# Making a big Solar Upgrade



## peakbagger (Jul 11, 2021)

Well time for another solar upgrade, my new plug in hybrid is using up my surplus generation. I had been looking around for options and one of these caught my eye. 

These were built by a company called DC Solar. They had a great idea but at some point the owners got greedy and decided they could do better with Ponzi scheme. They hooked Berkshire Hathaway and Progressive Insurance for 100s of millions. The feds seized the firm and the inventory and auctioned it all off along with a big car collection and lots of personal assets.  Most of them were auctioned off down south or out west. It turns out there was inventory in NH tied with the NH motor speedway. I bought mine from someone who bought six of them. 

Its an off grid power system on a trailer. They didn't spare much expense on the system components. Its got two large forklift batteries, a kubota 11 KW diesel, fuel tank and most importantly a set of stacked inverters and a charge controller along with 2300 watts of panels on a10,000 pound car trailer (minus ramps).  The inverters are hybrid inverters so they can run off grid or on grid. This one came with a pair of light towers that reportedly cover a football field but to me its nothing I plan to get a lot of use from. It puts out 50 amps at 240 volts. The solar panel mounting is a compromise but I have some ideas. The system is designed to  charge the batteries with solar and then if the batteries drop too low the diesel kicks on and recharges them. The other use for the diesel is to equalize the batteries which effectively overcharges them slightly. This is needed to keep the full capacity of the battery. These have been sitting for a couple of years and battery life is  a question but usually they can be recovered. Worse case is the other parts are worth about what I paid for it. 

I may be building a house in a year or two so I will be keeping the trailer complete until them. Therefore a permanent install is on hold. So what to do in the short term?. I have a grid tie system pumping power into the grid through my main panel so I cannot put a transfer switch on the main panel. So right now the plan is pull a bunch of circuits from the house panel to a transfer panel and run the house off the trailer.   I do need to revise the panel angles temporarily. The light towers are real slick but with 48 volt LEDs not very useful.  I think a ham radio person might have some use for it.   I may take them off for the short term but they may be handy on occasion for a house build.   

These would be ideal for someone with an off grid camp or in an area with poor power quality. The inverters are Sunny Islands that are designed to coordinate between multiple sources of power and switch from on grid to off grid. 

There are several variations of these units out there, this one appear to be the deluxe unit. I have some basic info on them if someone is really interested.


----------



## clancey (Jul 11, 2021)

That's amazing looking and there is quite a history there and I like the idea it can be taken off grid or on--neat...Those lights will come in handy when you least expect it...clancey


----------



## peakbagger (Oct 16, 2021)

Well, one of these days its going to snow and the solar trailer is not set up very well for snow conditions. The original design intent was that the trailer would be towed with the panels vertical facing in towards the center of the trailer. When it was delivered to the site the panels would be rotated horizontal for the duration of its use. Since the panels rotate inwards there has to be space to clear the equipment mounted in the center of the trailer (Diesel, Two big forklift batteries and fuel tank). This meant that when snow came down it would build up on the diesel. As the sun angle gets lower the shadow from one set of panels shades the other set unless they are flat which means low production. So the plan was to rearrange the mounting so that all the panels face one way with no shadows and get the diesel under cover.  As usual this is solo project so a part of the job is figure out how to do it without help.

So first thing was to modify the trailer frame by adding  new higher mounting posts for one of the arrays. The two posts are bolted in place, they could be removed and the trailer put back the way I got it with a few extra holes if need be. I had to fire up my MIG Welder and get some of my limited welding skills back in order.




That white beam to the right on the ground is what the other panels pivoted on. It weighs a lot more than I thought and I had to lift it up in the air to line up bolt holes on top of the new posts.

I used my Unimog backhoe as a crane, the yellow ratchet strap is to adjust the distance between the posts to line up with the bearing blocks on the end of the beam.




Once in place the panels were attached and this is close to the final setup. I still need to stiffen up the panels so that they stay flat over the winter and do some touch up paint. Now the snow will slide (or get raked) down to the lower edge and the panels will get sun over the winter. The Kubota Diesel is under cover so I can run it every 60 days or so to equalize the batteries. Big batteries like these need to be deliberately overcharged every so often or the cell voltages will get unequal reducing the available storage capacity . By overcharging them the cells will equalize.




Once I clean up some details I then need to move it to its temporary home for the winter and then buy some expensive copper wires to tie it to the household system. It can put out 50 amps at 240 volts although at some point when the forklift batteries run down the diesel starts up and its only good for 7 KW (240volts at 30 Amps).


----------



## Solarguy3500 (Oct 16, 2021)

peakbagger said:


> Well, one of these days its going to snow and the solar trailer is not set up very well for snow conditions. The original design intent was that the trailer would be towed with the panels vertical facing in towards the center of the trailer. When it was delivered to the site the panels would be rotated horizontal for the duration of its use. Since the panels rotate inwards there has to be space to clear the equipment mounted in the center of the trailer (Diesel, Two big forklift batteries and fuel tank). This meant that when snow came down it would build up on the diesel. As the sun angle gets lower the shadow from one set of panels shades the other set unless they are flat which means low production. So the plan was to rearrange the mounting so that all the panels face one way with no shadows and get the diesel under cover.  As usual this is solo project so a part of the job is figure out how to do it without help.
> 
> So first thing was to modify the trailer frame by adding  new higher mounting posts for one of the arrays. The two posts are bolted in place, they could be removed and the trailer put back the way I got it with a few extra holes if need be. I had to fire up my MIG Welder and get some of my limited welding skills back in order.
> 
> ...


Nice work on the solar trailer! Looks like it should work out well.

That Unimog is just what I need around my place. Where did you find it?


----------



## peakbagger (Oct 17, 2021)

Thanks 

The Unimog Special Emplacement Excavator - SEEs (Called the Freightliner 419 in the US or a FLU 419) are former US military units. They were bought for the cold war in the mid to late eighties but the Soviet Union was gone before they were deployed.  Many were never used and just have maintenance miles on them. This one had 350 miles and 47 hours on the engine. The government has sold most of them off but they are available on the private market. Good ones sell for about 17 K to 25 K. Bad ones can go for far less but not worth buying as SEE specific parts are expensive. Like a lot of specialty equipment if you do not have the skills and ability to work on them yourself do not buy one. Many were rebuilt from scratch as make work projects by the military and then parked. They are called Recapped units and are the best deal as the originals have a lot of deteriorated rubber parts from sitting out in the weather.

Seeing your location , their one major issue is when Mercedes designed the bodies in the early 1960s they did not design them well to prevent rust. The cabs do rot out and modern deicing chemicals will rot them out quick. Park them for the winter or use them away from road salt.  The military would sell these to various municipalities and many of the ones I have seen in New England were sold by towns and local governments in pretty poor shape.


----------



## gthomas785 (Oct 20, 2021)

peakbagger said:


> buy some expensive copper wires


No aluminum?


----------



## peakbagger (Oct 20, 2021)

No Aluminum, I need the flexibility and the connectors are hard to find for AL.


----------



## peakbagger (Nov 4, 2021)

Well I am getting close, I hooked up the expensive extension cord and shut off my main breaker today then backfed the main panel. I plugged in the charger to my Rav 4 and then flipped the trailer breaker backfeeding the house. The three solar arrays on the main house flipped off when the main breaker was turned off (just like they were supposed to )and then 5 minutes after I turned on the trailer feed they all started up again. So I was running the house loads and a 3300 watts charging load to the Rav 4 using a mix of all my solar arrays including the trailer and the batteries making up the difference.  I made sure I had plenty of load as there is a question if the other arrays will respond to signals from the trailers inverter to shut off if there is not enough load. In the rare combination where there is little or no load and the batteries are fully charged there could be problem where the power has nowhere to go.  

The final stage will be to open the main breaker and have the PV on the trailer feed into the grid. The challenge is the inverters on the trailer will do lot of things and have 50 pages of potential settings that I may have to mess with to get it to sync to the grid. Note this was just a test, backfeeding a panel is not legal until I set up the inverters so that they disconnect if the grid drops out, it supposed to be possible.


----------



## begreen (Nov 5, 2021)

Sounds like the trailer is providing clean and stable power if it fooled the grid detect systems for the solar.


----------



## clancey (Nov 5, 2021)

Me knowing nothing that sounds scary to me--you be careful--I can imagine it back firing and every one of your appliances going down or something but all that is 'out of my knowledge area and I only say--be careful...but you are making progress ..old mrs clancey


----------



## peakbagger (Nov 6, 2021)

The inverters used in the trailer are Sunny Islands which are very well regarded. They are set up to shut down if they get confused on what is going on and  that is why there are so many parameters that can be set. As long as there is battery in the system, modern inverters can put out very stable power as this inverter was designed to.  It uses a concept called AC  coupling where it intentionally shifts the frequency of its micro grid when the system is generating more power than there is demand for. By shifting the frequency that tricks the other PV systems into shutting down using the protection circuits  are required to be installed by law in them. Once the power demand increases, the Sunny Island brings the frequency back to 60 HZ and the other PV inverter go through a 5 minute count down and then reconnect to the microgrid.  The problem is I have two other brands of inverters that I can not determine if they have been tested to work with frequency shifting, they should as its UL requirement but it needs to be tested.

The reality is I rarely if ever lose power so when the system is connected to the grid, the grid frequency and voltage calls the shots. It would be the equivalent of mosquito tying to turn a tanker ship.  The current problem is that the panels on the  trailer cannot get to the grid even though the Sunny Island is set up for that capability.  It looks like I need to order another $180 "extension cord" to get that capability operational.  As I mentioned the intent is to possibly build a house in the future with it where there will not be power until the house is built so I need to make sure I can but it back in microgrid mode. 

It is interesting professionally as I have very similar combined heat and power project with similar equipment getting just about ready to run designed to switch to microgrid if the utility power goes out for an industrial client. No PV but a 3MW natural gas generator and a 2.6 MW Tesla battery. The microgrid controller for that system is lot more complex and expensve (designed and built in Pullman Washington). No 5 minute outage on this one, it does it on the fly so the lights do not blink and its all automatic.


----------



## begreen (Nov 6, 2021)

Yeah, I looked into the Sunny Island when our system went in. It's a good product.


----------



## Woodsplitter67 (Nov 21, 2021)

this is very interesting.. pretty cool


----------



## lml999 (Dec 20, 2021)

Solarguy3500 said:


> That Unimog is just what I need around my place. Where did you find it?



Was walking around my neighborhood and ran across a similar Moggie in someone's yard.  Looked like it was being well used, too!


----------



## peakbagger (Dec 20, 2021)

lml999 said:


> Was walking around my neighborhood and ran across a similar Moggie in someone's yard.  Looked like it was being well used, too!


The FLU 419 is definitely a very distinctive vehicle. Not something to drive for the fun of it. Freeze in the winter until the engine is warmed up and roast in the summer. Not great on anyone task but it does a lot of them good enough.


----------



## peakbagger (Feb 13, 2022)

A big update. Prior to my broken ankle in November, I had purchased but not installed the final parts to get the system to feed back to the utility grid. I had to put in a big California grade twist lock plug and circuit plus another expensive #6 four conductor extension cord. Given the run up of copper prices that extension cord probably increased in value since I bought it. My ankle is definitely still on the mend but I am now able to move around a lot better and even able to do some work on a step ladder. Yesterday was a warm day so I mounted an outdoor box and ran PVC conduit to my main panel, made some room for a dual pole 50 AMP breaker and hooked up all the wires. I tried to put the new function on-line but managed to get an error code. A bit of research overnight and it looks like I confused the logic so I gave it another try today. I turned the trailer inverters on and then turned on the AC power feed to the trailer from the utility and 5 minutes later I watched it go into grid export mode. Only 1.2 KW for now as my panel angle is low for February but as the sun gets higher the output will go up.

I used the minisplit a lot more this winter than normal as running the wood boiler with one good leg was a challenge. That used up more of my normal power surplus than usual so a bit of extra generation is a nice thing. I also got my plug in hybrid so that eats up power when charging.

So as of now this is completely functioning hybrid solar system. When the grid is on line it exports power from the trailer panels to the utility like a regular grid tie system. If the utility goes down it can push 7 KW into the house generator panel and will automatically stop feeding power to the grid. I do not have a Automatic Transfer Switch (ATS) so its a manual transfer. I did have to compromise hooking up the AC feed to the trailer. I unplugged the diesel generator and used the receptacle to plug  in the big extension cord. The inverter manufacturer recommends a transfer switch but given the rarity of power outages at my place, I think just plugging and unplugging a twist lock is a worthy compromise.  I do have some loose ends at this point. I need to move critical loads over to the generator panel. I also would have to make a major upgrade to the house panel and service entrance to allow a legal microgrid. If I shut off the main utility breaker on the panel I have proved that the trailer puts out clean enough power for my other grid tied arrays to contribute to a now 7.1 KW microgrid but due to rarity of power outages I probably will not upgrade the panel. 

At this point, I have proved to myself that the DC Solar Trailers from the auction are a very cost-effective option for someone who needs or wants on and off grid capability. My guess is the folks in California who have their power shut off due to possible utility arcing starting fires would be hard pressed to assemble a system with this capability for anywhere near the price. The only weak spot is the flooded lead acid batteries. They are not going to last forever and their rough life while waiting for the government to sell them means caveat emptor. The trailer with a bad or damaged set of batteries is still of value, it just means replacing the batteries or upgrading to a potentially smaller lithium pack.


----------

