Cargo Trailer Camping Converting

[Sunking]

Poor Grandpa, still doesn't realize you're building this for camping.

OK my bad. Part time is different. At 3 days no solar is really needed if the battery is sized correctly. You can save a ton of money and headaches.

Anyway I can say one thing you cannot, I have been thanked 4 times today already and counting, Happens almost everyday when folks have good questions and take time to listen.

One thing I was thinking about, I used to have a printer that would kill my inverters when it powered on sometimes, because of a spike. That all ended when I started buying pure sinewave inverters, not sure if that was a factor (could also just be that the sinewave inverters are better in general).

I rest my case.You are dangerous because you do not understand what you are working with.

There is absolutely no doubt or questions TSW is far superior. Fact is anything with a motor like a fridge, or non linear loads like a printer can burn your fridge and printer up with a MSW Inverter. Not to mention the Inverter may not start and trip off-line if you are Lucky. You got lucky again your Inverter shut down. You could have easily started a fire or burnt your equipment up.

In an RV or any application today you should only use a TSW Inverter. About the only thing a MSW Inverter can power up today without damaging the equipment, unnecessary Inverter tripping off-line, or risking fire is incandescent light bulb, or electric resistive heating element as those are linear loads. The last thing you would ever want to use in an RV is incandescent lighting and resistive heating for hot water or heat. Everything in an RV is either going to have a motor, or non linear electronics. Even LED lights are non linear loads. A MSW Inverter will burn the driver out. If they are cheap chi-com LED's like most things made for RV's can catch fire if powered by a MSW Inverter. Lastly anything powered by a MSW Inverter is going to use a lot more power off the batteries unless it is a Linear Load. Where is all that extra power going you ask? It is being burned off as extra waste heat in your gizmos cooking their power supplies and motor windings burning them up.

Ever hear that buzzing sound in a electric motor when being ran with a MSW Inverter and wonder why? Its your motor windings beating against each other damaging the insulation for a short circuit in your future. The process is speeded up because the MSW is heating the winding up more than they were designed for weakening the enamel insulation.

[Wrybread]

Poor Grandpa, still doesn't realize you're building this for camping.



Anyway, a 60 watt part time load is dead simple to power. One thing I was thinking about, I used to have a printer that would kill my inverters when it powered on sometimes, because of a spike. That all ended when I started buying pure sinewave inverters, not sure if that was a factor (could also just be that the sinewave inverters are better in general).

[UrbanElite]

I was just updating you guys with the data so far to let you know what it is running at as it. So far I know I the fridge rubs under 60 watts while running and will need an inverter that can handle a spike of 800 watts and above. The fridge is still running and I am still recording data from it as well.

like I said for the most part I will be camping over the weekend and sometimes I will do 4 day trips when I have holidays or more time to camp. I'm aiming for having 2 maybe 3 solid days of power without recharged so if I camp over the weekend in crappy weather I will not have to worry about sun being great or at all. For the most part I will have 4-5 days beaten using the system to recharge and get the battery's up to full strength without a load on them, and sometimes I might not camp for a week or more until my next trip.

[Sunking]

Ok, now that we got the pissing matches out of the way lets get back to the topic, as I have an Update with some specs from the fridge. :P

Here are the specs for my panels again, with some other details I got off the spec sheets, as well as data I collected so far off monitoring that fridge.

Solar Panels: 320 Watt, 72 Cell Panels

Positive power tolerance from 0-5 W
Nominal Max. Power (Pmax) 320 W
Opt. Operating Voltage (Vmp) 37.1 V
Opt. Operating Current (Imp) 8.63 A
Open Circuit Voltage (Voc) 45.08 V
Short Circuit Current (Isc) 9.10 A
Module Efficiency 16.5 %
Max. System Voltage 1000 V (IEC) or 1000 V (UL)
Max. Series Fuse Rating 15 A
Power Tolerance 0 - + 5 W

FRIDGE DATA:

I started my testing with the fridge warm with nothing in it to start up, I then loaded the fridge with all different drinks, packed it right full as it will be that way once we go camping. My test results were any different after resetting the test 5 hours later with a cool fridge and cold drinks. I was opening the door on the fridge every so often as well. Here are the numbers

In 7.5 hours I used 0.367 KWH, 122.2 Volts plugged in, 0.68 Amps, 58-46 watts ( When it kicks on, then lowers slowly to run around 46 watts on the lowest. The fridge isn't on often from what I hear either, It has 5 power settings and just through testing I've been running it on 4 to get stuff really cold to see how much it actually pulls. Lowest wattage recorded is 1.1 watts, the highest spike is 748.3 watts.

So from what I get from this so far is that the fridge will spike under 800 watts to kick on, but during operating it is under 60 watts, as low as 46 watts.

You still do not have the data you need. As I said you need to run the fridge a week to get accurate date, 12 hours is not going to cut it. I suspect you will find it uses roughly 1 Kwh/day. Just that alone wil require a 12 volt 400 AH battery alone. Keep in mind you are not running a Part Time System. All the junk Weybread does not apply to a full time system. You don't have the luxury of letting the system rest and recharge for 3 or 4 days every week. You are going to need an alternate source of power. Otherwise you have no means to CYA for cloudy spells and no way to Equalize your batteries every 30 days or so.

Panel specs are useful, but all I need to know is how many cells and total power All 72 cell panels Voc is 45 to 47 volts, and Vmp of roughly 36 to 37 volts. Given that Imp is easily calculated from Power. 320 watts = 37 volts = 8.6 amps. Exactly what the spec says. What is very important is the Voc as it is critical in determining the controler minimum Voc rating. To maximize efficiency and keep wiring cost low you want to wire the panels in series unless you have shade issues. Minimum correction factor for your panels is 125% so that turns your panel Voc from 45.08 x 1.25 = 56.35 volts. 2 in series put you at 112.7. That eliminates any 100 Voc controller. At a minimum 120 volts, higher is better. At 640 watts you are looking at a minimum 45 to 50 amp controller, and that wil not allow any growth at 12 volts. Go to 24 volts and you can grow to 1200 watts.

[UrbanElite]

Ok, now that we got the pissing matches out of the way lets get back to the topic, as I have an Update with some specs from the fridge. :P

Here are the specs for my panels again, with some other details I got off the spec sheets, as well as data I collected so far off monitoring that fridge.

Solar Panels: 320 Watt, 72 Cell Panels

Positive power tolerance from 0-5 W
Nominal Max. Power (Pmax) 320 W
Opt. Operating Voltage (Vmp) 37.1 V
Opt. Operating Current (Imp) 8.63 A
Open Circuit Voltage (Voc) 45.08 V
Short Circuit Current (Isc) 9.10 A
Module Efficiency 16.5 %
Max. System Voltage 1000 V (IEC) or 1000 V (UL)
Max. Series Fuse Rating 15 A
Power Tolerance 0 - + 5 W

FRIDGE DATA:

I started my testing with the fridge warm with nothing in it to start up, I then loaded the fridge with all different drinks, packed it right full as it will be that way once we go camping. My test results were any different after resetting the test 5 hours later with a cool fridge and cold drinks. I was opening the door on the fridge every so often as well. Here are the numbers

In 7.5 hours I used 0.367 KWH, 122.2 Volts plugged in, 0.68 Amps, 58-46 watts ( When it kicks on, then lowers slowly to run around 46 watts on the lowest. The fridge isn't on often from what I hear either, It has 5 power settings and just through testing I've been running it on 4 to get stuff really cold to see how much it actually pulls. Lowest wattage recorded is 1.1 watts, the highest spike is 748.3 watts.

So from what I get from this so far is that the fridge will spike under 800 watts to kick on, but during operating it is under 60 watts, as low as 46 watts.

[littleharbor]

Panels are pretty cheap these days. I am forced to sell mine for 39 to 42 cents a watt to keep the phone ringing. Anything higher and I just watch them collect dust.

[Wrybread]

And the reason I suggested 60 cell panels. If you find yourself in a cold clear mountain morning your Voc. will exceed 100 volts. there are 60 cell modules being made these days in the 360 watt range if you really need that much power.

But they probably don't cost $150 to $200 each like the 72-cell 300+ watt panels... Remember, like most RV systems I'm trying to keep mine cheap. My whole 600 watt system including charge controller and wires (but not batteries) cost under $500, which I'm guessing is less than the price of a single 300+ watt 60 cell panel. Or do you have a link to a cheaper one? That would definitely be useful for people building out their RV solar systems.

But anyway, agreed that for wiring 72-cell panels to a 100 volt charge controller, parallel wiring is a better way to go if cold mountain mornings are a possibility.

[littleharbor]

And the reason I suggested 60 cell panels. If you find yourself in a cold clear mountain morning your Voc. will exceed 100 volts. there are 60 cell modules being made these days in the 360 watt range if you really need that much power.

[Wrybread]

In bulk charging mode it dips down to ~36 volts. But my point is that it routinely goes higher than that, hence the issue with series wiring two 72 volt panels to a 100 volt charge controller.

Also, I edited my original post to reflect that.

[littleharbor]

You are only taking only 1,2 amps from your array because your battery is nearly full. There is nearly no load on your array and it is nearing Voc. What numbers do you see when in bulk charging mode?

[Wrybread]

Huh? Attaching a picture of the MT50 remote monitoring box for the charge controller, showing typical usage. In case the graphic doesn't come through, it's showing 85.3 volts.That's in about 65 degrees F.
mt50.jpg

[littleharbor]

Not possible. 72 cells at approx. .5 volts per cell is 36 volts period. Unless you have those panels in sub zero temps it just cant happen.

[Wrybread]

How do you figure you are at 46 volts? open circuit voltage does nothing. I just mentioned that. Those 72 cell modules when hot will only output in the low 30 volt range. Is sounds like you don't understand the difference or how to apply temp. coefficient values.

From both my charge controller (it reports the voltage at all times, as well as logging it), and a multimeter. The panels put out a pretty consistent 36 to 46 volts each while the sun is reasonably high.

Note: I edited the above from "40 to 46 volts" range to "36 to 46 volts" range

[littleharbor]

How do you figure you are at 46 volts? open circuit voltage does nothing. I just mentioned that. Those 72 cell modules when hot will only output in the low 30 volt range. It sounds like you don't understand the difference or how to apply temp. coefficient values.

[Wrybread]

So why waste money on an MPPT controller?
If you were to use 60 cell modules which have a more versatile Voc. and Vmp then you have no need to worry about running too high of voltage and you gain the benefit of MPPT.

Because I still get a *massive* power improvement over a PWM controller. Remember, even in parallel wiring I'm at 46 volts, which is plenty of over voltage to my 12 volt batteries for the MPPT controller to work with. And I don't "waste" much money on my charge controller anyway, my Tracer 4210a 40 amp charge controller costs all of $160 shipped.

And I'm not throwing away any significant wattage, I'm still getting 95% (or more) of the benefit from MPPT even in parallel.

And I know that in theory the 60 cell panels are more versatile, but the 72-cell panels have been working just beautifully for me for over a year. That said, if someone doesn't want to take any risks and wants to wire 72-cell panels in series, I recommend getting 60 cell panels.