Did you know a standard Lithium-ion battery experiences 10 times more degradation when operated near 100% cycle DoD compared to when operating at a 10% DoD for the same amount of charged power (DOD = Depth of Discharge)?
So why is that important to know? Well, in practical terms, when maximizing the longevity of your battery, it is recommended that you keep the battery SOC between 30 and 70 percent.
Being aware of information like this can help minimize degradation and have a positive impact on the battery lifetime. However, the question remains: how do you keep track of such KPIs?
This is where a monitoring system for your electric buses comes in handy.
A telematics system allows you to keep a close eye on important KPIs such as (average) state of charge (SOC), depth of discharge (DOD), charging cycles, cell temperatures, and current rate. Such a system will provide both real-time insights as well as historic reports.
Having a telematics system in place can also prove to an OEM that you have respected the battery warranty conditions in case there are any issues with the battery, and can pinpoint where the origin of the issue lies.
Understanding the Battery Warranty Contract for electric buses
The battery is generally the most expensive part of the vehicle. Currently, an EV battery could make up 33%-50% of the total cost of the vehicle.
We know from some of our customers that certain OEMs have a 12- year warranty with a maximum of 30% capacity degradation. In other cases, it’s a 6-year warranty with a 30% capacity degradation.
To make the most of the warranty of your battery, it is important to understand the battery warranty contract. While every contract is a bit different, most battery warranty terms and conditions will refer to parameters such as battery temperature, State of Charge, energy used and full cycles.
Monitoring these aspects of the battery allows for the battery to be within the limits of the contract for as long as possible.
Here is a brief overview of the most common parameters that OEMs include in their warranty contracts, and what insights a battery monitoring system provides into each of them.
For temperature, it is generally the case that you should not rise above or go below a certain temperature, as this can damage the battery.
For example, with some OEMs, the battery temperature should be kept below 55 degrees centigrade or 131 Fahrenheit, so that the 6-year warranty is still valid. With battery monitoring you can have both real-time and historical information, allowing you to see if you are within your contract limits or not.
Alerts can be set so your maintenance team can act if the temperature continues to rise.
State of Charge
The warranty contract can state that the battery should not go below a minimum charge. As a general rule of thumb, it is always a good idea to not go below 10% SOC as this will accelerates battery degradation.
With a battery monitoring software, you can receive alerts to let you know when the battery is about to reach that threshold, so you can take action and charge your vehicle accordingly.
Battery warranty conditions regarding energy used vary between each contract, but as a reference, we have encountered conditions that state you can use 100.000 kWh of a battery.
Thus, this is important to monitor on a day to day basis, so you can see how close you are to the upper kWh limit.
Another condition within the contract is the number of complete charge cycles. We’ve seen that a common number within a contract can be around 3000 battery charge cycles.
Monitoring charge cycles allows you to see how many full charge cycles your buses go through each day. Based on this information it is possible to determine how fast you are approaching the limit stated in the battery warranty contract.
The benefits of a battery monitoring system
To recap, a battery monitoring system will allow you to keep a close eye on important KPIs stated in the battery warranty agreement. This data can help you stay within the limits specified by the battery producer or the electric bus OEM. Furthermore, it will also provide proof for insurance/liability or warranty contracts in case of problems.
In short here are the main benefits of a battery monitoring system:
- Real-time alerts
- Actionable insights through historical data analysis
- Document compliance with warranty conditions
💡 Keep in mind that when it comes to the battery warranty it is important to have your own data, independent from the data of the bus manufacturers or battery producers.