I am about to build out this system and need some advice.
Rv_Adventure_Couple
Registered Users Posts: 29 ✭✭
So this diagram is for a system I am putting into our RV. I would appreciate if anyone would chime in and tell me if the diagram is correct. From the shunt I would also have a chassis ground. The inverter has low voltage disconnect at 10.6v. This system will be separate from the dc side of my RV, purely to power ac loads when we need them while dry camping.
Comments
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Fuses/breakers are sized to protect wiring but wire size not shown. In particular, the 300a inverter fuse would be for really big wire.Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
Oh sorry, The 300 amp fuse should be 150 amp for 1/0 and the CC wiring is 6awg. I realize the battery protect is overkill for the battery monitor, and I may not end up using it. The power wire for the battery monitor will probably be 14awg with an inline 15a fuse.
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That sounds better. You might want to consider a DC rated breaker instead for the inverter tho. It could surge to 500adc or so. Or carry lots of spare fuses.Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter -
I highly suggest that you measure your loads (will a Kill-a-Watt type power meter) to figure out what you need for energy. And that you focus on conservation (almost always cheaper to conserve vs generate power).
Are you looking at a LiFePO4 battery bank? If so, the bank needs to be kept above freezing when charging/discharging--Or you will kill your cells (or worse).
For the battery bank, if not using LiFePO4, I would suggest the first bank use 6 volt @ ~200 AH "golf cart" batteries. 2x 6 volts in series for 12 volts, and 1-3 parallel strings (depending on your loads). Cheap, rugged, relatively forgiving. And most people probably end up "murdering" their first bank or two.
A 3,000 Watt AC inverter is (in my humble opinion) serverily oversized for your battery bank. For flooded cell lead acid, a 300 AH battery bank @ 12 volts would suggest a 750 Watt maximum AC inverter. And for an RV, I would suggest that a 300 Watt PSW inverter is a better fit.
For a 12 volt battery bank, suggest around 1,200 to 1,800 Watt AC inverter is the "practical limit" for 12 volts (cable size, voltage drop). A 3kW inverter at full load takes:- 3,000 * 1/0.85 AC inverter eff * 1/10.5 battery cutoff = 366 Amps max draw
You don't list any backup genset--A 400 Watt solar array, mounted flat to an RV roof does not collect that much energy... For example, a flat mounted array in Austin Texas:
http://www.solarelectricityhandbook.com/solar-irradiance.htmlAustin
Measured in kWh/m2/day onto a horizontal surface:
Average Solar Insolation figures
Say, 3 hours minimum sun (spring/fall) per day:Jan Feb Mar Apr May Jun 2.83
3.41
4.40
5.25
5.62
6.36
Jul Aug Sep Oct Nov Dec 6.56
5.94
4.97
4.05
3.07
2.63
- 400 Watts * 0.52 off grid system eff * 3.0 hours of sun per day = 624 Watt*Hours per day
- 624 Watt*Hours per day / 30 Watts Tare loss = 21 hours (no other AC loads)
-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Based on your diagram, it looks like you have (8) 150 AH, 3v batteries?
I always have more questions than answers. That's the nature of life. -
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BB. said:I highly suggest that you measure your loads (will a Kill-a-Watt type power meter) to figure out what you need for energy. And that you focus on conservation (almost always cheaper to conserve vs generate power).
Are you looking at a LiFePO4 battery bank? If so, the bank needs to be kept above freezing when charging/discharging--Or you will kill your cells (or worse).
For the battery bank, if not using LiFePO4, I would suggest the first bank use 6 volt @ ~200 AH "golf cart" batteries. 2x 6 volts in series for 12 volts, and 1-3 parallel strings (depending on your loads). Cheap, rugged, relatively forgiving. And most people probably end up "murdering" their first bank or two.
A 3,000 Watt AC inverter is (in my humble opinion) serverily oversized for your battery bank. For flooded cell lead acid, a 300 AH battery bank @ 12 volts would suggest a 750 Watt maximum AC inverter. And for an RV, I would suggest that a 300 Watt PSW inverter is a better fit.
For a 12 volt battery bank, suggest around 1,200 to 1,800 Watt AC inverter is the "practical limit" for 12 volts (cable size, voltage drop). A 3kW inverter at full load takes:- 3,000 * 1/0.85 AC inverter eff * 1/10.5 battery cutoff = 366 Amps max draw
You don't list any backup genset--A 400 Watt solar array, mounted flat to an RV roof does not collect that much energy... For example, a flat mounted array in Austin Texas:
http://www.solarelectricityhandbook.com/solar-irradiance.htmlAustin
Measured in kWh/m2/day onto a horizontal surface:
Average Solar Insolation figures
Say, 3 hours minimum sun (spring/fall) per day:Jan Feb Mar Apr May Jun 2.83
3.41
4.40
5.25
5.62
6.36
Jul Aug Sep Oct Nov Dec 6.56
5.94
4.97
4.05
3.07
2.63
- 400 Watts * 0.52 off grid system eff * 3.0 hours of sun per day = 624 Watt*Hours per day
- 624 Watt*Hours per day / 30 Watts Tare loss = 21 hours (no other AC loads)
-BillThank you for the in depth input.The panels are on the sides of our RV so tilted slightly, I plan on adding 2 more 200 - watt panels eventually. I've got the inverter at 3000 watts so that I could power our ac for short periods from time to time. The battery bank is LifePO4 and depending on how well it impress's the misses, I will add another 300ah to it eventually. The DC side of the camper will stay as it is and wont connect to this battery bank, I have a 100ah deep cycle 12v lead acid for the DC side of my breaker box that has been doing the job for a year now.I suppose I could return the 12v 3000 watt inverter and grab a 24v 2 or 3000 watt inverter. I just want to be darn certain I can run the ac on a 2000 watt inverter as that is what I promised the system could do. The AC unit itself uses 1,000 watts when running. I also installed a hard start capacitor in our AC unit so that the inverter can kick it on.Our charge controller has low voltage disconnect, plus we hate freezing weather so we travel around it. -
Thanks
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RV solar power systems and A/C. Not a good match in general. If you can find an "inverter-compressor" type AC (or heat pump) system, that can help a lot... Inverter type systems tend to have no surge current, and when you dial back the cooling, the smaller units can get down to 400 watts or less. Much easier on the power system. LG is making a window based inverter A/C. And many of the mini-splits (such as Panasonic) also have inverter based models.
Hopefully, some folks here can add their comments if they have an A/C equipped RV and what they are doing.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Yea I understand, I recently had 2 6v 225ah deep cycle batteries on our RV and while it would power the ac it would only power it for about 15 mins due to lead acids huge voltage drop. I have done some research on camper AC units and I have seen people with 13500 BTU units and only 200ah of LifePO4 run for an hour and a half safely. I do not intend to run ours that long, just long enough to cool the camper down in times of extreme heat before bed, or if it is raining and we cannot open the windows. So I figure that just to start our 300ah with our 12500 BTU unit will be good. LifePO4 cells on aliexpress are pretty darn cheap so I will prob be adding another 300AH for less than $900 sometime in the future, as well as 2 more 200 watt panels.I found dometic makes a invert-compressor model but it also uses 500 more watts at its lowest compared to ours according to the website.
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Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
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littleharbor2 said:Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.
I had been told on another solar forum to run the BMS on the charge side only, to not connect it to the inverter because a 3000 watt inverter would need two 250a BMS's in parallel turning that pack into 2 12 batteries.
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littleharbor2 said:Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.Like the first or second new diagram, or neither if you could explain.
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Rv_Adventure_Couple said:littleharbor2 said:Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.
I had been told on another solar forum to run the BMS on the charge side only, to not connect it to the inverter because a 3000 watt inverter would need two 250a BMS's in parallel turning that pack into 2 12 batteries.Or do you mean like this? I was told like this the inverter would burn up the bms. is this true, if so can you tell me why?
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Using 12V nominal is a mistake with large loads, my opinion naturally, 24V would be better, allowing the same batteries to be utilized in a 8S arrangement. The BMS should be sized appropriately to handle the loads as it is responsible for over discharge protection, the low voltage disconnect of most inverters, designed for lead acid batteries, is far to low for LFePo4 and will cause permanent cell damage.
LiFePo4 are very sensitive to low and high cell voltages, the extreme speed at which the voltage collapses near the discharge knee is incredible making overdischarge protection essential. This phenomenon will be amplified at the high discharge currents associated with lower voltages.
Based on experience using an inverter type 9000 btu 26 SEER AC unit which uses 500W maximum, powered by a 24V nominal 400Ah LiFePo4 bank in a 200 square foot room, my opinion is your useage would be very limited. Actually I'm surprised a 12500 btu unit would be 120V not 240V, to tame inrush when the compressor starts up.
You really need to think this over if the system needs to be reliable.
.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding. -
If an inverter is capable of burning up a BMS, then the battery bank/BMS (they work as a pair) is too small or the inverter too big.
a 3Kw inverter on a 12V system is STUPID DANGEROUS. 3Kw at 12V 90% efficient is 275 amps. I defy you to find a 12V 3kw inverter under $500, that has internal wiring that is safe at nearly 300A.
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister , -
The bottom pic looks right to me.Rv_Adventure_Couple said:littleharbor2 said:Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.Like the first or second new diagram, or neither if you could explain.
I agree with others here regarding the 12 volt inverter. Can you sell it and get a 24 volt version?
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
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littleharbor2 said:
The bottom pic looks right to me.Rv_Adventure_Couple said:littleharbor2 said:Looks like the neg. output of the CC connects directly to the battery. It really needs to connect to the shunt to monitor the battery charging.Like the first or second new diagram, or neither if you could explain.
I agree with others here regarding the 12 volt inverter. Can you sell it and get a 24 volt version?I am looking into returning it for a 24v, one of the two belowThen I will just run all of the cells in series for 24v 150ah bank.So to be clear - instead of the bms connecting direct to the batteries main negative, I should run it through the shunt's loads side and connect the shunt direct.The charge controller wont be an issue as it can switch between 12/24, so I guess this is what I am going to do.
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Guess you already made the purchases. I'd be in favor of running a genset when boondocking. You face several challenges with solar and RVing and wishes to run A/C. 400 watts of panels is probably too little. Then again, I don't know the particulars of your RVing. The campsites I have used are generally heavily wooded - a disaster for solar. If you camp in the open the sun heats your RV faster than a 400 watt panel can cool it - I would think.
Why not use more solar panels? Another possibility is charging the batteries with genset or shore power.
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
The BMS needs to be connected directly to the battery negative in order to provide protection, the shunt should be downstream of the BMS, failure to do this will negate all protection if the connection of the shunt were to fail .
Should the BMS be incapable of supporting the required current then a suitable one should be sourced, don't mess around attempting to bypass the safety features, that would be a fools game. The BMS needs to have priority, that can only be achieved if it is first in line, better yet get a bi directional BMS with separate charging and dischargeing ports, they can be had for around $1001500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding. -
mcgivor said:The BMS needs to be connected directly to the battery negative in order to provide protection, the shunt should be downstream of the BMS, failure to do this will negate all protection if the connection of the shunt were to fail .
Should the BMS be incapable of supporting the required current then a suitable one should be sourced, don't mess around attempting to bypass the safety features, that would be a fools game. The BMS needs to have priority, that can only be achieved if it is first in line, better yet get a bi directional BMS with separate charging and dischargeing ports, they can be had for around $100I have revised the diagram, am I correct in this draw up?
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Much better. Use the smallest inverter that you can. Why not two 400 watt panels?
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
softdown said:Much better. Use the smallest inverter that you can. Why not two 400 watt panels?
I had already purchased the 2 -200 watt panels a year ago, I have been kinda building the setup in stages so it wasn't as much of a financial hit. I have room in my CC and roof to put 2 more - 200 watt panels if it comes to that.
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I made a similar mistake at first. Too much battery and too little paneling. There are 100 pitfalls waiting for the newcomer. I really think you need more panels. How much are these 200 watt panels you bought and/or can buy?First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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softdown said:I made a similar mistake at first. Too much battery and too little paneling. There are 100 pitfalls waiting for the newcomer. I really think you need more panels. How much are these 200 watt panels you bought and/or can buy?
$185 US each, however the ebay supplier I got them from is out of stock currently
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If you can get more panels they need to closely match what you have.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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softdown said:If you can get more panels they need to closely match what you have.
Just checked, the same seller has some 210 watt panels same amperage, is that close enough?
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You need to match Vmp for parallel connected panels within 10% or better.For series connected panels, Imp needs to match within 10% or better.BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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BB. said:You need to match Vmp for parallel connected panels within 10% or better.For series connected panels, Imp needs to match within 10% or better.Billcurrent panels are vmp 21.052 and imp 9.50, the ones i found are 22.4 and 9.30So if I did my math correct I can series and parallel them?
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One more question. Being that my CC is 150v / 40a mppt does that mean that I could run 4 of those panels in parallel since they are only 9.5 and 9.3 amps
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