Being in Charge with a Dual Battery Management: Part 2, the DCDC charger

Touring 4x4s need some sort of dual battery management system..should that be a DCDC charger?

In Part 1 Steve Cassano explored why he needed a dual battery management system, and is now exploring the benefits of a DCDC charger.

What is a DCDC charger and how does it work?

A modern DCDC charger is a compact electronic device often known as a smart charger or in-vehicle battery charger.   Its main purpose is to ensure that your auxiliary battery (you’re whole battery systems really) is working at its peak capability, making sure the alternator is fully topping the battery’s capacity and ensuring that it works for a longer period.  This is especially useful when you may be staying off-the-grid and away from mains power.
The DCDC charger has two main functions. Firstly to act as an isolator and secondly to manage the auxiliary battery.  Some DCDC chargers on the market can also come with built-in solar regulator as an option, thus making use of solar panels much simpler.

DCDC charger manufacturers highly recommended that they be secured as close as possible to your auxiliary battery, preferably within 1 metre to maximise efficiency and minimise any voltage drop often associated with long cable lengths.  Reputable manufacturers will clearly show recommendations on the charger’s positioning, cable size for varied lengths, which should be strictly observed for your particular set up.  Any good DCDC charger identifies the battery type, ensures the auxiliary battery is working efficiently (with LED indicators) and that the auxiliary battery gets to 100% capacity.

Even though it’s cabled to the main starting battery, the good thing is it does not interfere with the starting battery or the alternator’s function.  An alternator generates power and feeds charge to a battery.  A DCDC charger receives this charge from the alternator and maximises the voltage to the auxiliary battery.  The alternator and any linked computer system and even those commonly found it modern 4WDs treat the DCDC charger as just another 12v dependant accessory, such as a pair of driving lights for example.  Therefore, for modern vehicles which are inundated with computers and sensors, the vehicle will continue as standard, while the DCDC works’ it’s wonders monitoring and charging the auxiliary battery.  It can also determine or be manually set up for the type of auxiliary battery in use, such as sealed, wet cell, AGM, Gel and even the new lithium style batteries.
Most DCDC charges like those offered by Redarc, can work in the range of 9-32V making it suitable for all 12v and 24v vehicle systems.  The enhanced models come with features such as dual battery isolation, protection against water ingress, reverse polarity and overheating as well as integrated solar regulators.

Choosing Redarc and what I needed to know.

After repeatedly reading through Redarc’s literature over several weeks, and even though I still had some questions, I came to the conclusion that one of their DCDC in-car chargers was what I needed. But which one?

Some features of Redarc DCDC chargers that stood out from others on the market that impressed me was the ability to differentiate between the different chemistries for start and auxiliary batteries while delivering maximise  state of charge to the auxiliary while protecting the starting battery.  Another was the ability to compensate for any voltage drop while ensuring the necessary charge voltage is always delivered for any battery chemistry via 3 stage charging.  A sort of self-diagnostics I suppose, while all this in an efficient rather small package and being “green” due to solar priority (if fitted of course).

The first port of call is to check REDARC’s Product selector BUT not all vehicles are listed, so call their excellent support for additional assistance

While they have an on-line “Product Selector” that had listed a few model vehicles, my Jeep Wrangler along with many others wasn’t listed.  Disappointingly, it seemed to have only a few main-stream models.  This is because you need know the type of alternator that you have in your 4WD to determine which DCDC charger suits and how it’s to be wired up for correct operation.

The Redarc 1225D slotted in just but nice and secure while still being close to the auxiliary battery

As I understand it, there are basically three types of alternators found in 4WDs (or any vehicle really).  I needed to know exactly what type my Wrangler had before outlaying my hard earn cash.

This was my biggest hurdle as I was getting different opinions on what alternator I had under the hood.  Could it be a “fixed voltage” or a “variable voltage” or a “temperature compensating” alternator?  I tried all manner of sources from Jeep experts, dealers, forums and friends and still wasn’t convinced.  Even though Redarc’s comprehensive details and installation manuals were available on-line and while I still had some doubts, I excitedly (some would say blindly) opted for the Redarc BCDC1220 ING charger based on my reading and watching a few on-line videos.  Initially the set up seemed simple enough and after a few days a new parcel arrived in my post box.

It was soon after opening the box I realised what I perceived as a small issue.  The box and the advertised image from the seller did not resemble the item I purchased on-line.  The unit’s facia was different.  So I contacted the seller and they assured me that I had the latest version and the case and internal workings were exactly the same.  Even though the seller was very professional and apologetic I was not totally convinced I had even chosen the right product.  So they were happy to refund me in full, which was very gratifying.

This now left me with the two batteries installed and no way on how to manage them.  My first instinct was the easy fix and buy another solenoid but I knew there had to be a better solution.

Redarc Great (appreciative) Support

I then rang Redarc in South Australia, who I must say, have been very professional, responsive and most importantly patient with the many questions I bombarded them with over the week.  I felt certain of getting the right answers because I knew I was getting support directly from the manufacturer unlike some other 4WD accessory suppliers.

The support personnel did however stipulate that I knew correct details of the battery, in particular the “maximum voltage charge”. With Optima D34 it’s 15.6v, as I found out from Optima’s support in the USA, who answered my email overnight and the type of alternator in my Wrangler.

Knowing the type of alternator posed the biggest headache and whilst Redarc support were understanding, they limited their support (or rather were hesitant) when it came to unlisted vehicles as per their “Product Selector”.  This left me a little daunted but still determined. This changed a few days later, when my editor Robert Pepper suggested I contact Robert Chadwick, business development manager of light vehicles at Redarc.  Robert Chadwick was not only kind enough to phone me and help me determine which model DCDC charger I should choose and how to wire up the available options to suit but most importantly how to determine what alternator I had.
Robert suggested I opt for the BCDC1225D as it has the latest design, is easier to set up and had built in solar capabilities (see earlier requirement 4).  He clearly explained what wires/cables I needed to connect and to what, plus on where best to mount the charger under the hood.  I now felt confident that I was heading in the right direction and happy I was meeting my requirements.

Next Step – Redarc 1225D Installation, Wiring and Setup.

Soon after speaking with Robert from Redarc, I got hold of a new 1225D 25 amp, solar capable in-vehicle charger.  At well over $400+, they’re not cheap but the quality clearly shows through as did the support so far.

With heightened anticipation, I opened the box to find the Redarc 1225D unit and a set of instructions the same as those that I’d previously downloaded from Redarc’s web site.  A quick read through the paperwork, outlined simple yet detailed instructions plus a few diagrams of suggested setups depending on your circumstances.

Using a quality crimp tool ensures proper contact and life much easier

Redarc suggests that the charger be installed as close as possible to the auxiliary battery, preferably within 1 metre but as far away from heat as practical.  Luckily I had room just behind the left head light that allowed a sturdy mounting, free flow of air, was away from direct heat and all within 600mm.  Perfect.  (There are actually some customised brackets for a few 4WD models available in cyber world too).  I also needed to consider where to mount the two fuse holders, which should be fixed in place as close as possible to each battery.

Hankering to install the unit as soon as possible, I had pre-purchased the necessary hardware to suit my setup.  Redarc clearly outlines minimal sizes for cables, fuses, fittings and the importance for proper electrical practices.  I won’t go into great detail on the installation here as other implementations may vary from my own.  Suffice to say, they should all be quite similar.

So on my shopping list was:

  • 1 metre of Narva twin sheath 8B&S battery cable rated to 85amps, part #5808, $13
  • 2 Midi fuse holders with matching 40amp fuses plus a spare fuse, $27.
  • 6 Narva cable lugs part #10-8, $6.
  • Butt splice crimp, to join thick cables (more on that later)
I prefer adding solder to all terminals like this Narva Lug which ensures maximum security for all joints.

Other necessary hardware which is required but I already had on hand are:

  • Crimping tool.
  • Soldering iron and solder.
  • Heat Shrink to suit cable size, preferably double walled which has internal glue that seals even better against corrosion.
  • Split conduit to protect cabling 7 and 13mm.
  • Cable ties (DIY’s best friend).
The 2 x 40amp midi fuses are secured and protect the system against unforeseen electrical shorting.

In Summary

In my case I found the implementation went through smoothly and the unit worked properly from the start.  I had to customise some bracketing to securely hold the unit but needed just to drill one hole to do so.  I’m very happy with the quality of the unit and the available features and options that would suite most 4WDs.  The built-in MPPT solar regulator is a bonus, when it comes time for me to go down that path.  All this was very assuring as it would be a simple exercise to migrate this unit to another vehicle when the time arrives.

Finally installed and easy to read the REDARC’s status via bright LEDs. Happy Days!

There are however are a few things that I think Redarc could address or at least include in the box.  First the cables from the back of the unit are quite short, about 30cm.  As Redarc stipulates that the unit be within 1 meter (of course not always possible for some), I cannot see a reason why they don’t have them at 1 metre long.  The additional cost would be nominal but most importantly it would alleviate the need to join cables in most cases.  Which brings me to my other issue and that’s the recommendation to use a butt splice crimp to join the two main cables.  I had great difficulty locating an outlet that supplies 8B&S crimps or 6B&S if you happen to need to run thicker longer cables.  They are very difficult to locate from the usual suspects but I managed to use some smaller ones with ample solder to ensure minimum loss of conductivity.

Overall I found the Redarc BCDC25D to be a very robust, well-built and easy to install unit that suited my needs perfectly.  I was very fortunate in that it fitted with just a just a few millimetres to spare all round.  Perfect.

Steve Cassano

Steve Cassano