CTEK CS Free battery charger: the heavyweight power bank is here

We've tested the CTEK CS Free charger, a portable battery pack that trickle charges your vehicle battery and boost one that’s flat to avoid jump starting.

CTEK CS Free battery charger

by Lawrence Cheung |

It’s stressful enough when your day grinds to a halt, but circumstances are inevitable when you don’t use your vehicle frequently enough. Plenty of us will have been through this recently, going to start up our car and being left with a few flickering dash lights instead - the silence is deafening, and that’s if we’re lucky enough to even unlock the car remotely in the first place.

There are ways to minimise that anxiety in the future and opting for a trickle charger is one of them. We’ve been getting to grips with the CTEK CS Free charger: A portable battery pack that can trickle charge your vehicle battery and also be powerful enough to boost one that’s flat to avoid jump starting altogether.

You can also order the CTEK CS Free with the solar panel charge kit for when you're out and about separately, which we’ve also tested here.

CTEK CS Free with the solar panel charge kit
©Photo: Lawrence Cheung


As well as the charger, the CS Free comes with a USB C cable, wall plug with adaptors for UK, EU and US sockets, and battery clamps. The solar panel charger comes with a storage bag and charge cable.

The charger looks and feels hefty, made with durable plastic and fitted with neat rubber grips on the base of each corner to stop it sliding around much.

It might feel weighty compared with a battery pack for your phone, but this is far beefier than that – it’s not just a lifesaver for your vehicle but multiple electronic devices, too, thanks to the additional USB A and C ports on the side.

The instruction manuals are diagram heavy, so you do need to spend time deciding what they’re all trying to convey, but it’s otherwise very straightforward and foolproof to set up and use.

With clearly labelled rubber tabs for the output and input sockets, you’d struggle to attach the cables at the wrong end, with a USB-C socket for the input side and a completely uniquely shaped port for the output.

Setting up the solar panel is just as easy. The storage case doubles up as a stand, and while it can be a little tricky hooking the panel onto it initially, this is as fiddly as it gets.

CTEK CS user manual
©Photo: Lawrence Cheung


We’ll start with getting the CS Free battery pack charged up.

For us, we went straight for the solar panel as our means of charging to test the worst-case scenario for when a mains power source isn’t available.

The smaller ring of lights surrounding the power button indicates how much battery life you have, with each of the four segments accounting for 25% increments.

On a mostly sunny day with patchy clouds, it took roughly three hours to get a full battery. Even if you needed just enough juice to start the car once, this wouldn’t take much time. Of course, it’s not as quick as jump-starting using cables and a donor vehicle, but it’s designed to balance getting your vehicle battery revived soon enough without damaging it in the process.

Ideally, if you are camping you could just leave the solar panel out while you were barbecuing for lunch or dinner.

Alternatively, you can charge via a three-pin plug, a 12v socket or even from a service battery, provided you have the correct accessory cable. Predictably, the wall socket is quickest, with charging time claimed to drop to an hour for a 0-80% charge.

The pack will hold charge for up to a year and has a life span of 300 cycles.


With the CS Free charger ready to go, you simply connect it to the vehicle battery using the clamps and switch it on. The charger then automatically assesses what to do, opting to use Adaptive Boost if your battery is that flat.

The larger ring of lights in the centre indicates how much time you need to get a full battery, lighting up in sequence until you get a full circle, with the respective markers indicating how many hours you are away from doing so.

Starting with a single flashing light under Start means the vehicle battery is flat and the charger will be using the Adaptive Boost function to try to give you enough charge in as soon as 15 minutes. For us, it indicated eight hours before it got our vehicle battery up to full health.

CTEK CS charging
©Photo: Lawrence Cheung

Any drawbacks?

The clamps, being small and portable, don’t feel as though they’ll bite onto the battery terminals that tightly. It’s fine for a quick charge, but if you plan to leave them on there for a longer period, you may attach them to a slimmer section.

The pack is smart enough to protect against reverse polarity, though, preventing damage in case the clamps are attached to the wrong terminals. The clamps themselves are also spark-free.


The CTEK CS Free is pricey and perhaps overkill for some needs, especially if your car’s flat battery was a one-off incident during the Covid-19 pandemic. If you know your car usage is going up again, a cheaper trickle charger will do just fine to use occasionally.

If, however, your short work commute is down to a once-a-week trip, this is more than up to the task. If you keep it in the car, you’ve got the adaptive boost function to fall back on if you ever get caught out.

For those thinking outside the commuter box who tend to spend more time away remotely, the CS Free makes more sense.

If you’re an avid camper, for example, this CTEK charger is more than a one-trick pony, also serving as a power bank for multiple electronic devices when a three-pin plug socket is far out of reach.

Read next:

The best car battery chargers

The best car jump starter power packs

The best digital tyre inflators

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