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Hold my (root) beer - we found our limits ...
4 years ago
General
I know you guys (gals/herms/others) are getting tired of this, so this will be the last one (for now!)
A very cloudy day has shown me the limits of my toy as it now sits.
For a quick recap, we are playing with a 48 volt solar system:
16) 210 watt solar panels wired in groups of four
12) 12.8v 100AH batteries wired in groups of four
1) 80A solar controller
1) 6000w 240 split phase inverter
powering an old house built back in 1967 ...
Other than today we've gotten a bit better than 12Kwhs each day, today we got just under 2Kwhs. Mornings the battery voltage has been 51.2 or so, evenings have been 52.2-52.4 ...
This morning (07:44) started off at 51.22 but by 17:25 we were down to 49.51 and when I checked less than an hour later we were down to 47.96 I wrote that down and looked up again and it was .94 .93 .92 like watching a timer ticking down ...
So I'll give it a sunny day or three to top off the batteries before I 'play' with it some more. (next time I'll pop breakers for rooms we don't need and see how much I can trim our power demands!)
I still have enough 'room' on the controller to add one or two more panel sets - not that that would have helped running out of juice in this case. I can also add a fourth set of batteries, though I'll wish I'd found a bigger 'bench' to hold all this!
Thoughts and comments welcome (yes, I already know I'm crazy - thank you!)
A very cloudy day has shown me the limits of my toy as it now sits.
For a quick recap, we are playing with a 48 volt solar system:
16) 210 watt solar panels wired in groups of four
12) 12.8v 100AH batteries wired in groups of four
1) 80A solar controller
1) 6000w 240 split phase inverter
powering an old house built back in 1967 ...
Other than today we've gotten a bit better than 12Kwhs each day, today we got just under 2Kwhs. Mornings the battery voltage has been 51.2 or so, evenings have been 52.2-52.4 ...
This morning (07:44) started off at 51.22 but by 17:25 we were down to 49.51 and when I checked less than an hour later we were down to 47.96 I wrote that down and looked up again and it was .94 .93 .92 like watching a timer ticking down ...
So I'll give it a sunny day or three to top off the batteries before I 'play' with it some more. (next time I'll pop breakers for rooms we don't need and see how much I can trim our power demands!)
I still have enough 'room' on the controller to add one or two more panel sets - not that that would have helped running out of juice in this case. I can also add a fourth set of batteries, though I'll wish I'd found a bigger 'bench' to hold all this!
Thoughts and comments welcome (yes, I already know I'm crazy - thank you!)
Of course if your lighting was straight off the battery you would save power there.
I think your system so far is working out very well.
And am considering more batteries.
Most 12 volt 100 amp batteries are 350 bucks each or a bit higher, four of them are 1400 bucks... One issue with pairing them up for 48 volts, some of them do not have BMSs that will handle that high of system voltage.
When buying batteries watch their charge/discharge rates as well as their temperatures. The ones I've got can be discharged so long as they are at least -10C (14F) - but you can't charge them if they're below 0C (32F)
The 100 & 200 amp batteries I was looking at were both 100 amp discharge max. Which meant two 100 amp batteries in parallel could give you 200 amp discharge where one 200 amp gives you only 100. As my 6000 watt inverter could draw a bit more than 150 amps, I had only one way to choose (since I was thinking just 200 amp hours at 48 volts.
Though now that I'm thinking I might want a fourth set of batteries, I could have gotten away with eight 200 amp 12 volt batteries.
If it all went to crap I can rewire things into a 24 volt system for my smaller 2000 watt inverter. (any two batteries with any charge to keep the heat on! )
Running the numbers tandem seating works best for lower horsepower engines. While with the 160 plus horsepower there is not much difference between tanden and side by side seating... you put the AM 20T at 230 to 260 horsepower it's a rocket on takeoffs.
Somewhere between 11-12k all told, though that included some new power tools. Bigger pieces from Amazon, but I tried to support local stores for wire and a new ladder.
If I ever did a solar system on my house (either by contractor, or by myself), I'd prefer LG panels and Enphase IQ6 or IQ7 string inverters.
Looking at their: 6000W 48V HYBRID SOLAR INVERTER SPLIT PHASE 120/240VAC
A little more in price as what I paid for my controller ($300) and inverter ($1100), but it would 'scale' a lot better as I could then gang several of them together as needed. And I'd need to rewire the house more than I wanted to ...
As for the: Enphase IQ 7 and IQ 7+ Microinverters
They appear to be grid inverters, solar to AC, no options to feed batteries, so not a very good option for off-grid type power (even if they'd feed batteries I'd need eight of them (@ $140) for my sixteen 210 watt panels - which would cost what I paid for the inverter)
If I ever decide to upgrade I might look at that 6000W option, but that's a ways down the road.
Also, you can use the string inverters with a battery system.
One of my quotes on EnergySage has the following for a 6.48kW system:
Panasonic Evervolt 360 panels (18): https://www.energysage.com/solar-pa...../2373/EVPV360/
With the Enphase IQ7 (18): https://www.energysage.com/solar-in.....s-72-x-us-240/
Enphase 10.5kWh battery: https://www.energysage.com/solar-ba.....43/Encharge10/
$15,550 for the solar system, the battery adds another $14,550. That's not counting the federal ITC credits, $4044 for the solar system, and $3783 for the battery. So, $30,100 minus $7827 in ITC credits = $22,273
My power rarely ever goes out, even during last year's winter storm, I never lost power. Oncor says on their website, that if you are on the same circuit as a hospital or critical infrastructure (like a water treatment plant), that circuit will never get turned off.
Solar 6480W vs 3360W - almost double! Which shows I badly underestimated how much power I'd have to replace each day!
Battery Capacity 10.5kWh vs 15.36kWh - even at 50% more I underestimated how much power I'd burn each day.
Giving you a recharge ratio of 0.617 to my much worse 0.219, so your quote would recover from spent batteries three times as fast (or give you more to sell to the grid.)
AC Rated (continuous) output power 3.84kW vs 6kW - I'd get yelled at if I told someone they couldn't use the microwave without me turning everything else off first!
I do have enough space and the solar controller has enough ratings (max 5600W) for me to add two more sets of panels, which would get me up to 5040W - which would let me recharge about 50% faster (and a slightly better recharge ratio of 0.328), but I really should also add another set of batteries to extend my endurance ...
More bits and thoughts for me to play with!
Sorry that I forgot to reply to this bit ...
Since this was a DYI and I wanted to see how well/poorly things would work, I do have each string of panels on a meter that gives me the current voltage, amps, watts and how many watt hours of power have crossed that meter since it was last reset. Each solar panel set also has its own circuit breaker, and the battery sets have cut-out switches. (one of my brothers looked it over and said I seemed to have too many switches and meters all over the place. )
V.
Pulling out the calculator, my battery bank is 15.36Kwhs of juice. Other than yesterday my daily charge from the sun has been a little over 12Kwhs, and you have to put a bit more into charging a battery than what you'll be able to get out of it - never mind that the inverter is also drawing from that 12K during the day. (That the battery voltages weren't dropping day to day suggests I have enough solar to charge the current batteries, but not quite enough battery to skip a day of solar and still make it to the next day - unless I run the house a bit more 'lean' ...
I have used one myself but your power supply seems somewhat different to my 240V single phase setup. I went for.a unit that did 0V transition switching to help avoid issues with transient voltages. I would expect a similar widget is available to suit your very different system.
In any case, glad to hear the system is more or less working for ya!
Then sit down a figure out what all you want to power with it. You need two things from each item, max draw and duration. Say I have a freezer that draws 300 watts, but only 20 minutes of each hour. So the inverter needs to be able to handle 300 watts, but your battery bank only needs 100wHs per hour or 2.4KwHs per day. (or you can wild-ass guess at it like I did and find you can't run 'everything' if you don't get enough sun each day! )
Once you've added things up you start throwing in loses. The inverters I have claim 90%, so that 300 watts might be drawing 330 watts from the batteries, and the batteries might require 125% charging to deliver 100% discharge to the inverter. (So that 300 watts for 20 minutes an hour may need 330 watts draw from the batteries, and 2.64KwHs cap per day and 3.3KwHs of panel power each day to keep things going.)
As to my system, a bit over 12KwHs seems to be enough to run the inverter and recharge the current batteries for another day, but my 15.36KwHrs of battery can only handle 36 hours of us running the house as if we have power to burn. An extra set of batteries/panels - and/or turning off things we really don't need seems to be the next step.
I've done most of my learning the hard way, lots of reading and making mistakes and learning from those mistakes. If I can save someone a mistake, it's that much sooner they get it done right.
One thing I forgot to put in that last block was that after you figure your daily 'need' you need to multiply it by the number of days you might need it to run in bad weather (and enough panel power to charge them if you only get a day or two of sun between stormy days!)
Good luck and have fun!