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

[bruss01]

Today's lunch-hour labor - mount the lid.

These hinges weren't the easiest thing in the world to get mounted but they allow the box to be right up against a wall, the lid will still open with zero wall-clearance.

Bits & Pieces:
#10 x 1/2" screws (4)

Power Box 3.4.jpg

PowerBox 5.jpg

Power Box 3.5.jpg

PowerBox 6.jpg

Power Box 4.jpg

[flock6]

Very nice

[bruss01]

Progress has been slow due to the Thanksgiving holiday and several other chores that have taken precedence. Got some holes drilled for cable routing... discovered one of my cables was the wrong type, and re-engineered how the solar panels will connect (I think you all will like this!).

The cells have been on the charger over a week now and at 3.6v they still draw 2+ amps. Not sure exactly what that's about... hope it's not some kind of internal self-discharge on one of the cells. Anyway, I'm about convinced that they've taken all the charge they're going to take at this point.

I'm reconsidering my heat-dissipation plans. I've been doing some research and haven't really found indications of these getting hot. Maybe I was recollecting lithium ion batteries instead of lithium iron phosphate? If anyone has a cite-able source, please send it my way. It would save me a lot of time and effort to avoid having to allow spacers between the cells. As well as being able to avoid cutting ventilation holes in the battery compartment. These cells do have a heat-tolerance limit, but I'm having difficulty finding any evidence they heat up when charging/discharging... maybe just not looking in the right place.

I've got an aluminum cutting blade on order for my table saw. The sabre saw was difficult to manage and didn't make a very nice cut. This will let me get the more precise cuts I'll need for the remaining aluminum hardware. Also I discovered a flux for aluminum brazing that supposedly makes it a lot easier. Going to try to score some and see if it works as advertised.

The bluetooth dongle ordered from the BMS manufacturer (in China) seems to have vanished in the shipping channel. Had to order a replacement. Until it gets here I'll have to access the BMS control features via the USB-UART interface connection. The bluetooth is a great convenience especially if going mobile but it isn't a full replacement for the hard-connection line, I've heard. I've been fortunate that everything else ordered has showed up within the advertised timeframe. Slow as molasses, but got here within the expected window.

If all goes well, paint happens this weekend and then mounting and connecting all the components.

[flock6]

Progress is progress

[91CavGT]

The only time I have heard of lithium batteries getting warm is only in these circumstances;


1. The charge voltage is above specified ratings.

2. The discharge amperage is extremely high.

3. When a fast charge is done(i.e. high amperage charge)


But even with the above, not all lithium batteries will react in those ways.



Personally, unless you plan on pushing these batteries hard, be it under charge or discharge scenarios, I would not bother with venting. If these batteries will be subjected to freezing temperatures WHILE being used, you might want to incorporate some kind of battery heater to prevent the batteries from dropping below 32 degrees. Although some lithium batteries are rated to work while below 32 degrees.

[bruss01]

The only time I have heard of lithium batteries getting warm is only in these circumstances;


1. The charge voltage is above specified ratings.

2. The discharge amperage is extremely high.

3. When a fast charge is done(i.e. high amperage charge)


But even with the above, not all lithium batteries will react in those ways.

I have a 75 amp charger for these... which are 840 amp hours of capacity... expressly for the purpose of putting a full charge on them in 2 hours of generator operation.

It's very common to have 100 degree days here in the summer (probably half of all daytime highs between June 1 and Sept 30... this year we had triple digit temps well into October). These batteries will be used exclusively indoors where we have climate control... however that climate control will be out of commission in a power outage.

I may install them without the air-gap between cells, and just monitor the temps to get a feel for whether re-doing it with the air circulation is warranted.

Good call out on the battery heat for sub-freezing temps. I have a solution for that on hand and will be demonstrating the installation.

[bruss01]

With calls for martial law and the increasing probability of supply-chain disruption (parts of Los Angeles is both locked-down and without power this morning) I caved and ordered the solar panels I had planned on waiting until spring to acquire.

Three 210w 12v panels - under a dollar a watt, total 630 watts. The MPPT charge controller I just upgraded to is capable of handling 700 watts/100 volts and will allow me to daisy-chain the panels in series for 36v, while still charging the 12v battery system at an appropriate voltage, so these look like a good match. The MPPT will also do a good job of capturing as much energy as possible in the late afternoon where some shade on the panels is unavoidable in this location. The fact that the panels are all 12v means I can decouple them individually for other uses, and still have a voltage that will work with the previous PWM charge controller and power various 12v devices.

Newpowa 210W 12V Solar Panel High Efficiency Monocrystaline
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



Victron SmartSolar MPPT 100/50 Charge Controller
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[91CavGT]

Good call.



Early this past spring I did the same thing when supply disruptions seemed to be on the horizon. I went ahead and bought a $350 MPPT charge controller that at 48 volt battery bank voltages(but it can be used on 12v, 24v, and 36v battery banks too) it can handle 5,000 watts of solar and is capable of 100 amps of current. It was overkill for my messily 750 watts of solar but it allowed a lot of future expansion. Well, I’m now VERY glad that I pulled the trigger!! They are only available now on the used market where they are selling for $500!!!

The only item that I have not received yet(but have ordered) to put my whole system together is the two copper bus bars. They are 3/8” thick by 1 1/2” tall and 6” wide each. These will be used to connect all 4 AGM batteries together(141 amp/hr each), 2 big power inverters will be connected to these as well as a power distribution puck. All of these will be connected with 1/0 power and ground cables.

So after we move boxes from our garage into our attic, I should(after the holidays) be able to start building a work bench in the garage where all of this will be installed.


Sorry Bruss, I just went off on a tangent. Sleep deprivation will do that to you.

[bruss01]

Panels arrived and went up on the roof. With the higher voltage pushing the current over distance isn't so prohibitive, so I was able to put them in a better spot with a beneficial tilt instead of laying flat, by using some extention cables with factory MC4 polarized plugs . That should help energy collection.

Learned from previous experience and tested each panel before going up. All registered 18+ volts with zero load, as expected. Wired in together in series, I measure 57 volts with zero load at the interior plug. I'll take it.

Soldered the new connectors onto the existing cables, all sealed with marine grade waterproof heat shrink tubing. Much safer than previous setup with the inline fuse and polarized DC connector.

Doesn't sound like a lot telling about it but it was a couple of afternoons up on the roof, considering that blowing the sticks, twigs and leaves off the roof and cleaning out the gutters (annual chores) were necessary prerequisites and since I had the ladder out anyway, it was a useful confluence. Weather was ideal for it, I love these crisp sunny days of late autumn.

Personal note, there was a death in the family over the weekend (not unexpected). As a result I have the week off from work but unable to travel due to lockdown. There will be many family-related phone/Skype/Zoom sessions in lieu of formal services. While certainly not what you would call "fortunate" I will be able to put that time to good use making progress on many efforts around the house this week, and hopefully get this Power Box into service at last.


Parts from today's episode:

Kohree 10 AWG Solar Panel Cable Wire 20 Ft for MC4 Extension Cable, with Weatherproof Female and Male Connector Adapter Kit (20FT Red + 20FT Black)
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

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LIXINTIAN 10AWG SAE Connector Extension Cable, (2Pack) SAE Quick Connector Disconnect Plug SAE Automotive Extension Cable, Solar Panel SAE Plug- 30cm/1ft
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

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Renogy 30A MC4 Waterproof in-Line Fuse Holder w/Fuse
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

61eNgsst3AL._AC_SL1500_.jpg

[bacpacker1513]

Nice system your putting together Bruss