Not every car has what it takes to keep every family member happy with fully-charged gadgets, and while some cars have USB sockets galore, there can still be times when more would be handy. This is where a 12-volt to USB adaptor comes in. These are designed to plug straight into a traditional 12-volt ‘lighter’ socket, splitting it to provide a number of USB outlets. 

Particularly useful are those that support the USB3 charging standard. Whereas USB 2.0 could provide provide 2.1-2.4 Amps of current at 5 volts (enough to charge older mobiles and tablets), the newer standard can output up to 5 Amps at anywhere between 5 and 20 volts. The result is more charging power – an increase from 12 Watts to 100 Watts. This is the technology that enables the rapid charging of mobile phones and tablets.

To find the best adapters on sale, we focused on the number of USB sockets provided, whether the USB output allows rapid charging, and whether rapid charging is possible even when several power-thirsty devices are connected. Naturally, extra credit was given for adaptors that make use of USB3 technology, and for compatibility with a wide range of devices.

Top 5: 12-volt Multi Socket Adapters

Price: £19.99 Buy from: Contact:  0113 213 2000 Web: www.ringautomotive.com Overall score: 3/5 Outputs: Four Type-A USB sockets

Converting one 12-volt socket into four USB outlets is a brilliant solution for charging an entire family's batch of mobiles, tablets, and other gadgets. But where this slightly pricey adapter really excels is that it can charge them all, simultaneously, reasonably rapidly. Outputting 34 Watts, even if four power-hungry devices are hooked up, each socket will still deliver what it’s supposed to. Two of the sockets output a genuinely fast-charging current of 2.4 Amps, the others can maintain a respectable 1 Amp each – sufficient to get most mobile phones charging nicely.

Price: £15.99 Buy from: www.celltrade.com Contact: 0113 213 2000 Web: www.ringautomotive.co.uk Overall score: 3/5 Outputs: Three Type-A USB sockets

Very much a case of you "pay your money, you make your choice" between this and the RMS21: twenty quid for four USB outputs or, three for just over fifteen quid. Under the skin we suspect both are electronically identical. As with the bigger device, there’s 34W of power, but this time the two 2.4 Amp sockets are joined by a single 2 Amp socket, and all can maintain full charging speed even with all three hooked up to thirsty tech. As with the RMS21, overall finish is impressive, the unit works in 12 and 24 volt sockets, and a light indicates when the adapter is live.

3. Scosche Dual-Port USB-C Car Charger 

Price: £24.99 Buy from: www.amazon.co.uk Contact: 0844 249 5060 Web: www.scosche.com Overall score: 4/5 Outputs: Two Type-C USB3 Sockets

Owners of the latest tech will love this tiny powerhouse. Beating Ring’s 34W efforts, this adapter kicks out 40 Watts from just two sockets, using rapid-charging USB3 technology. Put simply, this charger can talk to your tech and, if your mobile/tablet agrees, increase its charge voltage from the usual 5 volts to 9 for up to four times faster charging with suitable devices. Scosche has backed all this up with a three-year warranty, so don't have any fears about the technology being too clever for its own good.

Price: £11.04 Buy from: www.amazon.co.uk Contact: 01488 689400 Web: www.saxon-brands.com Overall score: 4/5 Outputs: Five Type-A USB sockets

Not only does Metro's SS5483 (formerly known as the Sakura SS5416) have a test-leading five sockets, but the adapter also splits the sockets between the front and rear of the car. The rear-seat pod, complete with three sockets, connects to the car's 12-volt socket via a usefully long 1.5m lead. Its plug then sports another two sockets for the front of the car. However, with a maximum output of 10.2 Watts overall, rapid charging is only possible when some of the sockets are unused, and the output is slightly biased towards the front two sockets. But a killer price and brilliant versatility bag this adapter a podium place.

1. Olixar QC 3.0 Dual Port 36W Fast Car Charger – BEST BUY

Price: £12.99 Buy from: www.amazon.co.uk Contact: 0844 249 5060 Web: www.olixar.com Overall score: 5/5 Outputs: Two USB3 Sockets: Type-A and Type-C

Scosche's dual-port adapter is good, but this Olixar alternative trumps it. First, despite a slightly lower overall output (34 rather than 40 Watts), this unit can potentially charge even faster – its USB 3 circuitry can output up to 12 volts rather than 9. And, on a practical front, that it has a Type A USB as well as a Type C make it more easily compatible with older devices than the Scosche's twin C layout. Finally, being 12 quid cheaper is the clincher. Particularly with Olixar’s two-year warranty, and the fact that it’s built around computer chip specialist Qualcomm's respected Quick Charge 3.0 technology.

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