Solar coming soon and a few questions

J

Jamesiam

Senior Member
Joined
Nov 1, 2010
Messages
237
Location
Stateline Nevada
Thanks to everyone who has written about their solar install, I will do my best to list everything I get and photograph my install as I go. I have a few questions though. I am ordering items as cash comes in so here are a few of my next items.
I have already purchased a Solar Cynergy 120 watt 12 V Solar panel weighing in at a whopping 30 lbs. for $163 including shipping, I think I did well.
Next on the list to buy is my Morning star Sunsaver SS-MPPT 15L Charge controller for $223.00
Then a Morningstar Remote Digital meter for 74.88
If both of these Morningstar devices look well I will go ahead and order in the next few weeks. It seems that this is what everyone has used in the past.
Another Question is I have I noticed everyone is using 10 g wire. Will I be running 10 g not only from Panel to Controller but also from controller to battery and 10 g from controller to fridge?
I have a 3.0, 3 way fridge/freezer in my 2005 hawk with no plans on getting a new fridge since this one has worked fine and for the money I’m spending on Solar energy. People seem to hook their 12 volt fridge to MPPT controller. Will I be able to hook my 3 way to MPPT controller and just keep the three way fridge on battery mode?

I have a few more questions but will read the Ultimate solar post a few more times.
 
Hi,

Here is some of my thoughts,I like to keep it simple.

I use a basic Morningstar Sunsaver controller, the 20 amp model is about $75, and it works fine. All you are doing is charging a simple battery and I don't see the need for an expensive MPPT controller for this application. Others may differ in their opinions. Do you really need an expensive voltage meter? If really serves no function as you get whatever the panel is producing. Not much you can do to change that.

I use a cheap LED voltage meter wired to a on / off switch to monitor battery level. Less than $10

Always error on the side of a larger wire gauge to minimize voltage drop especially on low voltage systems.

In simple terms think of a wire as a water pipe, would you run a large pipe and then reduce it in size half way to its fixture and still expect to get the same flow?

I wouldn't hook the fridge to the controller output, they pull about 120 watts and most people have problems trying to run their fridges on 12 volts. The low voltage cut off on the controller might prevent you from draining the battery when you forget to switch the fridge but I would go direct to the battery. Either way will work.

Do some basic calculations on your current draw and voltage drop, use a volt meter to check your voltage drop under load at the fridge. Those fridges are power hogs on 12 volts.

Hope this helps.

Dsrtrat






Thanks to everyone who has written about their solar install, I will do my best to list everything I get and photograph my install as I go. I have a few questions though. I am ordering items as cash comes in so here are a few of my next items.
I have already purchased a Solar Cynergy 120 watt 12 V Solar panel weighing in at a whopping 30 lbs. for $163 including shipping, I think I did well.
Next on the list to buy is my Morning star Sunsaver SS-MPPT 15L Charge controller for $223.00
Then a Morningstar Remote Digital meter for 74.88
If both of these Morningstar devices look well I will go ahead and order in the next few weeks. It seems that this is what everyone has used in the past.
Another Question is I have I noticed everyone is using 10 g wire. Will I be running 10 g not only from Panel to Controller but also from controller to battery and 10 g from controller to fridge?
I have a 3.0, 3 way fridge/freezer in my 2005 hawk with no plans on getting a new fridge since this one has worked fine and for the money I’m spending on Solar energy. People seem to hook their 12 volt fridge to MPPT controller. Will I be able to hook my 3 way to MPPT controller and just keep the three way fridge on battery mode?

I have a few more questions but will read the Ultimate solar post a few more times.
 
I would have to concur with DSRTRAT; not sure that you really need that fancy Morning star. I have been quite pleased with my $35 Morningstar controller (lower wattage cause I only have 85 watt panel) and a small analog volt meter.

As for 10 guage wire. Recommend it also. Of course, the length of wire you are running is also a factor. The longer the run of wire, the more voltage drop you have.

Good luck.
 
Have you read the HandyBob blog? http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
It is long and wordy and repetitive, but what I took away from it is this: full charge is 12.6 Volts. 50% discharge (the max for most batteries) is 12.04 volts. So you aren't playing with 12 volts, you're playing with .56 volts. Granted, that's the battery and not the ideal charging voltages, but voltage drop takes on a considerably different look when viewed from this angle.
 
I just replaced my stock 6 amp Morningstar controller with the SS-MPPT-15L. I graphed the charge voltage on the battery with the old controller as well as the new controller and did not see much difference. Well, I did not see any difference but I only get about three hours of sun where my Hawk sits in the driveway. The truck and camper has not moved since I updated to the new controller so time will tell.

I did decide to get the remote sensor. I am pretty sure the SS-MPPT-15L adjusts the charge voltage based on the battery temperature. If the controller is warm, it might drop the charge voltage on a cool battery. The SS-MPPT-15L manual says it is strongly recommended to use the remote sensor. I am seriously considering a second panel so the new controller will really be needed if I do that.

The last page of the SS-MPPT-15L manual lists wire sizes based on current and wire length.

You really can not run the refrigerator on DC for any long period of time with the engine off. It is hard to define how long "long" is. The refrigerator will draw about 15 amps of current from your batteries while on DC. I have stopped for a short hike on my drive to my camping location and left the refrigerator on DC, after the short drive to camp, my battery was much lower than I expected and the pine trees were tall (not much sun).

On one trip, I started the refrigerator on DC about 2 hours before leaving. I figured the truck would charge the batteries. But I think, because the refrigerator being on DC and low batteries pulled so much current that the circuit breaker (there are two inline on my camper) was tripping because I was pulling more than 30 amps to run the refrigerator and charge the camper batteries. This would only be a possible issue if you had low batteries in the camper and had the refrigerator on DC.

Before I increased the wire size from the camper battery to the refrigerator to 8 gauge, I measured a difference of 0.9 volts between the camper battery and the refrigerator. By running 8 gauge directly from the battery to the refrigerator (fused at the battery), I only see 0.2 volts drop. My observation is that the refrigerator works much better now. I feel my refrigerator works better than on gas when the temperature outside is not real hot.

Steve
 
Do you really need an expensive voltage meter? If really serves no function as you get whatever the panel is producing. Not much you can do to change that.

Ha Ha that is too funny but true. I'll definitely look into these less expensive options! I believe I saved a link a while back of a nifty little LED voltage reader that someone had placed over their water pump and battery gauge.
 
You really can not run the refrigerator on DC for any long period of time with the engine off. It is hard to define how long "long" is. The refrigerator will draw about 15 amps of current from your batteries while on DC. I have stopped for a short hike on my drive to my camping location and left the refrigerator on DC, after the short drive to camp, my battery was much lower than I expected and the pine trees were tall (not much sun).

On one trip, I started the refrigerator on DC about 2 hours before leaving. I figured the truck would charge the batteries. But I think, because the refrigerator being on DC and low batteries pulled so much current that the circuit breaker (there are two inline on my camper) was tripping because I was pulling more than 30 amps to run the refrigerator and charge the camper batteries. This would only be a possible issue if you had low batteries in the camper and had the refrigerator on DC.

Endorsing and extending what NCS says here: It's not only that running a 3-way fridge in DC mode pulls lots of juice, it also doesn't function very well at refrigeration in DC mode -- very inefficient. Barely keeps a cold fridge cold, and won't do much to bring down the temperature in a warm fridge.
 
I endorse the remote meter for its geek factor. I really enjoy watching, quantitatively, the performance of my system. I get a kick from seeing how many amp hours I can bank etc. Yes, it may be frivolous but I do enjoy it. So it's really just a matter of preference and money. The increased performance of the MPPT is also likely negligible, but again there's the geek factor, your enjoyment, and your wallet. Like most others, I ran 10 ga throughout.
 
You can learn a little more by looking at the real battery voltage than you can by looking at a few LEDs but not a whole lot. Once the battery is near full capacity, and the panel(s) are getting sun, the voltage to the battery will go up to over 14 volts. The LED solution will not indicate this. The lights on the SS-MPPT-15L do flash to indicate what mode of charging the controller is in.

I bought this meter that plugs into the DC accessory socket. It seem pretty accurate, except I ignore the three LEDs and just use the meter. I am thinking I may have seen it posted here before. I use it to monitor the alternator voltage while driving and the camper battery voltage while camping.

ntsqd has a good point with battery voltage. If you want your battery to last a little longer, you don't want to drain it down too far.

I will admit that I will probably end up buying the remote meter for the SSMPPT controller because, I guess, I am a Geek.

Steve
 
I endorse the remote meter for its geek factor. I really enjoy watching, quantitatively, the performance of my system. I get a kick from seeing how many amp hours I can bank etc. Yes, it may be frivolous but I do enjoy it. So it's really just a matter of preference and money. The increased performance of the MPPT is also likely negligible, but again there's the geek factor, your enjoyment, and your wallet.

My feelings exactly!
biggrin.gif


Necessary? No...but besides the subjective/intangible nerdy-coolness-I'm-just-into-it factor, knowing how much power is going into my battery helps me understand and predict how my system is working and how well it will work. For example: "Why is the battery voltage down so far? Is it going bad -- can't hold a charge?" "No, as the meter shows, the solar panel only put in 15 amp-hrs today...maybe I should consider giving it an adjustable-angle mount rather than having it lay flat on the roof."
I bought the Watts Up meter, which not only tells you what voltage and current it's currently feeding the battery (and watts, by their product), it tells you how many amp-hrs (and watt-hrs and other stats) it has fed the battery since its last reset. Really cool and useful.
smile.gif


I haven't done any A/B comparison between MPPT charge controller and non-MPPT, so I don't actually have any facts based on experience.... But I camp in the winter, and it's when they're cold that PV panels put out the highest voltage, so that's when they're most-likely to produce higher voltage than the battery can use, excess voltage-producing-ability that's wasted with a non-MPPT controller. I should say that I bought a less-expensive brand/model (Model # PT 12/24-10 TC) than the one that James lists, so it was easier to justify.

Bottom line for me: the cost of the gadgets is considerably less than I spend on truck fuel for just one trip from Bend Oregon to the eastern Sierra -- a trip I make 2 or 3 times a year, and these gadgets will last for years -- many, many trips, so they're really a minor line item in my overall long-term camping budget.
 
Have you read the HandyBob blog? http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
It is long and wordy and repetitive, but what I took away from it is this: full charge is 12.6 Volts. 50% discharge (the max for most batteries) is 12.04 volts. So you aren't playing with 12 volts, you're playing with .56 volts. Granted, that's the battery and not the ideal charging voltages, but voltage drop takes on a considerably different look when viewed from this angle.

I haven't but will give this a read
 
I didn't buy a meter when I installed my solar. Didn't need it and didn't want to spend that much. Now however, I feel my geekness in question and suddenly I feel the need for one. Now I just need to avoid the urge to buy more than I need. Ya know, a wireless remote would be cool, check on your solar from the comfort of your lawn chair! Must resist urge to spend foolishly :)
 
James, I am in the solar contemplation mode. This is what I gathered from the handybob paper. Pay attention to voltage drop, especially between the charge controller and the battery therefore have the controller close to the battery and use big wires here. He says to pay attention to what the battery manufacturer recommends for charge voltage and make sure that's what you are getting at the battery. Now I'm doing this from memory so be sure and check on my accuracy.
 
Wire gauge from the solar panels to the controller is also important. Voltage drop there means nothing else has a chance of working at it's best to charge the battery(ies).

I'm thinking to get a meter before I spec out the solar charging system. This is the unit that HandyBob points out and I'm not seeing a comparable unit for the price. I want to know what our usage is so that I can size the system appropriately. I'll also be replacing our single-sense VSR with a dual-sense VSR so that when the truck is parked at home the solar will also keep it's starting batteries topped off.

I'm not sure that for our needs that an MPPT controller is necessary. They seem like they're more hype than action in small amp systems.
 
Wire gauge from the solar panels to the controller is also important. Voltage drop there means nothing else has a chance of working at it's best to charge the battery(ies).

I'm thinking to get a meter before I spec out the solar charging system. This is the unit that HandyBob points out and I'm not seeing a comparable unit for the price. I want to know what our usage is so that I can size the system appropriately. I'll also be replacing our single-sense VSR with a dual-sense VSR so that when the truck is parked at home the solar will also keep it's starting batteries topped off.

I'm not sure that for our needs that an MPPT controller is necessary. They seem like they're more hype than action in small amp systems.

Don't believe the Hype (Public Enemy)
I'll definitely look into that handy Bob meter recommendation thanks!
 
You must log in or register to reply here.

Similar threads - WTW

R
Rear solar SAE port
Deancamp
D
buckland
PWM and MPPT question
craig333
craig333
K7MDL
Installed Renogy One Core monitor and Battery Shunt 300
K7MDL
K7MDL
D
Solar Questions and Troubleshooting
Doods
D
E
2011 Four Wheel Camper Fleet for sale -- Northern Virginia
Evader53
E

New posts - WTW

Back
Top Bottom