Frequently asked questions about CS FREE


Battery types

What type of batteries can the CS FREE charge?
The CS FREE will charge all types of 12V lead acid batteries, and lithium-Iron-Phosphate (LiFePO4) Sized 10-130 ah.

Do I need to know what type of battery is fitted in my car?
No, that is not necessary.  The CS free will charge all types of lead acid and lithium iron phosphate batteries.  Simply press the ON/OFF button and the charger will take care of the rest.

Will the CS FREE detect what chemistry the battery is which is connected to it?
CS FREE will charge lead acid as well as Lithium (LiFeP04) with the same charging algorithm.  The charge curve has been specially developed to charge both chemistries in a safe and effective way.


How do I connect CS FREE to the battery within the vehicle?
The standard approach is to connect the positive clamp to the positive battery pole or charging point and the negative clamp to the earth or ground point on the vehicle chassis, or recommended charge points. PLEASE NOTE: You should however, always follow vehicle manufacturer recommendations on how to charge your battery. These can be found in your vehicle manual.

Can the charger be left under the bonnet while charging?
Yes, but keep it apart from hot surfaces and sharp edges and ensure there is room for the charger and the cable. NOTE Do not drive your car with the CS FREE under the bonnet.

Can the CS FREE be connected to the battery when I try to start the vehicle?
Yes, we recommend that the charger is connected and switched on when you attempt to start the vehicle. Please make sure all consumers (Fan, headlights, wipers etc.) is turned off during the start attempt.

Can the CS FREE assist the car crank when the charger is connected?
Yes, as with all CTEK chargers - it is recommended to be left connected and switched on when cranking attempt is made.

How long does it work?
Not connected to mains or other power source, you can charge as long as the internal battery has got any power left (indicated by the smaller display on the charger). How long that will last, depends on how discharged your battery is.  When connected to a power source, you can use it as a regular battery charger & maintainer, for charging and for short- or long time maintenance.


Do I have to press a button to make the charger start?
The CS FREE will start automatically when it is connected to any input sources. If the CS FREE is used without any input - you need to press to ON/OFF button. On top of the charger there is two circles of lights, the smaller one is also the ON/OFF button.

Does the MMI for the external battery show the state of charge (SoC)?
No it does not show SoC of the battery. The MMI features a countdown display that shows you how long there is left to go until the battery is fully charged. Once the battery is fully charged the MMI will slowly pulse all six segments synchronously.

Can I use the CS FREE with my other CTEK connectors?
No, the CS FREE is too powerful for standard CTEK connectors. The CS FREE will charge with up to 20A, and the standard CTEK connectors can only handle up to 10A.    

Maintenance charging 

I have my car parked for a long time; how often do I need to recharge the CS FREE to be able to maintain the car battery?
That depends on how much electronic components are active when parked, and the battery state of health, and that will be very individual from case to case. For normal car/battery we recommend you to recharge your CS FREE approximately once a week for best battery maintenance.

If the CS FREE is connected to mains, can it be used for maintenance charging for long periods of time?
When connected to a power source, you can use it as a regular CTEK charger, for charging and for short- or long-time maintenance.


I have my car parked on the street, with no mains. What charger can I use?
CTEKs new CS FREE can be used without main power connected.

Can I charge my battery anywhere?
Yes, the CS FREE is a portable charger, that you can bring with you and charge wherever you are, no matter if there are mains available or not.

How "portable" is this, aren't all CTEK chargers portable?
CTEK's new CS FREE is a completely portable battery charger and maintainer that can be used without mains power - so you really can use it any time, any place, anywhere!

How big and heavy is it?
The physical size is 248mm x 98mm x 78mm.  and it weighs 1.4 kg, and there is also a smart bag as an accessory, so you easily carry the charger and the accessories with you.


The connection between the solar panel and the CS FREE, is this a CTEK solution, or can any panel be used?
We recommend that the CS FREE is only used with the CS FREE SOLAR PANEL KIT, specially developed to work with the CS FREE, for maximum performance and efficiency.

How big panel can be used?
THE CS SOLAR PANEL KIT features a 60W panel. We recommend that the CS FREE is only used with the CS FREE SOLAR PANEK KIT, specially developed to work with the CS FREE, for maximum performance and efficiency.

What is the maximum voltage from the panel to the CS FREE?
The CS FREE can handle inputs of up to 25V from the CS FREE SOLAR PANEL KIT - higher voltages risk damaging the CS FREE unit. To protect against this, we recommend that the CS FREE is only used with the CS FREE SOLAR PANEL KIT, specially developed to work with the CS FREE, for maximum performance and efficiency.

Is there a solar panel MPPT regulator inside the CS FREE or inside the solar panel?
The MPPT is within the CS FREE, and it works together with the safety box fitted on the cable to the solar panel charge kit. The safety box makes sure the voltage is within the range of what the CS FREE can take. For this reason, we only recommend you to use the Solar panel charge kit together with the CS FREE.

Tech (or other) specs

How long warranty time?
2 Years, for the charger and for the accessories.

Will there be any spare parts on cables and connectors available after the release?
For the time being, there are no spare parts available.

Is there an Auto Power Off?
If the charger has no input and no output for 10 minutes it will automatically power off.

Will there be a bag to store the charger and the accessories?
The CS FREE is not supplied with a storage bag. You can purchase a CS FREE storage bag (separate accessory), so you easily carry the charger and accessories with you.

What is the IP rating?
IP rating is 54.  Dust and flush safe. This means that dust in harmful amounts cannot get into electrical components so that insulation faults can occur. The luminaire must be tight, and gaskets are therefore necessary. Tested in a dust chamber. IPx5 requires flushing resistance (not high-pressure flushing). So, use the charger outside! In rain and fog - the charger itself is built with a "heel" so even if it stands in some mm of water - it will work fine.

Is it a jump booster?
CS FREE is an Adaptive Booster - it will talk to the battery to see how much charge it needs to get the vehicle started within 15 minutes. And it is safe for the battery and the electronics in the car.

What is the start voltage for the CS FREE?
The CS Free will detect a battery if the voltage is over 3V. It will also choose not to charge if the voltage is over 14V.

Why is the limit 3V?
3V is an extremely discharged battery, this is what makes the charger reverse polarity protected and short circuit proof.

How much is the charge Amp?
If you have any power connected to the charger - it will charge up to 5A. If you do not have any power connected to the charger, it will charge up to 20A as long   as there is power left in the internal battery of the CS FREE.

Is there a SUPPLY mode on CS FREE?
No, there are no selectable charge modes, it is fully automatic. If you need the SUPPLY-function I recommend you to use another CTEK charger.

Is there a Desulphation mode and a RECOND mode on the CS FREE?
There are no Desulphation or Recond on the CS FREE, as this might harm the LiFePO4 batteries. If you need Desulphation or Recond function I recommend you to use another CTEK charger.

If a LiFePO4 battery has shut down because of the UVP. How to charge?
The CS FREE does not have a wakeup function. If the LiFePO4 -battery has closed down, you have to use another power source to wake it up.

Can it take longer than 15 minutes to get the battery ready to start the vehicle?
15 minutes is the time it can take to empty the internal battery, if the receiving battery is empty. Most cars is ready to start within 15 minutes. If it does not - please recharge the CS FREE and try again, in any case it can be a good idea to get the battery tested it might be in poor condition and needs to be replaced.

To charge the charger

How do I charge the internal battery within CS FREE?
It can be charged in different ways. You can charge from mains with the PD adapter supplied in the box, or with additional accessories (not supplied) through a 12V output in the car (USB-C CHARGE CABLE 12V PLUG), from another battery with battery clamps (USB-C CHARGE CABLE CLAMPS) or from the CTEK SOLAR PANEL CHARGE KIT.

How long will it take to charge the internal battery from totally drained to fully charged?
From "Less than 10% left" - (first led blinking) to fully charged, it will take up to 60 minutes, as long as CTEK standard accessories are used. 

What type of battery is within the CS FREE?
It is a lithium Polymer-battery.

Can I recharge the CS FREE from my vehicle?
Yes, you need to have the additional USB-C CHARGE CABLE 12V PLUG. It will start charging as soon the motor is running.

Can I charge the vehicle battery through the 12V output in the car?
No, you cannot. The cables in your car, from the 12V output to the battery, are too weak for the high current (20A), so you cannot charge through the 12V output.

Can I have the charger connected and charge the internal battery whilst driving?
Yes you can! The internal battery will not get overcharged so when fully charged, it will stop charging even if the input is still active.

Is it possible to charge the internal battery from the USB-C port in the vehicle?
Yes, that is possible, use the USB-C to USB-C cable included in the box.

How long lifespan does the internal battery have?
The lifespan is 300 charges cycles with a remaining capacity of 80% or more. Warranty time for CS FREE is 2 year.


How do I know that the CS FREE is charging the vehicle battery?
The lights in the big circle on the top of the charger light up, and one of the LEDs is blinking, this tells you that the charger is charging.

How do I know when I can start my car?
When the first led "START" is lit with a steady light, the vehicle will most likely have power enough to start.

How do I know when the battery is fully charged?
All LEDs in the bigger circle are lit and the lights are slowly pulsing, the battery is fully charged.

Can I leave the charger unattended whilst charging?
Yes, like all CTEK chargers it can be connected for long periods of time. Please note that if the CS FREE is not connected to an external power source, the charger will only work as long as there is power left in the internal battery.