[4ePajero]

The DC-DC charger uses an input which can usually be 8-16V DC.

It then converts that into the correct voltage to charge your battery (same as a proper 220V AC charger).

The reason for thick cables in the solenoid option is to reduce the voltage drop over the length of the cable.
Even if you have no voltage drop, your alternator is not the ideal source to charge Deep Cycle batteries properly.

So, to summarize:

• Yes, charger as close to battery as possible.
• Thick cables not required 9as long as voltage does not drop below min. input spec (usually 8V)
• No solenoids
• Intelligent charging
• Charging is not dependent on input voltage

[Chris]

I installed 2 systems on my car. NL system in front on a 70 ah battery and a Ctek 12V to 12V at the back with a 105 ah battery. I installed two sets of 6mm² cables to the back. The 2 systems are independant from each other. When one battery is flat I change over to the other. The installation is still new and not tested on an extended trip yet but seems to work fine.

Chris

[paw_by_paw]

Hi Guys,
My 2c's here.
So if you install a DC-DC charger you do need all these fancy charging systems
Q 2:Do you wire it straight from your current battery or must you go directly from alternator as some of the drawings I posted earlier suggests

Q 3: Will thicker cables in the DC-DC mode not prevent a voltage drop and decrease the resistance hence less voltage drop
I am still curious though as how long this setup will take to charge a fully drained 130a/h battery or is it best to use a normal battery instead of a deep cycle battery
I am not electrically minded please excuse all the questions but I am just wondering if DC-DC is ultimately the better option to go.

[andre.loots]

What is the least requirement for installing a charge cable for a aux battery in a trailer or caravan? I saw the National Luna kit, but not sure if it is an overkill?

[Gemaskerde Tuinvurk]

Andre, are you asking for simplest or cheapest?
In my mind the simplest would be a DC2D system, cheapest (over the short term only) would be a solenoid with thick cables.

paw, with DC2DC you dont need all the fancy stuff. I dont think there's a major diff in going from alternator or from battery - personally I will go from battery, as the wireing is easier From what I see above, from battery/alternator to charger, you can use thinner cable with the DC2DC charger, as it requires a minimum voltage of less than 10V (unlike a direct connection). From charger to 2nd battery, you should have minimum distance.

NOW, I just have 1 question: so if you dont have a solenoid, and the DC2DC unit is left connected to the main battery, charging the 2nd battery. What hapenes to the main battery? Does the DC2DC device tricle charge till the main battery is dead?

[Chris]

Karl, the Ctek DC2DC that I have only kicks in at a constant voltage of 13,4V for approx 30 sec's. It cuts out at something like 12,4V IIRC. It will therefore not drain your main battery.

Chris

[Gemaskerde Tuinvurk]

Thanks Chris, I made the leap and bought one.

Oom fourie knows best - in the long run this is the better solution especially if one wants to add more / bigger deep cycle batteries.

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[4ePajero]

Karl, the Ctek DC2DC that I have only kicks in at a constant voltage of 13,4V for approx 30 sec's. It cuts out at something like 12,4V IIRC. It will therefore not drain your main battery.

Chris

DC-DC chargers are not similar or identical!

I checked the CTek's spec, as listed on Bushpower's Website.

It does in fact state that it will only connect at
"from 13.4V for 5 seconds",
and disconnect at
"below 12.8V for 10 seconds"
__________________________________________________

Compare that to the BC Series DC-DC charger:

Input: 10-15V
Cut-out when input voltage is outside these two figures.
__________________________________________________
Another alternative is the Waeco:

__________________________________________________

MHO:

• The Ctek DC-DC:
  • This is obviously aimed at being used with an alternator as the input source.
  • The cut-off values make it impractical to use with other "12V" sources.
  • The low cut-off makes it risky to run 'thin' cables/wires to the back of your vehicle - the voltage drop might just be enough to prevent it from connect. THIS DEFEATS THE OBJECT OF DC-DC CHARGING!
  • The intelligent charging is a benefit.
• BC Series:
  • This unit has intelligent charging.
  • The low and high cut-off values for the input source means that it can be used as an effective, intelligent charger, using ANY '12V' source, such as
    • alternator,
    • other batteries,
    • 'dodgy', cheap battery chargers,
    • cheap AC-DC converters
• WAECO:
  • NO intelligent charging.
  • The low and high cut-off values for the input source means that it can be used as an effective, but NON-INTELLIGENT charger, using ANY '12V' source, such as
    • alternator,
    • other batteries,
    • 'dodgy', cheap battery chargers,
    • cheap AC-DC converters
  • Provides a constant 14.2V output, with up to 40A current.
  • Acts like an alternator!

My choice?
The BC series, for the fact that it can use 'dodgy' input sources to provide intelligent charging.

• Choose according to your needs!
• If used in parallel with other batteries, cut-out can be controlled by diodes (non-return valves ), solenoids or low-voltage cutouts (such as fridge protectors)

[Gemaskerde Tuinvurk]

MHO:

• The Ctek DC-DC:
  • This is obviously aimed at being used with an alternator as the input source.
  • The cut-off values make it impractical to use with other "12V" sources.
  • The low cut-off makes it risky to run 'thin' cables/wires to the back of your vehicle - the voltage drop might just be enough to prevent it from connect. THIS DEFEATS THE OBJECT OF DC-DC CHARGING!
  • The intelligent charging is a benefit.

This is true - this why I still installed thicker wire to the back. The nice thing with the cut out voltage is that no solenoid is needed. So i dont have to worry that my main battery will be drained. Also, i need the higher output from the Dc2Dc to charge my deepcycle, as my alternator is regulated down to 13.9V when the main battery is charged. (with I get about 13.6V at the back)

I will just be using the alternator to charge, with the potential of adding a Solar panel at a later stage (I like the ctek one that has the solar input).

[CATS]

I also like the Ctek feature where, if I understand it correctly, it will actually condition your 'main'/starter battery if there is sufficient power delivered to charger by something like a solar panel, and the aux baterries are already full. Anyway that is how it sounded to me from the manual? I am still trying to determine if it will do the same when I have my AC DC Ctek charger connected to the aux batteries where electricity is available.

CATS

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