Ctek 250S + aux. battery problem





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  1. #1
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    Default Ctek 250S + aux. battery problem

    Looking for some input/advice!
    Just returned from a 3 week camping trip the Kgalagadi and experienced problems in keeping my auxiliary batteries charged in the hot weather (up to 39 deg C). I have two aux. batteries controlled by a Ctek 250S Dual + Smartpass and the sole job of the aux. batteries is to power a 90L Luna fridge which was set at "medium" battery protection.
    The aux. battery indicators showed that, while driving in the early morning cool air, they were receiving a 13v to 13.5v charge from the alternator, but after +-60 mins or if the outside temp was >25C, the charge displayed on the indicators dropped to 12v to 12.1v. It seemed that, as soon as the outside temperature was high, the Ctek was rationing the charge going to the aux. batteries and continued driving did not lift the charge. Needless to say, if the aux. batteries were at 12.0v by the end of the day, their voltage would drop overnight to 11.4v and in the morning my fridge would be in sleep mode and warming up.
    Friends traveling with us had a very similar issue with their vehicle which also had a Ctek controlled aux. battery and a 90L Luna.
    We ended up each doing a drive in the early morning, relying mainly on our solar panels to keep the aux. batteries going during the day and the fridges cold, and then running the engine as a generator to give the batteries a boost before going to sleep, but we ended up with diesel wastage, food loss, melting ice and lots of frustration!

    Before I raise an issue with my Ctek and aux battery supplier, I just wanted to check if anyone has had similar issues?
    Would appreciate any input.
    Thanks!

  2. #2
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    Default Re: Ctek 250S + aux. battery problem

    Ouch and bump for the morning.
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  3. #3
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    Default Re: Ctek 250S + aux. battery problem

    Need some more details of the batteries. Size (aH), type and whether High or Deep cycle. What size solar panels as well. I知 a bit of a novice but those are important details, I値l be reading with interest. Just kitting up a new camper, test run over Waster for 4 weeks in Bots and Namibia from 23 May.
    Love your neighbour. That痴 about it, it値l be the world we want.

  4. #4
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    Default Re: Ctek 250S + aux. battery problem

    A fellow traveller in Bots over Sept Oct had the same issues with the CTek unit mounted in the engine bay. Seems that it really dislikes high ambient temps and then restricts charging.

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  6. #5
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    Default Re: Ctek 250S + aux. battery problem

    The Ctek, like other imported DC-DC systems, has a sensor wire which is intended to measure the battery's temperature and taper off charging rate to avoid overheating the battery.

    I would look at where the probe wire is located and move as necessary. This is likely the culprit in instances such as is described.

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  8. #6
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    Default Re: Ctek 250S + aux. battery problem

    I have never had charging problems with my ctek but it is mounted in a cool spot in the trailer.
    I think it is worth the effort to do a test first. Let it charge a flat battery and then heat up the temp probe in hot water and see if the charging voltage drops.
    Choose life

  9. #7
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    Default Re: Ctek 250S + aux. battery problem

    It does sound like it is the battery probe which shut down the charging. It's supposed to be on on of the terminals on the battery to measure the battery voltage and prevent charging damage when the battery gets too hot. I assume that your batteries were not in the engine bay?

    Ideally you want the DC-DC charger to be close to the batteries to prevent voltage loss, as even over a short 5m cable run using 16mm2 cable, you will experience nearly 0.2 Volt drop.

    I did not have these problems with my Ctek in the same temperature scenarios, but my unit was in the cab, and not in the engine bay. My charging problems were related to the 2 x deep cycle batteries wanting more than the 20A charge, and did not charge up fully on our shorter trips, combined with 2 x 80W solar panels not giving sufficient charge during the hot days for 2 x 40l fridges.

    If the Ctek shuts down the charging because it's reading the high engine bay temperature instead that of the battery, then you can short out the positive input and output terminals on the Ctek, allowing the alternator to directly charge the batteries at the alternator voltage. I wired a Cole Hersee relay across my terminals to allow for higher amperage charging when starting to charge my batteries, and then switched it off later on to allow the Ctek to resume it's charging at higher voltages. This is basically what the Ctek Passthrough does.


  10. #8
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Gungets Tuft View Post
    Need some more details of the batteries. Size (aH), type and whether High or Deep cycle. What size solar panels as well. I知 a bit of a novice but those are important details, I値l be reading with interest. Just kitting up a new camper, test run over Waster for 4 weeks in Bots and Namibia from 23 May.
    Sure: My two aux. batteries are a 105ah deep cycle and a 90ah deep cycle. The 90ah was bought new last month after a pre-trip check was done on both.
    My solar panel is a 105w Flexopower foldable (Baja) panel which was connected via the Ctek system. I was impressed with the Flexopower performance - this light weight panel maintained my two aux. batteries at a better voltage in the heat of the day than my alternator did. Batteries were being maintained at 12.2 to 12.3v while the 90L Luna was drawing on them in 36 deg temperatures in the shade.
    My friend had the same Flexopower solar panel and a new single 70ah deep cycle battery and he experienced slightly worse alternator charging problems and good solar panel performance.
    By way of example of the alternator/Ctek performance: after doing two 3 hour 90km legs of the Motopi route to Mabua in 36 deg temp, our aux battery levels were just over 12v. However on our last morning driving 30km to the Mabua gate at 13 deg C, my aux batteries were looking a lot better at 12.7v.

  11. #9
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Lanners View Post
    Sure: My two aux. batteries are a 105ah deep cycle and a 90ah deep cycle. The 90ah was bought new last month after a pre-trip check was done on both.
    My solar panel is a 105w Flexopower foldable (Baja) panel which was connected via the Ctek system. I was impressed with the Flexopower performance - this light weight panel maintained my two aux. batteries at a better voltage in the heat of the day than my alternator did. Batteries were being maintained at 12.2 to 12.3v while the 90L Luna was drawing on them in 36 deg temperatures in the shade.
    My friend had the same Flexopower solar panel and a new single 70ah deep cycle battery and he experienced slightly worse alternator charging problems and good solar panel performance.
    By way of example of the alternator/Ctek performance: after doing two 3 hour 90km legs of the Motopi route to Mabua in 36 deg temp, our aux battery levels were just over 12v. However on our last morning driving 30km to the Mabua gate at 13 deg C, my aux batteries were looking a lot better at 12.7v.
    Your solar panel is not big enough.
    I have 2 x 100 panels feeding a 150Ah battery and this is just enough to power 2 x 50 l fridges.
    Choose life

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  13. #10
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by mikeml View Post
    It does sound like it is the battery probe which shut down the charging. It's supposed to be on on of the terminals on the battery to measure the battery voltage and prevent charging damage when the battery gets too hot. I assume that your batteries were not in the engine bay?

    Ideally you want the DC-DC charger to be close to the batteries to prevent voltage loss, as even over a short 5m cable run using 16mm2 cable, you will experience nearly 0.2 Volt drop.

    I did not have these problems with my Ctek in the same temperature scenarios, but my unit was in the cab, and not in the engine bay. My charging problems were related to the 2 x deep cycle batteries wanting more than the 20A charge, and did not charge up fully on our shorter trips, combined with 2 x 80W solar panels not giving sufficient charge during the hot days for 2 x 40l fridges.

    If the Ctek shuts down the charging because it's reading the high engine bay temperature instead that of the battery, then you can short out the positive input and output terminals on the Ctek, allowing the alternator to directly charge the batteries at the alternator voltage. I wired a Cole Hersee relay across my terminals to allow for higher amperage charging when starting to charge my batteries, and then switched it off later on to allow the Ctek to resume it's charging at higher voltages. This is basically what the Ctek Passthrough does.
    Thanks - I will look into the temperature sensor issue. My Ctek unit plus the 105ah aux battery is in the back (air-conditioned) drawer system area of my vehicle, and the 90ah aux battery is in the engine bay. I am not sure where the Ctek linked temp sensor is located. It could be that if the Ctek detects a high temp in one of the aux batteries it will shut down voltage to both?

  14. #11
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Lanners View Post
    Thanks - I will look into the temperature sensor issue. My Ctek unit plus the 105ah aux battery is in the back (air-conditioned) drawer system area of my vehicle, and the 90ah aux battery is in the engine bay. I am not sure where the Ctek linked temp sensor is located. It could be that if the Ctek detects a high temp in one of the aux batteries it will shut down voltage to both?
    I am finding it hard to visualize your system. Are you running cables from the main bat in the engine bay to the Ctek in the drawer system and then more cables back from the Ctek to the aux in the engine bay.

    Which battery did you take the voltage readings on.
    Cheers

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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Coenoes View Post
    Your solar panel is not big enough.
    I have 2 x 100 panels feeding a 150Ah battery and this is just enough to power 2 x 50 l fridges.
    Thanks Coenoes - I am considering doubling up on my panel.
    Has anyone come across a reliable table showing fridge size vs battery requirements vs solar panel requirements in different ambient temperatures? Has National Luna published anything?

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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Fluffy View Post
    I am finding it hard to visualize your system. Are you running cables from the main bat in the engine bay to the Ctek in the drawer system and then more cables back from the Ctek to the aux in the engine bay.

    Which battery did you take the voltage readings on.
    My electronics knowledge is rather basic, but yes there are cables from the cranking/main battery to the Ctek unit at the back of the vehicle, from the Ctek unit to the adjacent aux battery and then also back to the additional aux battery in the engine bay. Not sure if this complex wiring system would contribute to charging problems? I am not sure what a temp sensor looks like - but have unsuccessfully searched for it.

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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Fluffy View Post
    I am finding it hard to visualize your system. Are you running cables from the main bat in the engine bay to the Ctek in the drawer system and then more cables back from the Ctek to the aux in the engine bay.

    Which battery did you take the voltage readings on.
    Sorry - answer to your 2nd question: I have a voltage display reading in the front cab for each of my aux batteries and can constantly monitor them.

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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Lanners View Post
    My electronics knowledge is rather basic, but yes there are cables from the cranking/main battery to the Ctek unit at the back of the vehicle, from the Ctek unit to the adjacent aux battery and then also back to the additional aux battery in the engine bay. Not sure if this complex wiring system would contribute to charging problems? I am not sure what a temp sensor looks like - but have unsuccessfully searched for it.
    There is a thin black cable from the ctek, terminating in a flattish plastic temp sensor, about the size of you last Pinkie finger digit


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  20. #16
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    Default Re: Ctek 250S + aux. battery problem

    Locate your 250 dual and then trace the sensor cable from 250 to see where is the sensor. If possible, post a few pictures for us.

    I had exactly the same issue December in Kgalagdi and only option was to compliment charging with my solars.

    Your solar panel is too small as well to load to batteries!

    You will also need to make sure the smartpass is working correct as its very sensitive to voltage drop.
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by Hendrik du Toit View Post
    Locate your 250 dual and then trace the sensor cable from 250 to see where is the sensor. If possible, post a few pictures for us.

    I had exactly the same issue December in Kgalagdi and only option was to compliment charging with my solars.

    Your solar panel is too small as well to load to batteries!

    You will also need to make sure the smartpass is working correct as its very sensitive to voltage drop.
    Thanks - will try and locate the sensor today

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    Default Re: Ctek 250S + aux. battery problem

    What are you using the smaller battery in the engine bay for, or is it wired in parallel with the big 100Ah battery which is in the back of your vehicle next to the fridge?

    In theory with the CTEK and 100Ah battery in the back of your vehicle you should have no temperature issues with the CTEK, but as said that tempreture probe must be on your battery, even some experienced installers get this wrong and just leave the probe dangling somewhere.

    I still don't quite get how your system is configged, how the Smartpass and engine bay battery links in to the system.

    Any chance you and your friend who had similar issues on your trip have very similar systems which was also installed by the same workshop?
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  24. #19
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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by bigboy529 View Post
    What are you using the smaller battery in the engine bay for, or is it wired in parallel with the big 100Ah battery which is in the back of your vehicle next to the fridge?

    In theory with the CTEK and 100Ah battery in the back of your vehicle you should have no temperature issues with the CTEK, but as said that tempreture probe must be on your battery, even some experienced installers get this wrong and just leave the probe dangling somewhere.

    I still don't quite get how your system is configged, how the Smartpass and engine bay battery links in to the system.

    Any chance you and your friend who had similar issues on your trip have very similar systems which was also installed by the same workshop?
    My sentiments exactly. We simply don't have enough information to make informed guestimates as to what is going on.

    A wiring diagram would help enormously.

    The possibilities are endless. For instance a charge voltage of 13 - 13.5V is probably quite normal in a system when the battery is fully charged and the charger has regressed to float voltage.
    Cheers

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    Default Re: Ctek 250S + aux. battery problem

    Quote Originally Posted by bigboy529 View Post
    What are you using the smaller battery in the engine bay for, or is it wired in parallel with the big 100Ah battery which is in the back of your vehicle next to the fridge?

    In theory with the CTEK and 100Ah battery in the back of your vehicle you should have no temperature issues with the CTEK, but as said that tempreture probe must be on your battery, even some experienced installers get this wrong and just leave the probe dangling somewhere.

    I still don't quite get how your system is configged, how the Smartpass and engine bay battery links in to the system.

    Any chance you and your friend who had similar issues on your trip have very similar systems which was also installed by the same workshop?
    The smaller 90ah aux battery in the engine bay is wired in parallel with the larger 105ah aux battery in the back. There are a lot of connecting wires! I don't have a wiring diagram but will get one from my installer. In the meantime I will try and upload a couple of photos. I still have to search today for a temperature probe - would Ctek only have one probe or one per aux battery?

    My friend's aux battery system was done by a completely different installer in the Cape. Our only common feature's are the Ctek system and the solar panel.
    Thanks!

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