National Luna smart soleniod dual battery system -time for a upgrade

Time for thinking caps folks -esp those with electronics/auto electrical experience.

Currently have the system installed, bcdc weren't really a thing back in 2008 when Prado was purchased. This was the most suitable system at the time, in short it isn't due to the much hated smart alternators. The wonders of modern technology not always better but atlas way it goes.

I made a observation some time ago that when I put the start battery onto charge using the trusty ctek charger I would notice a audible click or clunk when a external source was applied. I also vaguely recall it occurring when i attached a solar panel as well.

It had me wondering if the addition of the external power supply could in fact pull the solenoid closed to allow charging (and possible discharging) of the auxillary battery, not a 100% confirm but just niggling feeling.

I then discovered despite only the start battery being attached to the charger that overnight the auxiliary battery would also be charged as well.

I came to this conclusion after i observed that the auxiliary battery was almost as charged as the primary start battery despite it not being connected to the charger physically.

Does this sound correct ?

That's the q for the electronics gurus - sure I know my stuff but not a engineer either !

Now onto the upgrade in short can't justify the cost of redarc like the intervolt unit but its physical size is bit difficult to install nor can I quite justify that expense either.

So this brings me down to the lower tier product Projecta IDC25 - ticks off all the boxes I need doesn't have the price tag of redarc and slightly lower than intervolt.

So how many had them fitted how reliable unit are they get what you pay for or not worth the hassle ?

I also looked at GSL but can't find anybody who sells them locally apart from making a special order of qty 10 from one of the leading electronics supply stores in Perth WA

Thoughts welcome & appreciated
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Reply By: Member - Phil G (SA) - Saturday, Jan 27, 2018 at 21:03

Saturday, Jan 27, 2018 at 21:03
I now have two of the Projecta IDC25's. Brilliant unit. Takes the charge from the solar panels before it takes anything from the alternator. And has decent temperature compensation - attach a probe to the casing of the battery so it doesn't get trashed by the heat.

I have one under the bonnet on the 200series to charge the aux AGM battery and I have installed one in the caravan. Both work as thye are supposed to, I have solar panels on both car and caravan, so the MPPT charging does the job.

I also have a Ctek D250S in our Tvan which has been very good too.
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Follow Up By: Dean K3 - Wednesday, Jan 31, 2018 at 11:27

Wednesday, Jan 31, 2018 at 11:27

Thanks for the input, according to one supplier there are two versions a newer variant and a older variant.

Newer variant was rejigged to allow for ignition sense issues. Any ideas what variant you have, all indicated on the model number and possibly serial # on base of unit near where the mount screws are installed.

2ndly where did you mount in the 200 series ?

I'm thinking somewhere in front of radiator for air flow and cooling, this is biggest killer of any bc/dc charger unit, always de-rate themselves when they get warmer than liked.

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Follow Up By: Member - Phil G (SA) - Thursday, Feb 01, 2018 at 00:19

Thursday, Feb 01, 2018 at 00:19
Wasn't aware of any variants. The Caravan one I installed April last year and the 200series one went in a few months later. Too hard to find any serial numbers now they are installed, but I expect they were the first models out.
200series unit is installed vertically between the battery and headlight on the drivers side. Just made up a aluminium plate to hold it.
The Projecta has the temp probe which I attached to the back of the battery so it shouldn't overcharge a hot battery. I've used it on some over 40degree days and it cuts back the voltage when things get hot - which is great in my opinion. So it will come down to 13.0V on a fully charged battery but still be supplying 3 amps to the Engel. I have an AGM under the bonnet so happy to see good temp compensation.
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Reply By: HKB Electronics - Saturday, Jan 27, 2018 at 21:21

Saturday, Jan 27, 2018 at 21:21
Connecting a charger to the main battery will also cause the isolator to turn on and charge the aux once the main terminal voltage rises.

Why change what you already have if it is working ok?

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Follow Up By: Gronk - Sunday, Jan 28, 2018 at 08:50

Sunday, Jan 28, 2018 at 08:50
I agree, why change something if it still works ?
If you have money to spend, think about your battery health or solar size first !!

BTW, I had a GSL isolator in the 200 series and only recently changed to a Narva ......both do the job......
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Reply By: RMD - Saturday, Jan 27, 2018 at 21:24

Saturday, Jan 27, 2018 at 21:24
Yes you are correct. As soon as the battery sees the charger voltage as being sufficiently high enough the VSR does to and so the click is the solenoid closing which then connects aux to main and charges it all.
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Reply By: Allan B (Sunshine Coast) - Saturday, Jan 27, 2018 at 22:23

Saturday, Jan 27, 2018 at 22:23
Yes Dean, your observation is correct. The connected charger raises the terminal voltage of the crank battery enough to trigger the solenoid on and thus connect the aux battery also to the charger. Both batteries are now being charged. The aux battery will not be discharging into the crank battery.
However, with the two batteries now connected in parallel, the charger algorithm is somewhat upset depending on the relative state-of-charge of the two batteries and the battery characteristics. It is not an ideal situation but not a big deal if only occasionaly practiced.

On the subject of dc-dc charger choice, I think any of those you suggested would be O.K.


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Follow Up By: 2517. - Sunday, Jan 28, 2018 at 10:24

Sunday, Jan 28, 2018 at 10:24
Hi Allan does that happen with a continuous solenoid wired off ignition?.
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 28, 2018 at 11:18

Sunday, Jan 28, 2018 at 11:18
No. In the case of an ignition-controlled solenoid, the aux battery will remain isolated whilst charging the crank battery unless the ignition is switched on.

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Follow Up By: Member - Rod N (QLD) - Sunday, Jan 28, 2018 at 14:09

Sunday, Jan 28, 2018 at 14:09
On the subject of DCDC chargers, my alternator is connected through a VSR and can supply the battery with up to 40 amps (measured). Given that the DCDC chargers mentioned are rated at 25 amps and are multi stage which is the best way to go to put 100 AH into the batteries?
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 28, 2018 at 15:27

Sunday, Jan 28, 2018 at 15:27
Rod, The current (Amps) that will flow into a battery from any source is a function of the applied voltage. It is not determined by the maximum current that the source (alternator or dc-dc charger) can supply. The charging current from either alternator or charger may not be the rating of those devices.
In the case of alternators, their output is maintained at a constant voltage so as the voltage of the battery rises during the charge, the current will fall as a consequence of the diminishing voltage differential. In other words, it is a tapering charge.
With dc-dc chargers, the output voltage adjusts to keep the "bulk charge" at a constant current until moving to finishing phases. This current will be the rating (25A) of the chatger.

So the direct alternator charge may provide greater current to start but may diminish in short time whilst the dc-dc charger may provide a lesser current but maintain that current throughout the whole period.

The determination of which will charge the battery in a shorter time depends on the behaviour of the altenator, i.e. the output voltage of the alternator. This is further complicated by the behaviour of modern controlled alternators.
An alternator with higher voltage will charge quicker but possibly at a current which is higher than what the battery manufacturer may recommend. On the other hand, the dc-dc charger will limit its current to a selected value. There are other practical benefits to dc-dc chargers.

So there is no simple answer as to which method is faster charge. Generally there is not a lot of difference but 'direct alternator' charge is cheaper whilst dc-dc charging offers additional benefits.

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Follow Up By: HKB Electronics - Sunday, Jan 28, 2018 at 18:55

Sunday, Jan 28, 2018 at 18:55
It all depends on the alternator voltage, the type of battery and its state of charge.

If one compares a 20A charger, charging a battery that will accept high charge rates, to an alternator with an output around 14.2V, charging a battery the battery that has been discharged to 50% SOC, the alternator will charge the battery to around 95% SOC in a much shorter time. You'll need a charger with an output of round 40A to match the alternator and that assumes the charger can handle the under bonnet temps and doesn't derate.

Please don't wish to get into arguments regarding the above, I have real time data to support the above, if you can put up real time data to the contrary then we can compare data. If you don't have the hard data to support your case then no discussion will be entered into, please no "what I have found" or "been told" statements without hard data to support your case:)

Still waiting for any DCDC charger manufacture to post up real time data showing their chargers will charge a battery faster in an in vehicle install.

If your talking 95% SOC up then the charger will win, personally I'm more interested in getting my batteries from a low SOC to a reasonable high SOC in the shortest time possible.

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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 28, 2018 at 19:51

Sunday, Jan 28, 2018 at 19:51
Leigh (HKB), Despite having "real time data etc.) your example nominating the need of a 40A charger to equal the alternator implies that the alternator is pumping in at least 40 Amps.
The typical auxilliary battery should not be charged at that rate so it is not a fair comparison. It is easy to quote a "real time" example to make a point but it does not satisfy the general case, or even answer the question asked.

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Follow Up By: HKB Electronics - Monday, Jan 29, 2018 at 11:27

Monday, Jan 29, 2018 at 11:27

It depends on what you call a typical auxiliary battery, Optimas, Century Marine pros, wet cell deep cycle and many more batteries will happily pull much more than 40A when they are in a low state of charge so for a lot does satisfy the general case not to mention the many who have a couple of batteries in parallel.
Many AGM's will also tolerant high charge rates when they are low, they just don't like them when they are approaching fully charged which is when your typical DCDC charger is trying to maintain a high charge rate.

One question I get asked quite frequently from those using DCDC chargers is will a booster diode work with their DCDC charger as it is taking to long for their batteries to charge. Some of these are users have gone from VSR setups to a DCDC charger setups only to find it now takes longer to charge their batteries to usable levels.

In my own setup I use a VSR in car and a DCDC charger in the camper, why because the VSR setup will bring the Marine pro Aux in the car up to around 95% SOC from around 40% SOC in around two hours. The DCDC is needed for the Lithiums as they require a higher charge voltage, Pre Lithiums the camper batteries were charged directly off the car without any problems. Obviously when you put the system in you use components that will compliment each other, anyone with common sense is not going to use a battery that can't handle high charge currents if its directly connected to an alternator.

As for does not answer the question, the question was:

"Given that the DCDC chargers mentioned are rated at 25 amps and are multi stage which is the best way to go to put 100 AH into the batteries?"

In a well designed VSR setup with suitable batteries the batteries would recharge much faster to around the 90% SOC mark. I see have seen this on trips where there has been a mix of setups in vehicles, on long daily runs there are no issues, with both types of system performing well. It's a different story though when you get a few days where you can only do a couple of hours driving a day and this applies to me too with my 30A charger in the van. The setup in the car has no problems putting enough back into the car aux to keep the freezer in the car running, it is not the same for the setup in the van, the 30A charger just can't put enough back in a couple of yours to keep things ticking over and I need to deploy the solar. I would have gone for a 40A unit for the van but at the time they were not available form the company concerned, and there were other considerations that generally aren't mentioned, for instance even with 26mm2 cable from the car to the charger the input voltage at the charger when its drawing 30A is marginal and that's with booster fitted to the tug. At idle the charger can't supply 30A, it throttles back to around 22A, car is around 13.5V with the car at 1500RPM, car around 14V-14.2V it can supply 30A. It would be interesting to see how many DCDC chargers are actually output their rated current when connected to a low voltage charging system?

I really don't see any logic in your argument a 20A charger is sufficient because the batteries may only be able to handle 20, if you have two 100Ah batteries and you have discharged them to 50% SOC it is going to take you at least 6 to 7 hours driving to bring them back up, don't know about you but personally if I can't bring my 300Ah of batteries up to full in around 3-4 hours driving I would not be happy.

As a matter of interest are you using a DCDC setup in your vehicle?

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Follow Up By: Member - Rod N (QLD) - Monday, Jan 29, 2018 at 12:10

Monday, Jan 29, 2018 at 12:10
My setup is in a motorhome but could quite easily relate to any aux battery system.
I have 2 100AH lead crystal batteries as the aux.
I have 300 watts of solar.
The vehicle alternator is connected to the aux batteries via a VSR.
My typical load is about 90 AH per day.
When I do drive it is for 2 to 3 hours but not every day.
The solar controlled is a basic PWM. I am looking at upgrading the controller to a MPPT so I have to decide on a stand alone controller with the vehicle alternator though the present VSR or a DCDC item with both solar MPPT and alternator input. Charge rate would be another factor to consider.
If I go with the stand alone I have been looking at Victron controllers.
With a combined item I was looking at a Redarc BCDC1240D.
Any comments welcome.
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Follow Up By: HKB Electronics - Monday, Jan 29, 2018 at 13:08

Monday, Jan 29, 2018 at 13:08
Hi Rod,

The bottom line is you need to put back in what you take out no matter what system you use. If the car is the only charge source then alternator or DCDC charger must replace this in your drive times. You may not need to replace it in ones days drive, you might be prepared for instance to let the batteries run down over two or three days of short trips knowing that the next trip will be long enough to recharge them fully, or you may just use your solar or other charger to top them up. I have four charge sources in my setup, the alternator, solar and a fuel cell for when the sun don't shine or I don't want to setup up the solar for some reason, and AC charger.

In your case your going to replace around 100Ah daily be so the minimum in a DCDC charger would be a 40A unit for a three hour drive time, if you run the batteries down to 30% your looking at 5 to 6 hours drive time. Of course that's charging off car only, if your supplementing with solar then you need to work out what the solar is contributing and then size the charger appropriately, personally I would size the charger without taking into account the solar to allow for solar charger failure, but depending on how you use your setup you may not need to worry about that.

How are you finding the lead crystal batteries, I have read they don't like high charge currents, I have also read some comments by another that did some testing of various size batteries and indicated charging them form zero% SOC straight off an alternator was not a problem?

Personally I don't believe in putting all your eggs in one basket, when I'm travelling I like enough redundancy that I'm not going to need to purchase equipment or do repairs in the field if something fails as it usually ends up mucking up the trip or cost an arm and a leg.

In my set car aux is charged via a VSR. Van batteries by a DCDC charger which also has an inbuilt MPPT controller. I also have a PWM solar controller in the van that was there before I installed the DCDC, either controller is switch selectable to charge the vans batteries but I usually use the PWM as I find it puts a little more into the batteries on overcast days contrary to the popular belief the MPPT should. The DCDC can be bypassed so that the Vans batteries can be charged directly off the car, or the cars aux charged via the vans chargers, this comes in handy in caravan parks etc as I just leave the car connected to the van and use the van A/C charger to maintain both van and car batteries. Also when camping as most times I can just get away with setting up panels for the van and bypass the DCDC to charge the car as well without having to set up panels for the car too.

Personally I'm not a fan of Redarc equipment it tends to be expensive for what you get and generally well behind other brands with allow user many user defined parameters. Their about to bring out a new unit that does everything, DCDC/Solar as well as controlling all the electrical equipment, lights, water pumps, heating, fridge, water levels display etc all from one display unit. Form one perspective it is the only piece of electrical controller you need to install, but from a redundancy perspective if it breaks down I imagine you'll loose everything. Do the people that come up with these ideas actually use them on a day to day basis I wonder and for remote travel etc. Suppose if you only travel the main roads and never far from someone who can replace the unit then not so bad, but if you do a lot of remote travel/camping etc doesn't seem like a good idea to me. I also wonder if they will be providing a repair service other than warranty for these units or will they be throw away? The other issue is most auto electricians and van manufactures etc never label anything, I would hate to have one of these unit replaced by your typical outback repairer, I certainly wouldn't be expecting all the cables to end up connected to the correct terminals.

Getting back to your question, I would go with the Victron or maybe have a look at the Enerdrive units etc.

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Follow Up By: Allan B (Sunshine Coast) - Monday, Jan 29, 2018 at 14:34

Monday, Jan 29, 2018 at 14:34
Leigh, the OP Dean asked a general question without specicics so I answered with generalities. Your response challenged that with very specific examples and "if this" and "if that" that becomes a complex answer likely to confuse. Dean referred to a Projecta IDC25 charger so it can be assumed that 25A suits him and to "the aux battery" so it can be assumed there is o ly one and it is probably nothing exotic. Finding altenatives outside the envelope simply to refute me does not help Dean. Perhaps we should ask him for his setup details?
Please don't joust with me mate. Just answer the OP's question without overloading him with technicalities.

To "satisfy your curiosity"I use a Redarc BCDC1220 into a 110Ah AGM battery that serves my humble load and fully recharges in 3hrs driving.

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Follow Up By: HKB Electronics - Monday, Jan 29, 2018 at 15:40

Monday, Jan 29, 2018 at 15:40

I was following up on your reply to Rod, not the OP.

As for the OP, my reply was specific to his situation also, he stated he has a 2008 Prado and VSR. The Prado has a temperature compensated alternator, he may or may not be using a booster, in either case the aux he presently has to be able to handle high recharge currents, so it seems he has one of those exotic setups you refereed to:)

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Follow Up By: Allan B (Sunshine Coast) - Monday, Jan 29, 2018 at 18:13

Monday, Jan 29, 2018 at 18:13
Your'e right Leigh. I'm working off my phone and paying attention to family at the same time and getting totally confused.
Sorry. Just ignore me.

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