Projecta IDC25 DC DC charger

G'day Ivan. Just setting up my batteries for the new van and had almost settled on a Redarc unit Would be good to know of any problems I might encounter with it. Might have to think again.
Dave.

Not sure why they failed. Both were on dual batteries mounted in the vehicle, one was mounted in the engine bay next to the second battery the other in the cab with the battery under the tray. I only installed the first one as per Redarcs guide but I wasn't happy installing it in the engine bay.

Cheers Ivan. Their factories just down the road from me so I might call in for a chat.
Dave.

G'day Dave,
I have the 40 amp Redarc BCDC1240 charger installed in my Dmax ute charging 2 off 120 AH AGM batteries.
Been working just fine for 18 months.
Mate had some issues with a Redarc brake controller & he was happy with how Redarc resolved his problems. That was the reason I bought that brand.

Cheers Stu.

Got the same charger as Bushranger around 4yrs ago charging 2 x 105ah agm's mounted in the canopy next to the batteries no problems. I would go with something larger like these to get the power into the batteries.

Thanks for the information. It’s going in the van behind the front seat in a “battery area”. I’ve got an Iveco daily.

Even so, if the place the DC unit is in doesn't allow full cooling air supply, when charging a large AH battery bank will mean the IDC25 will create it's own heat internally and if it can't get rid of the internal heat while working hard, then it will also derate it's output to some degree which lengthens the charge time as mentioned below.

COOL is good. Some add a switchable computer fan to gently blow airflow over the unit. A very small milliamp draw keeps it cool. Works for fridges and most electrical gear subject to elevated temps.

The main drain will be the fridge which is an Engel 40ltr eclipse. I have 3 lights, a fan, a laptop and will probably be charging a couple of phones. I’m in an Iveco daily van. 2 batteries were suggested as I like to stay remotely. Thanks for your information.

Trevor, OK that's a bit different to what I was thinking.
240Ah of storage and 250W of solar is heaps for what you are running in the Daily. IDC25 will be fine because I don't believe you'll be running down the battery much at all. In fact you could easily get by with a single battery but its nice to have plenty of power in reserve.

thanks for the information but I don’t really understand much of what you have written. I’m not being disrespectful but I have very little technical knowledge on this. Thanks anyway.

In addition to the projecta I mentioned I have above I also have a ctec 250/smartpass setup in the Ute. This gives up to 120a charging when the battery can handle it which isn’t very often. If you aren’t deeply discharging your batteries while off grid, larger chargers are a waste of effort. If you run a 24v cpap all night through an inverter such as my old man does for example, you want the fastest recharge money can buy. The system you first mentioned, wired correctly, is an excellent choice for most people. 25a is quite a solid charge rate and is right on the commonly recommended 10% of your rated AH capacity so you’ll have no issue with it. As I also mentioned, I’ve been using one on my 360ah bank in the camper since 2016 with no issue at all.
Yes, a 40a charger will require heavier cabling, and yes it will charge a deeply discharged battery quicker than a 25a charger, but that all depends on what the battery will accept, not which charger you bought, and batteries don’t accept monstrous current for very long.

Hi Trevor
If your usage stays low as you indicated on Wednesday, your existing setup should do it easy IMO . I have been running various solar plus vehicle charging for a few years. I haven’t got very technical about it , but with trial and error (and information gleaned from forums, google etc ) it works. Not everyone is into having all the monitoring equipment ( and it’s not absolutely necessary).
Pretty simple really , if your running out of battery power you probably need more charge , panels are cheaper than ever so if you’ve got space to put them , use more. all you need is a regulator to handle the amount of panels. One thing is on an overcast day you can hook in more solar to the same regulator, ie using a portable to add on panel capacity.
Hope this makes sense to you.
Cheers
Shane

Trevor,
It all depends on how low you discharge the batteries as to what current/time factor is required to replace the charge. The 25A DC DC unit coupled with sufficient solar input will charge the batteries ok for normal discharge amounts. In the event you sometimes DO have a lower SOC, then catering for that can be done if engine running by having what Gbc mentioned. As an alternative to that and cost effective, is to fit a heavy constant duty solenoid to link vehicle battery/alternator to your battery bank. Yes cable size has to be sufficient, but as mentioned above, the batteries only take a heavy current for a short while. Most alt charge volt readings indicate that is so. Your alternator 180 amp I believe, will surely recharge via sufficient cable size, a high current which then reduces quite quickly and settles as a normal charge rate which the two batteries require. This solenoid when activated can be done after startup and used to provide the majority of charge and then switched off to leave the DC DC unit to complete the absorb and float as it sees fit to do for a finish to the charge. Having healthy sized cable, not the lowest resistance super large cable size, between main and aux of this solenoid system will cause some advantageous voltage drop while heavy current demand is happening, but healthy current flow all the same and the alt/aux batt voltage will have risen and self limited the bulk charge to the aux batteries. This replaces faster, IF needed, the state of charge if solar time factors or DC DC ability versus time are an issue.
Some may scoff at this idea but I am still using a Full River 105 ah AGM which I bought in 2009, it now only holds about 50% Capacity but has been charged all it's life from the above type of setup. I think it works and cost of it all was a distinct factor for me.

I'd be hesitant to have a solenoid effectively bridging the input-output of any DC-DC charger without the explicit sanction from the MANUFACTURER.

Connecting the input to the output should not cause any problem as the DCDC will just remain in constant current mode, not very efficient though as a 40A charger for instance could be pulling 60A if the charge voltage from the alternator is low and the charger providing no voltage gain in that situation. Think of it this way, the alternator is running at 13.8V, the charger on the other hand is drawing 60A trying to raise its output voltage but can't as it is bypassed and has the cars electrics connected to it. If it does manage to raise the "system" voltage ie car is using less then 40A then the alternator will back of its charge to maintain 13.8V and the charger will be effectively providing the difference. You could end up drawing 60A through the charger just trying to run the cars electrics. You could be just converting 20A to heat, granted you only wasting 20A but 20A is 20A.

Would be more efficient to turn off the charger when its bypassed.

Zippo
Good point raised there. Yes one or the other not both. I don't mean having the DCDC input also connected to the alt system while the alt is doing it's major bulk run though. Maybe I should have been clearer. Yes, DON'T have the DC DC input active while the engine alt is doing the bulk pump up of charge. I didn't intend it that way. Simple changeover of solenoid/ and DC DC input. Maybe the solenoid select switch DPDT, would switch off/break the sense lead of a VSR which supplies the DCDC. I will not have it connected all the time.

Pretty much the same as a smart pass but cheaper. Sounds good.

HKB/RMD I asked Redarc that very question, more than once. The first reply was "we'll need to check and get back to you". A follow-up email some time later quoting the previous exchange was met with silence.

It may well be OK, but if it lets the magic smoke out then you are out both the charger function and a pile of $$.

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No no no HKB. You have it all wrong!
What will actually happen if you connect the output to the input of a dc-dc charger is that the charger will raise the output above the input voltage which will then feed directly back to the alternator. The alternator will begin to behave as a motor and add drive to the engine via its belts. This drive will cause the vehicle to increase its speed and go racing up the highway straight past a cop waving you down.

At least that's the story I'm going to put to the cop if I get pulled up for speeding!

"It may well be OK, but if it lets the magic smoke out then you are out both the charger function and a pile of $$."

The input is isolated from the output internally. Nothing untoward will happen apart from wasting power.

Perpetual motion Alan, if only I could achieve that.

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There are days Leigh, when I feel that I am in perpetual motion. lol

Allan.
When traveling with the solar feeding my DC DC unit ,when the sun comes out I do feel the alternator add power to the system as it gets a surge. To compensate, I have fitted a row of large dia driving lights to the roof to act as an airbrake and to keep below the highway limit. Seems to calm it down ok.

"The input is isolated from the output internally. Nothing untoward will happen apart from wasting power."

There you have it folks, the warranty statement that I couldn't even elicit from the manufacturer. So go for it, Leigh will provide the warranty replacements ...

Been inadvertently done by novices in the past with no damage to the charger.

This setup exists in many vehicles where they have installed a jump start bypass solenoid and have a DCDC charger.

Rather surprised that Redarc could not answer your question.

Actually it appears they do know the answer Zippo, well their engineering section anyway, you must have been asking the wrong person:

Redacr diagram showing jump Start

Zippo.
HBK didn't give a warranty statement at all and didn't announce it as such, but to claim he did is not correct. He simply stated what the unit will do because it is a switchmode device with separate, isolated, input and output.

These devices are VERY different to a PWM regulator which is toast if incorrectly used. I scrape of the burnt bits on toast, it doesn't work with PWM regs though. Lightning or some hidden force zapped one of my cheap PWM units.

Leigh, it was exactly that diagram which I queried - and which they were unable (or unwilling) to back up or qualify in any way.

RMD - I have been designing in power electronics for decades, so I do know the odd bit about magic smoke.

It would seem to be a lack of communication between the Redarc engineering section and their technical support staff.

As they have published a document stating the unit can be wired in such a way then they would have no case to deny a warranty claim if doing so was to cause the unit fail, but then it shouldn't anyway.

.
Note that the Redarc diagram shows a pushbutton activating the solenoid. On that basis it would not be expected to be closed for long..... only a brief cranking. Closed for lengthy periods could be another 'kettle of fish'.
Redarc may recognise this but not wish to get into debate over it.

Bear in mind that the charger differential voltage, that is the difference between the input (say 12v) and the output (say 14v), being only a couple of volts limits the power being dissipated in the charger loop.
And also, maybe Redarc has some crafty circuit magic that effectively shuts the charger off in this configuration, but I doubt it.
Me? I have trouble getting my head around it. It is not what I would design.

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I think that the Redarc technical support staff IS the engineering section.
At least that is the impression I gained when I have spoken to them.

Allan if there was an issue they would have some warnings ie don't use override for extended periods etc. From memory the start assist has an on duration of 10 seconds once triggered.

To raise the terminal voltage of a battery you need to apply a charging current. The charger is not 100% effiecient therefore its output power will always be less then its input power. Therefore if we connect the output of the charger to the input it will try to raise the voltage it 14.4V which it can never achieve as it can't supply more power than it is drawing. The charger will therefore go into current limiting mode ie 20A. It will be supplying 20A to the battery but drawing more than 20A from the battery o the battery will naturally be discharging. How much discharge current will be flowing will be dependent s on the conversion loses within the charger.

This is exactly the same thing as would occur when connecting the charger to a discharged battery .

This reminds me of the good old days when a trainee seriously asked if you could use a generator to power an electric motor and then use the electric motor to turn the generator, wonder why no one else ever came up with that idea!

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Leigh,
You didn't grasp my point which related to the power being dissipated within the charger.
There is only a couple of volts differential between charger input and output therefore at your nominated 20A the charger would be dissipating about 40W or so which is of not much concern.

Alan switch mode power supply and this got thinking also, if we look at the case where the supply is 14V and the aux at 11.5V. The Redarc wants to raise the voltage to 14.4V but it can't as the battery terminal voltage is 11.5 at 20A so it current limits at 20A. One would hope the Redarc is around 95% efficiency but they don't say, the Enerdrive unit is 95% so will use that figure, therefore 11.5V at 20A gives 230W. Allowing for a 5% loss, around 13W.

So I'm revising my initial statement of 20A being wasted.

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I give up!