REPLACING & REGISTERING A BATTERY
As with many consumable components, battery specification and replacement procedures are becoming more bespoke on newer cars. As a typical AGM battery ages, smart alternators adjust their charging algorithms, which would be inappropriate for a brand-new battery. Therefore,
a replacement might need to be registered to the car after fitting, but note that this is not necessary on every vehicle.
To find out if it applies to your particular make and model, enter your registration number or Vehicle Identification Number (VIN) at http://fit.yuasa.com
1 Select a gear or ‘Park’ and ensure that the handbrake is engaged. Chock the road wheels, if necessary. Research your particular make and model to see which settings might be lost if the battery is disconnected.
2 Switch off all electrical loads and remove the ignition key. Some cars lock their doors and activate the alarm when the battery is disconnected, so be wary of the keys being trapped accidentally.
3 AGM batteries can be protected from excessive engine bay temperatures with covers. Ensure that you do not cause damage as they are removed and store them in a safe place. Omitting to refit the covers will decrease the new battery’s life.
4 First, disconnect the earth pole. This is the negative terminal on modern vehicles. Position the terminal away from the battery post, so that it does not make accidental contact after being removed.
5 Next, disconnect the live (positive) connection. Note that, in many cases, there may be a protective cover placed over the terminal. On this VW, a plastic cover hooks over the post beneath the connector.
6 Make a note of the means by which the battery is secured to its tray and remove the clamps. Store the parts carefully. An insecure battery is not only dangerous but is also an MOT failure.
7 Lift the battery out of its aperture carefully. In some cases, you may have to dismount other components to facilitate access. Do not swing the heavy battery so that it strikes nearby components, or bodywork.
8 Compare the original battery size against your replacement to verify that they are the same. Should the battery be too tall, there is an increased risk of the terminals striking the bonnet, possibly leading to a major short circuit.
9 The replacement battery's voltage should not be below 12.5 volts before you fit it. If found to be so, recharge it with a smart charger and test its voltage. Check its state of health after a few weeks of use and compare it against its specifications.
10 The new battery should have insulator caps over its poles. It has been known for users to forget to remove them after the battery has been fitted and connected! Fit them to the old battery, once they have been removed from the car.
11 Many batteries will feature a vent plug. No battery should be fitted with a vent plug on both sides. Some cars are equipped with a pipe that can be connected to the battery – consult your car-maker’s instructions.
12 Check the integrity of both the battery leads and their insulation. Some battery terminals can crack if overtightened. Should any earth straps become accessible, when the battery is removed, check their condition.
13 Verify that the battery tray is both clean and dry. Consider that even a small piece of sharp grit can puncture the base of a heavy battery, so ensure that all foreign objects have been removed.
14 While plastic battery trays can split, steel ones rust. Wire-brush away any surface rust and treat the surface with a rust converter, followed by paint. Allow any coatings to dry before refitting the battery.
15 As with removal, take care not to damage any surrounding parts, bodywork or cabling, when lowering the battery into the tray. Refit the fixings, as shown in Step 6, but do not overtighten them.
16 With the battery in place, refit any surrounding trim removed earlier. Connect the positive terminal first, followed by the negative; do not overtighten their clamping bolts, if fitted.
17 Do not forget to refit any covers, especially for AGM batteries. Many cars have plastic guards, to stop the battery from getting wet. While water will not damage the plastic case, it can cause corrosion to build on the terminals.
18 After reconnection, you might lose some settings, such as the clock time, trip computer information and, possibly, the radio code. You may also have to reinitialise certain functions, but consult your handbook to be sure.
19 Not all vehicles that are equipped with emission-saving technologies require new AGM batteries to be recoded. This one does. The operation is performed via the universal OBD socket, which is situated beneath the fascia on this Volkswagen.
20 Yuasa has its own equipment for programming batteries, but some more advanced Diyoriented diagnostic equipment has this facility. Should you need to buy diagnostic equipment, check if this function is present.
21 Diagnostic equipment will display the battery management function in its main menu. For some cars, you can buy a wireless OBD interface and programme the battery using a mobile phone app.
22 On the pictured Yuasa professional equipment, because it is not vehicle specific, the car make and model is dialled in manually. Alternatively, the vehicle ID can be detected automatically via the VIN number.
23 You'll need to follow the on-screen instructions. Some devices may require you to enter the serial number printed on the new battery, while other software may guide you through several steps, as indicated here.
24 To be registered successfully, the new battery must match the specifications of the original battery. Some cars offer battery upgrading options. Should this be the case, the new battery data must be entered.
25 Run a global diagnostic check before registering a new battery and delete any fault codes. This professional configuration tool conducts this process automatically and warns if any permanent faults will hinder the registration process.
26 You may have to enter the maker of your replacement battery or simply the serial number on the battery label. In this case, because a new like-for-like battery is being fitted, no programming is required.
27 After pressing the ‘Enter’ key, the battery is registered successfully. You can conduct another global diagnostic check, prior to disconnecting the equipment from the car’s OBD socket.
28 Note any accessory reinitialisation procedures (such as radio codes, window anti-pinch, et al) by reading the advice in the owners’ handbook. Start the engine and check that it runs correctly.