# Going nuts need input!

Posts: 15Registered Users ✭✭
Hey guys, I have looked at and ran dozens of calculators for my loads and come up with watt hours amp hours and kWh etc etc and it’s driving me nuts.

i just need simple dumb down awnsers.

I will be installing 1000w of panels on the ground in southern New Mexico connect to a midnight classic feeding three 200ah gel batteries run to a rengoy 2000w inverter/charger, I am trying to keep my 9.9cu ft fridge and 5cu ft chest freezer powered overnight without going below say 50% of my battery’s. The entire tiny house with everything turned on draws 2000w or about 17 amps minus two laptops and a 32” lcd tv. I have to run a gen for the ac in the summer months and am ok with having to top off at night sometimes, but with a normal useage two people home all the time up from like 6 to 10 will this system be enough or do I need more
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• Posts: 4,668Solar Expert ✭✭✭✭
Not knowing your loads we won't be able to give you specific answers. If you only need to run the fridge and freezer over night and have full batteries, you are likely fine, I am assuming they are 12 volt deep cycle batteries? Gel is generally a poor choice, many people get AGM confused with Gel batteries. Gel batteries tend to only absorb current (amperage) at a lower rate and don't handle high discharge rates very well. (from my feeble memory) I think they do handle heat better - fwiw.

Something to keep in mind is Amps x Volts = Watts

So you have 3 - 200AH batteries at 12 volts. The math is a 3 x 200 = 600 ah at 12 volts
Amps x Volts = Watts so 600x12=7200 watt hours.

Your home running on 2000 watts or 17 amps, is at 120 volts, so 17 x 120 = @2000 watts but as a draw from your battery bank, it looks more like 2000 watts x 1.17 since the inverter runs at around 85% (85/100=@117) or 2000x1.17=2340 watts

2340 watts/12 volts = 195 amps or 195 amps at 12 volts or 1/3 of your battery bank capacity. In fact your battery bank is rated at a discharge of 1/20th of it's capacity, when you draw more than that your effective battery capacity is less.

I'm sure you've seen this before, but each time you see it, you'll relate/understand it a little more!
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 2,164Solar Expert ✭✭✭✭✭
The two cooling loads, refrigerator and freezer, are the loads of concern, which may require a larger array, there comes a point when moving to the next voltage is a wise decision, to increase the PV without changing the controller, naturally the inverter would be incompatible, including batteries, a pragmatic approach would be to change to a higher voltage, but without clear load demands , speculation is as close as one could get.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank

• Posts: 2,750Registered Users ✭✭✭✭
Like Photowhit says, getting a good handle on loads is the key to a well balanced system. Using something like a kill-a-watt meter to measure actual consumption would be a good start.

Absent that, a rough guess is the fridge and freezer will use ~3000 watt-hours per day. Another 1-2000wh/day might be a reasonable wild guess for other loads in a livable but efficient home (but not including air conditioning).

In southern New Mexico, you likely have some good sun, ~6hours full sun equivalent according to pvwatts.nrel.gov. 1000w of panel will produce ~750w at reasonable operating temps, so around 750x6=4500wh/day, which may or may not be enough to cover your daily loads. With battery and inverter losses, my guess is probably not, but without measuring or better estimating actual daily consumption, it's just a guess.
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
• Posts: 15Registered Users ✭✭
edited October 2017 #5
Yes the battery 12V, everything came from Renogy:

https://www.renogy.com/renogy-1000-watt-12-volt-monocrystalline-solar-cabin-kit/
https://www.renogy.com/renogy-2000w-pure-sine-wave-inverter-charger/
https://www.renogy.com/renogy-deep-cycle-pure-gel-battery-12-volt-200ah/

Ok the fridge and freezer according to there yellow tags use a combined 43KWH a month. I have 10 60W LED 120V replacement bulbs 1000W AC draw microwave 700W output, a toaster and coffee maker that are like 600W a pop, two HP laptops that come stock with 45W power bricks a 32" LED TV likely a sat receiver and some cell phone chargers.

Use wise I can see 3-4 lights a day going for 5-6 hours, Laptops (2) and TV sat reciver going close to 16 hours a day Fridge Freezer 24/7 microwave maybe 15-20 mins a day, hour coffee pot and 5 mins toster.

All of these goodies will be mounted to power strips to kill off all power off at night, "TV laptops chargers etc"

Is it worth while to covert the TV Laptops and Phone charges to the 12V style cig lighter?
Is it worth while installing 12v lighting?
Would one more battery and say two more 250W panels give me any benefit?

• Posts: 78Registered Users ✭✭
OK, just refrigeration only is ~1400 watthours per day (43kwh/month / 30days = 1433 watthours).  Lets say for simplicity the rest of your stuff uses another 600 watthours.  So, your daily needs are at least 2000watthours, or 2.0kwh.  You are really handicapping yourself by limiting the battery bank to 12V.  Even with 3 batteries 200ah X 12V X 3 batteries =7200 watthours total.  Assuming you don't want to deplete the batteries more than 50%, that's only 3600wh.  For loads like this your better designing a 24V system using significantly larger batteries, say Trojan L16's.  Assuming their capacity is ~420ah X 24V =10,080wh, about 2000wh per day consumption would result in 20% depletion of the batteries, a much more acceptable rate of consumption.

With that setup, a better charging system would be (10080wh / 8)= 1260 watts.  1260w /0.8 derating) = 1575 watts.  I'd purchase two more of those 255 watt panels, then wire them in a 2S3P configuration.  Can you return the inverter to get your money back?  I'll assume you can't return the batteries.  Maybe at this point the best thing you can do is buy one additional one of their batteries, wire the four batteries in a 2S2P configuration, then use that to power a 24V inverter.  That would work out to (200ah X 2 strings X 24V= 9600wh) In a couple of years after you've trashed these Renogy batteries you can replace them with bigger Trojans.

BTW, my own system started with Renogy's 3600W cabin kit, but I myself added an additional three-300watt panels.  With that I'm running a 1.5hp well pump for 6-8hours per day, with hardly any battery depletion (48V Schnieder inverter).  But, I've already purchased enough panels for an additional array, because I'm greedy for even more power!  My first system had also been 12V, but I've learned from my mistakes and have designed a second-generation system that puts the first to shame.
15 Renogy 300w panels,  Midnight 200 CC, 8 Trojan L16 batteries, Schneider XW6848 NA inverter, AC-Delco 6000w gen.
Full time off grid usage? Not emergency backup?

If so, then you are probably way under designing the off grid power system. Some warnings:
• refrigerators/freezers use more power in summer than winter. They use more power freezing ice, cooling fresh food, and just opening the door often (if you have kids). While the Energy Star tags seem to be good for new appliances, as they age, they do draw more power (condensers get dusty, parts wear, etc.).
• In general, in the US, GEL batteries are typically designed for UPS applications (uninterruptable power supply for computer backup). And many mfg. have a 5% rate of charge maximum limit. So, if you use 50% of battery capacity with a 5% rate of charge every day--That takes 10 hours of full sun + 4-6 hours of absorb charging to fully recharge a typical lead acid battery bank--At best, you only have ~6 hours of full sun per day and a few more hours of declining sun.
• Bad weather, temporary heavier loads (guests), etc.--You should be planning on using (on average) about 65-75% of your predicted available solar power per day. When you have good weather, run the vacuum, washing machine, well pump to top off the cistern/water the garden, etc.
• Using 120 VAC vs 12 VDC... For smaller systems, 12 (and 24) VDC can be interesting solutions. However, if your average 85% efficient 120 VAC inverter is used instead, just make the system (1/0.85=) 1.18x larger to account for the inverter losses. Much easier to send 1 amp * 120 VAC (120 Watts) 100's of feet over normal wiring vs 10 amps * 12 vdc (with 0.5 volt maximum drop) (typically, only efficient over 10-20 feet). DC to DC converters (12 vdc to 19 volt computer adapter) are just about as efficient as a 120 VAC inverter--They do not save much energy, limit you to 12 volts, and many times do not "like" the wide 12 VDC battery bus voltage of 10.5 to 16.0 volts or so (discharged battery to equalizing charging).
For a full time off grid home, just to give you some number--I like to suggest a 3.3 kWH (3,300 WH) per day system for a refrigerator, LED lightning, LED TV, laptop computer, router, satellite dish, well pump, washing machine, etc. Such a system might look like this (continue posting on next page):
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Posts: 15Registered Users ✭✭
edited October 2017 #8
Sadly I can't return anything, It's been over a month since I bought all this stuff. Yes it's full time off grid home (well 40ft school bus) No wells or pumps just a 12V RV water pump from a above ground 2500 gallan tank. No kids no guest's two people no gardens

Why are they selling these batteries for solar use if they are UPS battery? And only meant to last a few years? I was hoping to get 10 years out of this system I have a lot of money tied up in those batteries

Thanks guys for all the help and feedback really helpful.
Using our (relatively) conservative off grid rules of thumb (give you a reliable system, batteries will last many years, you don't have to plan every day/activity based on hours of sun per day, can use 120 VAC/240 VAC appliances that are Energy Star rated--And with good conservation practices on your part):
• 3,300 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 maximum discharge * 1/24 volt battery bank (minimum bank voltage) = 647 AH @ 24 volt battery bank
Assuming you choose flooded cell or AGM (not GEL), 5% to 13% rate of charge for solar is typical. 5% for weekend/summer season cabins, 10%+ for full time off grid:
• 647 AH * 29.0 volts charging * 1/0.77 panel+charge controller deratings * 0.05 rate of charge = 1,218 Watt array minimum
• 647 AH * 29.0 volts charging * 1/0.77 panel+charge controller deratings * 0.10 rate of charge = 2,437 Watt array nominal
• 647 AH * 29.0 volts charging * 1/0.77 panel+charge controller deratings * 0.13 rate of charge = 3,`68 Watt array "cost effective" maximum
The above calculations are based on battery bank size (larger battery bank, needs larger charging current for long battery life). Then you need to base the sizing of the array on your daily loads and hours of sun per day. Fixed array, facing south, for Butte Montana:

### ButteAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 44° angle:
(For best year-round performance)  Jan Feb Mar Apr May Jun 2.70 3.70 4.67 5.13 5.10 5.37 Jul Aug Sep Oct Nov Dec 6.07 5.86 5.15 3.89 2.82 2.31
And the first thing we see is that 6 hours per day is for July only... Say you want to not run a genset for 9 months of the year (just winter)... That would give you February of 3.7 hours of sun per day (break even month for genset):
• 3,300 WH per day * 1/0.52 off grid AC system efficiency * 1/3.7 hours of sun (Feb) = 1,715 Watt array minimum (Feb break even month)
For the above system, you would need a minimum of 1,500 Watt (24 vdc) AC inverter (to start the refrigerator/freezer). And for a 647 AH @ 48 vdc flooded cell battery bank, a maximum of (500 watt inverter per 100 AH @ 48 volt battery bank) ~3,235 Watt AC inverter (useful/reliable for flooded cell battery bank)... Or roughly a [email protected] to 4kW maximum 24 volt inverter.

If you think you will want a larger system in the future, think about a 48 volt system now or in the future.

The above is a starting point for discussion. Lots of assumptions. My "optimal" energy usage will not be your optimum energy usage. Power needs are highly personal.

I have shown the equations and where to look up further data/information and my assumptions. Questions/updates to my guesstimates?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Posts: 15Registered Users ✭✭
edited October 2017 #10
BB Thanks for the input, I live in Butte (Anaconda) for the moment, but the system will be installed in Southern New Mexico were my bus will be parked. I am not worried about trying to make it two days, I have no issue with running the Genset a few hours on cloudy days. But not something I have to do every day I hope
• Posts: 15Registered Users ✭✭
With a 57 degree angle in Dec I would get 4.75 hours so that means a 800 watts out of a 1000W panel setup would give me about 4000WH?
• Posts: 639Solar Expert ✭✭✭✭
edited October 2017 #12
@bigskypc50
So, If you've already bought the equipment and can't return it, then might as well make the best of it and install the system. I think you will need another battery, and may need 2 more panels, but wait until the system is up and running to see what you really need.
Many solar enthusiasts buy equipment before they know what they really need. So we'll try to help you get things going with any questions on installation if that's what you would like to do.
I do make one initial recommendation. Wire the panels in 2 strings of 2 in series instead of 1 string of 4 in series as shown in the drawing. This will waste less power and make the Classic 250 a lot less noisy.

Rick
3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
• Posts: 5,087Solar Expert ✭✭✭✭
So far there has not been any discussion of actual use / PV needs for fridges.  For example we have a GE 18 cu ft Top freezer rated at 319kWh/ yr .874kWh /day  so lets call it 1 kWh per day for simplicity..and that it does consume more than that at times... number of times door opened, fresh food added, warm refreshments etc, all add to the power used... .  Yes it can run at that low consumption in the spring and fall, winter is below that and summer higher, mind you occupancy in winter raises the ambient temp ,, again an upward pressure...
Now, in winter I use 1680 (name Plate) watts of PV and is a good example of the 70% (actual) efficiency figure we apply to PV output. This also accounts for some other losses too, inverter, battery, wiring etc.
In Summer I can run the fridge etc on ~ 1120W if I get FULL sun hours, after 2 days no sun I am getting the charger out...
Don't forget that in the day time if the draw is more than the Sun is producing, the extra comes from the batteries.
Just my experiences.......

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
Or even better (what town did you use?):

### Las CrucesAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 43° angle:
(Optimal winter settings)  Jan Feb Mar Apr May Jun 5.45 5.81 6.39 6.25 5.73 5.35 Jul Aug Sep Oct Nov Dec 5.06 5.07 5.55 5.82 5.60 5.15
• 4,000 WH per day * 1/0.52 off grid AC system eff * 1/4.75 hours of sun per day = 1,619 Watt array "break even"
If you are planning on being full time off grid (>9 months of the year), the problem is that a 50% discharged flooded cell lead acid battery bank just takes too much time to fully recharge (more hours of charging vs light in the day--10% rate of charge 5 hours + 4-6 hours of absorb--You might need the genset ever day or few days to get ahead of a (possible) deficit charging bank.

If the physical size/weight of the battery bank is of concern (RV/Bus--Not an uncommon issue)--Perhaps looking at LiFePO4 type would be a better choice (no absorb stage). LiFePO4 batteries are not cheap, but they can work well. You would be at the cutting edge of battery technology...

Perhaps one of the battery experts here can recommend an AGM type battery that would work better with 50% daily discharges.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Posts: 639Solar Expert ✭✭✭✭
OP's battery has a 20% charge rate. Pretty good for a GEL.

Renogy Deep Cycle Pure GEL Battery 12V 200Ah
Cells Per Unit: 6Voltage Per Unit: 12
Capacity: [email protected] to 1.75V per cell @25°CWeight: Approx. 132 lbs
Max. Discharge Current: 2000 A (5 sec)Normal Operating Temperature Range:25°C±5°C
Float charging Voltage: 13.6 to 13.8 VDC/unit Average at 25 °CRecommended Maximum Charging Current: 40A
Dimension:20.6X9.5X8.6 In.Container Material: A.B.S. UL94-HB, UL94-V0 Optional.

Rick
3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
• Posts: 4,668Solar Expert ✭✭✭✭

Looks like it can handle high discharge as well!

Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 15Registered Users ✭✭
edited October 2017 #17

Ok guys sorry being dense, check my thought and see if I am on the right track!

My daily usage sounds like it will be about 2400watt hours so with 1400WH being fridge and freezer. And lets say 1000WH with other stuff.

So it sounds like I need to add two more 200AH batteries so that in turn 30% of the 5 200ah bats is 3600wh out of 12000wh total

Then I need to add 2 more panels for a total of like1500W with what output of 1300 Watts x 5hours a day 6500wh per day being divided to  useage 3000wh max and battery recharge 3000wh max.

Also someone said above to 2S3P for the panels I assume that means three panels plus to minus with a plus and minus on each end of three panels, then splice those two together. So I have two plus minus wires going into my combiner box?

Also the inverter use's 4a on idle is that included in my overhead above or would it worth while to turn off the big inverter at night and just run a small one at night for the fridge and freezer and lights.

• Posts: 2,750Registered Users ✭✭✭✭
2S3P would be wired in pairs of series connected panels (+ to-), leaving one + and one - per pair. The + wire for each pair goes to a breaker in a combiner box, which in turn combines on a bussbar with the + wires from the other two pairs. The three negative wires are combined on a negative buss in the combiner.

Your description would be 3 in a series string, 2 strings combined in parallel.

At single + and - go from the combiner to the controller, carrying roughly Imp amps x 3 at Vmp volts x 2.

You probably won't be able to run fridge and freezer overnight on a much smaller inverter. They'll generally start and run at different (keeping the inverter out of search mode, if it has one), but could start at the same time. A small inverter might fault and need manual reset, so probably better to just live with the self-consumption loss than risk a freezer full of thawed food in the morning.
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
• Posts: 15Registered Users ✭✭
edited November 2017 #19
OK I will be adding two panels so that I have three sets of two panels, however I only have one MNEPV10-300 breaker, do I need two more of those? Or do I need two sets of Y connectors? Also why to the breakers have plus and minus signs on them when clearly the negative go's to the negative bus bar?

Also can I mix in a sealed lead acid AGM battery to my 4 sealed lead acid GEL batteries bank?
• Posts: 4,668Solar Expert ✭✭✭✭
Also why to the breakers have plus and minus signs on them when clearly the negative go's to the negative bus bar?
They are just breakers and used for other things, I think you are talking about a comb used to connect multiple breakers in a combiner? Like the combs at the top of these boxes?

But they are also used in other breaker boxes with out combs and they are polarized!

Like those in the top left here, I think they have been importing non-polarized breakers for a couple years now, likely using the remaining stock in Combiner boxes.

Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 4,668Solar Expert ✭✭✭✭
I would not mix different types of batteries or old and new batteries, perhaps if they aren't too old <6 months, some say 1 year...
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 639Solar Expert ✭✭✭✭
OK I will be adding two panels so that I have three sets of two panels, however I only have one MNEPV10-300 breaker, do I need two more of those? Or do I need two sets of Y connectors? Also why to the breakers have plus and minus signs on them when clearly the negative go's to the negative bus bar?

Also can I mix in a sealed lead acid AGM battery to my 4 sealed lead acid GEL batteries bank?
You don't need the more expensive 300 volt breakers. You can use three 15 amp 150 volt breakers like these:
https://www.solar-electric.com/mnepv.html

If you have 4 of the 200 amp hour batteries, go with that for now and see if it meets your needs.

Rick

3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
• Posts: 15Registered Users ✭✭
edited November 2017 #23
Thanks guys for giving me all of this help! The batteries are all brand new 200AH 12V Four GEL and One AGM.

The kit I bought included a MidNite Combiner Boxes MNPV6-250 and a MidNite Solar MNEDC- Quad Enclosure, I assume the one breaker with two studs on it go's in the quad box what every that is.

So I would need three of those 15AMP 150V Breakers?

The kit is here
https://www.renogy.com/renogy-1000-watt-12-volt-monocrystalline-solar-cabin-kit/
• Posts: 639Solar Expert ✭✭✭✭
As Photowhit indicated, I would not use the AGM battery with the GELs.
Looks like the MNPV6-250 will work with the 150 volt breakers (yes you need them) installed in positions 2, 4 and 6.
The Quadbox is for the installation of the MNEDC100 CC to battery breaker. You will need another one of this type rated at 80 amps for the combiner to CC cable.

Rick
3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
• Posts: 2,750Registered Users ✭✭✭✭
Gotta go, but on a polarized DC breaker, both ends connect to the positive wires. The "+" side of the breaker connects to the current source *in a fault conditon*. For example, a charge contoller to battery connection *normally* has the current coming from pv. In a fault condition, it shorts the battery, so the "+" terminal connects to the battery (opening the circuit on the positive wire between battery and controller.
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
• Posts: 9Registered Users ✭✭
Never combine batteries of different types. Bad JuJu.

Here is how your kit is intended to be installed:

4 x 255W panels in series -> 10 AWG -> Midnite combiner box (PV6-250) w/ the 10-300 breaker installed in it -> 10AWG -> Charge Controller PV in.

Then:

Charge Controller Batt Out -> 8AWG -> [Breaker that was not included - Recommend 40A] -> 8 AWG -> [Batt + Bus not included] inside Quad Enclosure -> 4AWG -> 100A Breaker -> 4AWG Batt + Terminal

Your kit is intended to be run at a minimum of 24v.

Denver Area
Off Grid: 1.2kW, 48V, Midnite Kid, Grundfos SQFlex
Industrial design and automation.
• Posts: 15Registered Users ✭✭
edited November 2017 #27
OK guys I am getting confused!  If I look at the next kit up on renogy the 2kw kit, they show two strings of four panels, and then they included two "MNEPV10-300" breakers everything looks the same and says it's meant for a 12v battery. Why is it meant to run at min of 24V

So since I am adding two panels to my kit (the 1KW) I will end with up three strings of two panels so I would need to order two more MNEPV10-300 or the 150's breakers. Then I should be pushing 155 volts DC at 25 amps into my charge controller, I assume the charge controller will step that down to charge my 12V batteries, how many amps will that be dumping into my battery bank?

• Posts: 4,668Solar Expert ✭✭✭✭
In the end, by the time you have a properly designed system, you'll learn enough about solar to write and complain to renogy about this crappy system.

There is a place for this system, but only if the panels are very remote to the cabin.

A combiner box isn't needed unless you have more than 2 strings of panels. The Midnite Classic 200, is designed for higher voltages, which is fine but not needed if you will be using a combiner box and/or if your panels are near your battery bank.

So... knowledge data base, generally you will have less loses in heat if you run the array voltage closer to the battery/system voltage.

If you are adding 2 additional Renogy 255Watt panels, you will have 1530 watts coming into the charge controller. Solar panels typically produce 75% of their panels rating, this is called Normal Operating Cell Temperature (NOCT) value. If you just work with the Panel values and plug them into Midnites string sizing tool, you will find that you are well over paneled. If you were using a midnite 150 you would be in the cost effective range.

http://www.midnitesolar.com/sizingTool/

PDF with the info provided is attached.

Basically the math is you will have 1530 watt array, which under NOCT will produce 1530x.75=1147.5 watts, when charging your 12 volt battery bank you will charging at roughly 14.4 volt When you hit Absorb, 1147.5watts/14.4amps =79.7 amps.

The maximum allowable current for the Classic 200 is 79 amps. I don't think you are too far out of bounds. But pushing electronics to the limit is hard on them. You should be able to limit output and Midnite classic may be self limiting to 79 amps. When you have a very weak battery, say you have taken it down to 40% state of charge ad are bulk charging at 12 volts, you will only have the 79 amps available max.

Combiner boxes are normally used near the array so you only run a single set of wires to the charge controller, I would suggest having a shut off between the array coming in and the charge controller also, a single breaker. This might be what Renogy was thinking, when they had a combiner box for a single string of panels (as diagramed in the kit).

Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 4,668Solar Expert ✭✭✭✭
Normally it's recommended to switch to a higher voltage system when you go above 1000 watts, for just this reason, at 24 volts you could handle a 2300 watt array on the same charge controller. So this piece of equipment doesn't need to be duplicated. Again generally we would recommend 48 volt system voltage above 2-3000 watts. You can effectively use about a 3000 watt array on a Classic 150 at 24 volts.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
• Posts: 639Solar Expert ✭✭✭✭
OK guys I am getting confused!  If I look at the next kit up on renogy the 2kw kit, they show two strings of four panels, and then they included two "MNEPV10-300" breakers everything looks the same and says it's meant for a 12v battery. Why is it meant to run at min of 24V

So since I am adding two panels to my kit (the 1KW) I will end with up three strings of two panels so I would need to order two more MNEPV10-300 or the 150's breakers. Then I should be pushing 155 volts DC at 25 amps into my charge controller, I assume the charge controller will step that down to charge my 12V batteries, how many amps will that be dumping into my battery bank?

You can order 2 MNEPV10-300 breakers or 3 MNEPV15-150 breakers, the 300 volt breakers are about 10 dollars more. Your choice. The string voltage of two 255 watt panels in series is about 75 volts. Charging amps should be near the charge controller max, about 75 amps. Close to a 10% charge rate for an 800 amp hour battery.

Rick
3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
• Posts: 15Registered Users ✭✭
edited November 2017 #31
Ok guys thanks for the input will I kill my controller with that setup? I wish I had a 24v 2000w pure sign wave charger so I could up my voltage. But dumb me got a 12v one
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