Warranty Procedures


Upon receiving your battery, please report any physical damages or leakages within 24 hours of receipt. Please call on 01784614192 or email on info@mlperformance.co.uk quoting your order number along with photos of damage. Please note: Damages reported outside of 24 hours will not be taken into consideration.  

If the battery proves to be faulty, you will need to return this to us for testing. We will charge and run an inspection test on receipt. However, we strongly recommend you check the below first: 

  • Has the car been left for a week or more? If the answer is yes, and your battery performed reliably before this time then the car has drained the battery and it requires re-charging. 
    This problem can occur in a shorter time in cold weather. 
  • Is the car used for mostly short journeys only (less than 10miles). If the answer is yes and the weather is cold the battery is undercharged and needs to be re-charged. Under these conditions the battery is supplying more power to start and run the car (lights, heater, etc) than is being returned by the alternator.  This is not the fault of the battery. 
  • A discharged, or flat battery, while inconvenient, does not have a fault, so is not covered by the manufacturer’s warranty. 

When a battery is discharged enough not to start the car it must be fully re-charged with a battery charger. A jump-start and a drive will not do. The alternator is not able to re-charge a fully flat battery, it is not what it is designed for; only a battery charger can perform this function. 

Allow the battery charger to complete its cycle, or program.  The charger will usually have some indicator that confirms the battery is fully re-charged. Failure to allow enough time will result in more non-starts. If only partially re-charged the battery will probably provide several starts and then again fail to start the car. We often hear the term “the battery will not hold a charge”. This is always as a result of a discharged battery not being fully re-charged before being put back into service. 

It is a common misconception that a fully discharged battery can be fully recharged in a small number of hours. It can take days so allow your charger to tell you it’s ready rather than assuming the time that you have had the battery on the charger is sufficient. 

Battery technology has changed radically over the last ten years and so have the chargers needed to support them. I have alluded to your charger having some indication (usually a green light) to show the battery is fully charged and the charger has finished its program. If your battery charger does not have a means to confirm the battery is ready, then it may be too old and not be compatible with modern batteries. It may still charge the battery a little but may not be able to complete the job, which could result in you experiencing your initial problem again a few days later. 

Modern batteries can be model specific as many cars have different charging systems; therefore, you must choose the battery listed for your car, failure to do so will invalidate the warranty.  

The following faults are not covered under the warranty: 

  • Wear and tear - During the charge and discharge cycle, material from the battery plates (active mass) is in motion, through the electrochemical reaction that produces electricity. Every time the battery goes through a charge and discharge cycle, a small amount of the active mass is lost from the plates. Because the ultimate life of a battery depends on so many factors, it is impossible to stipulate a minimum/maximum life expectancy. This process of normal ageing through the charge and discharge cycle will eventually cause the battery to lose capacity, and it will come to the point where the battery can no longer start the vehicle/equipment. This is not a manufacturing fault. 
  • Incorrect application – If the battery is not compatible with the car, then the warranty will be invalidated automatically.  
  • Physical damage - If the battery is fitted incorrectly, if the connector leads are hammered onto the terminals, or if the leads are not properly fastened, the battery will have obvious damage to the casing or the terminals. This is not a manufacturing fault. 
  • Overcharging – Any voltage under 10.6 volts will not be processed as a warranty claim as this indicates more than 100% discharged. If the regulator is not set properly, then the battery can be subjected to an excessive charge. If left unchecked the battery will overheat and will start to evaporate the electrolyte. The overcharging will cause the accelerated breakup of the active mass on the plates and the battery will lose performance. This is generally obvious from the examination of the battery – the acid levels will be very low, and quite often a black coating will be visible on the filler caps. This is not a manufacturing fault. 
  • Deep or over cycling - As mentioned above, every time a battery goes through a charge and discharge cycle a small amount of the material from the plates is lost. If a battery is subjected to deep discharging (i.e., over 40%) and then rapid charging, this process is accelerated. Additionally, if during the recharge the battery is not adequately compensated for the discharge cycle, the battery will quickly exhibit loss of performance. Even after recharging the voltage will be low (under 12.4v) but the cells will generally give even readings. This is not a manufacturing fault. 
  • Sulfation - If a battery is allowed to stand in a discharged state for an excessive amount of time, a chemical reaction takes place, which can permanently impair performance- this is sulphation. Sulphation can be seen as a fine white/grey coating on the plates. In most cases this signifies irreversible damage, and the battery will not be serviceable. This damage can occur either in storage or if the battery is installed in a vehicle (or equipment) that is not used for a period, for example a tractor, motorcycle or boat. Even a car or truck that is stored with the battery connected can still damage the battery in this way. This is because there is a permanent drain from the clock, alarm etc. As a result, the level of charge in a battery falls, and after a period sulphation will build up on the plates. The sulphation (lead sulphate) hinders the chemical reaction between the acid (electrolyte) and the active mass (lead compound) in the plates and prevents the battery operating as normal. This is not a manufacturing fault. 
  • Contact us with your order number to notify us of the return. Please ensure you pack the battery carefully with sufficient protective packaging. We will not be liable for any damage caused in transit.  
  • We will then charge and test the battery; we may also need to return some items to our suppliers for testing.
  • If the battery is faulty, (if applicable & subject to your warranty) we will issue refund or replacement. 
  • If your battery is not faulty, we will send the battery back to you or we can safely dispose of the battery. Please note, you will be liable for any carriage costs incurred.  

All specialist batteries (non-automotive) may need to be returned to the manufacturer for testing. 

Please note we are unable to proceed with a warranty claim if the faulty battery has been disposed of prior to notifying us of a potential fault. 

ML Performance are not responsible for any third-party claims resulting from a faulty item. The faulty item will be replaced but third-party losses will not be reimbursed.  


For Safe Battery Use: Immediate Removal of Transit Bungs

To ensure optimal performance and prevent potential safety hazards, please remove the transit bungs from your battery immediately upon receipt. These small plugs, located on the battery are present for transportation purposes and must be removed before use or storage. Some batteries have these in red colour.

Failure to remove the transit bungs can:

Cause the battery to malfunction or swell.

Lead to potential risk of explosion.

Need Help? We're Here:

If you encounter any difficulties or have questions about the transit bungs, please contact our customer support team immediately.



Damage caused to the battery due to failure to remove the transit bungs is not covered under any warranty.

Continued use of the batteries after receiving this notification signifies your acknowledgment and understanding of these important safety instructions.



There are many reasons why your car battery might keep going flat. The most common causes are corroded or loose connections, excessive electrical drains, or power demands on an alternator. Charging problems could also be the reason why you have a flat battery all the time. 


Discovering that you have a flat car battery is perhaps one of the most frustrating experiences in life, as it never comes at a convenient time. A potential option is to use jump leads to connect your flat battery to another car's charged battery. You'll need to ensure that the leads are connected, noting the correct polarity: (+) and (-). It is also essential to refer to the manufacturer's handbook first. The ECU (engine control unit) in some cars can be damaged if they are jump-started so always check the handbook to see if that is the case for your vehicle. 


If a car battery is not recharging, this can indicate a mechanical issue. This is most likely going to be with the alternator, which should be generating energy to charge the battery. We tend to find if a battery is discharged too low, when then attempting to re-charge the battery, the charger will run a current through but the battery will not retain its charge as it will not recognise it as a battery.


So, following the next steps will “trick” the battery into regaining a charge, in most cases.

Please try the following to recharge your battery:

  1. Connect a flat battery to any other battery with jump leads. 
  2. Leave for 10 mins and then connect charger to flat battery at same time.
  3. Turn on charger and charge like this for 1 hour. 
  4. Then take off jump leads and charge battery normally with charger for minimum of 12 hours. If the unit gets hot or starts to give off a bad smell, please stop immediately. 
  5. 12.73v will be 100% charged.

Leave disconnected and monitor the voltage over a 24-hour period to see if/when the voltage drops off and provide us with a photo of these readings. 


Occasionally, a small amount of leakage escapes from the breather holes of the battery. The manufacturer ensures the batteries are prefilled as much as possible to avoid any disappointment on arrival Please follow these steps before using the battery:

  1. Clean the batteries carefully ensuring no acid touches your hands or clothes. Please do this outside, wearing suitable protective clothing/gloves to prevent skin irritation. 
  2. Check for physical damage. If no physical damage, please use batteries as normal and monitor their performance. We specify the batteries to be slightly overfilled in the first instance in order to cope with a small amount of leakage in transit. 
  3. If you have any issues, please contact us immediately. Your warranty period is unaffected. When reaching out to us, please confirm the severity of the leakage. Is it more than half a cup full?  


If you have a multimeter, you can test your car battery at home. When using a multimeter, it's important to be aware that your battery should have no fewer than 12.6 volts.


You should never dispose of car batteries in a household bin. Not only is this dangerous due to the hazardous waste but it is also against the law. Most landfill sites and household waste centres will accept used car batteries.


An alternator is commonly associated with the battery. It converts the engine's energy into an electrical current for the battery. This in turn powers the electrical system. For this reason, your alternator can be a good first place to investigate if your car battery isn't working. 


CCA is the rating that states a battery's ability to start a car's engine in cold weather. This is also referred to as 'starting capacity'. 


RC is the time in minutes that it takes for a battery to discharge 25 amps while maintaining at least 10.5 volts. 


Ah is the number of amps that the battery can provide over a period of 20 hours – e.g., a 100h battery can deliver five amps for 20 hours.


AGM is a material made up of glass microfibers. It's used as a separator in a battery – with the microfibers absorbing the battery acid (electrolyte) to avoid spillage.



It is important to note that all Genuine BMW parts come with a warranty of two years for customers in the United Kingdom, and a one-year warranty for international customers. However, this warranty is contingent upon the provision of the Vehicle Identification Number (VIN) at the time of purchase.

Please be advised that the warranty coverage is administered directly by BMW, and it does not involve ML Performance. In the event of any issues arising with the parts, they must be diagnosed by a BMW dealership while the parts remain installed on the vehicle. Once deemed faulty, the initiation of a warranty claim with BMW Germany can be facilitated through their workshop

We are able to provide a detailed cost invoice as evidence, though it is important to note that this documentation cannot be furnished to the customer directly.

It is worth mentioning that some BMW dealerships may quote a labor charge for the initial hour of diagnosis, typically ranging from £120 to £125 inc vat. This fee is applicable only if the diagnostic concludes that the parts themselves are not defective, and the issue lies elsewhere or is attributed to an installation error.

We kindly request that you notify us once you have scheduled an appointment with your local dealer and send us a contact email for the service advisor. We will then liaise with them and provide the invoice to initiate the warranty claim process. Your satisfaction is of utmost importance to us, and we are committed to assisting you through this process.