Want to install solar, questions

[Butch50]

We recently got our new 2017 Nexus Ghost and I had it pre wired for solar. Nexus provided (in a box) a Zamp 30 amp Digital Controller with the pre wire.

My question is how many 100watt paneles well this controller support? It is a PWM not a MPPT controller.

I'm a newb when it comes to solar and looking for help.

My coach currently has 2 grip 27 batteries but I want to go to 4 Grp 31 AGM batteries. Right now our 2 Grp 27 batteries won't even last a night. I turn the furnaces down to 60 degrees for the night . We have all LED lighting and when we are dry docking we do not run the inverter nor run TVs. We use our IPads and IPhones but do not try to charge them till we start driving the next day. While driving I see 14.2v from the truck alt. After being parked I we'll see the voltage level off at 12.5 to 12.6V but after the night I see 11.8v in the morining. My wife does run a CPAP at night that operates off 12VDC.

We are on the road right now so I can't really start looking for parasite voltages draws.

When I return home I can do more trouble shooting.

Thanks for any help.

I don't have access everyday to the Internet as we use our IPhones for hot spot but have to watch our data usage.

[BFL13]

Yes with a low sun tilt matters more. I ran a test at 49N on 18 May with a 130w panel and got 8.3a tilted, but 7.2a flat at noon.

On 23 Sep I was in the same spot but with a 255w panel. With it flat I was only getting approx 11 amps at noon instead of approx 16a tilted at noon. (noon at 1300 )

1.1/7.2 = 15.% boost from tilting in late May
5/11 = 45% boost by tilting in late Sep (at 49N)

The bigger problem here in winter is just getting the sun to be above the tree tops.

[ktmrfs]

BFL13 wrote:
Down South in summer, sun is so high flat panels can be close to max.

"roof panels have one downside for most uses. the optimum tilt angle for getting rated power needs to be about the latitude your at plus solar declination. That means something around 45-60 degrees tilt. depending on location and time of year. "

Actually that's for winter up here. In summer,

Lat MINUS Dec = Tilt in northern hemisphere with north Dec

Since tilt (up from flat) = Zenith distance (90- sun's altitude above horizon) and ZD plus Dec = Lat at high noon, sun bearing S.

EG, 21 June Dec 23N at 49N---- Alt 64, so ZD is 26. 26 + 23 = 49

Same day down at 32N, tilt is 32-23 = 9 (almost flat)

Optimum tilt for a panel fixed pointing south is less than the noon angle so it can get more light in the shoulder hours. See macslab.

If you have a tilted panel on a twirler always pointing at the sun, however, you want it tilted higher in the shoulder hours than at noon which is your lowest tilt.

yup, your correct on summer vs. winter, my mistake thanks for the correction.

Since we are almost always near or above 45 Lat, angle does make a noticeable difference in the early spring and late fall. And that's when we use the furnace more and less sunlight hours. All adds up. But your correct, not near the effect in mid summer months.

Still, 45 degrees tilt error is a 30 percent hit, however if you can get below a 30 degree tilt error then you get around a 15 percent loss, not bad, anything less than a 15 percent tilt error is basically lost in the noise as you mention.

[BFL13]

Down South in summer, sun is so high flat panels can be close to max.

"roof panels have one downside for most uses. the optimum tilt angle for getting rated power needs to be about the latitude your at plus solar declination. That means something around 45-60 degrees tilt. depending on location and time of year. "

Actually that's for winter up here. In summer,

Lat MINUS Dec = Tilt in northern hemisphere with north Dec

Since tilt (up from flat) = Zenith distance (90- sun's altitude above horizon) and ZD plus Dec = Lat at high noon, sun bearing S.

EG, 21 June Dec 23N at 49N---- Alt 64, so ZD is 26. 26 + 23 = 49

Same day down at 32N, tilt is 32-23 = 9 (almost flat)

Optimum tilt for a panel fixed pointing south is less than the noon angle so it can get more light in the shoulder hours. See macslab.

If you have a tilted panel on a twirler always pointing at the sun, however, you want it tilted higher in the shoulder hours than at noon which is your lowest tilt.

[Boon_Docker]

According to your post you are using about 100-110 AH. Flat mounted 500 watts will top your batteries back up no problem on a sunny day.

[ktmrfs]

roof panels have one downside for most uses. the optimum tilt angle for getting rated power needs to be about the latitude your at plus solar declination. That means something around 45-60 degrees tilt. depending on location and time of year. If they are If they are laying flat and you need 45 degrees tilt, max power out of the panel is about 70 percent of the panel rating, at 60 degrees, max power is around 50 percent of panel rating.

the derating is the cosine of the angle error you have.

Now if the panels are portable and you can adjust the angle, 500 watts in parallel should get you close to 30A.

But then how many amps hours do you need to replenish each day. assuming 6 hours of sun, and 20 amps average output you'd put 120AH back into the batteries. That's a pretty healthy amount.

We dry camp a lot, use a cpap, furnace, fans etc and my typical daily use is at most 100 AH out of a 500AH bank. A 15A MPPT controller with 240 Watts of portable panels will keep me charged up if I have good sun for about 8 hours during the day with the panels angled correctly and pointed south.

So, for roof mount with a 30A controller you may need 500 or more watts to get what you need.

but the downside to portable panels is storage and the opportunity for them to gain legs.

But then we often camp in the shade and one of my favorite spots needs about 100 ft of cable to get the panels in the sun. That pretty much dictates series panels to keep IR loss down and MPPT controller.

[time2roll]

Butch50 wrote:
We recently got our new 2017 Nexus Ghost and I had it pre wired for solar. Nexus provided (in a box) a Zamp 30 amp Digital Controller with the pre wire.

My question is how many 100watt paneles well this controller support? It is a PWM not a MPPT controller.

Add the Isc (short circuit amps) specification and do not go over 30 amps.

Probably 4 maybe 5 panels in parallel. Although 2 to 4 is plenty for most usage.

[Harvey51]

I also have never seen more than 5 amps from my 100 watt Renogy panel, mounted flat on the roof - so up to 6 panels on the PWM controller. Make it 5 for safety and because the sun is higher in the sky in the USA.

I had about 14.2 volts to the house batteries from the engine, while the engine battery saw 14.5. The voltage drop wasn't in the wire (about 50 ft of #12 I think). The flow was from engine to battery area, then way over to the battery isolator switch (no relay in my rig) and back to the batteries. The drop was in the switch and a Ford connector under the floor. It took a while to find using a voltmeter and long a long wire to a good ground. I eliminated the switch and 30 ft of wire by running the charging wire direct to the battery rather than through the switch. It helped quite a bit to get 14.4 V to the batteries for part of the driving anyway. I thought engine charging was doing quite well until I learned that the voltage method of estimating battery state of charge deceives high until at least 8 hours after charging ceases.* My batteries died from that deception. The thing is the alternator voltage drops down when it thinks the engine battery is charged so the batteries don't accept even 5 amps from the alternator. A single 100 watt panel with PWM controller made the difference from not enough to all the charging we need in summer.

*see the graph in the last post of this Thread to understand why I call it a deception - and then measure voltage on your own batteries for 24 hours after charging.

[Butch50]

The 14.2,(might be a little a little higher) is measured in the coach at a 12V outlet not at the truck alt. I'll take a look tomorrow as we well be moving tomorrow and then I can see. The converter is a PD4560 60A

We have been plugged for 8 days while we were in Montana, so the batteries should have been fully charged..

The Zamp model is ZS-30A

I know I need to do an audit but we headed out on this trip before I had a chance to hardly even get it loaded before we had to take off. We had commitments that had to be made and the manufacturer took a little longer than was expected to get our rig done.

It sure seems like we are busier since we retired than when we worked all the time.

We should be home in a about 3 weeks so I can get thinks going then. Just trying to get a head start before I get home.

Thanks

[BFL13]

KD4UPL wrote:
30 amps would be the total of all the Imp ratings of the solar panels wired in series. This would be around 500 watts total.
Assuming the panel's Vmp is 18v then it would be 18V x 30A = 540 watts.

Probably just a "typo" mistake, but in series you add the voltages, not the amps. PWM controllers have a low max Voc input limit, so are not suitable for panels in series anyway.

PWM controllers do not use Imp or Vmp. That is for controllers with buck converters in them, with MPPT. The MPPT sets/finds the Vmp and the Imp is what you then get on the line from the panel to the MPPT controller. The Imp is used when calculating the line loss on that path. (The higher output current is used for calculating the line loss on the controller to battery path wiring, which has to be fatter gauge when the buck converter is stepping down eg 24-12)

With PWM controllers you get the Isc of the panel when aimed at full sun. When flat you would normally get less than the Isc so it might work to use five 100w panels, but "it depends"

I forgot the Bogart PWM does clip its amps somehow. Most don't.

You can "over-panel" an MPPT controller, since with their buck converters, they do have self-limiting outputs.

From reading the Tracer MPPT manual it appears it limits the input watts as the way to limit its output. So it does not actually "clip the amps" I may be reading that wrong, though--it is not very clear.

[pianotuna]

Different battery profiles are not adjustable voltage set points.

Which Zamp controller do you actually have?

Does it allow you to set the length of time it stays in each type of charging? (i.e. Bulk, Absorb, float)?

14.2 volts at the alternator is not going to be 14.2 at the RV battery bank. It is unlikely that the alternator will do a good job of recharging the battery bank. Since you are in a class C it may be wise to beef up the thickness of the wire in the charging circuit. I chose to add a second charging path and have manual control over whether it is on or off.

To fully charge the RV bank may need to see between 14.4 and 14.8 volts for a considerable length of time.

The reason the existing battery bank is not doing well may be that it is not fully charged before you start your trips.

Do you know what make of converter (battery charger) is in your RV?

Are the group 27 batteries Marine or are they true deep cycle jars?

To design a solar system that may meet your needs requires an energy audit to be done.

[Butch50]

First off, my wife is not using her humidifier with her CPAP.

I know 11.8V is not good for the batteries that is what I'm trying to stop happening.

Presently I have no idea the size of the wires from the roof. They are behind a panel in my lower kitchen cabinet.

My Batteries we'll be about 2 to 3 feet from my batteries so that we'll be a short run.

The Zamp controller that I have does have the capability to use a battery t4mperature with sensor with it. It also has capabilties of an remote meter. It also has the capabilities of setting it for different batteries and has 5 levels of charge capacity.

I'm still can't figure out why my 2 GRP27 batteries should drop down to 11.8V just over night. We have a Lithum battery for my wife;s CPAP and it well run her CPAP for 2.5 nights from a full charge. It is a small battery. I really think I have something that is pulling a lot of power that it shouldn't. Also my coach has an absortation fridge and is ran on propane when we are stopped.

I want to be able to dry dock more do I need to be able to run for more than one night. I could set met generator to start up when my batteries drop to a certain level as it has a smart controller that a person can program for all kinds of different things. But who wants a generator to start up in the middle of the night even though it is a quiet diesel and is very quite and can hardly be heard inside the unit.

I know I'll eventually get this figured out but in the mean time I'll still be using the GRP 27 and running them down I guess till I get home and get the bigger battery bank. I really don't care about them as they are just going to be core charge when I buy new batteries.

Thanks for every bodies comments I apprecitate them all/

[pianotuna]

Replace the Zamp controller with one that has adjustable voltage set points and a battery temperature sensor.

Ebay the Zamp.

Do you know the thickness of the solar wire pre install?

[Boon_Docker]

KD4UPL wrote:
30 amps would be the total of all the Imp ratings of the solar panels wired in series. This would be around 500 watts total.
Assuming the panel's Vmp is 18v then it would be 18V x 30A = 540 watts.

Couldn't run 5 panels in series with a PWM controller.

[Searching_Ut]

I've had 5 100 watt panels flat mounted on my roof through this summer, and most of the time they peak out at around 25 amps. My Bogart SC 2030 will only pass 30 amps, but will handle quite a bit more than that and just clip the excess. As a result I've just recently added a 6th panel. If you tilt the panels, climb up on the roof occasionally and clean them off etc they put out a fair bit more output so results can vary significantly.