A compact PV/LiFePo4 setup for our van

[recursinging]

Hi everyone,

I just wrapped up a little project building a house battery with PV into our Pössl Vanster and I thought I'd share the results here.  First off, thanks to Dacian who's openness and transparency about his products and knowledge made it much easier for me to find my way into this topic.

So, on to the build.  The Vanster is not a dedicated camping mobile, but our daily driver.  We need the seven seats, so building anything that would be in the way of seating was out of the question.  Fortunately to qualify as an "RV" according to German regulations, a vehicle needs to have a permanently installed cook top.  So the fine folks at Pössl built a small induction stove into a box in the back left side of the Vanster.  This stove is useless to me, as we need shore power to use it, but the box it is built into has the perfect size to hold some LiFePo4 cells and some chargers.  So I went about building a self-contained battery box which would fit into this space in the back of our van. Here's the result:

...and the box itself...

...and the inside...

...along with two 160w PV modules on the roof.

...and here is a schematic of the system.

So far the system seems to be working quite well, I've tested all the over and under-voltage functions, as well as the low temperature protection.  I've sized everything at at least 2x the expected current capacity. Charge is at 0.1-0.5C, and I expect around 0.3C discharge at peak.   The PV panels aren't producing what I'd hoped, but it's spring, perhaps the low angle of the sun is playing a role.  The Orion-Tr gets pretty warm, and the fan of the RCP-500 is l *loud* so I put an extra 120mm fan on top of the box to move more air through it when charging, and hopefully keep things cool enough in the summer.  I also set the voltage of the RCP-500 and the Orion-Tr to 13.6V which slows the current flow as the cells reach ~80% SOC - this causes the fan to run far less often.  

I haven't any use for the diversion function just yet, but I have some ideas for the future.

So that's it,  I'll try an report back here with real-world experience after I put it though its paces this summer.

[Dacian Todea]

Thanks for sharing the build.  That is fairly compact and the RSP-500-15  (you have a typo RCP instead of RSP) may heat up a bit to much considering 12% loss from 500W is 60W and that is just huge for such a small restricted space.

Regarding the 160W panels.  I guess those are 6" cells tho I did not seen before flexible panels with 6" cells but if they are 6" cells then they will output 9 to 11A each not sure where you got the 27A number from and maybe that is the reason you are disappointed with the output. Also due to vibrations usually those cells will crack so they will perform worse over time as they get damaged.

[recursinging]

Yeah, I forgot about those numbers on the schematic, they are from the planning stage when I was considering installing four panels.  None of the numbers reflect what I've actually measured. The panels are cheap Chinese flex modules - Vmp 18V Imp 8.88A.  I've yet to collect more than 100w from the two on a clear sunny February midday in Germany.  I don't have an MPPT to compare against, but it would surprise me if the difference is that great - I was expecting better performance from brand new units. I am aware of the longevity issues with such panels, but I need to stick with low profile flex type to keep my overall vehicle clearance under 2m.   

The RSP-500-15 actually outputs about 570W in current limiting mode, making the power loss closer to 70W.  For that reason, the box is open on the bottom, and the top, to allow the fan of the RSP-500 to exhaust out the bottom.  I've also mounted the Victron Orion-Tr directly to the RSP-500 hoping the combined thermal mass will assist in dissipating heat (both ways, as they will never be both charging at the same time).  Still, 70W is a lot of heat to move, so I added the 120mm fan to help as well.   I've performed several full charge cycles, and at an ambient temperature of 18C, the temp inside the box never got above 40C.  Time will tell if the cooling is adequate when the ambient temp is closer to 40C!  

That being said, I only have a couple of small DC loads planned, so I expect to keep this system at a high state of charge anyhow.

[Dacian Todea]

Are those 100W from the panels as seen parked in that photo as they do not look to be facing the sun.   If the panels are facing the sun you should see at least 230 to 240W and in best conditions up to around 290W.  Maybe one of your panel is not connected or defective. If even a single cell is shaded that panel with the shaded cell will not produce anything as half of the panel will be disabled and so the other half 18 cells will only have around 9V or so max power point way to low compared to battery.

Also check the polarity maybe one of the panels is connected with wrong polarity (it has happened to many times before so I need to ask).

I was not aware box was open on the bottom that should help the fan get rid of the heat.