"The Nest" and its solar setup

scrubjaysnest · November 2014

We have a pop-up style trailer, actually its called a bifold. Since it is a hard sided folding camper real-estate for solar panels is a premium. There is room for two 2x3 foot panels on the back when closed. Our solution was to have the panels movable around the camp site more because of sun then anything. Living in Fl the first thing you want in a camp site is shade.

What we have, a RV kit of 2 80 watt panels, Imp 4.47 A, Vmp 18.1 V, Isc 5.08A, and Voc 22.3 A. The kit included a MS Sunsaver 10 and 30 feet of NEC approved 12 AWG wire with MC4 connectors. The wire went straight to the scrape wire bin. Made up an extension cord from 10 AWG marine grade wire(15 feet) and MC4 connectors at the solar panels. This still left about 7 feet of interconnecting 12 awg wire. Over all it has worked well since 2012. I have even measured 10.5 amps from the cc to the batteries under perfect sun conditions. But I couldn't reach the absorb voltage Interstate batteries wanted.

Some background: all lighting is LED or Fluorescent. Loads as measured with a Sears clamp on 0.14A for a single LED assy(26 SMD's) and 1.34A for the fluorescents. Two pumps @ 4.58A. A ceiling vent fan on low 0.23 A, 0.01 A for the CC and then the furnace is 3.44A during ignition, 3.03A during the heating cycle and 2.85A for cool down. From this our loads are fairly low for several reasons. One pump isn't used, the pump is used 3 or 4 times for about 10 seconds each time. The furnace is only used to take the chill off in the morning and can cycle 2 to a max of 5 times in a two hour period.

We were boarder line or slightly below on getting the 5% minimum charge rate for the Interstates. This year we up graded from the 95aH Interstates to a pair of 105aH Exides. Changes in progress to address this. Replaced the Sunsave 10 with a TS-45; over kill I know for two 80 watt panels. But plenty of expansion room. Current inverter is 400 watt, draws 6.35 amps when charging a laptop and netbook. Takes 3 hours for the laptop.
The extension cord between the solar panels and the new CC will be 8AWG, I think 25 feet, replace the 12 awg panel interconnections with 10 awg and make as short as practical. Terminate the extension cord at the CC also gets ride of 2 feet of 12 awg.
Wiring from the CC to batteries is 8 AWG; and the parallel connection of the two batteries has been up graded to 4 awg, to better balance the batteries.
May add a pair of 100 watt panels if we decide to put in a small microwave(900w). That means a larger inverter about 1500W.

Anything I missed? Oh, the TS-45 uses 0.05 A vs 0.01 for the SS 10
For now I have the TS-45 set for L-16 battery which gives 15.03 volts at the batteries during absorb. Exide calls for 14.7 to 14.9 so I may drop it back.

But on a cloudy day like today only saw absorb for 30 minutes so may require further thought. Need to check the SG on the batts when I get them up to 100% again.

Cariboocoot · November 2014

Re: "The Nest" and its solar setup

Given the distance between the array and the charge controller combined with the increased battery bank capacity (105 Amp hours X2 = 210 Amp hours if this is two 12 Volt units in parallel) you probably should have gone with an MPPT type charge controller and a couple of larger panels connected in series.

The TriStar 45 PWM is $160 whereas the SunSaver MPPT 15 is $225 and would solve the long-run problem.

If you have two 80 Watt panels and you're scraping 10 Amps out of them that's pretty amazing. It's also about half what that much battery should have (if I've got the bank size right).

A SS MPPT15 maxed out with about 234 Watts of PV would serve you better, but of course there are always issues with fitting panels in space (and budget) available. That controller alone could be advantageous to you even with the two 80 Watt panels.

scrubjaysnest · November 2014

Re: "The Nest" and its solar setup

I had looked at the ss 30 models before making the decision on the TS-45. A couple of reasons for my choice: Didn't think I would achieve the desired absorb voltage from the ss 30's, probably an incorrect thought; The NEC limits would have the ss 30's limited to a max of 24 amps using the 80% rule. From the limited testing done by others mppt doesn't pay below about 400 watts of array. Next month when we reach Yuma I can pick up a pair of 100 watt panels @ $.94/watt(current price). These panels will be a close match for the 2 80 watt panels I now have. The 80 watt panels shouldn't suck down the voltage the 100 watt panels produce very much. At ~.32 volts drop for the 25 foot run of the 8 awg wire @ 10 amps(not usually seen) that would be a 3.2 watt loss. Now at a total of 360 watts for the four panels a ss 30 mppt might have been a better choice. Using the four panels in a series/parallel combination may also be a choice. The manual isn't real clear if the TS-45 will take a 24 volt input.

update
At the present time. 10 AM est, and 50 deg F both panels are holding at 19.34 to 19.42 vdc as measured on a fluke 787 and 2.4 amps as measured with the sears clamp on.
CC is in absorb mod with 15.09 vdc at the batteries. the wire run is 5 feet of 12 awg connected to 20 feet of 10 awg via mc4 connectors. At the current presently measured the fluke isn't coming up with a significant volt drop, bouncing between 2 and 3 mV. This will get worse once the current goes up.
From Exide absorb should be "Charge with 14.7V - 14.9V limit for 12 to 24 hrs or when current drops below 1% of the C20 rating (example; C20=100Ahr, the low current shut off is 1%x 100 or 1A)."

Cariboocoot · November 2014

Re: "The Nest" and its solar setup

Okay, which TriStar 45 did you buy? One of them is a PWM and the other (more expensive) is MPPT. The PWM version will not down-convert higher array Voltage, the MPPT will. That is where you are losing power; trying to run long wire from the array in the sun to the controller

There is no part of NEC which limits the SS MPPT15 or TriStar 30 or 45 to 24 Amps. The derating for continuous devices is debatable for charge controllers as they probably will not be at their maximum power for 3 hours straight. Basically the NEC is not applicable to mobile installations anyway.

If your battery bank is now 210 Amp hours @ 12 Volts 10 Amps is going to be very minimal charge rate and they are not going to last very long. You either have to up that rate or periodically recharge from another source to achieve full charge.

scrubjaysnest · November 2014

Re: "The Nest" and its solar setup

Cariboocoot wrote: »

Okay, which TriStar 45 did you buy? One of them is a PWM and the other (more expensive) is MPPT. The PWM version will not down-convert higher array Voltage, the MPPT will. That is where you are losing power; trying to run long wire from the array in the sun to the controller

I have the TS-45 PWM

There is no part of NEC which limits the SS MPPT15 or TriStar 30 or 45 to 24 Amps. The derating for continuous devices is debatable for charge controllers as they probably will not be at their maximum power for 3 hours straight. Basically the NEC is not applicable to mobile installations anyway.

The TS-45 owners manual says NEC requirments are to limit it to 36 amps; which is 80% of 45 amps. The manual for the ss 10 doesn't say anything about de rating but like the TS-45 it must be wired per NEC. Specifically they say wiring needs to clamped/ty-rapped to limit movement in mobile applications. RVIA also requires RV's wiring to meet NEC. The NEC does have a section on RV's also but it is more directed at the fire codes.

If your battery bank is now 210 Amp hours @ 12 Volts 10 Amps is going to be very minimal charge rate and they are not going to last very long. You either have to up that rate or periodically recharge from another source to achieve full charge.

True, very hard to do any kind of bulk charge. Most times it is gotten from the tow vehicle when me move to another campsite. If we are at a site that has shore power I carry a 3 stage charger because the on board convertor is worse then the two solar panels.
The system settled out at float about 2:30 PM EST @0.45 amps and 13.45 volts. Exide wants float to be between 13.2 and 13.4 V at no more 1 amp, so it looks like the system made up the 4 weeks of self discharge while the batts were out of the camper. If I can find my hydrometer I'll check the SG tomorrow some time

BB. · November 2014

Re: "The Nest" and its solar setup

I do not understand the 80% derating of 45 amps for the controller... Do we somehow derate a 100 watt lamp to 80 Watts maximum? No.

What we do is rate the wiring/breakers to 1/0.80 to ensure that the wiring supports the loads per NEC requirements:

45 amps / 0.80 = 56.25 Amp rated wiring+breaker+etc.

If this issue is that you can get 1/0.80 x more sun in some cases (edge of cloud, etc.), then make the wiring bigger:

56.25 amps / 0.8 solar derate = 70.3 amp rated wiring+breaker

The mfg should have, designed their controller to run at rated power on rated panels.

One of things is with PWM controllers, the current from the solar array does not change due to temperature (or, to be exact, Imp-panel drops a tiny bit as the temperature drops). So temperature cannot be a factor here.

For solar panels Vmp rises as temperatures drop, so MPPT output can rise as panels get sub freezing (p=v*i). However, MPPT controllers can limit their output current to rated value (safely, reliably) because they are switching power supplies. A whole different animal vs PWM.

-Bill

Cariboocoot · November 2014

Re: "The Nest" and its solar setup

Bill;

I think it's an often-repeated misinterpretation of the NEC 80% rule for "continuous use devices" meant to apply to circuit breakers and wiring.

Since a charge controller is in "continuous use" (more than 3 hours by NEC) some think it should be derated. Certain manufacturers flat-out state that such derating is unnecessary with their units, and it is easy to see why: whereas the controller may be in operation for up to 6 hours the combination of bell-curve input and steady-decline output (under most circumstances) makes it highly unlikely the controller will put out its full power rating for 3+ hours.

It would have to be a heavily over-paneled MPPT unit with significant loads on a long, sunny day to do that I think.

In reality with a PWM controller as long as the Imp of the array does not drastically (20%) exceed the controller's maximum rating there is not likely to be an issue with a good controller.

scrubjaysnest · November 2014

Re: "The Nest" and its solar setup

I think ya'll may be right, especially when you look at the physical size of the heat sink on the TS-45 PWM CC. Some where some one had a problem that resulted in property damage or injury with maybe a resulting law suit and the resulting knee jerk reaction by regulatory agencies. The best protection is proper wire sizing and fusing/breaker sizing. We had to deal with this on our 125 vdc battery banks feeding a pair of 25kw inverters at the power company I used to work for.
The SS 10 PWM I had saw 10.5 amps out a couple of times but it was no more then 1/2 an hour. My main reason for changing out the cc was better absorb. But to finally achieve this end I need to increase panels and get rid of all the 12 and 10 AWG with 8 AWG. All the wiring upgrades are done inside the battery compartment. Although the trailer maker used an enclosed battery box with external venting, via hose, to meet RIVA requirement. When the trailer is closed down the exterior vent is covered. This is pretty unique to this trailer version, they make other versions where the batteries are tongue mounted. On ours the batteries go in an enclosed battery box inside a 3X3X2 foot enclosed storage area. For most RV'ers this won't be a problem.

Cariboocoot · November 2014

Re: "The Nest" and its solar setup

A lot of current handling capacity is a matter of being able to dissipate the generated heat. I know of one system using MidNite Classics on wind turbines where the owner complained about how the fans were on all the time: he'd not mounted them according to instructions, they were in a small and hot space, and were trying to handle their maximum current 24 hours a day. Naturally the fans were on all the time!

If the TS 45 can't actually handle 45 Amps for 3-4 hours a day they shouldn't promote it as a 45 Amp controller. It's as with anything else; there is a difference between peak current capacity and continuous. A lot of shady generator sellers promote the surge current their units are capable of rather than the steady output capacity. False and misleading.

scrubjaysnest · November 2014

Re: "The Nest" and its solar setup

The method I use(d) with the SS 10 and now the TS-45 will be to open the access door to compartment. One thing I have noticed and needs to be addressed is the SS 10 could be installed with the batteries but not the TS-45. This will require some major thought as the only other place to mount the CC is behind the shower, and to do this the shower will need to be removed. Another place would be the inside storage which joins the battery compartment. This will require external venting for air flow and a means to prevent flammable items, clothing, books, etc. from coming in contact with the CC. A third spot with good air flow is AC/DC distribution panel. That may be the best, no fire hazards but will require upgrading the wire from the CC to the batteries as that will be about a 6 foot run. Maybe 4 AWG or even 2 AWG. Got some of both. Running the RTS and sense lines a piece of cake; the bigger wire a bit of challenge.

scrubjaysnest · November 2014

Re: "The Nest" and its solar setup

Finally got around to checking the SG of the batts. First thing wish I had done this the day I brought them home from Tractor Supply. The at rest voltage has always seemed a bit high for 100% soc at 13.3 volts. The batteries are now 10 / 11 months old from date of manufacture. That was the closest I could match them. At 46 deg air temp, the hydrometer I picked up had been at that temp for over an hour, the SG is between 1.275 and 1.280. Seems high for a cold battery, we got down to 23 deg over night, but agrees with 12.78 rest voltage I measured. Its been 4 days since the batteries were last charged with the solar panels. By the way the hydrometer is the glass tube/ glass float type. Reading some of the other threads all I can say is the different numbers cross check each other but the values still seem to be a bit high.

scrubjaysnest · March 2015

After two months of winter desert camping the two 80 watt panels have showed how marginal the system is. They produced rated but....at 4 1/2 amps each that is below the desired 5% minimum. Although the batteries are reaching 100% soc it takes all day even as conservative as we are. Will have to add a third panel to cross that hump. If we had to do it over I think about 300 watts or so with 24 volt panels to reduce line losses with a Morningstar Pro 30 would be the way to go for us. Keeping the panels portable would be the big issue so as to keep weight down and handling size reasonable. Although pricey the Renogy flexible panels might be an answer. 4# vs the 17# per panel. Just some thoughts.

scrubjaysnest · March 2015

Well, bit the bullet and ordered a panel but just realized the KC120-1 is 16.9 Vmp vs the two UL Solar we currently have are 18.1 Vmp. Wonder what the over all impact will be? During boost We normally see about 13 volts input to the CC so things may not change much there other then getting over the 5% minimum. Absorb is where I expect to see CC input voltage a bit lower. Float shouldn't be an issue. Although equalize may be an issue, we move the camper enough it keeps the fluid in the batteries pretty well stirred up.

BB. · March 2015

You are using a PWM charge controller--Then during normal charging everything should be fine.

You could have some reduced current at Equalization on a cold battery bank (high battery voltage)--But for the most part, equalization is done at less current (around 2.5% to ~5%)--So, you should be OK.

-Bill

scrubjaysnest · March 2015

Thanks, Bill
That was my general line of thinking although I may drag my Morningstar Sunsaver 10 along and treat the Kyocera as a separate array after reading the thread on using more then one controller.
It is easy enough to set up and I may run everything through the TS-45 and then split for comparison. I'll have to keep in mind the roof mount isn't as efficient and looking the Kyocera over it appears to be a 13 year old panel but in good condition.

Got the used Kyocera 120 watt panel in yesterday; it's a little awkward for a portable set up at 2ft X almost 5 feet so will most likely end up on the roof of the trailer.
Laying flat on a ladder the panel produces 92 watts; not bad for the conditions

scrubjaysnest · March 2015

Ran a test today with all 3 panels in what may be their normal mode. 120 w flat, 2 80 watt at 30 deg. The CC was in equalize at 11:10 am est and had the following readings.
80 watt into the CC, 70 watt output
18.1 volt in 15.36 v out
4 to 6 amps in 4 to 6 amps out
Disconnected the 120 watt V in dropped to 17.5, amps stayed around 6
With the 120 watt carrying everything, 80 watt disconnected V in dropped to 15.35 and I in about 6 amps with 15.34 V at the batteries. I think this confirms earlier thinking the panels won't have a great affect on each other during equalize.

scrubjaysnest · April 2015

Have the Kyocera mounted to the roof using a hinge system to tip the panel in either of fore or aft direction. Took a little bit to get it worked out. Added a terminal strip to make easier local monitoring of CC input and output voltages.

scrubjaysnest · April 2015

Borrowed BB's, Bill's, figures and plugged in my numbers so things look better with the addition of the 120 watt panel.

WH usage based on battery bank
·
·
·
· " 210 AH * 12 volt * 0.85 AC inverter eff * 1/1 days storage * 0.50 maximum discharge = 1071 WH per day (RV/Boat)
· 210 AH * 12 volt * 0.85 AC inverter eff * 1/2 days storage * 0.50 maximum discharge = 535 WH per day (off grid cabin)
· 210 AH * 12 volt * 0.85 AC inverter eff * 1/3 days storage * 0.50 maximum discharge = 357 WH per day

Charging wise--Based on a 5% to 13% typical rate of charge. 5% is OK for weekend/seasonal use, 10% or above is recommended for full time off grid charging (and if you have "significant" day time inverter/battery loads:
· 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.05 rate of charge = 198 Watt array minimum
· 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.10 rate of charge = 395 Watt array nominal
· 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.13 rate of charge = 514 Watt array "cost effective" maximum"

280 watt array*0.77panel+CC derating/(14.5volts charging*210 AH) = 0.0708 or 7% rate of charge

At 280 watts we fall between 1 and 2 for charging. The way the Trailmanor is configured real estate for panels makes 2 or 3 questionable.
The inverter is a 400 watt and most likely isn't 85% efficient.
It's only used about every 3 days for about 3 hours to charge laptops. Although that is 1200 watts and more then 1 day @ 50% discharge; actual usage is more like 50 watts per hour based on measured DC volts and amps.

scrubjaysnest · May 2015

Some load figures for the "nest", all loads off, one turned on at a time and measured with a Sears AC/DC clamp on amp meter.

Load ItemAmpsWattsWattHcomments

reefer fan0.597.18512 hours, night before we leave on our trip

1 - LED0.141.710.16 hours, per day

2 - LED0.283.420.26 hours, per day

flor1.3416.116.11 hour, per day

toilet p-p4.6550.15310 sec per flush, single flush converted to WH 55*10/60*1/60

fantastic fan0.232.7633.1212 hours, per day

CC-TS450.230.4811.524 hours

Furn avg3.1237.318.642 times per hr, 37.3*1hour*0.5 30mins per Hr

Total WH197total all WH used per day

Battery WH1260AH * 12 volts

1 day usage SOC %84.6Total WH / Battery WH * 100

That is worst case with out the inverter; run the inverter for 3 hours at around 12 amps and % SOC drops to 47/per day

BB. · May 2015

Other than the typo (I think), looks good:

WH 55*10/60*1/60

-Bill

scrubjaysnest · May 2015

BB. wrote: »

Other than the typo (I think), looks good:

-Bill

Hope I didn't mess up 1 10 sec flush should be 10 sec/60 sec per minute * 1hour/60 minutes to get it from seconds to hours? Have been known to not keep my units straight.

BB. · May 2015

Opps, you are correct... I saw the 10 seconds per flush and thought that was in your math equation--But it is not. So the 10 is correct as you have it.

-Bill

Anawa · May 2015

Say Jay, I'll be fishing at Econfina, Aucilla, and Rock Island for the next few days. Are you anywhere round them parts?
Paul

scrubjaysnest · May 2015

Anawa wrote: »

Say Jay, I'll be fishing at Econfina, Aucilla, and Rock Island for the next few days. Are you anywhere round them parts?
Paul

Maybe 30 minutes by back road to a boat ramp on the Fenholloway then 15 minute run to rock island. About 45 minutes if we launch at Keaton

Anawa · May 2015

Roger. Sounds like you're not to far from Perry. How bout Deal's Oyster House, have ever seen the "show" on a Saturday night?

scrubjaysnest · May 2015

Anawa wrote: »

Roger. Sounds like you're not to far from Perry. How bout Deal's Oyster House, have ever seen the "show" on a Saturday night?

12 minutes to the wally world that looks like it is going out of business in Perry. Haven't been to Deal's; usually hit Roy's in Stein for a fish basket at lunch time.

scrubjaysnest · May 2015

And here are pics of our solar set up: A few things left to clean up, run 4 awg from CC to batteries and wire in test points to measure CC input and output when the camper is folded up. Also replace the home made vented battery box.

scrubjaysnest · September 2015

The used, 120 watt panel failed at 8 volts output when it gets hot; puts us back to marginal here in OR. Had to make up a 30 foot extension cord to get the two portables in the sun. We are making up our usage plus a slight gain so far even with cloudy days.

inetdog · September 2015

scrubjaysnest wrote: »

The used, 120 watt panel failed at 8 volts output when it gets hot; puts us back to marginal here in OR. Had to make up a 30 foot extension cord to get the two portables in the sun. We are making up our usage plus a slight gain so far even with cloudy days.

Check the bypass diodes in the panel in case one of them is shorting out. But it is more likely that one or more cell connections is opening up and leaving you to see just the output of the remaining good section(s) carried through the bypass diodes of the failed section(s).

PNjunction · September 2015

scrubjaysnest wrote: »

The used, 120 watt panel failed at 8 volts output when it gets hot; puts us back to marginal here in OR.

Ouch. Was that one of the circa 2000-2002 KC120 panels?

http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/advanced-solar-electric-technical-forum/4021-defective-kyocera-solar-panel

You were not alone.

scrubjaysnest · October 2015

Yep, it is a 13 year old panel; tested a little further and output is 4.5 amps when shorted and open circuit voltage is about 10. When we get home next month I get to see if I can repair it. We are doing fine on the 2 80 watts since our typical usage is 2 to 5% per day and the lowest SOC seen this trip has been 89%

"The Nest" and its solar setup

Comments

Categories

&quot;The Nest&quot; and its solar setup

Comments

Categories

"The Nest" and its solar setup