Renogy DC DC Charger w/ MPPT

[berndpfrommer]

The wire is plenty big enough and I am measuring the voltage of 13.6V right at the alternator. We are talking about a current of 8A, that is really small so even an undersized wire would suffice. I can't access the van at the moment but will check if any of the connections aren't tight. I doubt it though.
From what I found on the sprinter forum my T1N sprinter van's alternator output voltage is typical for that model.
The chap in the YouTube video I linked did more extensive tests and claims that other Renogy DC to DC chargers work just fine with low alternator voltage. He also said he will no longer reply to suggestions his wires are too thin .

 

[boondox]

The wire is plenty big enough and I am measuring the voltage of 13.6V right at the alternator. We are talking about a current of 8A, that is really small so even an undersized wire would suffice. I can't access the van at the moment but will check if any of the connections aren't tight. I doubt it though.
From what I found on the sprinter forum my T1N sprinter van's alternator output voltage is typical for that model.
The chap in the YouTube video I linked did more extensive tests and claims that other Renogy DC to DC chargers work just fine with low alternator voltage. He also said he will no longer reply to suggestions his wires are too thin .

Interesting to know that they typically work with such a low input voltage. Good to know.

What I don't understand is why the Sprinter has such a low alternator output. I assume that it has a lead acid battery and if so then 13.6V will never charge it correctly. Are you measuring the voltage at idle and perhaps at higher RPM the voltage goes higher?

 

[HRTKD]

Don't just look at the specs. Get the owners manual from the webb and read is closely and critically. Guessing at how it was designed to work is not of much use. WHile I believe friends do not let friends buy RENOGY, if you already bought, read the owners manual. It ain't perfect, but does explain the basic operation of the device. It will charge 50a solar, or 50a alternator, or 25a max solar and 25a solar if both inputs are active.

Glad you corrected yourself.

 

[berndpfrommer]

Interesting to know that they typically work with such a low input voltage. Good to know.

What I don't understand is why the Sprinter has such a low alternator output. I assume that it has a lead acid battery and if so then 13.6V will never charge it correctly. Are you measuring the voltage at idle and perhaps at higher RPM the voltage goes higher?

It seems to charge my (lead acid) starter battery just fine. For modest float charging around 13V are enough (https://www.powerstream.com/SLA.htm).
The alternator output voltage seems to vary (note that this is *not* a modern smart alternator). It starts out in the low 14V range and then drops over time, fairly quickly. I see it others report the same so it's not that my alternator is unique: (https://sprinter-source.com/forums/index.php?threads/75210) or defective.

I'm very much aware that I'm starting to hijack this thread, since it's not about the sprinter T1N alternator but about the Renogy DCC50s. I think the question is: should (or can) the DCC50s boost an input coming through the alternator terminal? I wonder whether I should try connecting it to the solar input terminal (since I don't have any solar panels yet and was just using it as a DC/DC charger).

 

[boondox]

It seems to charge my (lead acid) starter battery just fine. For modest float charging around 13V are enough (https://www.powerstream.com/SLA.htm).
The alternator output voltage seems to vary (note that this is *not* a modern smart alternator). It starts out in the low 14V range and then drops over time, fairly quickly. I see it others report the same so it's not that my alternator is unique: (https://sprinter-source.com/forums/index.php?threads/75210) or defective.

I'm very much aware that I'm starting to hijack this thread, since it's not about the sprinter T1N alternator but about the Renogy DCC50s. I think the question is: should (or can) the DCC50s boost an input coming through the alternator terminal? I wonder whether I should try connecting it to the solar input terminal (since I don't have any solar panels yet and was just using it as a DC/DC charger).

Oh, I don't think it is really a hijack.

I'll have to dig out my manual. Maybe you could connect a well charged battery and energize the ign sense line? Mine just comes on when the voltage gets high enough and I am not sure what the minimum voltage is.

 

[HRTKD]

I wonder whether I should try connecting it to the solar input terminal (since I don't have any solar panels yet and was just using it as a DC/DC charger).

A typical MPPT solar charge controller will require input voltage to be as much as five volts higher than the battery voltage before it will commence charging. I don't think it would do any good to switch the starter battery wires over to the PV input.

 

[Butcher]

Read the specs on the Renogy unit. The way I read it, yes it will take your incoming voltage and do what it needs to to charge the battery. There is a spec for the input voltage so it will begin to charge. I could put that down, but then there would be no reason to read the specs.

Reading what the factory has to say about any item is probably a bit more reliable that opinions from people you do not know.

As for the alternator charging, depending on where you are testing the voltage, 13.6v may not be too far out of the norm. As a factory trained Mercedes tech for 35+ years, if you want to see what the alternator is putting out, start at the source. The back of the alternator. Every wire and connector will reduce that voltage and over time, the ground and power leads may cause excessive resistances. If your Sprinter is loaded up with a lot of consumers that the factory did not install, those consumers may bring down the voltage too. A good voltage drop test will confirm if the wiring is good or not, don't forget the ground side too.

Without any testing, I'm willing to say the alternator is doing a fine job, it's the wiring, where you are testing, or the voltmeter you are using that is causing the low voltage. If you are using a Fluke, replace the 9v battery. They are known to cause bad readings and not let you know your 9v battery is weak.

 

[berndpfrommer]

Oh, I don't think it is really a hijack.

I'll have to dig out my manual. Maybe you could connect a well charged battery and energize the ign sense line? Mine just comes on when the voltage gets high enough and I am not sure what the minimum voltage is.

Next time I get to the van I'll try connecting the ignition sense wire of the DCC50s to see if that makes a difference. It's not supposed to be connected but it may cajole the DCC50s into delivering a higher charge current by suggesting it's a smart alternator. Because another possibility is that the charger is trying to protect the alternator from overload. When it sees the alternator voltage drop to a low value it reduces the current to the house battery, figuring the alternator is under heavy load from other consumers already. Just a theory. (The alternator in my van is 200A rated alternator so I'm not too worried about overloading it). Per manual the DCC50s is supposed to cut in once the alternator voltage is > 13.2V for 15s (traditional alternator) or > 12.0V for 15s (smart alternator). I couldn't find any mention of it regulating the current when the voltage is close to 13.2V. However since the cut in voltage differs connecting the ignition sense may well make a difference.

 

[Butcher]

I always suspected that the smart alt wire was to tell the unit that indeed the engine is running. That way, it will deliver current to where it is needed. If it did not have this wire, the alternator could be charging and the DCC50S would think it was not.

I go about thinking about current flow a bit different. If the voltage is the same, the current will not flow. If one is higher than the other, current will flow. The bigger the difference, the more current will flow. With computers, that current could be regulated and this is what I think the DCC50S does. The settings would have to be set right to set the voltage [and therefore current] to charge the battery correctly.

Yes, this is a very simplistic way of thinking, but then, I'm pretty simple minded.

 

[RandyP]

I always suspected that the smart alt wire was to tell the unit that indeed the engine is running. That way, it will deliver current to where it is needed. If it did not have this wire, the alternator could be charging and the DCC50S would think it was not.

I go about thinking about current flow a bit different. If the voltage is the same, the current will not flow. If one is higher than the other, current will flow. The bigger the difference, the more current will flow. With computers, that current could be regulated and this is what I think the DCC50S does. The settings would have to be set right to set the voltage [and therefore current] to charge the battery correctly.

Yes, this is a very simplistic way of thinking, but then, I'm pretty simple minded.

The installation and operations manual for the Renogy DCC50S is pretty specific detailing how the device works. Review it again, pay particular attention to the section on Operations, Pages 12-14. If you read it carefully and critically you can surmise what the intended operations of the device are. If you read the manual for understanding, stopping to consider each point made, you can make more educated comments about its intended function.
_

https://www.renogy.com/content/Manual/DCC50S%20DC-DC%20MPPT%20Manual.pdf

 

[Butcher]

Yup, exactly what I mentioned but in a simplistic way.

With the smart wire attached, the unit will know when the smart alternator is charging. With the dumb alternator at the proper charging voltage, it will charge. If you had a smart alt and the smart wire was not hooked up, the DCC50S may not charge but the alternator could be.

This unit is really not that sophisticated. It is capable of charging a variety of battery types using PV or an alternator. As long as you give it the right voltage and set the parameters correct for your battery, there is not much more you need to know.

Follow the instructions to a tee and if the unit is working, you'll be fine.

 

[mkaye]

since you're dealing with a sprinter with a smart alternator i think the alternator sense wire should be connected
it is not ign sense, it feeds back to the alternator to alter it's output

 

[John Frum]

since you're dealing with a sprinter with a smart alternator i think the alternator sense wire should be connected
it is not ign sense, it feeds back to the alternator to alter it's output

You mean this wire?
"IGN Signal Wire for Smart Alternator" -- https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf

 

[Felt]

Could a member possibly advise on the photo attached. I am presently following Will's thread and hoping for some clarification. I have a 2 x 200w panels with 50a DC-DC charger. A Giandel 2200w 12v inverter. Two 100ah lithium batteries.My run from the battery to inverter is 20 inches. Is 1/0 suitable or should I use 2/0? Is a 250amp circuit breaker (circled) ideal or should a this be a 300amp mega fuse. Finally should I install a 80 amp inline fuse at the house battery? Sorry for re-asking some of these questions. My neighbor has placed the fear of Thor in me.

 

[Butcher]

I'm really certain the alternator on a Mercedes is data driven by the engine control module. Not certain how Renogy will change that data and not cause the engine module to set some type of code.

I believe that extra wire could let the Renogy unit to understand that even less than the standard 13.2v of a standard alternator it still would allow charging to the solar battery. Otherwise, it could stop the charging since the standard shut off is 12.7v

 

[rickst29]

Could a member possibly advise on the photo attached. I am presently following Will's thread and hoping for some clarification. I have a 2 x 200w panels with 50a DC-DC charger. A Giandel 2200w 12v inverter. Two 100ah lithium batteries.My run from the battery to inverter is 20 inches. Is 1/0 suitable or should I use 2/0? Is a 250amp circuit breaker (circled) ideal or should a this be a 300amp mega fuse. Finally should I install a 80 amp inline fuse at the house battery? Sorry for re-asking some of these questions. My neighbor has placed the fear of Thor in me.

Felt, you're a bit off topic, but here's your answer: Depending on how much load you're going to put on that Inverter, you should size the wire to more-than-handle that current load. Then you size the fuse to protect the wire. That diagram seems kinda bad (to me), because the "DC fuse box" has no separate fuse.

In that diagram, an "upstream" short circuit at or before the "DC fuse Box" allows all 250 or 300 amps to occur without blowing a fuse along the "fuse box" input power line. Your downstream circuits 12v circuits (from the fuse box) are definitely not supporting all of that current, AND the 4-AWG wire could start a fire in that.

From a common "12-VDC Bus connection", capable of extremely high current", every connected wire should be fused. The battery "+" wires (big ones) should each have a fuse built into the battery pack. The small Renogy "70A breaker" should perhaps be smaller, and perhaps be a faster-blowing fuse instead. Your output wire to the "12-VDC fuse box" should have a fuse, at perhaps 50-70A (it depends on maximum concurrent DC loads you intend to run). "Your 12-VDC Bus connection" might also have a120-VAC -> 12 VDC power converter input wire, which should not be run through the fuse box in order to reach the batteries.

"+12v" input to the Inverter comes from a really big wire with a good fuse (rather than a slow and cheap-looking DC "circuit breaker switch"). You might also need a switched precharge wire. If you intend to run a microwave or coffee maker, you need continuous power of about 1400 output watts. (That Giandel might not handle a microwave, due to high reactance of microwave oven circuits.) The input power could be up to 20% higher due to power consumption by the inverter itself. What appliances do you have in mind?

If you use 1400 AC output watts, input power would be about 1400w /.80 "efficiency" = 1750 watts. With input Voltage of roughly 12.7V, that takes about 140 Amps. 2/0 wire might be OK, although 4/0 would be better. The fuse should probably not be bigger than 200A for 2/0, and probably not bigger than 250A for that Inverter in any case. Your 2*100Ah LFP batteries shouldn't run more than 1C for anything more than 3 seconds, that could also provoke BMS "over-current" shutdowns. I've got a 300A fuse on my own Inverter connection, but it's a bigger Inverter. That wire is 4/0 and pulling from multiple battery packs totaling around 450Ah. It's also a lot shorter than yours.

1/0 wire would be inadequate running a toaster, household coffee maker, or microwave. Don't forget about precharge, it was totally missing in your picture.

 

[Felt]

Thanks Rickst29! I appreciate the detailed response.

 

[Felt]

For the van battery to DC-DC max will be 50 amps (25 amps max when solar is connected to the charge control) so 25mm2 wire will be fine.
I prefer to match the cable 35mm2 to the rated output of the house battery 200A even if you never intend to pull that current. What is the difference in price between 25mm2 and 35mm2 cable for the length ?
It gave me the option to add the inverter at a later stage, which I did.

A "Heavy-Duty Module Design Bus-Bar Box Terminal Board 300A w/ 4 Terminal Studs" on ebay in the UK is priced at around £25 GBP so adds about £50 to the build. For me it was worth every penny.

I don't have a circuit diagram but it is very similar to your diagram except for 4 x 160 watt Renogy solar panels. Based on Will Prowse's "The Classic 400 Watt Solar Package" .


This is a list of the components I used
Description
4 x 160 Watt 12 Volt Monocrystalline Solar Panel RNG-160D-SS-EU
1 x Solar MC4 Y Branch Connectors MFFFF + FMMMM Pair RNG-CNCT-MC4BC-EU
4 x MC4 Waterproof In-Line Fuse Holder w/ Fuse (FUSE Amp: 20A) RNG-CNCT-FUSE20-EU
2 x 15 Feet 10AWG (6 mm2) Solar Extension Cable with MC4 Female and Male RNG-EXTCB-15FT-10-UK
1 x DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT RBC50D1S-EU
1 x 2000W 12V Pure Sine Wave Inverter With English Standard Socket R-INVT-PUH1-201235-UK
2 x 12V 100Ah Smart Lithium Iron Phosphate Battery RBT100LFP12S-EU
1 x BT-2 Bluetooth Module RCM-BT2-UK
1 x Monitoring Screen for Smart Lithium Battery Series RMS-LFPS-EU
1 x Cable Entry Housing RNG-MTS-CE-EU 1
4 x Solar Panel Roof Drill-Free Corner Bracket Mount RNG-MTS-CB-EU
2 x Heavy-Duty Module Design Bus-Bar Box Terminal Board 300A w/ 4 Terminal Studs
1 x Blue Sea Battery switch OFF ON m-Series 6006 IP66 master cut off isolator in RED
1 x ANL Fuse holder and 200A fuse
1 x Plastic Consumer Unit 12 way IP40 Distribution Board MCB RCD Din Rail Enclosure
2 x 63A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P TOB1Z-63 C63
2 x 32A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P TOB1Z-63 C32
1 x 25A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P TOB1Z-63 C25
1 x 16A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P TOB1Z-63 C16

35mm2 cable between batteries and bus bar
35mm2 cable between the inverter and bus bar
25mm2 cable between charge controller DC-DC and van battery via 63A MCB
16mm2 cable between charge controller MPTT and solar panels via 63A MCB (6mm2 cable from solar panels positive + to the MCB) (could use 6mm2 but I had a spare length of 16mm2)
Each of the solar panels has an MC4 Waterproof In-Line Fuse Holder 20A fuse on the positive side

Note that the Renogy 50A DC-DC with MPPT will max out at 25A for DC-DC and 25A solar when both are connected.
If you want the full 50A for DC-DC isolate the solar panels when driving. Useful in bad weather when solar is producing less than 4 amps.

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I wish I had read this yesterday. What a fantastic build! If I'm not mistaken, the largest wire in your system is 35mm? Which is equivalent to 1awg... I noticed that NV200 also has same/similar gauge wire in some of his schematics. I was all set to use a 1/0 until yesterday. A member advised 4/0 which is what I have ordered.
If I may, the very reason this thread exists is due to Will's video tutorial. There are recommendations of circuit breakers that many members have questioned and offered alternatives. I wonder how difficult it would be to revise the attached photo with better alternatives. I understand that there are many variables. Inverter size, appliance demand etc. Many novices, like myself will find this forum and have similar questions. If there are better alternatives, for example, to a circuit breaker i.e. a mega fuse then which? If there is a fuse need to protect the fuse box, which would you recommend. Again, I'm a novice who found this forum as a result of solar intrest and YouTube. It's easy to glaze over a " new member" with beginners questions. I have read all 40 pages of this very thread. There are many conflicting opinions and ideas. Not looking to hi-Jack this thread. Again if there are better alternatives isn't this the right place for them? I appreciate anyone's advice and recommendations.

 

[mkaye]

You mean this wire?
"IGN Signal Wire for Smart Alternator" -- https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf

yes, definitely says connect for smart alternator
i don't have a smart alternator, so i don't use it

 

[rickst29]

Many of those circuit breakers are "too slow" to fail, and some will fail only once (and never accept a subsequent reset attempt). Some fuses are also too "slow", and some fuses have had the relatively disastrous problem of melting the sides together (rather than breaking the connection) in extreme high-voltage/high current situations. More expensive "class-T" fuses generally won't do that, and fail quickly in cases of over-current.

It would be "world class" to use such fuses in your situation, but I only have TWO - dedicated to possible PV lightening strikes. All of my other high-current fuses are ANL, and I would not disapprove of ANL fuses for your case. (ANL fuses cost less than $10, and the holders are also cheap.) A good class-T fuse @ 250A would be this one, but it's a lot more costly and requires a special fuse holder (due to the cylinder width).