So, what triggers me to start my generator? What piece of data (and there is a LOT!) do I look at to tell me that I need to supplement my PV system with some generator-produced power? It is a 24-volt battery bank.
And, just as importantly, what piece of data tells me that the generator has run long enough and I can turn it off? I must start the generator manually, as it sits in an enclosed shed.
I have a fairly new system, just commissioned this summer, and we have had a great amount of solar input. But the summer is winding down, and I need to be able to understand my system as the sun arcs lower and lower.
In advance, thanks for your help!
Hello,
Could you please give us a rundown of your system:-)?
P.s. welcome 2 the forum :-)
Here is a list of the "primary" components of my system...
4 Trina 255W Solar Modules
1 Classic 200 Charge Controller
2 MidNite MESPD300 Lightning Arrestors
1 Magnum MS4024 20000W 24VDC Inverter
1 Magnum Control ME-ARC50
12 Trojan T105 Batteries
So, what triggers me to start my generator?
well if I got down to 50% DoD , or SoC , (take your pick) , in one day , everyday, AND my Solar could not get me to FLOAT at least every other day (min once per week) I would be BULKing up with the gen set in the mornings...
Sorry it isn't an exact number but it is location and needs dependent... as well as how your system works over time.
hth
Quote from: clint7434 on August 20, 2016, 11:07:07 AM
1 Magnum MS4024 20000W 24VDC Inverter
I suspect this is a typo?
20 KW @ 24 volts would be 800 plus amps and seems a bit much.
When I had an active system using Outback inverters, I set the inverters to charge from the grid if below a specific voltage for X time. That was before the WizzBang JR was available to count amps in and out of a system using a Classic. Relatively the same as "time to fire up the generator". You are aware some generators can be remote started?
As WB noted, it is system and location / usage dependent.
Just from here.
Tom
you are right... it is a typo.
about the generator... it is enclosed in an old shed that has 3 sets of doors -- left, right, and 2 in the front. They all have to be opened (manually) in order for the generator to exhaust properly. So, I bought a generator that does NOT have auto-starting capability.
We are located in northern NY -- Adirondack Mountains (~43 degrees lat). And there is about 4-6 hours of good direct sunlight during the summer each day, sometimes more. We have a 3 bedroom, 2 bath cabin, 1400 sq ft. So our power consumption is pretty strong at times.
Quote from: clint7434 on August 20, 2016, 05:24:22 PM
....... We have a 3 bedroom, 2 bath cabin, 1400 sq ft. So our power consumption is pretty strong at times.
Strong, as in Air Conditioning, or electric baseboard heat in the winter ?
Generally, you want to trigger starting the generator on either of 2 things. High power draw or Low battery voltage
But first, what sort of loads are you expecting the batteries to be carrying ? (numbers, not guesses)
Historically, have you been able to get to float at least 3 times a week on solar ?
Winter with shorter days, do your loads decrease? Can you expect solar to power things in good weather, or are you going to have to supplement the solar with generator every day ?
Well, now you are asking the questions I need to address... but the system is new, and we will not be spending the winter there, but will retreat to Virginia (winters are NOT hard here.) So, the place will sit with virtually no load all winter.
But to address other questions (and sorry, I don't have a lot of data yet... I've been gathering it for a couple of weeks, that's all.) Main appliances are a small electric refrigerator (365 kw-hours per year estimated), baseboard heat (but not electric, just the pumps), a small clothes washer and a propane dryer (although we hang clothes outside most of the time.) Microwave (900 watts) that is used for about 2 minutes a day. All LED lighting. And the usual assortment of occasional power tool usage, vacuum cleaner, ... here's some numbers, based on 34 days of data taken in July and August... averages,
Hi VPV = 138.46
Hi VBatt = 27.7
KW hours = 2.62
Float time per day = 99.57 minutes. Note there was 20 days when float time was 0, and 14 that were NOT 0, and it was these that were used to develop the 99.57 minutes average flat time.
Hi Power = 0.930 KW
So, does this make sense?
well, based om your current use, you have a balanced system.... keep track of when you cease to get any float, that is the time to use some fossil fuel...
however that 90 or so minutes of float is still significant.
The next piece of data is what are your charge parameters? and how are you determining the end point for Absorb? Do you have a WBjr?
Quote from: clint7434 on August 20, 2016, 08:32:49 AM
So, what triggers me to start my generator?
I've only been living (and running two businesses) completely off-grid for 12 years, so a "n00b", but I've made my share of mistakes and live with them.
I run the generator on what superficially seems to be a complex set of conditions, but isn't really as bad as it looks.
I used to have 48V/1500AH (then 1000AH, then 500AH) AGM lead-acid, but changed a couple of years ago to 300AH LFP (and wish I'd done it earlier, and wish I'd got 600AH).
My generator is home-made, and auto-start/auto-stop. It starts if the battery volts are too low, or the load is too high, or if the SoC is too low, or if the time of day is (x) and the SoC is below (y), or once every (n) days just to exercise the generator.
With the LFP cells, I'm able to go to 85% DoD (although I have the genset autostart at 75% during the day, or if it falls to 80% SoC regardless of the time), and that means that I get the same "usable watt-hours" out of a 300AH LFP bank as I got from my 1000AH AGM bank. The LFP are also way stiffer than the AGMs ever were.