Cargo Trailer Camping Converting

[littleharbor]

So why waste money on an MPPT controller?
If you were to use 60 cell modules which have a more versatile Voc. and Vmp then you have no need to worry about running too high of voltage and you gain the benefit of MPPT.

[Wrybread]

Is that 46 volts Voc? Voc. has nothing to do with charging. If your panels are in the 35 - 36 Vmp. range once they get hot they will run in the low 30's Vmp. that is just enough to charge your 24 volt batteries with a conventional charge controller. You wont get much, if any benefit of a MPPT controller.

Yeah, the panels are 72-cells, 46 VOC. With higher voltage an MPPT controller pulls more power from the panels when the sun is low (morning and evening), so it does have to do with charging. (The other advantages to series wiring are the ability to use smaller wire and no need to fuse the panels). But my point is that in real world tests I'm finding the difference in power to be negligable, especially since I don't get much wattage when the sun is low anyway.

[littleharbor]

[QUOTE=Wrybread;n351792]



Sometimes I run my panels in parallel (when one panel might be shaded), and in my real world tests I get *exactly* the same watt output from my panels when they're in parallel versus series. They're still high voltage when in parallel (46 volts), so I'm still getting a benefit from MPPT. I'm guessing in series I'd get more power in the early morning and evening, but that's no big deal since I don't get much power then anyway. Translation: don't worry too much if you need to go parallel, in real world tests it works fine. You can easily repeat those tests for yourself.


Is that 46 volts Voc? Voc. has nothing to do with charging. If your panels are in the 35 - 36 Vmp. range once they get hot they will run in the low 30's Vmp. that is just enough to charge your 24 volt batteries with a conventional charge controller. You wont get much, if any benefit of a MPPT controller.

[Sunking]

I've got the same 640 watts of panels, going into a 40 amp, 100 volt charge controller. Panels are flat mounted, wired in series. Works great. I have a script that logs all my voltages and I've never gone above 95 volts. It'd be nice to have the 150 volts for some headroom, and I'm not recommending you use a 100 volt charge controller, but it's been working fine for me.

Then you do not mind being robbed and taking chances. I would bet you are a democrat and want to pay even higher taxes than you do now based on that.

[Wrybread]

With 640 watts charging a 12volt battery you will need a 60Amp MPPT type charge controller. That can get you about 50 amps of charging under that best conditions which means your battery system should rated between 400Ah and 600Ah to meet a C/8 to C/12 charge rate.

I've got the same 640 watts of panels, going into a 40 amp, 100 volt charge controller. Panels are flat mounted, wired in series. Works great. I have a script that logs all my voltages and I've never gone above 95 volts. It'd be nice to have the 150 volts for some headroom, and I'm not recommending you use a 100 volt charge controller, but it's been working fine for me. I should mention that I'm at sea level on the Northern California coast where it never goes below, say, 40 degrees F. I mention that because at higher temps and higher elevations morning voltages might spike higher.

Sometimes I run my panels in parallel (when one panel might be shaded), and in my real world tests I get *exactly* the same watt output from my panels when they're in parallel versus series. They're still high voltage when in parallel (46 volts), so I'm still getting a benefit from MPPT. I'm guessing in series I'd get more power in the early morning and evening, but that's no big deal since I don't get much power then anyway. Translation: don't worry too much if you need to go parallel, in real world tests it works fine. You can easily repeat those tests for yourself.

As far as the fridge, agreed that until there's some real world measurements posted, we can't really know. But I don't think it's any big deal, as the OP stated if the fridge doesn't work he'll use it for something else. He still wants and needs solar for his rig for lighting and other stuff.

As far as carefully measuring your loads before getting your panels, while that's of course how it's done when planning off-grid systems for a house, it's kind of unusual to apply that approach to an RV. Typically with an RV you just get the biggest solar system you can fit and afford and adjust your load to that, as opposed to adjusting your panels to your load. Realistically, the options for RV solar are 100 watts up to 650 watts. Anything above that is pretty unusual. You're on the right track with your ~600 watts of solar and you'll have the best RV solar system for a hundred miles, and I'm sure with minor tweaks to your loads it'll work great.

OK I cannot say this strongly enough, you will have to have an alternate source of power. Wyrbread gets away without having an alternate source of power because he never runs more than 4 to 7 days at a time.

While I generally use my RV on weekends, I also use it for weeks at a time a few times a year, and my panels have no problem keeping up then as well. Especially in summer, which is the OP's use, I can go indefinitely from just solar. In summer I never go below 12.4 volts even with 3+ weeks of super heavy use, and my batteries are fully charged up most days even as I'm using it. Summer is dead simple, even with cloudy days, since I have enough panel wattage that even with overcast I'm getting enough charge to keep my batteries up. And here on the Northern California coast summer haze is the norm.

or, you can go with a pair of cheap 6v 210ah golf cart batteries, run the snot out of them, take them way down, and just replace $250 worth of batteries every year as you kill them.

Just don't drain your batteries below 11.8 volts, which is SUPER easy to keep track of, and your batteries will be fine. No big deal and very easy. Get a battery monitor so you can easily keep track of the voltage and loads:

https://www.amazon.com/bayite-6-5-10.../dp/B013PKYILS

And learn how to check your battery fluid levels and be super vigilant about not letting them get low, and don't over fill them since boiling over causes a mess.

[UrbanElite]

That at is very true, price wise it would be a difference. I will only be using this system during the summer and every other weekend.

or, you can go with a pair of cheap 6v 210ah golf cart batteries, run the snot out of them, take them way down, and just replace $250 worth of batteries every year as you kill them.

Or buy big expensive 6 year batteries and worry all the time about keeping them up.

[Mike90250]

or, you can go with a pair of cheap 6v 210ah golf cart batteries, run the snot out of them, take them way down, and just replace $250 worth of batteries every year as you kill them.

Or buy big expensive 6 year batteries and worry all the time about keeping them up.

[UrbanElite]

I got these panels because they were the best deal for the wattage and price around. I mentioned it many times in my posts and you nor no one said anything about it, so I thought it would be fine. Plus starting the post you said I would need way more then the 200 watts on panels I started with.

those S550 should be a good fit as they are good AH, can do 2x 6v for a 12v system. From what I read they should be a good fit if treated well for 5 years minimum out of them maybe 7 if you want to stretch it, they seem like a good battery and quality as well.

charge controller I have been looking at that was recommend for these panels is the The KID MPPT charge controller from Midnite solar. Price tag of about $400

My meter should be in tomorrow, so hopefully start my testing. Question is will I get away with 320 panel and MPPT charge controller or will I need more wattage on panels?

Thanks

[Sunking]

thank you for the help, I will let you know soon here when I get my tester and start my testing of the fridge and what numbers I come up with. I am going to look at these 320 watt panels today because they have limited stock and my buddy is getting me a deal that won't be there if I don't take it, so I'm going to grab 2x 320 watt panels for this project.

OK that limits your Charge Controller options. It means you will likely need a CC with a 150 Voc input so you can wire at least 2 panels in series up to 3 in series. A 100 Voc controller can force you to wire all your panels in parallel adding cost using larger and more wire plus hardware. . At 640 watts you are looking at a minimum 50 amp controller. It also locks you in on a minimum battery AH capacity of around 450 to 500 AH. Not a problem using S550. You just need to understand the consequences of your actions. They can bite you in the butt.

No worries about using Rolls battery as long as you understand the product lines. They are in the Elite group like Trojan and been around a long long time. But both Trojan and Rolls make dogs aka entry level 1 and 2 year batteries. So you have to know what product line you are working with.

A great controller to look at with those panels is a Morningstar TS-MPPT-65. But you have built a trap with those panels you need to understand. Maximum Input is 800 watts. With the 320 watts panels you are done, no room to grow. At 50 amps you are done. To grow would require an 80 or 96 Amp MPPT Controller which is a $600 pain in the wallet. The common denominator panel wattage for battery systems is 200 watts. Perfect fit for 40, 60, and 80 amp controller. Just make sure you are OK with what you are asking for.

With the 320 watt panels and a 80 amp controller you would have room for 1 more panel, but that is it with a 1000 watt limit. Only exception is a Midnite Solar Classic 150 can go to 1200 watts @ 12 volts battery and you can go to 4 panels with that model. Pricey at $600.

[UrbanElite]

Yeah for the price, AH on them and years they should last with proper care they would be a good deal. Reviews look very good on them.

thank you for the help, I will let you know soon here when I get my tester and start my testing of the fridge and what numbers I come up with. I am going to look at these 320 watt panels today because they have limited stock and my buddy is getting me a deal that won't be there if I don't take it, so I'm going to grab 2x 320 watt panels for this project.

[Sunking]

Rolls S550 are great batteries, not top of the line, bu ta very solid 5 year battery. It is a step up from Trojan T-105 and equal to Trojan T-105RE. The biggest difference is capacity. Both Trojan T-105 models are 225 AH, and the S550 is 428 AH. Use this link to find all Rolls Battery. When you determine how many AH's you really need, select the battery to the closest match. To get high amp hour batteries requires using lower voltage of 2, 4, and 6 volt batteries. In Rolls line up as small as 85 AH (12 volt) up to 4860 AH (2 volts). Just make sure you understand the various lines. Las thing you want is a Gel or AGM 1 year battery. They cost twice as much and 1/5th the lifetime. That makes them up to 1000% higher long term cost.

Once you know Watt Hours and Battery AH, I will help you with Panel Wattage and Controllers. I can even show you how to wire everything up the right way. Here is a sample peak.

[UrbanElite]

Good points, I just like planning, specially when I'm in a stand still....... I will do That testing when my meter comes in should be in the next couple days!

Good thing to know. For me around my area I can't get a decent deal on those Trojans, but the S550 I can. But we will cross that bridge when I have to.

well that is something new that is a great point to make with the MPPT! Yes you will spend more on the controller but you will need less supplies, gain more power and more efficient, so I guess it is a win win.

[Sunking]

I will I'll be waiting for my meter to come in the mail and get some real numbers what that fridge will actually run, hopefully it puts out low numbers and is use able in this project.

Let it run at least a week under real usage conditions. That means open the fridge several times a day and rotate products in and out like bottles of water. Take cold botles out and replace with warm bottles. Then after 7 days divide by 7 to get a good running average.

With batteries why would you not go with 4x T105 225ah and only 2x 445ah? Is it to do with 2 are easier to charge then 4?

Simple battery Internal Resistance, and cable resistance cannot be balanced in Parallel Strings equally. The string with the lowest resistance does the Lion's work. Easy to eliminate, use 1 string. Parallel is fine for large Emergency Power on Float chargers because the batteries are rarely ever used if at all. Paralle suks on dialy cycle and wil just shorten the cycle life considerably. No reason to do that if you do not have to.

Talking to a dealer about the panels I'm looking at he recommend the Surrette S550. They're 550 AH and 6V, I will like you said wait until I get numbers out of the fridge before looking at batteries, but seeing what you guys know about those?

Rolls S550 are good batteries, an upgrade from Trojan Signature Line where the T-105 falls. Trojan makes 5 product lines from entry level to Industrial level. An Entry level battery is a 1 year battery, the T-105 is a 3 year battery (signature line), the T-105RE (premium line) is a 5 year battery, and Industrial line is a 10 year battery. Likewise Rolls makes 5 product lines from entry level 1 year batteries up to 7 years. Rols Line up is:

Gel and R Series. 1 year
S Series varies depending on if they are AGM or RE of 1 year for AGM and 5 years RE
4000 Series range from 3 to 5 years
4500 series 4 year
5000 series 7 years.

The S550 is a 4000 series model and is a 5 year battery used as RE. So the take away is it is better than a Trojan T105 Signature Line and equal to a Trojan Premium Line like the T-105RE. You get what you pay for. The T-105 is popular because of its price point and a decent 3 year battery. Having said that there is no equal to a Trojan Industrial Line. Not even Rolls can match it.

So I talked to 2 people that do solar systems in my area today, I was asking about a charge controller and what I could get by with to start this project as the cost of the panels isn't too bad, battery's add up quick and plus the huge cost of the charge controller. I was told:

Charge controller depends on how many panels you have and if you are gonna buy a PWM or MPPT controller. Mainly matters on the amperage of the panel. The ones you want are about 9A and you have 2 of them so you'll want a 20A controller and wire the panels in parallel. But if you have MPPT one you can get a 10 or 15A and hook them up in series. Just have to make sure the spec sheet says it can handle the 640 watts that the panels are.

That sounds correct, I was told if my budget can't handle the MPPT I could work with a cheaper PWM. I know I'll loose off of efficiency if charging compared to the MPPT, but budget also comes into play. I would be willing to spend around 200-250 on a charge controller, but I can't do more at the moment as I still have the upfront cost of the panels, battery's and other stuff I'm adding into the trailer.

I am trying to do this right, it's just all new to me and there is a lot of things to take into consideration. I also can't spend a million dollars on the system either. I just want to have a decent system where I can go camping and have power to supply myself with. My plan will be to go 3-4 days without needing solar if a person had a cloudy day or such. But everyday that is a good day will be topping up my battery's.

The truth will be I will most likely be camping 2 days max on weekends ( Saturday, Sunday ) but I also work 4x4, so I would like to go camping on my days off and could be out for 4 days or more. In July I have a trip booked for camping that is 4 days long.

Thanks for all the replays guys, advice and info is great! Keep it coming!

Forget about panels and charge controllers right now. What i will say is FORGET PWM. To use PWM you must use very expensive battery panels that cost 2 to 6 times more than GT panels. Additionally it takes 300 watt wat PWM system to equal a 200 watt MPPT system. Here is the kicker. Yes MPPT controllers are much more expensive, but are much less expensive to use. A 300 watt PWM system will cost you $700 to $900 wiht panels and controller. A equal 200 watt MPPT System will cost you $400 to $600 for the exact same amount of usable power.

With MPPT there are other cost savings you are unaware of. Most notable wiring and hardware. With PWM you must wire your panels in parallel. That means more wire wire and much larger wire. That gets real expensive. If you have more than 2 panels, you are going to need a expensive Combiner and Fuses. With MPPT you can wire the panels in series with a lot less and much smaller wire. But there are limits and if you do like some and use to high of wattage of panel can severely limit what you can do. Example wire 2 320 watt panels in series with a Controller wiht a 100 Voc limit cannot be done safely. It would require you to wire them in expensive parallel configuration.

So quit putting the cart in front of the horse, and forget about panels and controllers right now. Wai tuntil you know what you need. If you guess, you will fail.

[UrbanElite]

Great reply!

I will I'll be waiting for my meter to come in the mail and get some real numbers what that fridge will actually run, hopefully it puts out low numbers and is use able in this project.

With batteries why would you not go with 4x T105 225ah and only 2x 445ah? Is it to do with 2 are easier to charge then 4?

Talking to a dealer about the panels I'm looking at he recommend the Surrette S550. They're 550 AH and 6V, I will like you said wait until I get numbers out of the fridge before looking at batteries, but seeing what you guys know about those?

So I talked to 2 people that do solar systems in my area today, I was asking about a charge controller and what I could get by with to start this project as the cost of the panels isn't too bad, battery's add up quick and plus the huge cost of the charge controller. I was told:

Charge controller depends on how many panels you have and if you are gonna buy a PWM or MPPT controller. Mainly matters on the amperage of the panel. The ones you want are about 9A and you have 2 of them so you'll want a 20A controller and wire the panels in parallel. But if you have MPPT one you can get a 10 or 15A and hook them up in series. Just have to make sure the spec sheet says it can handle the 640 watts that the panels are.

i can get a Traccer MPPT 10a for $93 or a 20a for $145, I've heard these are pretty good controllers.

That sounds correct, I was told if my budget can't handle the MPPT I could work with a cheaper PWM. I know I'll loose off of efficiency if charging compared to the MPPT, but budget also comes into play. I would be willing to spend around 200-250 on a charge controller, but I can't do more at the moment as I still have the upfront cost of the panels, battery's and other stuff I'm adding into the trailer.

I am trying to do this right, it's just all new to me and there is a lot of things to take into consideration. I also can't spend a million dollars on the system either. I just want to have a decent system where I can go camping and have power to supply myself with. My plan will be to go 3-4 days without needing solar if a person had a cloudy day or such. But everyday that is a good day will be topping up my battery's.

The truth will be I will most likely be camping 2 days max on weekends ( Saturday, Sunday ) but I also work 4x4, so I would like to go camping on my days off and could be out for 4 days or more. In July I have a trip booked for camping that is 4 days long.

Thanks for all the replays guys, advice and info is great! Keep it coming!

[Sunking]

So the fridge does use 65 watt? I ordered a kWh, wattage, ect.. tracker once I get it I will do some testing on the fridge running and using and let you guys know what I find.

That is a great idea and will tel you exactly what you need to do.

So once you determine how many watt hours you need in a day, you can instantly determine what size battery it will take. The formula is super simple and you only need 3 pieces of information:

Battery Voltage = Bv
Daily Watt Hours = Wh
Number of days Autonomy.

Bv and Wh are straightforward and are what they are. Your battery voltage will likely be 12 volts if you keep panel wattage less than 1000 watts. Watt Hours is what you are going to measure and determine how many you need in a day. Autonomy is very important. The minimum number of days for a part time system like an RV is 3 days. That only gives you 2 days usable. Ideally you would like 5 days which gives you 3 to maybe 4 days usable. That CYA for cloudy days. You never ever want to fully discharge your batteries. NEVER. Ideally in a stationary system never go below 50%. A part time system you can go down to 33%.

So let's say you determine you need 1 Kwh per day, 3 day Autonomy, and a 12 volt battery. Battery AH = Autonomy x Wh / Bv.
So plugging in the numbers from the example we have 3 days x 1000 Wh / 12 volts = 250 AH battery. Ideally if you have room for the batteries 5 days works out to 440 AH.

i'm going to be looking at buying 2 of those 320 watt panels, that's 640 watts give or minus what I'll loose off the panels.

You are putting the cart in front of the horse and using 320 watt panels can force to make make compromises you do not want to take. Example you want to wire your panels in series. Two 320 watt panels in series can be to high of a voltage for the controller you end up using. Don't build that trap for yourself and allow someone to talk you into doing something stupid.

Second point you have no idea at this point what wattage is needed. You gotta have the daily watt hours and battery size first. 640 watts on a 12 volt battery using MPPT requires a 55 amp controller. If you were to use just a pair of T-105's 55 amps is a bit to much charge current for them. Panel wattage and Battery AH must be matched. Batteries have a minimum and maximum charge rate they can tolerate. Right now you do not know what battery you need.

So tap the brakes and do it right from the start. Do not put the cart in front of the horse. Don't make that mistake.

Im thinking of spending the money and going with 4x 6v batteries because of the AHs on the 6v batteries. Any other battery recommendations?

Very bad idea. Unless you have space restrictions you NEVER EVER PARALLEL Batteries. Never. If you do, you will cut cycle life in half. Don't Do it. Again you are putting the cart in front of the horse. You still do not know what size batteries are required.

Let's say you come up with needing 450 AH. You do not buy 4 x 6-volt 225 AH Golf Cart Batteries. You would buy 2 x 6-Volt 450 AH LR16 batteries.

I will be running the fridge constantly, charging some phones and running some led lights inside and out, i wont be using anything too powerful other then that fridge.

charge controller, anyone of you have recommendations without killing the bank for now?

OK I cannot say this strongly enough, you will have to have an alternate source of power. Wyrbread gets away without having an alternate source of power because he never runs more than 4 to 7 days at a time. His solar system has time to recover and recharges his batteries between outings. Even a wil deigned stationary solar system runs Deficit Charging. In an RV you will be running Deficit Charging. Al the Panels do is provide you with extra time. Once you have a cloudy day or two, there is no way to catch up. Even without cloudy days running a deficit is going to catch up to you, and without an alternate source of power, you are SOL. You have to shut down and wait a few days for the batteries to fully recharge. Anytime your batteries are less than 100% fully charged, damage is occurring, and each day not being fully charged is another nail in the battery coffin.

Additionally lead acid batteries must be Equalized every 30 days or so, and that is impossible to do with Solar as it takes up to 24 hours uninterrupted power. It is impossible for solar to do that because it cannot supply you with power to run your gizmos and EQ the battery for 24 hours. It is physically impossible.

That means you are going to need an alternate source of power. If not you are screwed.