DC Solar trailer questions.

[peakbagger]

An update, it took awhile as I managed to break my ankle in the meantime, but I did get the grid tied function to work. The trailer requires two heavy duty connections to the home, one feeds the inverter and feeds back power to the utility panel. It connects in place of the twist lock connector used by the diesel. For more money a manual transfer switch could be installed to select between the two or an automated transfer switch could be installed. The only trick is the inverter needs to be powered up and online prior to connecting it to the utility panel. When I did that, it counted down the required 1741 five minutes and started pumping out power. The other cable is the off grid inverter output to generator panel.

I still need to do a full system test but it looks to me that one of the later versions of the DC Solar trailer with FLAs and diesel is basically a hybrid inverter system "in a box". I think someone would be hard pressed to duplicate it with equivalent quality components anywhere near the price.

The final big test is to drain the battery down and then see if the inverter uses house power to bring it up to full. There is supposed to be an auto equalization function in the inverter. I still have some issues getting around so it will be month of two before I run a full equalization of the FLAs.

[peakbagger]

I am getting closer to my desired configuration of a full hybrid system. This past weekend as an experiment I shut the main breaker and switched the trailer to supply the house loads. I have three other PV arrays (two fronius and 4 enphase 215s on an orphan system. I switched them off and then went on the trailer for house loads. Once the power from the trailer was on I plugged in my EV charger which pulls 3300 watts. I then switched the arrays back on and they went through the five minute countdown and they came up on the trailer power with no issues. I ran that way for 4 hours until the sun was heading down. So the existing inverters seem to play well with the Sunny Island AC coupled. What I have not tested if they play well completely and are shut down by the Sunny Island frequency shifting control when the generation exceeds the demand. Reportedly the Enphase micros will respond to frequency shifting but I have been unable to confirm if my Fronius units will. This is a mode that I do not plan to run very often so not going to spend a lot of time on it now.

The next phase which reportedly is possible is to tie the system to the house and have the panels on the trailer go grid tied when the batteries are on float. The Diesel on the trailer get unplugged and battery equalization switches to house current. The Sunny Island has auto equalize capability but I am unsure if its connected. There are 50 pages of parameters that I need to go through to figure out what ones need to be changed. I also think I need to buy another expensive 50 foot power 50 AMP power cord to connect the trailer to the main panel.

[peakbagger]

BTW, I finished up the wiring and boy does that modification improve the output. 2350 watts at the charge controller on 2500 +/- watts of panels, despite the angle being bit low for this time of year, The combined panels are a lot better supported and no doubt should hold up better to wind and snow plus the diesel and batteries are under cover. I installed a set of trailer jacks onto the frame behind the wheels on either side so I can support it up off the tires. I do get some shadows off the remaining lights in the mid afternoon but until I remove a few trees its not worth messing with as the trees shade it out not much later. Worse case is I could remove the lights at the junction box an maybe put some quick connectors at junction box.

I did realize that my stiffeners could have been modified slightly to use hitch pins to make them easier to unlatch to rotate each row independently. I dont plan to move it very often but to someone who wanted to, it would be worthy upgrade.

[peakbagger]

I spent the weekend reconfiguring the trailer for use in snow country. The trailer was obviously designed by someone who does not live in snow country. With the panels horizontal there is 1 foot wide gap in between the panels that would bury the diesel and the batteries. The panels could be rotated at an angle to the sides of the trailer to shed snow but that would open up the gap further. So the modification was to fabricate and install new support posts for one array and move them in from the edge of the trailer. I could have just welded onto the trailer frame but the electronics box mount would need to be messed with. By using bolted in parts, they could be removed in the future if someone wants to put it back in stock configuration. So the stock mounting rail gets lifted up (with the panels removed) and set on the new columns. The stock brackets for changing the array angle were left in place but the locking pin base was left at the old location as its welded on. With snow load they would not hold anyhow. So once rotated into place I installed 1/4" aluminum strip on the sides of the panels bridging the upper and lower array. It was still bulging in the middle when the picture was taken so I added aluminum angles behind all the panels. That stiffened things up considerably. If I needed to go on the road again I would have to remove the bridge pieces and rig up a lock to keep the upper rain from rotating but for my use, that may happen once in the future.

The angle is not optimal for winter in my area (close to 45 degrees latitude) but I end up raking my arrays anyhow. I moved the array once working on it to another location in the yard and made sure to leave enough room to run my snowblower to keep the snowpile up front manageable.

The diesel and batteries now sit under a the upper panels with some overhang, sure snow will drift in but a lot less than open to the air. The seam between the panels is about 1/4" and it drips down in front of the generator. I may install a temporary gutter or squirt some goop between the panels in that area to redirect any drips.

I had noted the improper use of THHN on the home runs in a prior post. I rewired the panels I had removed with PV USE2 wire, I also discovered that whoever wired it didnt understand polarized plugs. Normally a PV wire is extended with a male female extension cord, in this case they made up a two extensions, one male male and one female female.

I need to add in two new screw jacks to take the loads off the tires for the winter. I have already touched up the paint on the columns.

dc trailer mod.jpg

[PSP]

I'm fine with 240 volt. I'm going to remove those California twist receptacles and put a 50 amp RV outlet and another 50 on the side of the box.

I can't get my batteries to charge past 82% as indicated on the Sma inverters Soc. I've tried it 2 days in a row running the generator and it just sticks at 82%. Is this a common thing or could the inverter Soc be wrong?

My panels charged the battery to 82% today then I ran the generator for another hour and it stayed at 82.

I got the batteries to 97% the other day.e
Could the batteries not be allowing a 100% charge or is it the inverter chargers fault?

I believe its rated for a 100 amp charger, but only puts out 85 amps.

Sounds like there is a problem with the battery's how old are they? Are they lead - acid or lithium?

[peakbagger]

FYI , I in process of modifying my trailer so it will survive a winter with snow. It means relocating one set of panels, so that all panels face the same direction. While removing the panels I discovered that someone used THHN wire which is not rated for solar use. My trailer is one of the white American Tower versions that appear to be late in the production. The panels cables are okay, its the home run wiring from the beginning and end of the string that plugs into the electronics box.. Mine are wrapped up in spiral wire wrap.The plastic coating on the wires I removed was flaking off along with the specs for the wire. The wires are two small for the MC4 connectors which means that connectors end seals are not effective.

I do not know what code applies to a mobile trailer but a FYI, that these wires at some point could cause a mysterious fault to ground. Its not that difficult to change out if you have the correct MC4 connectors and USE2 PV wire (check on fleabay).

[Mike90250]

desulfating pulse machines don't mess with the inverter, but their voltage pulses can confuse the chargers, trial and error. Maybe just disconnect the desulphinator while chargeing

[Fullblast]

Could you tell me what you mean by using a desulphinator? Is that a chemical additive, or is it something like a Battery life saver unit?

Does the battery life saver work to help de-sulphate the batteries? Can a de-sulphator mess with the inverters any?

I have my hydrometer now. I'm going to do an equalizing charge, then wait a night and check the specific gravity the next morning. Is that the proper way to do it?

[Fullblast]

I'm fine with 240 volt. I'm going to remove those California twist receptacles and put a 50 amp RV outlet and another 50 on the side of the box.

I can't get my batteries to charge past 82% as indicated on the Sma inverters Soc. I've tried it 2 days in a row running the generator and it just sticks at 82%. Is this a common thing or could the inverter Soc be wrong?

My panels charged the battery to 82% today then I ran the generator for another hour and it stayed at 82.

I got the batteries to 97% the other day.

Could the batteries not be allowing a 100% charge or is it the inverter chargers fault?

I believe its rated for a 100 amp charger, but only puts out 85 amps.

[peakbagger]

My guess is that they set the units up for 240VAC output which requires two inverters? My guess is with some reprogramming one SMA could run 120 VAC but my guess is it would also need to deal with the 240VAC input from the diesel. I think the Midnight Solar has additional input capacity but you would need to rework the combiner.

[Fullblast]

I was thinking I would have to fill them up some with water also, and was surprised they were topped off. I just hope he used distilled water. Anyhow, I ordered a Deka hydrometer and am going to try and equalize the batteries once that gets in.

I ran a 535 watt window unit ac for 10 hours last night and the battery only went down 7% according to the Sma inverter Soc.

Do those sma 6048 inverters draw much juice just by being turned on? They are 6kw each and it seems like they are drawing a lot of power just to stay on.

What is the point in having a master and a slave inverter? Can I turn one of them off for better efficiency?

I would like to add about 4-6kw worth of 435 watt solar panels to the system and mount them on a frame on the ground.

I'm assuming going with a a few midnite solar 250s will be best since it already has the midnite 250 and the midnite combiner box.

[peakbagger]

I did have two light towers, one of them has since been removed as it is in the way. I have to alter the panel arrangement so that snow sliding off one row does not bury the batteries and generator. I have tried the lights once or twice but did not run them long, I dont plan to use them long term except rarely. Until the trailer get tied into the house I am charging my Rav 4 hybrid for now direct off the trailer. My guess is the damage is done to the battery once the "dirty water" has been added and gone through a few charge cycles. The nasties will have plated out on the cells and the damage is done. I went through several gallons of Walmart distilled water topping mine up when I got mine. None of the plates were uncovered but they do hold quite bit of reserve. One of my "Blinkies" does not work but in my climate the only time the level drops is during equalization. I do not think DC Solar programmed the trailers to equalize but that option is available in the Midnight Solar Menu. I think that if they did equalize them they did so at wherever they stored them between rentals off line voltage. Of course most of the them were rarely if ever rented and sat for year or two so they all need equalizing. FYI when I equalize with the Midnight Solar, the diesel does not turn off automatically when the Midnight Solar indicates that the battery is equalized, I have to kill it with the fuel stop lever.

Ultimately the trailer will be used to build a house and then it will get stripped and reconfigured for a permanent installation. By that time I expect I will reprogram the equipment to suit my use.

[Mike90250]

Is there a way to find out if distilled water is in my batteries?

No. tap or well or creek water has impurities that slowly degrade the battery performance. The nastier the water, the faster the degradation.

[Fullblast]

Thanks, I am going to pick up a hydrometer today and learn how to test the cells. I'm trying to learn how to do an equalization charge and learn the system in general.

I have my suspicions that the batteries were topped off with water before I bought it because they were all full to the top and the owner told me he had only checked the batteries once before. I have no idea if they used distilled water or not. This is only speculation though. I highly doubt he ever did an equalization charge either.

Is there a way to find out if distilled water is in my batteries?

That sounds like a ton of fun replacing some bad cells, but it's better than paying several grand for new forklift batteries. I found a pair of 540 Gnb batteries on eBay for a great price, but I want to know whats wrong with my batteries first.

On another note, I ran a 535 watt window unit ac for 10 hours last night and it only drained the batteries 11% or so.

The tower lights are supposed to be 480 watts, but they drain the batteries very fast, like 65-75% over an 8 hour period.

*Do you have the tower lights and if so, how long can one of the lights stay on before it significantly drain your batteries?

[peakbagger]

I am not a battery expert but I think you need a hydrometer. You should have equal specific gravity readings on all cells after equalizing. Assuming you are keeping the batteries full of distilled water during the charge, its sounds like you have dead cells. The seller of my unit had one other array with a bad cell. He had to cut the bus bars off and replace one cell ( I do not know where he got one) He then had to drill and tap the posts and install copper bus bars to tie in the new cell.