CS STORAGE CASE

I bought the CTEK CS FREE 12V Portable Battery Charger five months ago to maintain my car’s battery charge when it sits unused for a couple of days. Since my car is parked in a garage with no power, I needed a solution that didn’t rely on mains electricity—this CTEK charger delivers exactly what I need. ✔ Works well – Keeps the battery topped up as expected. ✔ Recharges fairly quickly – No long wait times between uses. ✔ Portable and convenient – Ideal for garages or locations without power access. One minor drawback – The how-to-use manual is a collection of line drawings in a cartoon style, which can be confusing at first. A more standard format with text, diagrams, and tables would have been clearer. Still, you get used to it. I haven’t had to use its other features yet (reviving a flat battery, charging a phone, etc.), but for maintaining my battery’s State of Charge to a reasonable level, it works perfectly.

Fantastic item. A little expensive but does the job perfectly. Suitably impressed by its simplicity.

Never worked properly. It isn't a trickle charger, which is fine as I have other CTEK chargers for that but it doesn't actually charge. It did a couple of times but mostly just shuts off. By the time I got around to not thinking it was me or giving it long charges, my warranty ran out. So it's an expensive paperweight.

This is a multi-function charger/conditioner with it's own internal battery. It doesn't 'jump start' a vehicle, but instead cleverly charges the vehicle's battery without risking damage to modern electronics & ECUs. It takes around 15 minutes to get a flat battery ready to be able to start the vehicle normally. It can also fully charge or condition a battery without being connected to the mains, ideal for people with no driveway/ street parking, or mains connection if available. It can also charge USB devices and some laptops etc. It's not small, but is portable and is well made - a good bit of kit to have, would recommend.

I've had the CTEK CS FREE for over 6 months now, used it and even tested it with a multimeter and bench power supply. It's a really useful device in scenarios where you need to charge a 12v car battery and may not have easy access to mains power. It can give your battery enough of a blast to revive your car in a pinch and will also function as a maintenance trickle charger. But there are limitations with capacity and charge rate. Internal battery, USB-C charging and charge rates The CS FREE charges its internal 11.1v 66wh lithium battery via a USB-C connector using the PD standard consuming about 60w. It comes with a mains power brick supporting 60w (DC 5v, 9v, 12v, 15v and 20v all at 3amps) and USB-C to USB-C cable. It does seem to work with other cables and chargers that follow the required PD specs. It will function and charge a car battery running off this source but be limited to around 4-5amps. From the internal battery, the charge rate appears to be much higher - I've measured 10+amps (up to 20 amps on paper). These differences in charge rate make sense beings as the lithium battery can supply more current than the PD standard it supports but it's not really obvious or explained by CTEK from what I've seen. It doesn't appear to do anything fancy like utilizing both simultaneously. Internal battery life The internal battery is big but it's nowhere near the capacity of the car battery you're probably charging. This will give enough to charge a flat battery quite fast to get you started up again but that internal battery will be long dead before the car battery is fully charged. You'll need multiple recharges of the CS FREE to achieve a fully charged car battery. The same also goes for the maintenance and trickle charging - you're not going to get very long out of that internal battery. That could mean a lot of going back and forth but there's other ways to power this guy. Other power sources I super appreciate the ability of this device to run off an internal battery but there are other useful ways to power the CS FREE. I've not tried the optional solar panel but I did buy the 12v USB-C cable with clamps allowing the CS FREE to run (or charge its internal battery) off another 12v battery. In my scenario, I can connect it all up to my car that's been sat for a while, drop a fully charged leisure battery in the footwell and let that keep the CS FREE powered for a few days to fully charge and refresh the car's battery. I think that's super useful if you've got no mains. That said, it still may not be enough juice to set it up and forget it for any length of time. I'm talking days rather than weeks. Ease of use and quality The cables and device itself seem reasonably rugged. Bit of a weird shape but it generally stays put with its little rubber feet. I feel like CTEK's minimalist approach to the operation and buttons of this device let it down though. I'm still not totally sure how to use the damn thing, to be honest. Just plug it all in and press the button until it looks like its doing something. As other people have said, the instructions are simple diagrams and they sort of get the job done but definitely could do with some more explanation. The main LED ring shows time until the car battery is charged (>8h to 1 hour) and the smaller ring (with the single button in the middle) shows the charge of the internal battery in 25% increments. I honestly think a screen or some more labelled LEDs would've been much better. CTEK tried to dumb this down too much in my opinion. Value It's not too bad but not a steal. I think the ability to run off DC is great but this isn't expensive technology and the internal battery is of limited use. I think you're paying a little premium for the CTEK name and their expertise + battery charging tech. If you just need something that can charge a car battery (without trickle and maintenance) from another DC source, there's chargers aimed at the RC market that can do this for a third of the cost. Conclusion Handy device for emergency charging. You'll need to investigate another power source using the optional 12v crocodile clips or something that can provide 60w power delivery via USB-C at the required voltages if you want to fully charge or leave your car connected up for any length of time away from mains. The status and operation of the charger isn't too obvious from the dumbed-down LEDs and instructions so loses a star from me for that. Update Feb 2025: The internal battery/charging failed 8 months after purchase! The LED would show the battery as <25% and never finish charging. It was returned to Amazon under warranty after talking to customer services for a refund (they were unable to replace). Unfortunately, the price has since shot up from £148 to £240 and it just isn't worth it. The internal battery is rated to last "300 cycles, 80%" but this one (or the internal charging) has clearly failed way before that. The charger would run as normal when powered via USB-C.

Really brilliant and saved me an extra call to service centre. Great size, bit overly big or heavy. Charging so easy. I did buy the extension cables just incase.

I bought the CS Free to charge my battery up or maintain it as a plugged in trickle charger would but, with a 80Ah battery and a CS Free with a relatively small Li-ion battery, it turns out that it won't do much unless you charge the CS Free at home and top up your car battery 3-5 times in a row. Hence, a secondary Led battery is needed to transfer it's power to the CS Free and then to the battery installed in the car and then you effectively double the battery capacity of your car battery but have to carry around a second battery that you need to charge at home with the same CS Free but this time plugged into the mains. It is circumvoluted, kind of annoying, but it works very very well and to make that work, you need this accessory.

Works really well and is small enough to close the bonnet whilst it's charging. Depending on how discharged your battery is it may take 2 passes to fill it up but one will get you moving. It's great for me as I hate having the window open in winter. Recommended!

[Update after extensive use – May 2025] After a few weeks of real-world testing, I believe I underestimated the intelligence of the CTEK CS FREE in my original review. Initially, I didn’t observe any true maintenance or “pulse” behavior and assumed it continuously pushed 13.5V until its battery was drained. However, through monitoring with a battery voltage tracker and testing both with and without a connected power bank, I’ve seen that the CS FREE does adapt its behavior once the car’s starter battery is full — shifting to what looks like a smart, pulse-style charging mode that preserves charge without over-delivering current. This means it does act as a proper maintainer when the battery is near full. While its internal battery capacity still limits long-term off-grid use (you get about 2–2.5 days from a full charge), pairing it with a high-capacity USB power bank can extend this to 4–5 days, which is perfect for people like me who don’t drive their cars daily. In short: I now believe the CS FREE performs closer to how CTEK claims — but it takes some experimentation to really see its strengths. [My initial review] I bought the CTEK CS FREE for a very specific reason: I own a car (Mercedes C-Class convertible) that I don’t drive often, and it’s parked in an underground garage with no power outlet. Over time, I’ve ruined multiple starter batteries simply by not driving regularly enough to keep them charged. I was looking for a portable, plug-free solution that could keep the battery healthy — without having to waste time and fuel on pointless “charging drives.” ⸻ My findings through real-world testing: • The CS FREE starts by pushing 14.1V, even when the car battery is already full • It quickly drops to 13.5V, where it maintains a constant output • This 13.5V maintenance lasts for around 12.5 hours until the CS FREE’s internal battery is depleted • After shutdown, my car battery was holding at 12.82V, which confirmed a full and effective charge I plan to extend its use with a 70,000 mAh USB-C power bank, which should give me around 2 full days of autonomous maintenance without needing to recharge the device or drive the car. This could save both time and fuel while preserving battery health. ⸻ Clarification for potential buyers: CTEK describes this device as a smart, adaptive charger — and it works well in that role. However, in fully off-grid mode (using only its internal battery), it doesn’t deliver a pulsed or intermittent charge. Instead, it holds 13.5V continuously, which steadily drains the unit’s own battery. It’s possible that when connected to wall power or solar input, it may behave differently — but that’s not covered in detail by the documentation. ⸻ Pros: • Compact, portable, and well-built • Works perfectly for charging or topping off a battery • Helpful USB-C and USB-A outputs • Great solution for situations without access to a wall outlet Cons: • Not suited for long-term maintenance off-grid • Runs continuously until it shuts down — no low-drain mode when battery is full • Runtime is limited to ~12.5 hours unless used with external power ⸻ Verdict: The CS FREE isn’t a wall-powered trickle charger — and that’s okay. What it does offer is a smart, high-quality way to top off or revive a 12V battery without needing a power socket. It’s not a long-term maintainer in off-grid use, but when combined with a high-capacity USB-C power bank, it becomes a very effective routine charger for cars that sit idle during the week. A good investment if you understand its limits and use it strategically.

Fait bien son travail , sort 20A en charge sur une Porsche 718 Cayman S . Construction de bonne facture racé. Seul petit inconvénient il n'est pas prévu une charge de la batterie du véhicule par la prise allume cigare, dommage seule la charge du cs free peut se faire par cette prise suite à l'achat du câble prévu à cet usage . Mais cet appareil est à recommander.

Installé sous mon abri voiture et utilisé tous les jours pour maintenir la charge de ma batterie. Très bon produit, facile à installer et utiliser. Attention pour utiliser avec des cables fixes sur la batterie, il faut acheter un cable adaptateur ctek supplémentaire.

Article parfait en complément du chargeur CTEK …..

Die Tasche wirkt wie maßgeschneidert für das Cteck CS Free. Alle mitgelieferten Kabel und Stecker-Adapter lassen sich gut darin vestauen. Wenn man den Fachtrenner beim Kabelfach löst und flachlegt, erspart man sich die sonst fällige Montage bzw. Demontage des Stecker-Adapters, da bei uns in Europa meist nur einer der drei mitgelieferten Adapter benötigt wird. Sehr schade finde ich, daß es (noch?) keinen Bumper zum Schutz dieses relativ schweren und voluminösen Gerätes gibt, damit es, im etwas zu engen Motorraum meines alten VW-Polo Variant, sicherer zur Ladeerhaltung der Batterie bei geschlossener Motorhaube untergebracht werden könnte. Ich hoffe, daß dies zu einer Anregung bei Cteck zur diesbezüglichen Erweiterung ihrer Angebotspalette führt.