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

[bruss01]

HUGE improvement today (which Weather.com classifies as "partly cloudy") - at just past the noon hour we have already collected 620 watt hours compared to yesterday's day-end total of 270 watt hours. Battery capacity has already risen from 78% to 85% and the day is only half gone by. The remainder of the day is listed as "sunny" so here's to great hopes for an "energizing" afternoon despite a misty/foggy early morning!

I have seen the panels producing north of 450 watts on occasion and the battery taking in 35 amps. This is on par with expectations for this system and aleviates my concerns about performance. The MPPT controller is slightly warm to the touch - I suppose body temperature is a close reckoning so maybe 100 degrees? It is normal for the unit to generate some heat in operation, there are fins on the back to facilitate cooling. As we get into clearer weather and seasons change to provide more direct sunlight, I will want to monitor that to see if any additional cooling is warranted... maybe a small "computer" fan activated by a button thermostat. Due to space constraints this unit is not mounted vertically which would be preferred for passive cooling.

ETA: Just moments after posting the above I saw the panel output plateau strangely. Going out to inspect, I see the reason... a tree shadow gradually encroaching on the cells. This bears watching as it is impacting some of the best-producing hours of the day. I may be able to move them further east and buy another hour or so of prime daylight. Need more cable for that though.

20210105_125209.jpg

ETA2: Yeah, this is gonna be a problem... from 450 watts down to 40... with full sun in the sky at mid-day. Just put in an order for 15 more feet of cable, hope that's enough. Obviously any maroon knows to expect that the shadow of a tree (even one with no leaves) is going to impact your solar collection to an extent - but I wasn't expecting a 90% drop. Good grief. Problem with moving them... they'll then be visible to some folks who I'd rather didn't know about them. They're pretty much invisible where they're at now but changing the position in a favorable manner would definitely alter that. Maybe I'll just keep the extra cable stashed and save it for an SHTF grid-down event.

ETA3: Just received an interesting reply from Daly indicating that their BMS goes into a "sleep mode" when not being charged. This explains the issues I had with maintaining Bluetooth connectivity recently. I had noticed that charging or discharging the system seemed to improve connectivity, the message from Daly confirms this. Apparently it's a feature, not a bug. In retrospect, BT is a radio-frequency connection that requires power to transmit signal... no point in running it during downtime, needless waste of battery power... pretty good idea now that I have thought it through. In other news, it's amazing how well the cells have balanced out. Three of the four are reading identical(3.347) and one is tending a bit lower (.036-.038 lower than the others). Very pleased to see that.

ETA4: Gone past 3:30 pm now, watts are crashing(15w) and it's unlikely much will be added to the collection numbers for today... still, the present 840 watt hours on the books for today blows the 270 from yesterday totally out of the water. Weather indeed makes a huge difference. It would have been nice to see battery charge increased by a nice round 10% (still a slim chance!) but I'll definitely take the 9% it's showing now and be glad of it. Wish we didn't have the tree shadow (and it will be less of an issue as the season progresses due to the sun's height gradually increasing) but it is what it is for now. I have the option to relocate the panels more favorably if there's a grid-down event where we feel motivated to do that. The late morning collection today gave me a taste of what this little system is capable of, and I believe it's been a worthwhile investment in our power preparedness.

[flock6]

Thanks for the update.

[Rich_Vale74]

Just wondering if potential gain from the climbing angle of the sun might be offset by the tree branch leafing out? Any guesses as to how that'll work out?
Thanks for keeping us updated.

[bruss01]

Hard to say Rich. Until a couple of months ago we had a huge 300+ year old oak tree that basically blotted out the sun over the house after 1pm. The tree that is at issue now is further from the house, and the shadow is being cast by the upper 1/3rd of the tree. I'm hopeful that the sun angle will climb sufficiently to get above the tree in the next 2-3 months... in fact, I'm almost sure of it. At that point, foliage shouldn't be an issue - but as they say, the proof of the pudding is in the eating.

[bruss01]

A few rough back-of-the-envelope calculations predict that with the average of the days collected watt hours so far in the typical January weather we've been having indicate that starting from 100% we should be able to power our fridge about 10 days or so. Of course there are various factors like parasitic loss and conversion losses that have to be factored in. I'm planning to do an actual full test using an extension cord to the fridge later this month as I have something coming up that won't permit the full ten day run until afterwards. Looks promising, should really minimize generator use - stay tuned.

ETA: The Daly app is showing 100% charge but the BMS is still reporting 10 amps flowing into the battery bank and the charge controller is still reporting in "bulk" charging mode. I expect to see it transition over to "absorption" and then eventually to "float" as we get nearer to the true 100% capacity. I suspect that during this process it will re-calibrate the dial to better suit the true battery capacity. I think it was limited the first go-round due to the cells not being totally balanced prior to installation.

Explanation of the 3 Stages: Bulk, Absorption, & Float
https://community.victronenergy.com/...and-float.html

Victron MPPT controller & app explained
https://www.sunpoweredyachts.com/sin...-app-explained

ETA: Converting amp-hours to watt-hours, this battery bank set (840 amp-hours) converts to 11424 watt-hours at 13.6v. The charger just rolled over to absorption from bulk this morning after collecting 12720 watt-hours over the past few days at an average of around 52v, which works out to around 245 amp-hours. This isn't matching up 100% with the estimation of filling a 75% battery to 100% but this may be due to the BMS calibration being off due to the cells not initially being well balanced (works out to 980 vs the expected 840). Could also be due to conversion loss, as mentioned, the unit does produce some heat while operating. Ironically, the day the charger kicks over into absorption (reducing collected watts to single digits) happens to be the one totally cloudless, bright and sunny day in the past week. LOL. Gotta say, there's a huge advantage with this Victron charge controller because it tracks data over time, allowing you to make calculations of this sort very easy.

Convert Amp hour to Watt hour
https://convert-formula.com/ah-wh

ETA2: Just realized that my calculation above was based on an estimated value, when actually doing the math for the average max daily collection voltage should have been 55.8 instead of 52 . Running it backward, an average of 54v works out almost perfectly. That's in the ballpark of reality I think... factor in a bit of conversion/heat loss, I'm satisfied that at least the math is fairly spot-on here. That gives me pretty good confidence in being able to make projections based on the reported numbers from the BMS and the charge controler. Loving the Victron so far, this is valuable info.

[Crazy Uncle]

I have been paying attention to this discussion, and I think I am going to start building my own array. I am looking at batteries, converters and solar panels. Do you know of a decent calculator out there that can ballpark the system needed to unplug from commercial power?

[bruss01]

Try this Uncle-

OFF-GRID CALCULATOR
https://www.altestore.com/store/calc...id_calculator/

It's never been my objective here to take the whole house off grid and have it be roughly approximate to "normal".

That takes a lot of collection capacity, as well as DEEP storage banks to accommodate a series of cloudy days and overnight.

My goals are much more modest... to guarantee the refrigerator can reliably run 24/7/365 and have a bit of juice left over for light, communication, cordless tool batteries, etc.

As evidenced by this thread, I still haven't entirely met even those modest goals... the setup I have now can only accomplish this with the occasional assistance of a generator for a few hours 2-3 times a month. But it is good enough for what I think we'll need for "emergency" use. Start tacking on things like well-pump, washing machine etc and you start coming up short on watt-hours pretty fast. My system is fairly capable, but it is adversely affected by sub-optimal panel placement and afternoon shade. There will inevitably be some detrimental factors that affect all but the most ideal installations.

By living off-grid for weeks at a time in my solar-equipped trailer, I've learned there is a different mindset that comes with being off-grid. The same way one's mindset changes about water if stuck in the desert with only a trickle coming out of a rock for resupply. You think about every drop, and re-purpose every drop that is still usable in some capacity. You find ways of making do with less. And you live with one eye on the power panel and the other on the sky..

I've talked to my brother about my various systems starting from day one, when I started with the Harbor Freight 45 watt system years ago. He feels that if it isn't "just like the grid" then it isn't worth doing... and when he's looked at the cost to do that, it sticker-shocks him right out of that notion entirely. With advances in technology it is lower in cost now than it ever has been to mostly or totally replace the grid with alternate sources... but still out of reach for all but the most committed. Still, it's something that a few feel the need or desire to do, and are willing to make that committment.

One necessary prerequisite... monitor your own electric meter for a week in the winter and a week in the summer... or just collect your electric bills for the past year. This will let you know how much juice you are using at your present comfort level. Then spend a month or two living at a level of frugality that you think you could tolerate indefinitely. Then you'll be in a position to be able to ask the right questions regarding what kinds of compromises you'd be willing to make for your situation.

[bruss01]

"...the cause of the outage is unknown..."

We might be hearing more about random, mysterious outages. I've heard of many blackouts both domestic and international over the past few days. Here in the Sacramento metro area we are on a different (more localized) system than most of CA, but being the seat of state government, I highly suspect we'll see some outages in the course of the present situation settling out.

Outages leave approximately 2,500+ customers without power in north Fresno
https://www.yourcentralvalley.com/ne...-north-fresno/

[91CavGT]

Yeah, my wife and I have been talking about that too. In 2 weeks we have our shed scheduled to be installed. Once it is up, I’ll be finishing out the inside and then will be mounting my big panels and working on our small setup. Just like yours, it won’t be big enough to power our whole house but it will be enough power for our fridge, some lights, a fan or two, and to keep our portable electronics charged. I’ll start a new thread when that time comes.

[bruss01]

I'm looking forward to seeing your build Cav! Until then rest up and get your energy back, lotsa vitamins.

Funny thing, the huge national blackout in Pakistan... they are reporting that as "cause unknown" as well. I keep hearing about something called "Electric Rain" possibly a form of electronic warfare - nothing of significance surfaces via search engines. Not sure what I think about that yet. Pakistan is a nuclear nation, they're not an insignificant little backwater.

ETA: Apparently there are several major power outages in Iran as well now. Mexico and the Vatican apparently also had recent outages.