Will solar affect DC to DC charger

Submitted: Friday, Jan 07, 2022 at 16:52
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I am wanting to upgrade my Calcium batteries in the caravan to Lithium and will also need to add a DC to DC charger. I am considering the Itechworld 40amp charger or a 40 amp Redarc charger. My 240 volt charger has a Lithium setting so no need to replace.
The wiring is what I need advice about.
I have a 180 watt panel on the roof of the van which runs through an Itechworld 30amp PWM regulator which is inside the van. I also want the ability to connect a 300watt panel externally to chase the sun or use when parked in the shade.
Will a MPPT and PWM regulator work in parallel?
When I install a DC to DC charger will it see the batteries as charged when the roof mounted solar panel is working ( while driving of course)? The float voltage is 13.5 volts from the regulator.
Do I bridge the wiring together and use the MPPT in the DC to DC charger?
I do have some concerns with this as the Redarc requires 18 to 21 volts to wok and I am not sure what my current panel puts out, add in voltage drop and it may not work.
Am I over thinking this as there would be thousands of caravans with DC to Dc chargers and separate solar regulators?
My battery box is also fairly exposed on the side of the caravan and while the DC to DC chargers have an IP67 rating it will not be ideal. The good thing is air circulation so it should put out full current.

Any preference for DC to DC charger with the two mentioned.

Thanks for replies in advance


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Reply By: Keir & Marg - Friday, Jan 07, 2022 at 17:14

Friday, Jan 07, 2022 at 17:14
Hi Daniel,
Both the chargers you mention are dual input chargers and have a built-in MPPT regulator on the solar input. Either would be suitable. Your existing PWM regulator is pretty inefficient, old technology. In any event you cannot run the PWM regulator and MPPT together. So ditch the PWM regulator and run the solar panel directly into the solar input of the DC-DC charger. Make sure that both the solar panel wiring, and in particular the input from the car alternator have decent-sized wiring to avoid voltage drops. If you have a car with a smart alternator, you may need an additional trigger wire to get the input from the car alternator to work properly; the chargers come with instructions on how to do this.
The DC-DC charger will accept inputs from the car and solar simultaneously, and decide which to use in order to charge the caravan battery.
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Follow Up By: Daniel G3 - Friday, Jan 07, 2022 at 17:32

Friday, Jan 07, 2022 at 17:32
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.
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Follow Up By: RMD - Friday, Jan 07, 2022 at 19:22

Friday, Jan 07, 2022 at 19:22
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.
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Follow Up By: Daniel G3 - Saturday, Jan 08, 2022 at 06:53

Saturday, Jan 08, 2022 at 06:53
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?

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Reply By: RMD - Friday, Jan 07, 2022 at 17:47

Friday, Jan 07, 2022 at 17:47
As Kier and Marg said, you can't use the PWM for a lithium. Best to check the short circuit current of both solar sources, and added together, do they exceed the DCDC total wattage input of the MPPT reg? Best to check.. Some REGs don't worry if too much and simply run up to their max intake. others might not like any additional energy being present on high sun conditions with both solar panel systems paralleled. The 180w probably maxes at around 160w and the 300w aux at 250w in reality. Gotta a be good ones to be nearer. Knowing the shorted amps gives a good base to work from.
If you can run suitable wire size from battery to internal PWM position then it should work ok with the lithium seeing it is a Lithium profile charger. That input to the MPPT Solar input can have another cable to an Anderson plug outside for the 300w panel connection when used.
If temp is an issue with reg inside, a small computer fan blowing air over/up through it's fins will do the cooling job. Some make hardly any noise and at 100ma they can run all the time or switched if you wish.

With some voltage regulation, ie, a small integrated chip type reg can be across the MPPT input or inputs and if it's output is 12v the little fan should only run when solar or alt is driving the unit. I use a number of 7812 3 pin circuit board regs to do just that in different situations.
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Reply By: TrevorDavid - Friday, Jan 07, 2022 at 19:00

Friday, Jan 07, 2022 at 19:00

Yes you are overthinking this.

You should only need one controller.

Do not parallel the MPPT & PWN

The redarc bcdc dual chargers are solar priority, so solar first and then supplemented by the alternator. A long as you mount the controller in a shaded spot you should have no issues. There waterproof. Mine is mounted under the tray. Solar size input doesn’t matter.

Your battery bank should dictate what size charger you use.

Not sure what you mean by bridging wire’s together and using the MPPT. You will need to join two wires together to select your particular battery chemistry: e.g Lithium.

No affiliation with redarc, I just have one. Can’t comment on Itechworld.



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Follow Up By: Athol W1 - Friday, Jan 07, 2022 at 19:30

Friday, Jan 07, 2022 at 19:30
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.

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Follow Up By: TrevorDavid - Friday, Jan 07, 2022 at 19:40

Friday, Jan 07, 2022 at 19:40

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.



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Follow Up By: Daniel G3 - Friday, Jan 07, 2022 at 20:01

Friday, Jan 07, 2022 at 20:01
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

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Follow Up By: Athol W1 - Friday, Jan 07, 2022 at 21:07

Friday, Jan 07, 2022 at 21:07

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.

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Follow Up By: Daniel G3 - Saturday, Jan 08, 2022 at 07:03

Saturday, Jan 08, 2022 at 07:03
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
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Follow Up By: Athol W1 - Saturday, Jan 08, 2022 at 08:53

Saturday, Jan 08, 2022 at 08:53

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.

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Reply By: qldcamper - Saturday, Jan 08, 2022 at 07:59

Saturday, Jan 08, 2022 at 07:59
What is the capacity of your alternator?
The theoretical experts are very correct on what they are saying but seem only concerned with the outputs.
A 40 amp DC DC will put a lot of extra load on your already hard working alternator.
Yes a parallel circuit for the fridge is more efficient but it also means the load on your alternator is up by 15 amps to 55 amps additional load on your alternator.
Your existing system is helped by the diode it may or may not have and the surface charge affect of the flooded batteries which allows a high charge rate for a short time then the surfaces of the plates in the battery get saturated in electrons and limits the penitration of electrons into the deeper levels of the plates so the load on the alternator drops off in a few minutes.
Lithium batteries will suck as much power as your system can throw at them.
Just check your alternator can cope with the worst senario of flat lithiums and driving with your lights and AC on at night. Half hour of that could toast your alternator.
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Follow Up By: Daniel G3 - Saturday, Jan 08, 2022 at 09:00

Saturday, Jan 08, 2022 at 09:00
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
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Follow Up By: qldcamper - Saturday, Jan 08, 2022 at 09:49

Saturday, Jan 08, 2022 at 09:49
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.
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Follow Up By: Daniel G3 - Saturday, Jan 08, 2022 at 12:49

Saturday, Jan 08, 2022 at 12:49
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
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Follow Up By: qldcamper - Saturday, Jan 08, 2022 at 13:01

Saturday, Jan 08, 2022 at 13:01
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?
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Reply By: Sand Man (SA) - Saturday, Jan 08, 2022 at 08:30

Saturday, Jan 08, 2022 at 08:30

I use a Ctek DS250 DC-DC charger connected to an Itech 100Ah Litium battery.
My solar panel (200w) can be used either with the onboard solar controller, or direct to an external controller. As the Ctek has a built-in Solar MPPT controller, I use this for the solar panel input.
If you already have a DC-DC charger, it should be able to be configured in a similar manner.

Basically, I have a cable connection from the vehicle alternator connected to the DC input port on the Ctek and a cable from solar panel (uncontrolled) connecting to the solar input port of the Ctek.
The Ctek will recognise the best input port (usually the alternator input) and use that to maintain a charge of the battery. Works brilliantly. The only limitation with the Ctek DS250s is a maximum of 20a input from the alternator, but that is acceptable in my operation.

The Itech Lithium battery has its own built-in battery management system and will accept a charge from a standard AC charger as well, so no need to necessarily upgrade to a lithium specific charger.

Your use of a three way fridge is another thing altogether and I wouldn't like to be "free camping" with this setup. The high drain of the 3 way fridge on the lithium battery will not be suitable for sufficient charging from the solar panel alone.
My van has a compressor fridge and the input from the 200 watt solar panel, supporting a 100Ah lithium battery is a practical solution in my case.

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Follow Up By: Daniel G3 - Saturday, Jan 08, 2022 at 09:08

Saturday, Jan 08, 2022 at 09:08
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?
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Follow Up By: Sand Man (SA) - Saturday, Jan 08, 2022 at 09:43

Saturday, Jan 08, 2022 at 09:43
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.


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Reply By: Phil G - Saturday, Jan 08, 2022 at 15:06

Saturday, Jan 08, 2022 at 15:06
I run a similar setup. Can I offer the following comments:
#1 Running a 3-way fridge means you do not have huge power requirements when off grid. It is best that the fridge is powered directly from the alternator when travelling. That is the way the vast majority of caravans do it. I tried running my 3-way fridge directly off the caravan battery (to increase voltage) and for whatever reason my DC-DC charger seemed to be upset by the heavy load on the battery being charged. I kept arriving at camp with a half full battery. It is important that the alternator feed to the caravan fridge has its own dedicated circuit right back to the cranking battery - do not piggy back it on teh feed to the caravan anderson as the voltage drop from the fridge will upset the DC-DC charger in the caravan.

#2 Why do you need a 40A DC-DC charger? You will need to have very heavy wiring if you want it to work - much more than the usual 6B&S if you want it to be capable of charging at the full 40A (which actually means you will be pulling about 50A through teh anderson plug). I personally would be reluctant to use anything bigger than a 25A DC-DC charger and keep the wiring at 6B&S. Also make sure the charger is installed close to the caravan battery and have the anderson plug wiring take the shortest route to minimise the voltage drop at the DCDC charger input. I've measured a lot of voltage drop on the vast lengths of cable required with a caravan installation.

#3 I prefer to use a separate MPPT Solar controller on the caravan. That way you will increase the charging capability. Lithium will take anything current present to it. I run a Victron bluetooth 75/15 on the caravan and use the app to know what's going on. I run a separate 25A DC-DC charger and use it's solar input for portable panels.
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Follow Up By: RMD - Saturday, Jan 08, 2022 at 16:42

Saturday, Jan 08, 2022 at 16:42
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.
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 09, 2022 at 10:42

Sunday, Jan 09, 2022 at 10:42
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.

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Follow Up By: Daniel G3 - Sunday, Jan 09, 2022 at 11:25

Sunday, Jan 09, 2022 at 11:25
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
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 09, 2022 at 14:43

Sunday, Jan 09, 2022 at 14:43
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.

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Follow Up By: Phil G - Sunday, Jan 09, 2022 at 16:36

Sunday, Jan 09, 2022 at 16:36
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?

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!

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.

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Follow Up By: RMD - Sunday, Jan 09, 2022 at 17:02

Sunday, Jan 09, 2022 at 17:02
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.
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Reply By: Daniel G3 - Sunday, Jan 09, 2022 at 19:37

Sunday, Jan 09, 2022 at 19:37

RMD appreciate your informative replies.
I am not sure if my link will work. I am a little clearer on what the limitations are.
I will also speak to Redarc next week about the BCDC charger size as I may install a second battery in a few years when/if we get to travel more
AnswerID: 639042

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