Micro-Solar Setup : My First Experience w/Off-Grid Electricity

[bruss01]

My bus bars were lost in the mail according to the seller. He swears they shipped but the tracking number shows it never left his store. So I too have gone the copper pipe route for my bus bars. I guess I need to start a new thread on it once I get it started.

You didn't lose much Cav if your seller was anything like mine... the "bus bars" that came with the batteries were pathetic and unusable. At least these, I know will handle the load. And yes please! Do show us your build. The principles are the same but everyone's implementation will be a bit different.

[bruss01]

Today's progress -

Final color coat on the box - probably need one more on the lid, tomorrow.

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Serial (short) bus bars drilled & test-fitted... wire-brushed the contact areas to remove burrs and promote good electrical contact.

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The third and final set of cells arrived! Huzzah, now we're cooking with gas. These go on the charger tonight for top-balancing.
Not sure why the packaging was different... these were encased in cubes of packing foam. Great packing, no complaints!

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Looks like this will be the big weekend where it all gets put together!

ETA: Lessons learned from overseas shipping -
1 - in my case, despite initial concerns, they delivered everything as ordered.
2 - overseas shipping is SLOOOOOWWW!
3 - when they provide tracking - it's not what we think of as "tracking". At least it is not transparent to the customer.

[bruss01]

One is the lonliest number - This shot to show 1/2" square tube as spacer against the wall. The spacer provides "breathing room" for air to circulate (hot/cold) and provides clearance for some sensor wires that have to be routed into the enclosure from the BMS.

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Bottom rack being laid out. This will keep the bank from jostling around inside the enclosure when being moved. Bottom rails are 1" (1/8" thic) L bracket.

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Top rack in place. This will keep the tops together, to avoid putting strain on the terminals. Will Prowse makes a point of always binding his cells together, pointing out that the terminals themselves on LiFePO4 batteries aren't structural members and don't have a lot of strength - they can be torn/broken loose with too much shifting around. This should minimize or eliminate that. While Will uses tape (temporary) or hose clamp (less temporary) I don't like the idea of putting that kind of pressure on the square corners, which is why I went with square bracing here. It's a snug fit - constraining but not binding - on all four sides. There's no discernible play at all when trying to jiggle/jostle the batteries in the rack. The side and end of the top rack are 3/4" square tube - pretty rigid. Those long sections of square tube are fastened to the shorter cross member, but that cross member is a friction fit (snug but not jammed) in the two side L-braces. This allows it to glide if there is expansion in the longer square tubes due to heat, instead of being rigidly affixed which could result in bowing/warping. While in theory that same heat expansion could lead to jiggle room for the cells to move, the odds of that kind of heat and motion together in the same time-frame would be so rare as to be considered remote. Not going to sweat it.

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These are radiator fins made from 1/2" square tube. A set of RV silicone mat tank heaters (that prevent winter freezing for RV holding tanks) will be attached to these. This prevents the heat from being applied directly to the cells, increases radiating area inside the enclosure, and with the spacers holding them out from the wall, provides circulation on both sides of the fins. As mentioned previously, LiFePO4 batteries will be damaged if charged below 32 degrees. The tank heaters are temp-sensitive to come on only when temps approach freezing. While I don't anticipate using these outdoors in freezing temps, I can't guarantee that isn't a possibility, since I've designed this Power Box to be portable. And during a power outage, we would lose our climate control inside the house, making operating temps a question mark. This should eliminate that concern.


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Materials -
1" L- bracket (1/8" thick)
3/4" square tube
1/2" square tube
Various #10 screws (1/2", 1", 1-3/4")
18 #8 screws (1")
18 nylon spacers (1/2" diameter)

[bruss01]

And of course this thing really starts packing on those holiday pounds once you start adding the batteries... in the interest of saving my future self a sore back, it made sense to put wheels under it. Seriously this would be a pain in the keister to try to lift (or even move) once it's loaded up... it'd be a two man job and I don't have a second man handy. Fortunately there were four lurking in the garage, left over from a previous project, rated at 80 lbs each. That ought to be about right. (320 lbs).

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Materials -
(4) 2" wheels @ 80 lbs
(16) 1/2" #10 screws

[flock6]

Great job, thanks for the update.

[bruss01]

Today's effort... mounting the charger, BMS and terminals. Sensor wire routing.

[bacpacker1513]

Nice Work Bruss. Thats looking really good

[bruss01]

Making a bit more progress.

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I discovered the original screws provided with the batteries were going to be too short, so trip 157 to the hardware store got me the longer screws and a better set of washers. See pic for comparison of long vs short, and a successful thickness test with a lugged cable and two bus bars. The 100 amp fuse was simply the one within arms reach at the time... it's been swapped out since the pic with the proper 250 amp rating.

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Once cells are installed, there is a one inch gap between the tank heater mats and the cells to allow gentle indirect warmth instead of full contact. These heaters are designed to heat tanks with liquid, which is free to circulate... not the case with solid batteries and I don't want to over-cook anything by attaching the mats directly to the cells. So here, we'll allow the air to circulate (warmed by the mats and radiating fins) which then warm the cells.

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[bruss01]

Got all bus bars installed, sensors wired, heater circuit complete with manual disable switch and indicator light. First time using the aluminum spray paint, turned out all right.

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[Rich_Vale74]

Nice to see such a clean setup. If'n it was me, there'd be lengths of extension cord, pieces of coat hanger and three rolls of duct tape.