Will solar affect DC to DC charger

Thanks for the reply Keir. My Ranger has had the smart charger turned to dual batteries so that should be fine.
I am not keen to pull larger wiring through the roof to the solar panel so may go with the Itechworld charger.
I have just remembered that the 3 way fridge will be on so the DC to DC charger will work.

Daniel.
Can you explain further what you mean" the fridge will be on"? Maybe, but it will use 15amps constantly of the DcDc output or is the fridge wired in parallel with the feed from the alternator?
There should be no reason to alter the 180 W panel wiring to the regulator site. Nothing is changing with the wiring is it?? Can't work out why you mentioned that! Only possible bigger wires from MPPT Reg to battery may be needed if alt input and or solar requires it's output line to be upgraded in size
Perhaps have the fridge wired to only receive the alt input and use a VSR, voltage sensitive relay to switch the fridge ON when the voltage at that point reaches 13.2 v or so. It then switches off when applied voltage drops to 12.8v to preserve feed battery.
After reading David below. If the solar is priority and working, then the alt can provide for the fridge via VSR. I presume the alt input to MPPT can be connected to MPPT and feed VSR to fridge so battery charge can happen when solar drops off/clouds.
Just suggestions.

I was concerned that the DC charger would see 13.6 volts at the battery when the solar from the roof was charging. This is a separate circuit and if the DC charger saw this voltage it would not produce any charge to the battery.
My interpretation of the DC chargers specification is it reads voltage not current (amps) if it sees 13. 6 volts or even 14.6 volts from the solar regulator it would not turn on.
The way my current wiring is configured is a single circuit from my alternator controlled by a VSR feeds into the caravan via an anderson plug.
It then splits into 2 circuits one of which powers the 3 way fridge 12 volt circuit (only used when traveling) and a feed into the house battery. The feed to the battery must have a diode installed as the fridge cannot draw power from the caravan house batteries.
I intended to connect into the circuit with the DC charger before the split.
I intend to buy a 40 amp charger and fully understand that 15 amps will go to my fridge leaving 25 amps to charge my house batteries.
If I was to run a separate circuit for the fridge controlled by a VSR from the alternator I am back to my original question.
Why would the DC Charger supply if the solar on the roof is inputting 14.6 volts?

I'm with Trevor David on this one, only use ONE regulator for both, and the Redarc is a good unit that uses the solar as much as it can, then supplements that with the Alternator so as to achieve best, or maximum, charge.

Whatever you do make sure that the wire size, and plug capacities, are/ is at least that recommended by the regulator manufacturer, and also run a separate system for the 3way fridge. DO NOT try to supply both from the same supply cables, and ideally have the fridge wiring ignition switched via a suitable relay.

Wiring to supply either fridge and/or charger should be a minimum 6B&S (6AWG) to avoid voltage drop, depending on unit used and length of cables may need to be 4 B&S (4AWG)

My only association with Redarc is as a happy user of their products.

Regards
Athol

D

Sorry should have added, suggest you only use the 3 way fridge on 12v when driving, Switch to gas (best) or 240 v when stationary. Very power hungry on 12v.

Regards

TrevorDavid

TrevorDavid
Thanks for your reply I was referring to bridging out the existing solar controller which is located above my fridge in the caravan. If I join the positives and negative wires and disconnect off the battery terminals to connect to the solar input of the Redarc charger.
The caravan is a Kokoda and it only has one 12 volt feed in from the vehicle.
There must be a diode in the wiring at the moment as generally ( I tonged the load) 15 amps is going to the fridge and 4 amps was going to the battery.
I was thinking of leaving this circuitry and adding a DC to DC charger prior to the diode (I cannot locate the diode).
It looks as though I have a great deal of rewiring to do as it has a low voltage 40 amp cut out that is no longer required when I change to Lithium batteries.

Sounds like a trip to an auto elecy is required.
Changing to Lithium is not a cheap exercise

Daniel.

Make absolutely sure that the auto electrician that you get to do the job uses the correct size wires, most will say that is overkill and you only need 6mm Auto wire.

With 6mm auto wire over the lengths that are required you will get substantial voltage drop, sufficient that neither the BCDC nor the fridge will work efficiently. Most caravan manufacturers also use 6mm Auto for their fridge supply, it will provide some fridge operation but you will notice a difference if done correctly.

6B&S is about 3 to 4 times the size of 6mm auto, size being the cross sectional area of the copper.

Regards
Athol

Thanks for the information Athol.
I currently have one circuit of 6 B&S cable from my alternator to the rear of my tug. An anderson plug from the van is then connected which runs the fridge and charges the battery.
I am not sure that I need another circuit.
This system has served me well over the years with 2 x 100 amp/hr Calcium batteries.
The batteries are now almost 6 years old so thought that upgrading to lithium (single 120 amp/hr) would be a good idea.
Wanting to do it right first time so that I can enjoy my travels and not worry if my charging system is working at it's full potential

Daniel

For a single 100ah battery a Redarc BCDC1225D would be sufficient, and can be fitted to solar panels that have more than sufficient output as the max OUTPUT is 25 amps.

This should be wired to starting battery via its own 6B&S twin cable so as to avoid voltage drop, and its current consumption at full load will be slightly over the 25A when input voltage is @ better than 12v and internal losses are taken into consideration.

Your fridge will thank you if you supply a good power supply, and the use of a switched 6B&S twin cable from the starting battery will give you that supply, when supplied with the full 12v your fridge give the best cooling available, and by switching the supply you are eliminating the possibility of flat starting battery.

My system was set up for when my wife was on home oxygen 24/7 ( a 7 to 9 amp current draw to keep the machine operating), and includes a Redarc 1240D in the van charging 200ah of Lithium, a big 2 door 3 way fridge, a Redarc 1225 in the car charging 120ah Lithium running a 40 litre Engle as a freezer, the car and van batteries connected via their own Anderson plug (Grey), the fridge wiring of 6B&S twin cable from starter battery via ignition triggered switch and red Anderson plugs, a 4 B&S twin cable from starting battery to the 1240 charger in the van via 150 amp rated Anderson plugs, near 600 watts of Solar panels on the roof of the van feeding into the Redarc 1240, and 200 watts of solar on the roof of the car feeding the Redarc 1225.

As far as the Alternator is concerned I refrain from using both the Redarc chargers at the same time. I can easily remove either charger from the starter battery supply. The full use of the system will result in a low alternator voltage for about the first hour of driving after using the batteries for a night, so yes you can draw more current (Amps) than the alternator can supply. If in doubt just fit a Voltmeter to the starting battery, and if the voltage comes up as normal (normal being without the van) within a couple of decimal points then it is all OK.

My vehicle is Isuzu Dmax 2017 fitted with the 'smart' alternator, which has NOT been disabled.

Regards
Athol

Qldcamper you raise a good point, I also have a dual battery system in my Ranger PX2 which has a redarc 1225 Dc to DC charger. This is connected to a 140amp/hr AGM battery that supplies power to an Evakool fridge which draws about 3.5 amps. It also has a solar panel to help with charging duties mounted on the canopy roof.
I did a search for alternator size for PX2 3.2 litre and struggled to find specific detail. I did see 110 amps mentioned. This is not too bad in size and if it fails in the future I would upgrade to 150 amp/hr.
The huge benefit I saw with Lithium batteries is the ability to put bulk charge in very quickly. We will be free camping so may add an additional 120 amp/hr battery in the future.
I do not intend to take a generator but will use the vehicle to charge van batteries if sun is not available and batteries get low.
I do not intend to run an inverter or air-conditioning in van. Basically it will ruin lights (LED) and water pump.

Thanks for your input

That is now starting to add up, 55 amps to the van and 25 to the vehicle accessory battery.
If you search deeply enough you will find that a 110 amp alternator will a continious output rating at high revs, estimating 70 amps and a much lower one at idle. It will easily exceed this output if it is demanded of it, the reasons for these ratings is because that is the maximum amount of heat the alternators cooling fans are capable of removing at those engine speeds for an extended period of time, especially if the smarts are turned off.

If not designed properly your system in the worst senario especially at idle will cause you grief.
It has always been a rule of thumb to not demand more than 60% continiously of an alternators rated output since the first alternators were introduced and started melting when driving lights were fitted or aftermarket AC was fitted.

Just charging your batteries could put 80 amps of load on an idling alternator designed to run at 70 or 80 amps at 2000 engine rpm and remember there are the loads of the original equipment on top of that as well.

This senario may never occour with solar charging as well but it only takes once.

Put as much solar on the roof as you can fit so it covers load on overcast days.

Thanks qldcamper I did overlook the output of my alternator.
I have 13.57mm cable (6B&S) installed now from my starter battery in Ranger to an anderson plug at rear of vehicle.
I do not think that I will make thinks permanent at this stage but will try the following.

I will leave the VSR in place at my vehicles battery and add a connector and split the supply cable from my vehicle to: I will simply add an additional anderson plug to connect to.
I will connect one cable directly connected to 12 volt side of fridge.
Second cable connected to Redarc BCDC1225D which will charge my house batteries as well as solar from the roof of the caravan which is a 180 watt panel.

The average load would be 40 amps at worst scenario for the caravan when travelling

The 25 amp redarc will be a lot kinder than a 40 amp.

Think about putting the 40 amp supplying the accessory battery in the ranger then feeding the vsr from that battery to supply the van. At least that will limit the extra draw on the alternator to 40 amps but still try to increase the engine rpm to about 1200 if you use it to top up the batteries.
Try to get rid of the diode if there is one.
Does the ranger have a fast idle switch?

Bill
Thank you for the information. The fridge will be run on gas when free camping.The only time the fridge will be on 12 volt is when traveling.
Your compressor fridge would draw approximately 6 amps?
It obviously draws it's power from your house battery which is charged by the DC charger and this works for you.
My 3 way fridge will draw 15 amps but thought this would be fine with a 40 amp charger.
You have a solar panel on the roof of your van that feeds into the house batteries from its own regulator?
The voltage rise that occurs from this supply does not trick your Dc charger not to charge?

My solar panel is a portable one that came with a separate regulator, but I don't use this regulator, as my dc-dc charger has its own mppt regulator built-in. I simply plug in the solar panel unregulated into the solar input port of the dc-dc charger and it manages the multi-staged charging process.
I actually have a short cable connected to the solar input port and terminated with an Anderson connector and simply plug the solar panel lead into it when setting up camp.
As the charger accepts input from either alternator or solar, it automatically accepts input from one or the other, whatever it determines is the better quality input.

Phil G
That is interesting to read Phil.
We all seem to do things a bit differently because of our setup. I have a Projecta 25 DC DC/Solar in canopy and can run it from alternator or purely solar.
Although the alt can directly charge the van batteries and run the Fridge. I tried just the solar on the ute to run the Projecta to charge the aux in ute and the van batteries too. At the same time the solar on the van runs through an MPPT reg to the van batteries and when ute solar to van and van solar to van, easily runs the fridge and brings in the VSR to do it. Voltage drop and the VSR cuts fridge. So purely on solar IF sun of course. I set van reg to match the Projecta final voltage at batteries so no conflict.
I agree the gauge of wiring for fridges in vans related to supply and neg side too, is way too thin to achieve much at all. Slight cooling may happen. With it upgraded, on a 25C sunny day and 500km run my fridge was at 2c on 12v with fan assist. never had that on anything before. almost need to thermo switch the 12v into fridge.

.
Hi Phil,

You are quite right about supplying the 3-way van fridge via a separate circuit from the alternator and not piggybacking it on the charger circuit. The dc-dc charger will be confused by the fridge current load.
The charger is designed to only maintain operation so long as the alternator is operating. It achieves this by sampling its input voltage every 100 seconds (Redarc) under no-load conditions by a brief switch-off which suspends cable volt-drop and views the true voltage at the crank battery terminals (alternator output) to determine if it is greater than 12.7v thus indicating alternator operation. If below 12.7v the charger assumes no alternator contribution and shuts down the avoid discharging the cranking battery. If the fridge is piggybacked on the circuit supplying the charger it will cause a constant volt-drop on the cable and the charger will see a sample voltage of likely less than 12.7v and shut down, hence no charge to the aux battery.

A different problem occurs if the 3-way fridge is supplied from the van aux battery which is being charged by a DC-DC charger. The charger exits Absorption Stage and lowers its output voltage to move to Float Stage when its output drops below 4A. With a connected fridge load typically around 15A, the charger will not enter the Float Stage. This may not be highly significant but can degrade the charger's algorithm performance.

So yes, if using a 3-way fridge in a van, it is always desirable to supply it's 12v via a dedicated cable from the vehicle alternator/battery via an ignition-controlled relay or solenoid to prevent cranking battery drain when engine is stopped.

Hi
I appreciate everyone's perspective and will take the advice of running a second 12 volt supply from my battery directly to the caravan 3 way fridges 12 volt input.
I currently have an Enerdrive 140 amp VSR can I connect into the existing unit or purchase a second one to keep them separate?

I still have concerns about the solar on the roof of the caravan which is fed by a separate PWM lithium approved regulator.
Will the DC to DC charger see the charging voltage from the solar panel at the Lithium battery as charged?
I do not want to outlay this money to have a DC charger not supply a charge when the rooftop solar(180 watt panel)is operating.

If this could cause concerns I will connect the rooftop panel to the MPPT solar input of the Redarc Dc charger.
I think I will now purchase a Redarc 1225D to ensure I do not cook my alternator.

Thanks to all those that have responded

.
Hi Daniel,

It would be OK to connect the feed to the fridge from the output of your existing VSR.

The terminal voltage of the caravan battery will rise a little as a result of solar contribution. The charger will see this elevated voltage and apply it to its algorithmic action which may reduce its contribution to the charging. For the best result use a dc-dc charger which has input provision for solar and dispense with any other regulator in the solar circuit.

You cannot "cook" your alternator. All alternators incorporate a regulator which control the output voltage and automatically limit the delivered current to a design value suited to the alternator. If you attempt tp draw excessive current the regulator simply limits the output to the design rating.

RMD,
I think I know what you're saying - basically you can power the 3-way fridge in your caravan from solar on both vehicle and caravan (and no alternator input). I'm guessing you have a lot of solar. How many amps does your fridge draw? Do you have a DC-DC charger in the caravan?

Allan,
Thankyou for your superb explanation of what I was getting at. Would have taken me twice as many words and only be half as clear!

Daniel,
I agree with Allan that you can run both fridge and anderson plug feeds off the VSR, provided the VSR is located close to the cranking battery so not to be affected by voltage drop, and the wiring to the VSR is large (eg 25mmsq or 4B&S).
While I have done this in the past, these days I prefer to use IGN controlled relays ( two 70A Narva is what I have) because they do not contribute to any parasitic losses from the cranking battery. But its not a biggie.
As Allan says the simplest solution for your setup is to input your solar into say a Redarc 1225D charger which prefentially uses the available solar first. From your 180W panel, you might only get 5-8 amps while travelling on a sunny day. If you had a lot more solar then it would be worth using a separate solar regulator.
You could run your 300W portable panel via the 30A itechworld regulator - just be nice to check the amps coming from each setup so you know they are working OK together, which I think they will.

Phil G
My 3 way draws 15 amps and with three panels on the ute roof/canopy in parallel they run into the DCDC and battery in the canopy. Not ideal having DC DC not in van I suppose, but it charges the aux in tub. That linked to the van batteries and it's solar /reg and a direct to fridge via toggle switched small VSR there is 13.2 v at fridge with solar of van and the DCDC charging the connected batteries and runs the fridge. Originally without rewiring the caravan cable the original piddley small cable to fridge supply meant very low voltage to fridge even with a good Anderson supply from vehicle. The OE van fridge wire used to run up RHS of A frame to the rear, across the back and then forward to reach the fridge. At least 6 + metres of cable totally wasted and effectively useless. I can switch the system from the DCDC to run directly from alternator via a marine changeover switch. Even then the van solar 200w "claimed" runs the adjustable MPPT to match the running voltages. As mentioned, the whole lot will run on the solar inputs and supply the Engel or small Waeco too.

Plugs on DC DC input allow the vehicle electrics to be run from the roof solar if Alt stops charging. Just a couple of Andersons swapped over to change it to, no Alt running for emergency times.