36 Volt Solar Panel , 250 watts - Can I Connect to 12V Solar Regulator ?

[noelex 77]

Originally Posted by goboatingnow

Sorry noelex. The charge controller presents a different. Impedence then the battery. Hence the panels voltage will be a function of its PV curve into that load. It will not be at 14 ( the output will ) do the losses are nothing like you stated. There will of course be some losses stepping down to 14 v but these regulators are switchers. So heat loss is low.

Remember PV panels are primarily current sources. The panel voltage at the controller input will be near the max power point ( as the PV curve is fairly flat ) but obviously only a tracking controller will get to the max point exactly. The difference between switched regulation and mppt is about 15% in panel efficiency.

( ps take say a 30 vac output transformer , rectify it and then feed it into a 5v regulator , does the transformer output fall to 5v , no. , while not identical the similarities are the same )

You are confusing the operation of MPPT regulators and non MPPT regulators.
Regulators that are not MPPT do not perform any voltage conversion. Input and output voltage are essentially the same.
This can be confirmed with a simple multimeter.( edit I see other posts have confirmed this)

A panel with a maximimum power point at 35v will perform very poorly with a12v battery unless a voltage conversion is done, trading volts for amps only MPPT regulators can do this. This is the essential difference between MPPT regulators and non MPPT regulators.

If the nominal solar panel voltage is matched to battery voltage the gains from MPPT technology are small, but when there is a large mismatch between the panel voltage and battery voltage, only the voltage conversion in an MPPT will produce reasonable results.

[goboatingnow]

I know how MMPT works I have one, and yes I agree charge controllers just bang the panel onto the battery , which is a rotten way for any sort of high power panel.

but DC DC conversion isn't just the preserve of MPPT controllers. but it does seem that the off grid stuff seems to have broken down into simple controllers and DC DC ones that all have some sort of MPPT ability ( though i wonder at some),

Dave

[surfmachine]

Hi...
Well it seems I need a mmpt controller, whatever panels I use?
I now understand the difference between a switching controller and a proper charge regulator that uses an algorithm to maximise the input from he solar panels.

Maybe something like this one for around $160 aud landed?

30A MPPT Solar Charge Controller Regulator 12V 24V TRACER 3215 150V INPUT 30A AU | eBay

The Tracer series controller is for off-grid solar system and control the charging and discharging of the battery, especially suitable for the street light system. The controller features a smart tracking algorithm inside that maximizes the energy from the solar PV module(s) and charge the battery. At the same time, the low voltage disconnect function (LVD) will prevent the battery from over discharging.

The Tracer controller charging process has been optimized for long battery life and improved system performance. The comprehensive self-diagnostics and electronic protection functions can prevent damage from installation mistakes or system faults. In addition, the Tracer controller has a RJ45 interface to allow communication with a meter for remote monitoring.

Features :

·12V / 24V auto recognition.

·Advanced maximum power point tracking technology to optimize using the solar system.

·Peak conversion efficiency of 97 %, high Tracking efficiency of 99%.

·Very fast sweeping of the entire I-V curve, several seconds tracking speed.

·Widely used, automatic recognize day/night.

·Timer function with 1-15 hours option for street light.

·Unique dual timer function, enhance the flexibility of street light system.

·Sealed, Gel and Flooded battery option.

·Adopting temperature compensation and correcting the charging and discharging parameters automatically, improving the battery lifetime.

·Electronic protection: over charging, over discharging, overload, short circuit.

·Reverse protection: any combination of solar module and battery, without causing damage to any component.

·Excellent thermal design and nature air cooling.

·RJ45 interface with remote meter MT-5, convenient to check operating parameters of controllers.




Parameter :


Nominal System Voltage:12VDC / 24VDC Auto work

Rated Charge Current:30A

Rated Discharge Current:20A

Maximum Battery Voltage:32V

Max. Solar Input Voltage:150VDC

Max. PV input power:12V / 390W 24V / 780W

Self-consumption*:<10mA(24V)

Charge Circuit Voltage Drop:≤0.26V

Discharge Circuit Voltage Drop:≤0.15V

Communication:8pin RJ45

Thanks again from Keith.

[LeaseOnLife]

The MPPT controller should work fine for the 2x150W panels.

Now: Are the panels mounted together, same sun & shading? A whole new can of worms, when using multiple panels: Do you want to connect them in series or parallel. The MPPT can deal with both.

Disclaimer: I don't think either solution (parallel or in series) is good. A controller per panel make sense if the panels see different light.

I better put my tinfoil hat on, for the fall out...

Dirk

[surfmachine]

Ahoy Dirk, I will connect them in parallel.
Total of 4 panels.
2 X 135 watt Kyocera solar panels, nom output 17.4V
2 X 120 watt solar panles, nom output 18V/ 6.7A....yet to be purchased.

Total of 510 watts max.

All mounted on the same solar arch, same sun and shading and orientation.

Also have two wind gennys, at present only 1 connected direct to battery bank, an aerogen 400 watt genny, puts out max of 12 amps, I fit a stop switch. Going to put in another eclectic energy wind genny, 400 watt, with a stop switch, as well. Will run them through a charge controller that allows automatic charge divert to a resistive load.

I need to buy a new charge controller for the solar panels, so I will opt for a MPPT type, seems to be best? Although a lot more expensive. As I was adding another wind genny I was hoping to use a 1 charge controller fits all, like the westmarine one, but it is only a switching charge controller.

I am learning a lot from this thread, thanks to you and all the other contributors for your advice!

I am about to embark on another 6 months cruise of western Sumatra from Langkawi, so I will be anchored for up to 2 months at a time at deserted islands, just studying the back of my eyelids and surfing, plus running a danfoss fridge and sundry electronics, laptop etc, hf radio. So, I dont want to run the honda genny or motor to charge batteries. Hence the solar panles and wind gennys, given the limited wind in the equatorial regions.

Fair winds from Keith.

[capnorv]

Your ebay panel sounds great to me. I definitely agree an MPPT ( maximum power point technology) controller is needed, and that seperating sources with different controllers is the optimum way to go. That said, varying sources, with varying voltages/amperages can also be paralleled to an MPPT controller successfully, though not optimally. Make sure the controller will handle all inputs at maximum plus 10% for longivity and safety. Your smaller panels could be paralleled, but could also be series wired , which I would recommend.My experience, designing and installing for 20+ years, from 20-7kw solar, 200w-1250w wind, currently getting ready to install 78 22w panels on the houe, have an offgrid rental and 270w on the boat. My philosophy is the simpler the better when it comes to marine technology, because it WILL need repaired. Good luck!

[surfmachine]

Thanks guys.
Now, for a diversion load dump for the wind gennys?
I will have a D400 eclectic energy wind genny, can put out 400 watts and Aerogen 200, so 600 watts maximum.

What size wire wound ceramic resistor should I have, I have seen 200 watt resistors, but at varying resistance, some at 50 omhs, some 15000 ohms, some at 150 ohms.

I would put in 4 in a bank, mounted in series, on a fire resistant board, any advice on the size of resistance for each 200 watt resistor, or is it just the watts that is important?

3.3K Ohm 5% Lug Terminals Fixed Type Power Wire Wound Resistor 200W | eBay

Does anyone know of a MPPT controller that you can attach wind gennys and solar panels to, that will switch the output to a dump resistor bank when the batteries are charged?

All the best from Keith.

[capnorv]

Just a thought, have you thought about putting a 500 watt unit in your hot water tank instead of throwing that heat energy into the air? I use my excess wind energy to heat the hot tub instead, since I use a instant propane h/w heater, but it's a shame to throw free energy away. If I put wind back on the boat, this is what I'll do.

[surfmachine]

Ahoy Capnov, yes , that is an excellent idea! I don't have a hws as I spend all my time on the equator.

So for now, it's a dump resistor in the engine room. Those 12/240 volt hws elements are a great product.

Thanks from Keith.

[hellosailor]

"just the watts that is important?"
Generally watts is watts and for a dogbone resistor that's the main thing. There may be a voltage rating, a maximum voltage above which the resistor woulc break down, but as long as you are below that, wattage should be all that matters. With 36 volts or even 50 volts, I think you'd be safe as long as the wattage is adequate.

And assuming that's intended as a constant working rating--rather than an intermitttent one. If one of those resistors blows, your windgen will be operating without a load and it blows next. So a series-parallel setup that can tolerate one resistor failing might be safer.

3.3K Ohm 5% Lug Terminals Fixed Type Power Wire Wound Resistor 200W | eBay

We used to build resistors from the high resistance nichrome wire in burned out toasters. Yes, this is not rocket science.<G> For high resistance and small loads, you can actually "draw" a resistor from a lead (graphite) pencil!

"Does anyone know of a MPPT controller that you can attach wind gennys and solar panels to, that will switch the output to a dump resistor bank when the batteries are charged?"

The mythical "one ring to rule them all". Which so far does not seem to exist. The problem is building them to accomodate the wider range of power supplies that are out there, and the conflicting regulation schemes. MPPT and dump are totally different circuits. Your best bet is to shut down one when you are using the other, unless your batteries are hungry enough to simply suck both dry. Otherwise it is a random choice of which one will put out 13.8 volts first, and cause the other to shut down. (Or whatever the set points are in your regulators.)

[irwin37]

Surfmachine


Here,s what I would do with your solar system.


I would wire the panels in parallel, if its possible try to select panels with the closest max power voltage. Your trying to match them as best you can, for a 12 volt system this will most likely be in the 16 – 19 volt range. (You probably do not have this luxury if you already have the panels / no worry they should be close enough)


With 4 parallel panels I would not bother with an MPPT tracking charge controller, your gains would be minimal as you are not using matched panels (2 different manufactures will have different power curves) and the MPPT charge controller will just find the average of the max power. Switching charge controller should work just fine.


You do not want to run the panels in series as all you will do is rise the voltage but the current will actuality only be equivalent to the highest current from the lest powerful panel (current in a series circuit is the same anywhere in the circuit) and your more powerful 135 watt panels will only put out 120 watts, the same as your BP panels. Additionally when you run panels in series, if one gets shaded you lose the majority of your power. In parallel you only lose the power from the shaded panel.


I would also put an inline fuse (10 - 15 amp) is line with each panel before the parallel point as any fault in one panel (short) will then draw the full power from the other three, could be as much as 20 amps, and start a fire. (It does happen and I have seen the results, not pretty)


By the way your BP panels were most likely manufactured about 50 feet from my old desk as I worked in engineering at BP Solar (Solarex) for 15 years.


Hope this helps

[irwin37]

Correction, I was thinking 24 volt panels, the fuse for 12 volt 120 -135 watt panels should be 15 - 20 amp, and a short could draw 30+ amps from the other three panels. Even more reason for the fuses.

[deckofficer]

I'm soaking this up, thanks Dave. Dirk, thanks for shaking Dave out of the forum's woodwork.

[goboatingnow]

That reminds me, has anyone done any research on how good mppt regulators are. My application isn't on a boat . But I've been tracking the panels recently and I'm beginning to wonder how well it tracks, there's some anomalies. Anyone do any testing of boat orientated ones.

I have a nice 20a Mean Well DCDC converter it would make a nice basis for a controller add a micro, dac et .



Dave

[LeaseOnLife]

Originally Posted by goboatingnow

That reminds me, has anyone done any research on how good mppt regulators are. My application isn't on a boat . But I've been tracking the panels recently and I'm beginning to wonder how well it tracks, there's some anomalies. Anyone do any testing of boat orientated ones.

I have a nice 20a Mean Well DCDC converter it would make a nice basis for a controller add a micro, dac et .



Dave

Dave

I might have the tools and parts to do a test like it. Morningstar MPPT controller and a display for it, it can show quite a few values, telling me what the controller is doing. Logging would be by pen and paper. Verifying some key data by multimeter.

But I am not sure how to define the test parameters... thinking out loud.... I can tilt the panel and change the amount of sunlight coming in. Then track Watts, Volts, Amps on the solar side, and then? Compare with datasheet?

Let me know what would be some easy to reproduce steps to confirm functionality (or quirks) of a MPPT

Dirk

Edit:
PS: this is going to be a bit off topic....