12bcdc25 or 12bcdc40 to run van fridge?

kezngaz · Senior Member

12bcdc25 or 12bcdc40 to run van fridge?

Delta18 · Guru

I would think you would be better to run your Andersen plug (hopefully that has used 6B&S cable not auto 6mm) to a 40a dc-dc charger to charge the van battery then run your fridge from that battery.

The Phantom · Guru

Kezngaz, IMO you are over thinking a problem which may not exist.

Problems that you read about may not, in fact, be problems at all. If you haven't used your van on the road, how do you know the fridge will not maintain temperature?

A fridge works the same as an esky, it is insulated and if cold at the start of the day's journey it will maintain most of that temperature during the day, as long as you don't continually open it when stopping.

As the majority of people travel about 5 to 6 hours per day, if your fridge is cold at the start, is already on 12v and is not opened frequently, it should be OK.

That is the way I travel and have never had a problem.

I would be inclined to give it a go before you start forking out your hard earned on a comment that you have read, written by someone who may not have any idea whatsoever.

The Phantom

kezngaz · Senior Member

What i also never mentioned was wanting the house battery fully charged when arriving at camp. if we were lets say free camping for 3/4 days then turning up with less than 100% charged batteries could be a problem.

We are also considering mobile solar.

Other than the fridge,which will run on gas,we dont realy have much more draw, leds and radio.

We think a second battery is is a lots of unneeded weight, so a 680gram charger would put us in good shape.

If we ever lived in our van full time then a second battery would still be easily charged with the bcdc.

Phantom..
How is your fridge wired, through anderson or 12 pin plug?

Delta 18..
think its auto 6mill as this was fitted to run smaller battery on old off road camper. Coupled with the style of alternator, something more upto the job needs to be done!!

The Phantom · Guru

My fridge is wired through the 12 pin plug and an Anderson is connected directly to the batteries for charging whilst driving. I also have 2 x 100 watt solar panels on the roof.

The Phantom

rockylizard · Guru

Gday...

I agree with Mr Walker ... when travelling, my 175ltr Dometic 2-door 3-way fridge is provided with 12v power from the car via Pin 2 on my 7-pin plug - utilising 6B&S cable. Obviously, there is the "thingie" that ensures the fridge cannot drain the vehicle battery if stopped. (Although, if I am stopping during the day for more than 10 minutes, I always switch the fridge over to gas - better safe than sorry )

Unless, I am in the far north, the fridge is usually at 5degC in the morning and during a day stopped on gas or 240v it maintains close to that all day.

When travelling, 12v power provided from vehicle, it is 5degC when I head off and when I stop for lunch it is still 5degC ... and when I get to my camp it is still on 5degC.

Despite what others seem to be doing these days, I would not want to have the 12v to fridge provided from van's battery - despite having a DC/DC charger between car and van battery.

Potential for fridge to drain van battery would bother me - should something fail in that system.

My van battery is charged via an Anderson plug on the vehicle .... 240v smart charger when connected to 240v ... solar panels when not on 240v (and that includes when travelling). But of course, my old Landy doesn't have the modern alternator that doesn't maintain sufficient ongoing charge to auxiliary batteries when main battery is fully charged.

Works for me for the past eight years without a problem.

cheers - John

Aus-Kiwi · Guru

Each to their own here .. Why not two 120 watt solar on roof . Much much less hassle . Then for peace of mind 25 amp charger . Keep in mind while free camping more than a day you'll possibly need a top up of some sort ? Anderson plugs have better elect connections imo .. Another option is adding / fitting the old style Bosch built in regulator and having seperate charging system ?? Seen some smart guys run them off van wheels .

Brenda and Alan · Guru

The recommended maximum charging rate for all types lead/acid batteries is 20% of capacity. For a 100 Ahr battery that is 20 Amps so a 20 Amp BCDC charger would be best.

Alan

-- Edited by Brenda and Alan on Friday 17th of June 2016 09:16:23 AM

kezngaz · Senior Member

some interesting points of views guys.

from the info gathered so far im learning that firstly you must calculate what draw you have.
secondly, have enough battery storage for it, making sure your 100% charged.
Thirdly, find a means of maintaining the battery well bove the 50/60% charge it requires to keep it in safe territory.

Most batteries have the max amps in clearly stated on them, so maybe the 40 amp is to large for my 100amp/h then?

We are thinking mobile solar as the first thing you do when arriving for at camp is dive for the shade, plus the weight debate.

Roof mounted solar..is it possible to have this charging whilst driving as well as anderson connection, if so through what regulator/charger setup?

Thanks for all the feedback guys,really is helpfull.

cheers Kezngaz.

patrol03 · Senior Member

Even though your vehicle is fitted with a variable voltage alternator,it is quite capable of running your fridge efficiently and charging the battery in the Van without going to the expense of fitting a DCDC charger.You need to power the fridge directly from your Vehicle battery through a curcuitbreaker and use 6B&S cable right through to the fridge.It would be advisable to fit an ignition controlled solenoid in the line so you don't flatten the battery when the engine is off. To keep your van battery charged ,you can use a smart solenoid in a fused circuit from your start battery directly to your van battery using preferably 6B&S cable and appropriate plug connections. Your "smart alternator"is capable of sensing the draw on the Vehicle battery and increasing the voltage and current to suit the situation.

-- Edited by patrol03 on Friday 17th of June 2016 02:30:58 PM

Hylife · Guru

I'm going to disagree with some of the posted answers and say that almost without fail, even with a heavy duty 6AWG (13mm square) wire and an Anderson plug you will NOT be able to charge your van battery with a simple parallel connection to the tug. Wire resistance doesn't meant stuff all at 230V AC but at 12V DC it is crippling.
As much as a 1 to 2 volt drop (under load) from the tug alternator to the van battery will occur even using 6AWG wire and consequently you will never be able to either charge your van battery or run an absorption fridge properly from the van battery.
You need (depending on battery type) from 14.4 to 15.6 V DC to charge your van batteries and at most over a 10 meter or more run (there and back makes the circuit) using an old type alternator you would get little more than 12.5 under load.
That simply isn't enough to charge. If your batteries in the van are sensibly placed centrally over the axels and not in the front boot you might have a 20 meter wire run for the return circuit.

Using a tug with a smart (variable Voltage) alternator (they are designed to minimise engine emissions by disengaging unneeded loads such as alternators) it will cut out when your tug battery reaches approx. 80% capacity, which is quite OK for a cranking battery but won't charge up your van deep cycle battery, and certainly not with the voltage drop of the long run wire.

A DC-DC charger will get its power from your tug battery and NOT from the tug alternator. As the tug battery voltage drops the alternator will kick back in to keep the tug battery topped up at approx. 80%. When the engine is off the DC-DC charger will cut off when the tug battery reaches a pre-determined level, usually 12.5 volts, which is ample enough for starting your engine. You get 100% charge to your van batteries and have no need of a battery isolator because the DC-DC charger does that and you will never find yourself with a flat tug battery (like used to happen when you had no voltage sensitive relay and you forgot to disconnect the Anderson plug).

Most 3way absorption fridges suck 10 or more amps from your battery every hour, and your night time LEDs possibly 2 or 3 for the whole night.

Work out how long each day your van fridge is running on 12V without any power from the tug, eg when the tug engine is off.
Now you know how much you are drawing down from the batteries that needs to put back into your batteries (add those other 12V appliances current draw if you can).

Next estimate how many hours a day you will be driving, because if you have a 20amp DC-DC (and your fridge sucks out 10 amps), that leaves 10 amps per hour to put back into battery storage.
Is that enough to replenish that drawn down by the fridge whilst stopped and your night lights?

If you drive an equivalent amount of time that you also spend with the engine off with the fridge on 12V, and switch to Gas as soon as you reach camp a 20ap DC-DC will do you fine.

ie,
2 hours stopped at some attraction sucks down 20amps.
2 hours driving makes 40 amps but 20amps goes to the running the fridge leaving 20amps for the batteries.

If you think you are going to end up deficient then get the 40amp DC-DC charger.

Please make sure that you go a minimum of 6AWG wire and put the DC-DC charger right next to the van batteries or you just won't be happy with the results.

Hylife · Guru

kezngaz wrote:
..............

Roof mounted solar..is it possible to have this charging whilst driving as well as anderson connection, if so through what regulator/charger setup?.........

Yes, through a DC-DC charger such as the Redarc BCDC1225 or the Ctek D250S Dual.

Either of these units will take solar as precedence over the tug input but they are still limited to a combined maximum of 25 amps.

The great thing about these units however is that they still do charging from your solar whilst your tug is stopped with the engine off, whilst you go traipsing about looking at some local attraction or sampling the local pie shop/café.

And, when you reach camp, even though you have switched the fridge over to gas, the batteries are still being charged by the solar.

kezngaz · Senior Member

Thank you Hylife for your detailed reply.
Im running one 100ah battery so think a 40amp charger maybe to large?
A previous reply indicates only a 20% charge rate for any battery, can anybody confirm/contest this with fact?
I plan on gitting the charger within 100 millimeters of the battery and having a reletively small solar on the roof for charging/keeping battery topped up.when not in use. Running fridge on 240v for 24hrs before we take off the runni g on 12v whilst driving. This way im hoping to keep battery as near to 100%as possible knowing an alternator wheather variable or not will only ever achieve 80% charge.

Hylife · Guru

Yep, for a single 100AH deep cycle battery if it is AGM or Gell you shouldn't be charging at 40 amps. Wet flooded deep cycle batteries however can take a lot more charge at a time.

If you had a bank of 2 or more 100AH then I would say that the 40AH DC-DC would be OK but not so with one battery unless you are sucking out a big chunk of that as you go.
EG., if your fridge was sucking down 20amps that would leave 20 and that would be OK.

If your fridge is a 3way then other than 230VAC, gas is much more efficient for cooling than 12VDC, but you shouldn't be using gas whilst driving because it presents an explosion risk and the gas burner may get blown out by wind and then your fridge is off altogether.

Older 2way fridges are usually 230VAC and gas and are ok for free camping
Newer 2way fridges are usually compressor types running on either 230VAC or 12VDC and once stopped and free camping you must have sufficient battery power and solar charging.

So 230V at home and in a van park, 12VDC (charging from tug and solar) whilst driving, gas whilst free camping if you have an absorption style fridge.

All good. :)

kezngaz · Senior Member

My understanding is that a bcdc smart charger will only put out 25 or 40 amps if needed.
Similar to a 125 amp alternator, your batteries never get the full amperage.
Thanks once again.

PeterD · Guru

Gary (kezngaz,) The only limitation on the output of the DC-DC charger is its limiting of its maximum current. The current draw into the battery is entirely up to what the battery will draw. If you have a REDARC BCDC1240 it will deliver 40 A to a battery if the battery will accept it. A fairly flat battery 100 Ah battery will take all of that current. If you want to use a charger of that size then make sure it is equiped with a temperature to attach to the battery t prevent thermal runaway. Its very easy ro destroy your battery if it gets too hot during charging.

If you read through the link above you will see that Redarc recommend a 25 A model for battery banks under 200 Ah.

In addition, a multi stage battery charger relies upon the charge current reducing to around 5% of its maximum current to detect that a battery is fully charged. When the charge current reduces to that low value it switches to float mode. If you have an absorption fridge connected to the charger output that charger will never revert to the float mode and you will overcharge you battery. That is another way to bugger your battery.

-- Edited by PeterD on Wednesday 22nd of June 2016 04:24:29 PM

kezngaz · Senior Member

Thanks peter.
My intention is never to tun the fridge for longer than the journey, as soon as we stop ill swith over to gas.

oldtrack123 · Guru

patrol03 wrote:
Even though your vehicle is fitted with a variable voltage alternator,it is quite capable of running your fridge efficiently and charging the battery in the Van without going to the expense of fitting a DCDC charger.You need to power the fridge directly from your Vehicle battery through a curcuitbreaker and use 6B&S cable right through to the fridge.It would be advisable to fit an ignition controlled solenoid in the line so you don't flatten the battery when the engine is off. To keep your van battery charged ,you can use a smart solenoid in a fused circuit from your start battery directly to your van battery using preferably 6B&S cable and appropriate plug connections. Your "smart alternator"is capable of sensing the draw on the Vehicle battery and increasing the voltage and current to suit the situation.

-- Edited by patrol03 on Friday 17th of June 2016 02:30:58 PM

A big ditto to the above

First

A 3way fridge should always be installed to the FRIDGE makers instructions

Installed correctly, you should have no problem getting the designed 12V AT the element when switched onto 12V

That always calls for direct heavy wiring to the vehicle battery with some form of disconnect [which depending on fridge model may be inbuilt]when the engine is not running

Using a dc charger to charge the van battery ,then running the fridge from the van battery ,simply does not make sense especially if the REAL problem of undersized cables is not corrected first!

The load of the fridge will still lead to excessive loss of voltage to the dc/ dc charger, which will either cause it to shut down or try to draw even more power from the vehicle alternator

2nd it can lead to a false indication of the van battery SOC, possibly leaving it be held at too high a charge rate for some time[.short battery life &/or rapidly electrolyte use requiring frequent top ups]

-- Edited by oldtrack123 on Wednesday 22nd of June 2016 08:43:15 PM

oldtrack123 · Guru

PeterD wrote:
Gary (kezngaz,) The only limitation on the output of the DC-DC charger is its limiting of its maximum current. The current draw into the battery is entirely up to what the battery will draw. If you have a REDARC BCDC1240 it will deliver 40 A to a battery if the battery will accept it. A fairly flat battery 100 Ah battery will take all of that current. If you want to use a charger of that size then make sure it is equiped with a temperature to attach to the battery t prevent thermal runaway. Its very easy ro destroy your battery if it gets too hot during charging.
If you read through the link above you will see that Redarc recommend a 25 A model for battery banks under 200 Ah.
In addition, a multi stage battery charger relies upon the charge current reducing to around 5% of its maximum current to detect that a battery is fully charged. When the charge current reduces to that low value it switches to float mode. If you have an absorption fridge connected to the charger output that charger will never revert to the float mode and you will overcharge you battery. That is another way to bugger your battery.

-- Edited by PeterD on Wednesday 22nd of June 2016 04:24:29 PM

And ditto to that

-- Edited by oldtrack123 on Wednesday 22nd of June 2016 08:38:33 PM

PeterD · Guru

kezngaz wrote:
Thanks peter.
My intention is never to run the fridge for longer than the journey, as soon as we stop Ill switch over to gas.

Your battery will come up to full charge fairly quickly and then for the rest of the trip you will be overcharging your battery. I suggest you don't do it.

Warren-Pat_01 · Guru

Kezngaz, I agree with The Phantom.
We have a Jayco camper & we cannot run the fridge while travelling because of the chance of fire. Also I have covers over the fridge vents to prevent dust ingress on rough roads.
For the final couple of hours before we travel, I turn up the thermostat to the maximum & just before leaving my wife takes out a couple of frozen water bottles out of the freezer compartment & places them in the fridge area.
We often travel 8+ hours & on setting up camp, the fridge is still cold & frozen meat in the freezer is still frozen. This is in the summer (we note not too many "Nomads" like our summers) as well as the cooler times of the year.

Warren
PS we never get dust in the camper either, regardless of the conditions.

kezngaz · Senior Member

Thanks everyone. Plenty of food for thought there.
Thanks once again.
KEZNGAZ.

mjt57 · Senior Member

Folks, what difference does it make whether the fridge gets its power from the house battery or from the tug's battery?

If, as the OP is questioning, a DC-DC charger is installed, then wouldn't the house battery be sufficiently charged from the car's alternator and when stopped, the DC-DC stops drawing power from the car, thus preventing it being flattened?

I'm asking all of this as my first van which we picked up recently has a Dometic 3 way fridge. When the car is connected and running all I see is 10.5v at the fridge's DC terminals. The cabling appears to be 6B&S, but I can't verify this as I have no way to do so. But it's a heavy duty cable.

There is a wire on Pin 2, I think it is (keep getting it and P3 mixed up, one of which is earth). It has to see volts before the fridge can see volts. The wiring going into the trailer plug is not heavy duty. ie. it's standard trailer cabling for lights, etc..

I don't know how a 6B&S cable would fit into the trailer plug's connectors, even on the heavier Pins 8-12 on a 12 pin plug.

I cannot determine where the wires to the fridge start. Nothing is labelled. There is a battery isolator which has a blue wire "from ignition" as it's labelled. But it comes directly off of the house battery. And whether or not the car is connected or running there is power on input and output. That may or may not be the fridge supply.

When I got the car wired up one of the first things that I did was to check all this out. One test that I did was to disconnect the Anderson plug. The fridge remained running at 10.6v. Then I plugged in the 240v to the van. I did this to see what sort of loading there was on the van's battery if the fridge was running off of it. Showed about half an amp. Definitely not picking up the fridge load from there.

The former owner, to whom I spoke, said that he had no problems with the fridge's performance whilst on the road. (he had it for 3 years). However, we've done one trip, a 2hr drive to Cowes, 2 weeks ago. I had a ice cube tray of ice in the freezer. When we got there, one of the first things that I checked was that - the ice had started to melt. Only slightly (the cubes were loose in the tray). But obviously the fridge isn't working as well as it should be.

After all this I can only conclude that the fridge is getting is power from the trailer plug which P2 is tapped into the rear power outlet in the cargo area of the Jeep (it comes on and off with the ignition).

It's got me buggered as to why they did it this way. If this is correct I'm going to have to either run another cable from the battery to the plug, one that's capable of handling the load required, or tap into the Anderson plug and loop into P2 of the trailer plug. Then fit a relay which is supplied from the existing P2 cable to switch it so I don't get a flat battery.

Which gets back to my original question - what's wrong with running the fridge from the house battery and charging it from the car?

oldtrack123 · Guru

HI Mit7
Some answers to your questions
First, I would suggest you check the voltage @ both the fridge 12V element & the vehicle battery with the fridge WORKING on 12V & the engine running at fast idle

Just a note to all seeking infoi advise
It always helps if model number & fridge make is given as more accurate responses are possible

[1]The Dometic fridge makers instructions ALWAYS say run a dedicated direct circuit to the vehicle battery.
[2]THey also say the cables should be heavy enough to maintain the MIN 12V at the fridge terminals when it is actually running on 12V AND the engine is running @fast idle or road speeds
To do that 6B&S cable for both positive & negative is usually sufficient, even with a low voltage alternator provided it's output voltage is no less than 12.5V.

Ensuring that there is some automatic form of isolation to disconnect the circuit when the engine is not running[ ignition controlled relay , Voltage sensitive relay [VSR],Fridge switch or, depending on fridge model it may have inbuilt isolation , another good reason to give info on the actual fridge smile

Now If you try to run the fridge from the van battery you will need really BIG cables as they will not just have to supply the fridge & maintain it's voltage ,they also have to heavy enough to get much more than 12v up to 14V to the van battery for it to charge as fast & correctly

Again the best solution is to have a separate heavy cable charging circuit for the van battery

While many say a DC /Dc charger is the solution ,it is far from a solution on it's own

[2]It again requires heavy cables to reduce voltage drop that could actually cause the Dc /Dc charger to shut down

[3] running the FRidge off the Dc/Dc charger can lead to slow charging of the battery, especially IF the fridge rating is such that it draws heavily on the charger's output

[4] It can also lead to OVERCHARGING the van battery due to the fridge load holding down the peak voltage of the DC /DC charger
[holding the van battery in boost stage for unnecessarily long periods, actually overcharging & shortening battery life]

Install your fridge as the fridge makes say: HEAVY CABLES TO THE VEHICLE BATTERY
Not how most van makers do!!

If your alternator is the low voltage type then a DC/DC charger may be necessary to fully CHARGE THE VAN BATTERY
Let it do the job it is designed to do, CHARGING the battery in the required manner
Responding to the BATTERY condition, not some other heavy load giving false indications

If the system has worked OK previously ,that would be a good reason not to now get a DC/DC charge.
It is a clear indication that something has changed, usually that is a bad connection, dirty or loss, often a good sign is localized heating.

Your belief "After all this I can only conclude that the fridge is getting is power from the trailer plug which P2 is tapped into the rear power outlet in the cargo area of the Jeep (it comes on and off with the ignition)."
IF that is so you have no hope even with a Dc/Dc charger & who ever did THAT does not have a clue!!!!!! furious bleh
In fact I would cease using it immediately because you could easily end up with vehicle wiring burnt out. cry

ps 6B&S has a COPPER DIAMETER a little over 4mm & that is needed ALL the way from fridge to vehicle battery

DO NOT USE EXISTING WIRING of ANY VEHICLE OUTLETS for any heavy load purpose in van including van battery charging or fridges!

-- Edited by oldtrack123 on Monday 27th of June 2016 04:06:38 PM

mjt57 · Senior Member

Just a quick reply, Old Track.

When I had the van connected to the Jeep and the Jeep running, the Jeep indicated around 14v on its EVIC (Electronic Vehicle Information Centre) display. The charger, a Projecta, in the van indicated battery voltage of 13.9v (was it a 0.1v drop or simply instrument error?). At the fridge with it running on DC it indicated around 10.5v. When I turned the fridge off or back to AC the volts at the fridge jumped back up to 13.9v.

Whoever wired the van up (it's a Royal Flair Family, 2013) may have sent the fridge wiring from heavy duty down to whatever is in the trailer plug loom.

I'm going to pull it all apart and to trace where everything goes before our next trip. Then I'll run new wiring to ensure that the fridge will get full volts when it's running. Exactly how I'm going to do that will be the question.

kezngaz · Senior Member

Hi oldtrack 123.
Whilst i thank you for some of your opinions i must say i disagree with your previous comment saying a variable alternators voltage output is never less than 12.5 volts.
This is not true as they actually turn off, giving zero volts out.
Additionally, 12.5 volts output on vehicle alternator would struggle to even charge van battery at a distance of 4/6 meters complete circuit, never mind running a fridge drawing 15 amps (also a previously mentioned).

But yes, mjt57 never use anything less than 6b+s with genuine anderson plugs if thats your chosen method of keeping van charged.
You will get a lower voltage reading when the fridge is running as its drawing from its source.

oldtrack123 · Guru

kezngaz wrote:
Hi oldtrack 123.
Whilst i thank you for some of your opinions i must say i disagree with your previous comment saying a variable alternators voltage output is never less than 12.5 volts.
This is not true as they actually turn off, giving zero volts out.
Additionally, 12.5 volts output on vehicle alternator would struggle to even charge van battery at a distance of 4/6 meters complete circuit, never mind running a fridge drawing 15 amps (also a previously mentioned).

But yes, mjt57 never use anything less than 6b+s with genuine anderson plugs if thats your chosen method of keeping van charged.
You will get a lower voltage reading when the fridge is running as its drawing from its source.

Hi

The output voltages of Variable voltage alternators varies between makers & models & other factor. typical details are available

The general situation is that when driving normally they hold around 12.5V

But you are correct ,they do turn off completely BUT ONLY WHEN ACCELERATING, So most of the time they run @ around 12.5V or there is no electrical load

That Will get 12V to virtually ALL Dometic 3way fridges, if 6B&S cable is used for the full circuit

Knowing run length, Amps draw @12V & available voltage makes it easy to determine required size of cable to overcome voltage drop

You may also have noted that I DID say to use SEPARATE circuits for fridge & VAN battery charging

The 3 way fridge makers instructions ALL say RUN A SEPERATE CIRCUIT RIGHT BACK TO THE VEHICLE BATTERY & for very good reasons

Anyone putting them on the same circuit is asking for trouble, even with conventional alternators[unless they use very heavy cables, far bigger than 6B&S]

If you reread my post I made no claim that 12.5V would fully charge any 12V battery!! such a claim would be ridiculous, I would expect that most people know that, since it is below the voltage of a fully charged battery

It requires something over 13.5v for long periods or up to 14+volts for fast charging.

-- Edited by oldtrack123 on Monday 27th of June 2016 07:24:20 PM

kezngaz · Senior Member

We are obviously getting our info from seperate sources.
I never misred your post i just pieced your opinions together and mentioned that a 12.5 volt output is no good for charging a battery.

Hope i havent upset you further....
Kezngaz.

mjt57 · Senior Member

oldtrack123 wrote:
Anyone putting them on the same circuit is asking for trouble, even with conventional alternators[unless they use very heavy cables, far bigger than 6B&S]
-- Edited by oldtrack123 on Monday 27th of June 2016 07:24:20 PM

Here is where I don't understand. Why are you asking for trouble if there is a single connection (via the car battery) back to the van's battery through an Anderson plug and to have the fridge connected directly to the van's battery?

And let's assume that yes, we have the correctly rated cabling for the job (which I do in my case).

oldtrack123 · Guru

Hi MJT
Here is one very good reason from PeterD above
He is 100% correct Perhaps you missed reading it

[Quote]In addition, a multi stage battery charger relies upon the charge current reducing to around 5% of its maximum current to detect that a battery is fully charged. When the charge current reduces to that low value it switches to float mode. If you have an absorption fridge connected to the charger output that charger will never revert to the float mode and you will overcharge you battery. That is another way to bugger your battery.

-- Edited by PeterD on Wednesday 22nd of June 2016 04:24:29 PM

__________________
PeterD
Nissan Navara D40 diesel auto, Spaceland pop-top
Retired radio and electronics technician.
NSW Central Coast.
[End Quote]

Another is that the cables to carry the 40A plus ,[possible up to 55A if the input voltage is down to around 11V] for the charger input ,& will still have to be very large [like paralleled 6B&S cables for both plus & neg ]to again avoid excessive voltage drop.
Depending on the model DC /Dc charger If there is excessive voltage drop in the feed cables it may keep cycling on & off when ever the input voltage drops down to IT's shut down voltage point
They never were intended to do anything else than charge battery correctly, if the existing system could not do that. ie the alternator voltage available @ the Van battery was too low even with heavy cables

You have what sized cables for what job ?? perhaps that is only your belief.

Size is dependent on cable length , load on the cable , the minimum voltage from the source supply , the minimum voltage that the device will successfully operate with

-- Edited by oldtrack123 on Tuesday 28th of June 2016 09:33:10 PM