► A new battery can cost up to £200 for modern cars
► A trickle charger is less than half that
► A well-maintained battery could last twice as long
Very few things are as frustrating as a car with a failing battery. A hint of glowing lights, a short prayer to the Gods of Volthalla, and a twist of the key that results in a noise more like an elephant yawning than a ferocious burst of explosions and movement. In the digital age, even that faintly-optimistic ritual has gone, replaced by ‘computer says no’ as the voltage falls below the still-crucial 12V.
Read our Coronavirus driving guide
With so much technology on board, your typical 21st century car prevents the classic ‘left the lights on’ moment by switching off radios, lights and other accessories before they drain the battery, but there’s one thing that is guaranteed to wipe the spark out of your car, and that’s a long period of disuse.
Such as when all trips other than essential, short journeys have effectively been banned…
Best trickle chargers: prevent first
Got a tyre inflator in your boot? Got a pair of gloves for checking oil or handling diesel pumps? You’re the kind of person who likes to be prepared – but do you have a trickle charger for your car? There are literally hundreds of unknown-brand ones on Amazon and the like, and they’re probably fine, but there are experts in the field too – trustworthy brands that have been developed for long-term storage of supercars and classics, and these will naturally do a great job of maintaining your cars’ batteries if you have access to a plug.
C-Tek is the leading brand for smart battery chargers and conditioners, and offers a range of solutions from around £80. Accessories allow installation of unobtrusive extension cables and wrapping the charger in a protective rubber shell so it doesn’t bash bodywork. View offers on C-Tek trickle chargers here
Ring Automotive are well known for consumer and workshop products. Its smart battery charger includes diagnostic tests, seven-stage charging, jump-start boosting and battery conditioning in an easy-to-use package. The informative LCD display gives more detail than the usual red/green/amber status LEDs of most battery chargers and conditioners, too. View offer on the Ring RSC612 here
Best solar chargers: do your bit
If common sense kicked in with lockdown, every car you see parked on the road or driveway would have a little reflective square glinting off the dashboard. Solar chargers are cheap, and easy to use – most will plug into the 12V socket (or cigarette lighter, if you’re old-school) and they’re safe, spark-free and generate electricity for free.
On the other hand, they produce a fairly small amount of electricity, and cars with modern UV-shielded glass will reduce their effectiveness, so you really want to leave them on the roof of the car, in an untinted rear window or if you’re parking on a driveway, mounted somewhere to get the most light. Buy the biggest one you can realistically fit and afford.
For a healthy car, the solar charger will maintain the charge needed for systems like clocks, central locking, computers in standby and alarms. Few will recover an already failing battery, and they don’t provide enough kick to wake the ignition system if the battery is dead.
Gunson’s solar battery charger is affordable and designed to fold neatly when not in use, protecting the solar cells. Workshop-quality clamps and wiring ensure a long working life, too.
View offers on the Gunson 77108 Solar Battery charger
Best traditional chargers: recover an (almost) flat battery
Provided the battery hasn’t been drained to the point of damage, you can recharge it – and boost your car – with a mains-powered charger. This is often the most traditional technology you’ll find, fundamentally unchanged for decades, so there are cheap, robust options.
For the small amount extra it costs to get a more sophisticated charger with boost function, there’s little reason to skimp here. Chances are, if you’ve got a battery flat enough to need charging, you’ll benefit from the jump-start too.
View offers on the Ring RCB12 standard battery charger (shown above)
Or look at offers on an equally good Sealey product
Best jump packs: for when you've left it too long
Traditional jump packs were little more sophisticated than a car battery in a box – and yes, you can jump a car from another battery still; jumping from another car has become riskier as more sophisticated electronics proliferate. However, another battery is heavy, bulky and a bit of a faff; modern laptop battery technology has lead to the creation of pocketable power packs that can charge your smartphone or jump-start your car.
These are really only suitable for emergency use, but with the advantages that they can replenish USB devices and quickly recharge from your car’s 12V socket, taking up little more space than an owner’s manual, they’re also really easy to carry about for emergencies. The downside of the light, portable nature is that the clamps and cables can be quite flimsy – fine for occasional use but unsuited to workshop handling.
Mainstream marques have yet to really adopt this market; navigate the sea of made-up reseller brands and you’ll find decent models for around £60. Our tests of typical examples have found that they will give three or four attempts to start a typical 2.0-litre petrol car before needing to recharge – read the customer reviews to choose the best model. Noco is one of the best brands in this area - find offers on Noco car battery charger here
If you’re sticking to a workshop or garage environment, booster packs like the Ring powerpack are more robust and can be used many times, and often include extra features such as compressors for tyre inflation, inverters or emergency lights. They also have solid clamps and cabling to ensure a long working life. View offers on the Ring powerpacks here
Connecting your charger: a guide
As cars have become more sophisticated, they’ve also become more sensitive to fluctuations in voltage. When attaching a charger, you should connect the positive to the positive battery terminal whether using clamps or a quick-connect cable. The earth should be connected to the car bodywork or engine at a suitable point – not the battery itself. This ensures any voltage monitoring circuits are ‘aware’ of the battery status.
Always connect with power off, then switch power on to the charger. On older tech it avoids sparks, on newer tech it allows time for the electronics to optimise the charging programme. You can also avoid poor connections and make it easier to disconnect and drive by using manufacturer’s extension cables and permanent attachments – a very convenient way of keeping infrequently-used cars ready to go.
With lead-acid batteries, still common in production cars (even EVs), don’t leave a conventional charger attached longer than necessary. Trickle chargers, chargers with ‘float’ or conditioners are designed not to provide any more current than the battery requires to maintain the optimum voltage, but older chargers can damage older batteries.
When charging an older battery, you should leave access to it open (bonnet, boot or rear seat if it’s an old Beetle, for example) and ensure the space is ventilated. The hydrogen sulphide gas emitted is flammable (and toxic), and batteries can cause sparks. It doesn’t take a genius to work out how that’s going to end. Though the risk is small, it’s very real in an enclosed space.