DC Solar trailer questions.

[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]

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

[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 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]

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.