approach. You’ll understand the true conditions of your batteries. That means you catch faults early, with fewer breakdowns and unexpected costs.
Developing a workshop battery management workflow is easy to create and implement, and it’s a win-win.
Battery management is your business’s approach to measuring your EV’s battery behaviour, rather than just its condition. Testing and recording those results allows you to keep track of what’s working well.
Here’s what to do to keep on top of battery management for electric vehicles:
- For the 12-volt system, conduct regular, proactive conductance and dynamic load tests. Replace failing batteries early to prevent your cars from getting stranded. Check out the Midtronics xLVS-9000 for an EV-specific 12-volt battery tester.
- For high-voltage systems, you need to focus on EV module balancing. Balancing keeps the voltage spread evenly across the entire battery pack. Check out the xMB-9640 Aftermarket to get your EV propulsion battery back on track.
Rotronics works with workshops and fleets across the UK to put that management in place. Keep on top of the battery’s condition, and you stay in control of your vehicle’s performance. If EVs now make up a growing part of your workload, it’s time to treat battery management as core maintenance. Get in touch with us today to discuss more.
