You can use a voltmeter that you plug into the cigarette lighter socket. You can get them from China on ebay for about £3.55
or two for £5.51
Insert the jack of the product into a Cigar socket. Clean the Cigar socket. Compact design. Screen digital color: red. Help to extend and protect the battery and engine life. Color: black.
www.ebay.co.uk
or three for £7.50
Find many great new & used options and get the best deals for 3X(LCD Cigarette Lighter Voltage Digital Panel Meter Volt Voltmeter Monitor J1S9 at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk
or four for £9.34
Find many great new & used options and get the best deals for 4X(LCD Cigarette Lighter Voltage Digital Panel Meter Volt Voltmeter Monitor W2D1 at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk
I have one of these, and the display is big, clear, and easy to read. I've checked it against an accurate multimeter, and these give accurate voltage readings.
It's best to check the voltage after at least 12 hours since the engine was last run, to see what the voltage has dropped to. You don't want the voltage just after you have used the car because a bad battery's voltage will drop quite a bit after 12 hours of non-use.
If your battery's voltage has dropped to less than about 12.1V to 12.2V then that could indicate your battery has a bad cell.
A 12V battery is made up of 6 cells. A good cell will have just over 2V, so 6 times just over 2V equals just over 12V.
If you have been doing lots of short trips, perhaps less than 10 minutes each journey, then that can cause a drop in battery voltage. Hence, a lot of short trips and a low battery voltage won't necessarily mean a bad battery.
When I think I have a bad battery (usually when the battery is over 5 years old) I take it out of the car and charge it up with a slow battery charger. There's no need to charge it up fully, at least half full would be enough to identify a bad cell.
Then after charging the battery at least half full, wait at least 12 hours before measuring the battery's voltage off the car. If the battery's voltage is below 12.2V to 12.3V now, you know that you have a bad battery (as one of the cells will have gone bad).
You will often get advance warning of a bad battery. You should start to notice that the engine doesn't turn over as quick as normal. This is when you want to get your voltage meter out and start keeping a careful eye on the battery voltage.
Or you can confirm that the batttery has gone bad on the car, by disconnecting the negative terminal from the battery. Then charge the battery up to at least half full. Then after at least 12 hours, check the voltage with a multimeter. The purpose of disconnecting the negative terminal from the battery, is to prevent any drain on the car's battery from the car's electronics. Even with the ignition key turned off, the car's electronics can still cause a small drain on the car's battery (unless the negative terminal is disconnected).
Varta have a good reputation for car batteries.
Here's Varta's website so that you can use their battery finder tool:
You're looking for the best battery for your car? Find here the right VARTA® battery with detailed product information.
www.varta-automotive.com
It looks like Varta recommends either their 574012068 or 577400078 car battery for the Audi A2, with the 577400078 being the higher specification.
Here's a 577400078 on ebay:
Find many great new & used options and get the best deals for Varta E44 High Performance Car Battery 12V 77AH 096 5 Year Warranty 577400078 at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk
Note the physical size which you can check against your existing car battery:
Width 175mm, Length 278mm, Height 190mm
