Thursday, May 16, 2019

Total Teardown of our Solar Power System - Switching from Flooded to AGM L-16 Batteries

Our solar power system has been working very well for us for the past five or more years.  It has washed our clothes, cooked our food, boiled some of our water, kept the lights on, charged our devices, powered our internet connection and, occasionally, even thrown off some heat here and there.

Of course, so much of our experiences here on the homestead have been punctuated by "if I was doing it over again..." sort of thoughts.  I finally managed to revisit two of them related to our solar power in the past couple of weeks.

Originally I had intended to put the batteries under the cabin.  This was before I realized that flooded batteries off-gas and need to be properly ventilated.  I wasn't too enthused with having something potentially explosive underfoot, and I also wasn't excited about having to isolate them and ventilate them to make that situation workable.

Instead, I put thick insulation inside of a deck box, drilled large holes through the cabin, and hoped for the best.

This did work just fine for half the year, but once the mercury dropped to twenty below and further, the capacity of those batteries was severely curtailed.  We could have a full charge in them by four (on the very rare days when there was that much sun available), and yet, by morning, they were just able to make it to lunch when the sun was finally back on them.  I suppose it's unfair to expect them to do all their required work on only four hours of sun in that perspective, even if we do shut off the power after we go to bed.

I tried installing warming pads to raise the temperature, and thus capacity of the batteries.  This had a mild positive effect.

Finally, while freezing my fingers and watering the batteries, I rethought about bringing the batteries indoors.  If I switched to sealed AGM batteries, I could solve three issues at once.

I wouldn't have to water them anymore, as the water in batteries isn't normally permitted to escape to the atmosphere during electrolysis.

They wouldn't take up so much space on our back deck.

They would *stay warmer* - and thus have much more capacity available to us through the winter months.

The big question - where to store them indoors?  The crawlspace was inconvenient to access them if required.  The main floor simply didn't have any free space.  The upstairs rooms also were already pretty tight.  So I went even higher.  The attic?

Four L-16 batteries at 52kg is just over 200kg in total.  This is like having three copies of myself in the attic.  Something in that perspective would never concern me.
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Fortunately, two weeks ago my friend B! was visiting, so we purchased some 3/4" plywood and sliced it up to fit across the joists in the attic.  I had enough that I even doubled it up to be extra sure.

We also mounted the remaining pieces carefully on the end wall directly under the solar panels.  One other consideration is that the batteries really need to be kept as close as possible to the inverter to prevent too much in the way of line losses.

This is the first board mounted on the wall - ready for my electronics.

This is where the solar panel leads come into the cabin.  This is just a 4 gauge jumper cable I bought on sale - it worked great and was much cheaper than purchasing wire off the shelf!
This had the knock on effect of solving my other big issue with the existing solar power setup - all my electronics were in the master bedroom on the main floor, and the truth is, the Magnasine inverter/charger was a bit noisy.  It has a definite, noticeable hum.  We had learned to mostly tune it out, but it still was there whenever you were trying to listen to the radio or television quietly.

It also just made the room look and feel cluttered having the inverter, charge controller, and a small breaker box all in the same corner of our already cozy bedroom.

Most of the electronics are pulled out.  Look at that rat's nest of wiring!
All my cabin wiring congregated to this spot, so we did have to deal with that restriction - we ended up running conduit from that corner of the bedroom all the way through the loft room above, and into the attic, right between where the batteries would rest, and where the electronics would get mounted.  It looks just fine to me!  Just like the work I did in the kitchen.

In order to make the wiring fit, I still needed to add two more boxes.  I used this chance to mount switches or outlets in these boxes, so I could manually switch off circuits in the cabin without having to go to the attic to throw a breaker.  We also needed an outlet there for the digital electronics that were to remain - the modem, router, nVidia shield, bedroom television...

I ran two sections of conduit - one contained all the power related wires, and the other I pulled control cables (and the ground cable) through - the solar controller has a web server to show its state with, and I didn't want to give that up for anything.  So I pulled an RJ-45 wire for it.  Also, the inverter had its own controller on a standard telephone cable - I pulled that through too.

A view of the new conduit from the upstairs office/guest bedroom.
I hired my contractor to help me carry up the batteries - it was a three man job, but not too bad after that.

Batteries all lined up behind the access door.
Same with the inverter - the Magnasine is surprisingly heavy.

After about and hour and a half, my contractor and his hired man were finished, and I was left to slave most of the day away finishing the wiring.

I connected up the lines to the batteries, including two temperature monitors (one for the solar charger, one for the inverter/charger).  I plugged the network cable into the solar charge controller and...  no dice.  The cable was either too long, or damaged, or something.  I tried it a few different ways, and ended up having to pull ALL the lines out of that conduit, replace the network cable, and refeed them in again - that was NOT fun.  I added lots of dish soap to try to make it a bit smoother to pull them back through, and that definitely did help.

Batteries all interconnected, the two temperature probes are in the lower left of the picture.

Golly that inverter was heavy!  Note the baking sheet fireproof mount :).
Then, the really scary moment of truth - installing the 100amp fuse on the DC cable from the batteries.  As the capacitors in the inverter charge, there is always an off-putting spark.  It's not fun, but perhaps I'm getting use to it.  I believe this was the third time I've gotten to experience it (there's a video of the spark at this link).

Looking pretty good.  I've cleaned up and fastened the wiring since this picture.
Over the next couple of days, I finished up the wiring in the bedroom, and moving out the electronics has also given me a bit more wall space there, which I just filled with a few leftover chrome shelves that fit nicely.  Now I have a spot to hang a few of my "dress" clothes - and I was able to reposition the laser printer, and my tiny "work" shelf where I place computers and laptops as I work on them.  It's nice that I can have all my digital hookups in that one space.

I still need to repanel the wall now to go right to the corner.

Nice work area!  Sorry for the potato quality.
It's been a hard push to get this all dealt with, but watching the batteries charge up and hold such a good charge right through to the next morning has been very gratifying.  It's also so quiet in the bedroom now - the only sound is the fridge compressor in the other room, and that's only while it's running.  It also makes the room darker, without the lights of the inverter and charge controller (the latter of which ALWAYS displayed its state via bright LED lights (how's that for RAS syndrome?)).

Now in winter I'll only have to worry about the amount of sun we receive, and not so much the temperature as I believe the attic stays at a pretty moderate climate.

Bonus May 9 weather condition picture.

1 comment:

  1. Good decision to move to the AGM batteries. I have 12 of them and 39 panels that provide a lot of power for our cottage. Rarely see them drop below 90% charge although in winter with a few heavy overcast days it happens. I like the zero maintenance, zero off gas worries of the AGM but yes they are very expensive and very heavy!

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