Explain this new math to me, I’m quite intrigued ?
Vote early! 60amp scc vs 80amp - and - EPever vs Outback ? need your opinions.
- Thread starter Arikaree
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Explain this new math to me, I’m quite intrigued ?
sunshine_eggo
Happy Breffast!
Bluedog225
Texas
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- Nov 18, 2019
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Why does he need to calculate worst-case Voc at the coldest temps his panels will ever see (at night)?
I don’t understand. Or is that just a proxy for coldest morning temperature?
I don’t understand. Or is that just a proxy for coldest morning temperature?
Voc from factory is 19.4, but they don't provide temp info. Four panels amounts to <100 MaxPV.
Numerous reading sources indicate "safety factor" of 25%. I'm there even with a Tracer 3415 and similar scc makes and models. As indicated earlier, I am planning on the Tracer 4215 or Tracer 5415, both have max PV open circuit of 150v.
And this for the 4215AN (Triron edition): "7 battery type selection Sealed(AGM), Gel, Flooded, Lead-acid User, LiFePO4 Lithium, Li(NiCoMn)O2 Lithium, Lithium User(9~34V)." Amazon, $170.
Numerous reading sources indicate "safety factor" of 25%. I'm there even with a Tracer 3415 and similar scc makes and models. As indicated earlier, I am planning on the Tracer 4215 or Tracer 5415, both have max PV open circuit of 150v.
And this for the 4215AN (Triron edition): "7 battery type selection Sealed(AGM), Gel, Flooded, Lead-acid User, LiFePO4 Lithium, Li(NiCoMn)O2 Lithium, Lithium User(9~34V)." Amazon, $170.
Voc can be 15% higher or more in really cold conditions. Most panels have a Voc temperature coefficient around -0.3%/ºC. So it only takes a 6ºC drop in temp to increase the Voc 2%. Just getting to freezing will be 7%-8% increase for most panels.
Applying your numbers to my PV array:
(4 panels X 20V voc/ea) X 115% = 92V
Still within suggested scc's (in this thread even) with a PVmax of 100V.
But I agree totally with fudge factors, including the Rule-of-Thumb 25% safety margin
and have decided on the Tracer 4215AN or 5415AN each with PVmax of 150V (EPever gives PVmax at +77F deg at 137V).
Running the numbers backwards, an SCC with 150v PVmax and factoring in 25% safety yields a Voc of 30V for each of my 4 panels, that translates to a 50% increase from a Voc of 20V due to cold temps. The math works.
I'm comfortable with my Tracer choices above, and appreciate knowing your input as it validates my decision. Thanks.
(The 4215AN is on it's way!)
(4 panels X 20V voc/ea) X 115% = 92V
Still within suggested scc's (in this thread even) with a PVmax of 100V.
But I agree totally with fudge factors, including the Rule-of-Thumb 25% safety margin
and have decided on the Tracer 4215AN or 5415AN each with PVmax of 150V (EPever gives PVmax at +77F deg at 137V).
Running the numbers backwards, an SCC with 150v PVmax and factoring in 25% safety yields a Voc of 30V for each of my 4 panels, that translates to a 50% increase from a Voc of 20V due to cold temps. The math works.
I'm comfortable with my Tracer choices above, and appreciate knowing your input as it validates my decision. Thanks.
(The 4215AN is on it's way!)
If you look around online there's people reporting that those saws draw more than 40 amps on startup (some people even reported as high as 75 to 100a, of course there's tons of variables). The surge on compressors can be incredibly high as well.
"TBD" is not a great way to go with building a system. You need to spec out inverters now, BEFORE you buy a solar charge controller. What people are telling you is that the voltage you'd like to use might not be appropriate for your future inverter. You need to know that before you start buying expensive parts though. Build the rest of your system on paper first, and then buy it all at once.
I'm speaking from personal experience here too, I built a 12 volt system and almost immediately regretted not using a higher voltage. Trying to get 30 or 40 amps of 120v AC out of 12 volt batteries is quite a task. The higher voltage would have saved me hundreds of dollars, and would have made wiring MUCH easier (crimping and running 2/0 and 4/0 is not fun).
Get the inrush numbers, figure out the required inverter size / voltage, then what battery configuration you need, THEN figure out how to charge those batteries. The way you are piecing things together is backwards.
Edit: I just wanted to add that they do make something called a "soft starter". It's a device that spins the motors up at a slower speed, and pretty much eliminates the inrush current. If you run into any problems in the future, that might help.
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All,
"TBD" is simply a placeholder and not a design methodology, meaning my intent to pursue some real number crunchings before deciding on inverters, etc.
FYI: "etc" is also a placeholder. I have much research to do this winter. This thread has raised the bar so to speak, I have a new baseline to work from. Speaking of "bar"... cocktail hour cometh.
A recent reply provided a link to a clamp monitor for measuring 110 inrush and power use.
I have a couple of "soft-start" DeWalts, still good to know.
Basically I do not have nor use sizeable motors, my 12" DeWalt compound miter being the exception and that is used infrequently. Further, I only use one 110V tool at any given time, I work solo. Even my pancake compressor sits until end-of-day for blowing off residual sawdust. If that. And if the day is cold and cloudy, you will find me inside with my graph paper and calculator and bedside Solar DIY books.
My immediate quandary involves a battery balancer for lithiums in series. Victron continues to speak Dutch, so I cannot differential their various products because they describe how it does something but neglect to describe their purpose. Nuts.
I appreciate the replies.
"TBD" is simply a placeholder and not a design methodology, meaning my intent to pursue some real number crunchings before deciding on inverters, etc.
FYI: "etc" is also a placeholder. I have much research to do this winter. This thread has raised the bar so to speak, I have a new baseline to work from. Speaking of "bar"... cocktail hour cometh.
A recent reply provided a link to a clamp monitor for measuring 110 inrush and power use.
I have a couple of "soft-start" DeWalts, still good to know.
Basically I do not have nor use sizeable motors, my 12" DeWalt compound miter being the exception and that is used infrequently. Further, I only use one 110V tool at any given time, I work solo. Even my pancake compressor sits until end-of-day for blowing off residual sawdust. If that. And if the day is cold and cloudy, you will find me inside with my graph paper and calculator and bedside Solar DIY books.
My immediate quandary involves a battery balancer for lithiums in series. Victron continues to speak Dutch, so I cannot differential their various products because they describe how it does something but neglect to describe their purpose. Nuts.
I appreciate the replies.
I have two LiFePO₄ batteries in series. They have been in series most of this year. I do not have any sort of balancer. They have stayed in balance just fine. The trick is to first charge the two batteries together in parallel and let them settle in parallel so they start life at the exact same SOC. Then you can put them in series. I know they are still in balance because my battery monitor is setup to monitor the voltage of both. Both batteries are at the same voltage to the nearest 1/100th of a volt, according to the battery monitor.
Sounds good, can you recommend a batt monitor? I plan on 4 LiFePo4 batts, 2 in series for the 24 volts, then a second pair in series to make a 400Ah 2S2P 24V bank. Considering the costs, I prefer to NOT kill them. I have my LFPs set up for an external (1110v) batt charger so that each in the pair charges at the same time using an LFP specific charger. Seemed like a good idea at the time.
You can't go wrong with either a Victron SmartShunt or the Victron BMV-712. The real difference between the two is the included external display with the BMV-712. Both support Bluetooth so you can see the same info on both using the VictronConnect app on your phone or computer. Both support mid-point voltage monitoring which allows you to make sure your batteries are staying balanced.
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Ten years. Yeah, the Morningstar's are solid as a tank. No moving parts to fail. Silent. Programmable, networked.