remote work trailer application

newmexico

Hello, I’m very new to this.  I am working on powering a trailer used in the summer months for remote field work and just have a few questions.  Here is the equipment on hand for the trailer.

Two 12v Kyocera solar panels, one 120w and one 130w that I will wire in parallel.  These will put out about 15 amps as far as I can tell. 

A BZ240 PWM controller 14 amp, 12 volt .   http://kingsolar.com/catalog/mfg/bzproducts/bz240.html

Two Trojan L16H deep cycle batteries that I will wire in series to make a 12v output.  240 amp hours at the 20 hour rate/345 amp hours at the 5 hour rate. 

An AIMS 1250 watt DC to AC inverter PWRINV1250w.  Modified sine wave I imagine.

Will be using 12volt system of the trailer for the water pump, lighting, and the inverter for misc. 120v usage (small vacuum, radio battery chargers, water pump for truck to trailer transfer, laptop computer, etc.)

For making moving the panels on/off trailer easier I am going to mount them separately and use a sunlight resistant extension cord cut in the middle and attached to each panel.  Then you simply plug the cord into itself when panels are on roof of the trailer.
1). Is there any problem with doing it this way?

2). Will a 14 gauge wire be sufficient for approx. 12 feet of the wire panel to panel?  12 AWG wire 15 feet from panel to batteries?  ---Using huge cable for the battery to battery connections…

3). The panels and the inverter have connections for grounding them….   Should the panels be grounded to the earth, trailer, neither, or both… same for the inverter?

4). Will the el cheapo inverter ($115) cause any problems with laptop computers?  I’d hate to see an expensive computer with valuable data tank.

5). I put the BZ240 PWM with solar panels and batteries hooked up in the back lot and it seems to work…  Will I eventually fry the PWM rated at 14 amp by putting in the 15 (sometimes more with great sun) amps that the panels are producing.

6). Living at 32 degrees north I’ve read that 32 degrees off horizontal would be a good tilt for the panels, but given just summertime (April thru August) usage wouldn’t slightly less than 32 degrees be better.

7).  One web site says that the BZ240 has  battery temperature compensation.  Where it sits now is just below one of the solar panels and does not have any dedicated line (other than the positive and negative cables going to the batteries.  Should this unit be closer to the batteries or is it ok next to the solar panels where I imagine the temperature is different than the temperature next to the batteries.

8). Is the balance between the panels/batteries about right? I don't want to overcharge the batteries (I assume that the BZ240 will take care of this, but assumptions...) I don't want to leave the batteries less than 80%? charge for too long as this can damage batteries (though being deep cycle I may not have to worry about this so much?).

Any advice, comments greatly appreciated

mike95490

Re: remote work trailer application

newmexico wrote:

Two 12v Kyocera solar panels, one 120w and one 130w that I will wire in parallel. These will put out about 15 amps as far as I can tell.

250Watts / 14V = 17 amps x .75 [fudge factor for field output conditions, vs factory test] 13 amps at peak.
Peak will only exist for an hour, so figure 5 hours of daily production, at about 9 amps = 45amp hrs per day.
( at 13 V gives you 582 watt hours.)

Now figure your loads in amps . watts . hours, and see if you have 20% left over. Figure older laptops @ 60 watts, and newer ones at 80 watts
Mod Sine inverter will be about 75 - 80% efficient, so 200 watts out needs about 250W input @ 12.5V = 20Amps
Maybe consider a 24V system, and wire panels in series, less wire loss, but needs expensive inverter.

BZ240 PWM controller will be at it's limit, if you add a panel in the future, it will need to be replaced.

Using household extension cords, cut in half, has 2 problems.
1) Kind of thin on copper.
2) Very easy to make a tragic, expensive mistake, if anyone but yourself plugs one in where it should not be.

Use as heavy as gauge wire as you can. 14ga feels too small, 12 should, 10 would be better, for the panels

crewzer

Re: remote work trailer application

Newmexico,

Two 12v Kyocera solar panels, one 120w and one 130w that I will wire in parallel. These will put out about 15 amps as far as I can tell.

A BZ240 PWM controller 14 amp, 12 volt . http://kingsolar.com/catalog/mfg/bzproducts/bz240.html

Wired in parallel, the two modules are rated for 14.49 A. Assuming clean modules and good alignment, I’d think that you’d see this amount of current on a regular basis around mid-day in your high-altitude, low humidity location. “Edge of cloud” events (i.e., the Sun reappearing from behind a passing cloud) could easily increase array current by ~25% to >18 A for brief periods. I recommend you use a controller that can handle such excursions.

Two Trojan L16H deep cycle batteries that I will wire in series to make a 12v output. 240 amp hours at the 20 hour rate/345 amp hours at the 5 hour rate.

The 20 hour rate for the Trojan L16H is 420 Ah, not 240.

An AIMS 1250 watt DC to AC inverter PWRINV1250w. Modified sine wave I imagine.

Will be using 12volt system of the trailer for the water pump, lighting, and the inverter for misc. 120v usage (small vacuum, radio battery chargers, water pump for truck to trailer transfer, laptop computer, etc.)

There are plenty of products that don’t like the waveform from an MSW inverter. Even if they work, the 120 VAC items plugged into the MSW inverter will likely run somewhat on the warm side.

For making moving the panels on/off trailer easier I am going to mount them separately and use a sunlight resistant extension cord cut in the middle and attached to each panel. Then you simply plug the cord into itself when panels are on roof of the trailer.
1). Is there any problem with doing it this way?

You need rugged, polarized, low resistance connectors. These Anderson connectors are very popular for this type of application: http://store.solar-electric.com/anhicupoco.html

2). Will a 14 gauge wire be sufficient for approx. 12 feet of the wire panel to panel? 12 AWG wire 15 feet from panel to batteries? ---Using huge cable for the battery to battery connections…

I’d recommend #10 or #8 wire. This stuff will work fine: http://store.solar-electric.com/10-2-tc.html

3). The panels and the inverter have connections for grounding them…. Should the panels be grounded to the earth, trailer, neither, or both… same for the inverter?

Unless the trailer is connected to to a real ground, then nothing connected to the trailer will actually be grounded…

4). Will the el cheapo inverter ($115) cause any problems with laptop computers? I’d hate to see an expensive computer with valuable data tank.

Ya pays your money and ya takes yore chances… my laptop has survived several long trips running off a cheap MSW inverter… but I’ve had several of the inverters die…

5). I put the BZ240 PWM with solar panels and batteries hooked up in the back lot and it seems to work… Will I eventually fry the PWM rated at 14 amp by putting in the 15 (sometimes more with great sun) amps that the panels are producing.

I don’t know what the BZ’s overload capacity is… However, I typically do not spec equipment for operation at their limit.

6). Living at 32 degrees north I’ve read that 32 degrees off horizontal would be a good tilt for the panels, but given just summertime (April thru August) usage wouldn’t slightly less than 32 degrees be better.

Yes. ~17 degrees would be better from April through September, and ~47 degrees from October through March.

7). One web site says that the BZ240 has battery temperature compensation. Where it sits now is just below one of the solar panels and does not have any dedicated line (other than the positive and negative cables going to the batteries. Should this unit be closer to the batteries or is it ok next to the solar panels where I imagine the temperature is different than the temperature next to the batteries.

Temp comp applies to batteries, so the controller’s sensor should be as close to the batteries as possible.

. Is the balance between the panels/batteries about right? I don't want to overcharge the batteries (I assume that the BZ240 will take care of this, but assumptions...) I don't want to leave the batteries less than 80%? charge for too long as this can damage batteries (though being deep cycle I may not have to worry about this so much?).

The array’s 14.49 A rating is ~3.5% of the battery capacity…. That’s just good enough if the daytime load on the batteries is low. 5% is a good working number, and Trojan recommends a charger rated for 10% to 13% of battery capacity. Any good 3-stage charge controller will probably not overcharge the batteries.

HTH,
Jim / crewzer

newmexico

Re: remote work trailer application

Thanks much Mike and Jim. The connectors and wire I'll definitely use. And also start looking for a better charge controller. Perhaps in the future we'll be able to upgrade to 24v, but that would require new batteries, either two twelve volt or four six volt and a new inverter plus then the trailers 12 volt things wouldn't run off it unless they make a device for reducing voltage. For the ground wire I can come up with some wire the electric company uses to ground houses, connect it to the panels aluminum frame, dig a trench, bury about 10 feet of it and hope the lightning likes that route…… parking on ridges has it’s advantages and disadvantages… or better off not grounding?

My bad on the 240 / 420 amp hour mistake thanks for correcting that.

We will have a truck and jumper cables, any problems supplementing the PV’s with alternator juice on high use days, cloudy days, etc.? And I suppose I should let the people using the trailer know that the laptop hooked to speakers and projector for movie nights isn't going to fly... easier to get enough power if you're not using too much.

fyi You mentioned high altitude low humidity making more current... just took the panels outside wired with the extension cord that will be replaced. It's 10:30am mountain daylight savings time 8720 feet elevation with a relative humidity of 35% and the panels are putting out 16.8 amps where they'll be connected to the batteries...

makes me want to start investing in panels for My house...

mike95490

Re: remote work trailer application

newmexico wrote:

We will have a truck and jumper cables, any problems supplementing the PV’s with alternator juice on high use days, cloudy days, etc.?

The factory alternator may work, but not much till the batteries are really low. When the batteries are low, they will really load down the alternator, and it could overheat. You WILL have to use some sort of battery isolator to keep from draining your truck battery, and don't try to hook up jumper cables - you will melt something. Have solid connections established.

Battery isolator info (and sales pitch) http://www.hellroaring.com/rv.htm
some isolators need regulator adjustments.

Get a big alternator : http://www.balmar.net/Page5-X-largecasealts.html
Get a batt isolator : http://www.balmar.net/page20-Duocharge.html

Roderick

Re: remote work trailer application

2). Will a 14 gauge wire be sufficient for approx. 12 feet of the wire panel to panel? 12 AWG wire 15 feet from panel to batteries? ---Using huge cable for the battery to battery connections…

Last I checked, you could go to Home Depot and get #8 THWN-2 wire for around 65 cents a foot. That's the 19-strand type, so it's even more flexible than some of the thinner wires. I know, 65 cents sounds expensive, but if you're only going say, 30 feet, then that's $19.50, if I did my math right. Even if the 14-gauge wire were free, that's still less than 20 bucks difference, and you would have margin and headroom, in case you ever got more panels, or higher-output panels.

crewzer

Re: remote work trailer application

fyi  You mentioned high altitude low humidity making  more current... just took the panels outside wired with the extension cord that will be replaced.  It's 10:30am mountain daylight savings time 8720 feet elevation with a relative humidity of 35% and the panels are putting out 16.8 amps where they'll be connected to the batteries...

8-)

System2

Re: remote work trailer application

You mentioned radio battery chargers.

If these chargers are transformerless your modified sinewave inverter will probably blow them up. Any 120V motors will run hot, also.