From truck camping to an RV

[Electwistery]

Hello All from not very sunny New England,
First post , thanks all for all the great information on this forum ,this is a great resource for everyone
My first setup was put together back in 2012

12 volt system
Est 288ish watt hours a day load
140 watt panel flat on pickup truck cap 8.89 short circuit current
232 Ah interstate 6 volt pair
prostar ps30 PWM
solar insolation in Mass 2

been running almost 4 years , the only reason this works is the load is an ARB fridge and doesn't cycle on in the winter hardly at all , tried to size this system with a small DOD

Fast forward to 2015 and got myself a small class C RV it's a 1987 20' tioga chevy chassis , so I will be upgrading this system to support slightly larger load
keep in mind this full load is for intermittent use a week here and there and weekends , the hope is that I don't have to plug in unless I want air conditioning
the RV gets winterized but the fridge will be year round

Est Load between 500-800 watt hours day (got a trimetric and will measure and adjust my load as needed)
added 3 100 watt panels to the 140 with mixed ratings and will be in parallel for 26.56 short circuit current, should help if I can't avoid shading at campsite, will prob remain flat most of the time but the plan is tilt mounts for longer stays or parked
232 Ah interstate 6 volt pair
prostar ps30 PWM
Magnum inverter/charger to handle things when plugged in , don't plan on AC loads but wanted to be able to run power tools if needed

I have all the hardware just need to install ,
10awg from panels to junction
10amp fuse ea panel
4awg from junction 20-25' to controller
4awg 3' to battery (should I just use 6awg here?)
40 amp breakers in and out of controller

I plan to upgrade the interstates to 4 Trojan T-105 or T-105RE but not until these interstates can take no more (right now my cheap hydrometer says they are good)

Alright I know it could be better but do you think it is at least OK? , I am ready for criticism , but please don't call me names for using PWM or 12 volt
just expanding an existing setup
Yes I know it is expensive (already bought)
I know i could run a generator or alternator (prefer not to)

just wish I had found this site years ago

Thanks again
Bracing for the replies

Electwistery

[Amy@altE]

Hi there from a fellow freezing cold Massachusite (what happened to this weekend's beautiful weather?!?!) A few recommendations. I know you have a PS30, but you may want to get a 15A charge controller for the 140W panel, maybe a PS15, and use the PS30 for the 3 100W panels. You run the risk of the 100W panels pulling the 140W down to their level, and losing a lot of power.

800Wh / 2 sunhours / .6 losses = 666W of solar. Luckily you said you are only powering the fridge in the winter, so you can use a better sun hours of maybe 4, bringing it down to 333W of solar, so you have enough.

800Wh x 2 (50% DoD) x 2 days autonomy (weekend) x 1.2 temperature deration (assuming not too cold in summer when running full loads)
/12V = 320Ah battery. You have 232Ah, so you are going to run it down pretty hard if you have any non-sunny days. But it's what you have and are willing to use it till it dies. Just keep an eye on it with the Trimetric and adjust your loads as needed.

Amy

[Electwistery]

Thanks Amy

[Electwistery]

thanks Amy I just picked up that trimetric from Alte , I am new to parallel panels , I thought the 140 would only get pulled down in a series configuration, in my case the voltages line up

[Amy@altE]

Unfortunately, the current might get pulled down in parallel. I'm waiting for a nice sunny day to record a video outside showing the results of mismatching solar panels. Hopefully soon.

[Electwistery]

Thanks Again, I was unaware and now want to look more into paralleling downfalls, last weekend might have been your last chance for a while , and thanks for that battery calculation , the plan was to eventually get the 4 trojans but in the meantime I should be able to adjust my load down as needed, the only critical load is the fridge , I'd like to hear any information you get on mismatched panels maybe the 140 will find a home on my shed Electwistery

[Amy@altE]

As long as you have the 140 on its own charge controller, you can still use it in the same system with the other 3 on their charge controller.

[Electwistery]

well I was thinking about the SC2030 but can anyone point me to more information on the mismatched current of parallel panels , I am having trouble finding anything , maybe my google foo isn't what it used to be??,,, Thanks Electwistery

[inetdog]

well I was thinking about the SC2030 but can anyone point me to more information on the mismatched current of parallel panels , I am having trouble finding anything , maybe my google foo isn't what it used to be??,,, Thanks Electwistery

Very simple:
If you parallel two panels of the same voltage (within 5%) into an MPPT input it does not matter what the currents are. Your loss will be less than 2%.
If you parallel two panels each of which is a high enough voltage to use on its own with a PWM CC it does not matter if the currents match.
Matching current is only necessary when you put panels in series.
If you have too many panels for the capacity of one PWM CC you have to split them up, regardless of current matching.

[Sunking]

Before you get to far, first thing to do is get an Electronic Battery Isolator and upgrade the RV alternator. The alternator can generate more power in 30 minutes than a roof full of panels can do in couple of days.

[inetdog]

Not to recommend their specific product line (which is complete overkill for you), but there is good discussion of the ins and outs of charging house and vehicle battery together at www.smartgauge.co.uk.

[Electwistery]

Thanks Inetdog, that was what I was thinking on parallel and different current with the same voltage , after what Amy said I kinda want to check myself once I get hooked up
Also I plan to run 26.56 short circuit current into my 30 amp controller , I was thinking with my panels flat and losses and such that I should be ok ( knowing I should have a controller at 125% panel rating)

Thanks Sunking , I have been running the truck with an isolator to recharge last year as needed, just trying to get away without having to run it,, peace and quiet is nice while camping, but again I will run it when I have to or if my load goes up , there is no way I would tell my other half she can't fire up the furnace if she is cold :P

thanks all
Electwistery

[Amy@altE]

I'm setting up to do a video today, I might luck out with a stretch of sunshine (the luck of the Irish is with me today). So far I have two 50W 12V panels, a 100W 12V panel, and a 100W 24V panel. I plan on showing the different voltage and current outputs with them in series versus parallel in different combinations. I can show them with a PWM and an MPPT charge controller.

Any requests on certain configurations that aren't obvious?

[Electwistery]

Hi, it was raining when I came to work this morning but it looks pretty nice out there now
the configuration that would concern me is the current output of the 12V 100 alone against the current output of just the 12V 100 with the two 50's on the same PWM controller
even with this it would be tough to prove without a controlled setting
Thanks
Electwistery

[Amy@altE]

Hi, it was raining when I came to work this morning but it looks pretty nice out there now
the configuration that would concern me is the current output of the 12V 100 alone against the current output of just the 12V 100 with the two 50's on the same PWM controller
even with this it would be tough to prove without a controlled setting
Thanks
Electwistery

I like it. I do have an insolation meter, so I can compare the outputs with the intensity of the sunlight, that way if the sun is 25% less from one test to the other, I can factor that in. Not a perfect solution, but should be pretty fun none the less.