DCDC charger outputs

[Chriso1988]

Hey guys just after some 12v dc electrical advice / info

Rigging up a camper trailer with a projecta IDC 25 . I understand that the DCDC will boost the volts from the alternator to the correct charge rate for the AGM battery and the amps will be 25amps as specificied. Happy days, makes sense to me.
However, im also have a 120w solar pannel i will run through it when parked up, i done some output amp tests on the pannel on my previous set up and it puts out about 5-6amps from memory, so im curious to know if the DCDC will boost the amps up 25 ? Or will it just boost the volts to the correct rate for the specified battery and output the same amps as what is being put in ?

Any advive or info on DCDC chargers and similar findings or tests would be awesome tia .

 

[Lesgold]

Hi Chriso,

No expert on this but I did install a dc to dc charger in my Ute. The 25amps is the max rating of the unit. The soar panel if rated at 120w, should in a perfect world deliver 10amps at 12v. The reality is closer to what you have stated. The solar panel will still run through the unit and charge the battery but it would generally be a bit slower than the alternator. As long as the panel is large enough to keep your battery charged, you shouldnt have any problems. Will basically come down to what you plan to run on the battery (lights, fridge etc) I am sure that some of the wizards on the forum should be able to give you more precise advice if needed.

Cheers

Les

 

[user 7268]

Make sure you get a late model IDC25 as the earlier stock had a problem and kept tripping the solar over voltage fault and you had to disconnect to reset. This was caused by a problem in the circuitry that as it switched across was creating a voltage spike. The rectified this in the later / current versions. The later or current versions no problem and have been running one for 3 months now without issue. Had a hand in sorting them ................. long story with many hours involved.
As for amps of unit as has been already answered. The amp rating is the current flow the unit will handle ie the amp rating of the unit.
If you find the solar over voltage trips (Will show red light) contact Brown and Watson they will sort it for you :Y:
It's just an intelligent charger that provides voltage depending on battery type and the good part is you get an MPPT controller along with it which allows you to get the most out of your panel. If your running a large fridge you may need a bigger panel as after a few days it may struggle to keep up. Depends how long you plan to stay camped in one spot and also how many amp/hr your battery is, and how hot it is ..................... Vic versus FNQ..

 

[Moneybox]

I've had the Intervolt and I've had the Projector but in the end it's best to just spend the extra and get the Redarc.

The Intervolt was wrongly installed by Bruno's Batteries in Mareeba. I finally sorted it out to some extent but it always tripped out the solar controller as Bogger said. In the end it died when we hit wet weather in Karratha and the dust inside turned to mud and fried the insides. No warranty and not worth the insurance claim. We had a ligitimate claim against the installer but the chose to not answer my calls or emails. I gave up and bought the Projector.

The Projector is 9v to 32v but the problem is it can only output 14.4v so not suitable for a 24v system. Another useless piece of gear sitting on the self.

I suggest you do yourself a favor and the best. Redarc is tested and proven to be the best.

 

[BigWave]

I agree with MB. I went the Redarc first up. Has worked flawlessly.
https://www.redarc.com.au/dual-input-25a-in-vehicle-dc-battery-charger

 

[Occasional_panner]

Good advice Moneybox, FYI the redarc needs to be purchased as either 12v or 24v, they can't do both voltages.

Also be careful what solar panel you buy as it needs to have a max of 32v input, which is bloody silly, a decent mppt should handle 100v.
I now run an epever tracer mppt to power the aux from solar, running panels in series and feeding the mppt a higher voltage really improves the dcdc efficiency.
https://www.ebay.com.au/itm/EPEVER-...var=640493007592&_trksid=p2060353.m2749.l2649
(that unit will do both 12 and 24v systems)
I got the 1225D like Bigwave, it's been fantastic, but I personally don't like the limited input voltage of solar, but for most 4wd'ers, campers it would be fine.
If you set up a solar system with a bit more grunt you'de want more than 25A capability anyway.

Christo, if you put in 5-6 amps that unit will not boost it to 25amps, that in effect would be creating energy.
What it will do is bring in the peak power voltage of the panel and dcdc convert that to the charge voltage of the battery.
That voltage will vary between panels but one designed for a 12v setup will probably be around 20v.

Very different to PWM controller which basically pulls the panel voltage down to a tad above the battery voltage.

 

[condor22]

Chriso, to answer your Q (and this applies to any solar controller or DC-DC charger.

You are correct in that the multi stage chargers regulate the voltage (V). However re amperage (A), the simple analogy is "You only gets out whats you puts in..." (forgive the deliberate grammar error .

I have a Redarc BCDC1220 rated at 20 A, the most I've seen it output in Boost mode is 16 A (at idle), this may be because that is all the alternator can spare or all the battery wants.

A 120W panel will typically output a maximum of approx. 8 A, then there's an efficiency loss, so your charger may only output 6+ A. When I mention a solar controller, DC-DC charger or a 240VAC smart charger, I refer to the multistage (minimum 3 stage) type. The 3 stages are BOOST, ABSORPTION and FLOAT. This is approximately and simply what happens in the 3 stages.

BOOST - most will enter this stage on startup, have a constant maximum current (input dependent) and if a "soft" start, gradually, but fairly quickly increase voltage. The amperage may vary to maintain a safe battery temperature. This can be anywhere between 80 to 90% battery State of Charge (SOC) before moving to Absorption, so the quicker of the stages. If the battery is already charged, this stage only holds briefly as the smart charger interrogates battery state.

ABSORPTION - When the battery Absorption voltage is reached, it switches to this mode. Here the voltage is constant and the A gradually reduces for a set time or as in the Redarc, the charge rate drops below 4 A. This can take the longer time to achieve.

FLOAT - Here the V are set to maintain the battery at full (to counteract self discharge) and the A are very small to zero.

The time to charge is not simply the charger max i.e 20 A (Redarc) against the required amps. i.e. if you need to pump in 40 AH with a 20 A charger it is not 40/20 = 2 hrs.

Assume a 100AH battery will take 25 AH to go from 60% SOC to 85% before it moves to Absorption and in my case all I get is 15 A from my Redarc. This will take roughly 25/15 = 1.6 hours, but more likely nearer 2 hours. Then as the charger goes to Absorption mode for the remaining 15 AH with a reducing A output, this may take another 2-3 hours, giving a total of nearer 5 hours to charge 40 AH.

AND, If solar output and therefore controller charge is much less, then to charge takes much longer.........

Hope this makes sense, and it is as simple as I can make it.

 

[Jaros]

Very nice explanation Condor22. :Y:

 

[condor22]

Very nice explanation Condor22. :Y:

You're welcome Jaros

 

[jamie]

Thank you condor22, that is exactly what I have been looking into at the moment and you just about answered all I needed to know
Cheers
Jamie

 

[Moneybox]

I have a 250w 24v rooftop solar panel so I stuck with the Morning Star solar controller. I need more solar so next time it will be a 12v panel that will operate through the Redarc. I set up the whole system on 24v to reduce current flow but now I think it may have been a mistake. It's very difficult to buy 24v components. I would have been better off going 24v start batteries to 12v auxiliary. It would have been a lot easier to buy the fridge, inverter, compressors etc but it's too late now. Perhaps next time if we build a new one.

 

[Occasional_panner]

I have a 250w 24v rooftop solar panel so I stuck with the Morning Star solar controller. I need more solar so next time it will be a 12v panel that will operate through the Redarc. I set up the whole system on 24v to reduce current flow but now I think it may have been a mistake. It's very difficult to buy 24v components. I would have been better off going 24v start batteries to 12v auxiliary. It would have been a lot easier to buy the fridge, inverter, compressors etc but it's too late now. Perhaps next time if we build a new one.

Hahahaha
What a pisser! I did exactly the same thing, but I only went as far as buying a 24v inverter, that now runs the backup at home. I switched the van to 12v after I saw all the difficulties it would cause. Now it's compatible with the vehicle charge system and the redarc 1225d in the tray.
Solar is all 24v (30v max power point) panels but the tracer dcdc's it to 12v charge voltage, only prob is you need twice as many controllers for 12v amperage.
If I was on a decent bit of land again for a home system it would be 48v and wind turbines all over the place, I loved making them years ago when I was a sheep farmer. Don't miss that hard farm work though.

 

[Chriso1988]

Thanks for all your replies! Some really good info and advice!

Thanks condor22 awesome write up thanks for taking the time to post it !

 

[condor22]

I have a 250w 24v rooftop solar panel so I stuck with the Morning Star solar controller. I need more solar so next time it will be a 12v panel that will operate through the Redarc. I set up the whole system on 24v to reduce current flow but now I think it may have been a mistake. It's very difficult to buy 24v components. I would have been better off going 24v start batteries to 12v auxiliary. It would have been a lot easier to buy the fridge, inverter, compressors etc but it's too late now. Perhaps next time if we build a new one.

I sympathise, but myself have avoided the 24VDC route for exactly the reasons you give. In this day and age, most of the DC equipment available is 12 V and largely low draw amps. As an example, here are the ratings in Amps of my vans kit (measured, not spec)

LED Lighting

Main Roof 3 off = 0.5 (on full)
Main Roof 3 off = 0.1 (on blue night lite)
Main Shower = 0.5
External Light = 0.5
Single Down lights 3 off = 0.2
Reading Lights 4 off = 0.15
Dinette Down light bank of 3 = 0.6
Robe 2 off = 0.2
Sink LED Strip = 0.1
Range Hood Light = 0.1
Vanity = 0.4

When watching TV, I have one reading light on and switch on/off others as required. If the TV is off and I'm planning where I'm detecting on the laptop, I'll use the Dinette 3 bank LEDs.

Range Hood Fan = 1.2
Shower Fan = 1.3
TV = 1.8
Water Pump = 3.4
Diesel Heater Startup = 10 (maybe 15 seconds)
Diesel Heater = 1.0 (when running)
Stereo = 0.4 (12V car stereo/CD/DVD)

So as you can see, nothing with a huge current draw and most of the higher current items are very short use items. If I'm sitting in the GT in Winter, watching TV, with a couple of lights on and the diesel heater running, I'm generally pulling about 3 to 3.5 amps. It helps that the fridge is on gas.

The biggest thing some use is a large (i.e. 600W+) inverter. I stated this in another thread...... I use a 150W pure sinewave in the van for things like my 240VAC satellite receiver, DVDR and ultrasonic cleaner. In fact it will run all 3 of these items within its 150W at the same time. I carry another in the 4x4 for similar small loads. If I need more than that, i.e. van hot water system or microwave, the Honda 2kVA gets to play...... (having said this, I am aware some need 240VAC for things like sleep apnoea machines)

 

[Glenmec200]

condor22

Not to add a Dumb question to the DCDC charging info, which i found informative, but -

The DCDC chargers take a voltage range up to 23volts or thereabouts.

So Assuming 100% efficiency, (Which it wont be)

130watt - 12v solar panel = 10.8amps

If you disconnect the regulator on the panel you get:
130watts - 23v = 5.6amps

Are you better to provide high voltage, low current (130w - 23v) input to get best charging result, or low voltage high current (130w-12v)?

 

[condor22]

condor22

Not to add a Dumb question to the DCDC charging info, which i found informative, but -

The DCDC chargers take a voltage range up to 23volts or thereabouts.

So Assuming 100% efficiency, (Which it wont be)

130watt - 12v solar panel = 10.8amps

If you disconnect the regulator on the panel you get:
130watts - 23v = 5.6amps

Are you better to provide high voltage, low current (130w - 23v) input to get best charging result, or low voltage high current (130w-12v)?

I'll try to make it simple - Your math doesn't work that simply.....

My example - You have a fully charged battery and at rest (no load) it reads 12.9 V on the meter. You then run a water pump pulling 4.0 amps and measure the voltage on the battery, you will see it go down to something like 12.5 or so V. This is simply due to the resistance in the circuit. So, this is a load situation, however, a similar thing occurs with Solar input.

A solar panel spec may give Max Pwr (Pmax), Voltage at Pmax (Vmp), Current at Pmax (Imp), Open Circuit Voltage (Voc) and Short Circuit Current (Isc). To explain what they mean;

Pmax = Maximum Power Output of the panel i.e. 130 W, however that is in perfect conditions and brand new, so not normally achieved.
Vmp and Imp = The voltage and amperage output at Pmax. So if Pmax is lower, so are V and I, which is why on overcast days or the further south you go, panel output reduces.
Voc = The voltage measured across a battery or solar panel when not connected to a circuit and therefore no current can flow.
Isc = The short-circuit current is the current through the solar cell when the voltage across the solar cell is zero.

A further example of outputs = A Blue Apple 120W solar panel has the following specs;

Maximum Power (Pmax) 120W - Voltage at Pmax (Vmp) 19.5V
Current at Pmax (Imp) 6.44A - Open Circuit Voltage (Voc) 21.50V
Short Circuit Current (Isc) 7.38A

If you do the math 120 divided by 19.5 = 6.154 and 120 divided by 21.5 = 5.58, so an Imp of 6.44 (spec) is neither but closer to Vmp.

Most folding or portable panels, especially the cheapies, have a small solar regulator on the rear of the panel, the output is already regulated, but the output is around 13.8VDC, similar to an alternator output voltage and although they will work, not the ideal charging voltage for an AGM deep cycle. My choice for these panels would be to disconnect this regulator and take panel output directly to a DC-DC charger.

However, the reason I chose Redarc over CTek is that their operating range is 9V to 32V, whereas CTek is 23V and they don't spec a minimum.

Last point - If you have a panel that is regulated it should go directly to a battery (fused). If you want to power a DC to DC charger via solar, then bypass its regulated and, If you want to use a DC-DC charger supplied by both alternator and solar, it will need to be either auto sensing re input or have a relay to switch from one input to the other. DO NOT POWER A DC-DC FROM BOTH AT THE SAME TIME.

 

[reefer]

All great stuff here...what I can gather from it...not a very good head for electronics I'm afraid..but I would like to know if it is possible to connect my car battery to my electrical system while it is still hooked up to the solar panel, in order to boost the van battery?..My regulator has functions to alter the input from the solar etc..but it will not provide those functions if the main battery is not at or near to full charge.I am not at this stage aware of the capacity of the solar unit..it's about 750x 350 in size and I think it's about 110W or so.Sorry to be so vague.. (THE UNIT WAS PART OF THE SETUP GIFTED TO ME BY THE INCREDIBLE 7.62 MARKSMAN) :YHe may well be able to elaborate further as to the specs ect but Ithought Imight well be able to glean some knowledge about what Ineed to know(if that makes sense" ...but it appears as though I am not getting much trickle charge if any ..and the whole thing is in full sun.The regulator is showing that the solar is out-putting(the little battery icon is pulsating..but there just doesn't appear as though my battery is getting charged at all) could I have un-wittingly altered the required output by my incessant pressing of the 'functions button'..or? ...please explain!..as the red-head said. ] the system is 12V..running the 35ltr capacity fridge for two hours appeared to suck the life out of the battery..it went from 12.2 v. to 9.8 over those two hours...and while the last two days have been cloudy..today has been bright and hot with the solar panel in full son...what on earth is going on?regards..REEFER. ]

 

[Occasional_panner]

9.8!!!!!! Sounds like that battery is rooted, was that under load or resting voltage (nothing draining on it)
By the way 12.2 is almost dead flat to begin with.
They should rest with no load at around 13v full charged and dead flat at 12.0

 

[reefer]

Oh!...shite!..yeah it was 12.2..but had been laying around his place and was charged up at some point before he got it here.He did say that he had used something on it... lights or something, but that it had rested and not lost the 12.2 ..or was 'stable' at that for a few days.
So can anyone tell me if I can bring the Prado around and hook up to charge it? or will I blow something up! ] Sorry once more for my naivety..but them's the breaks! ]

 

[Occasional_panner]

Well if it isn't stuffed you really need to put it on a smart charger that will give it the required amps and voltage at each stage of the charge process.
I'm guessing you don't have one though.
Hooking it up to the vehicle will put some charge in it but it's usually a bad way to charge batteries.
However if the battery is under 12v you need to do something to get it above that fairly soon.
Charging a battery badly is better than leaving it dead flat.
But if it went to 9.8 in 2 hrs with only a fridge attached it may be rooted already.