Solar system suggestions for trailer

[Ironhead72hd]

Don here. Newbie but lots of research done. I have a travel trailer I want to put on solar only on a piece of land I own. Cannot get grid power there just yet.

what I have purchased so far:
10 255w solar panels trina solar 30.5v max 8.3amp max

my eventual plan is an off grid small house with 12 100ah 12 volt batteries and the 10 panels which will cover the roof of the small house on the back side of the roof.

if I use 10 panels and 12 100ah agm batteries I am thinking of using a flexmax 80 charge controller. Also not real sure on inverter size yet as I have not determined loads on the trailer yet. It has a 30 amp system in it now and I already know air conditioning will not be feasible. Or would it with a large battery bank?

looking forward to suggestions from the more experienced folks here. Thanks.

[littleharbor]

How do you plan to configure those 12 batteries? The least problematic way would be 3 strings of four for a 300 ah 48 volt bank. I say least problematic because even at 48 volts it still is a bad way to go. Why would you PLAN a system that has parallel strings of batteries. You need to research battery bank design and problems a bit more.
If you want a 300 ah. battery bank then buy 300 ah. batteries. Look at l-16 size batteries, lots of choices.

[OldSmokey]

Don here. Newbie but lots of research done. I have a travel trailer I want to put on solar only on a piece of land I own. Cannot get grid power there just yet.

what I have purchased so far:
10 255w solar panels trina solar 30.5v max 8.3amp max

my eventual plan is an off grid small house with 12 100ah 12 volt batteries and the 10 panels which will cover the roof of the small house on the back side of the roof.

if I use 10 panels and 12 100ah agm batteries I am thinking of using a flexmax 80 charge controller. Also not real sure on inverter size yet as I have not determined loads on the trailer yet. It has a 30 amp system in it now and I already know air conditioning will not be feasible. Or would it with a large battery bank?

looking forward to suggestions from the more experienced folks here. Thanks.

Don't buy anything else until you have done some better research, there are several good articles here posted by the venerable Sunking on correct design go read them..

your not even in the ballpark with your suggested "design".. I'm not sure what you intend to do with 12 12V 100ah agm's, but off grid is not one of them, you are still stuck in the "RV must be 12V mentality"

as a ballpark suggestion consider something like a 5S2P array feeding a midnite classic 200 and a 48Volt 500Ah bank of FLA's
or a 10S array feeding a morning star tristar mppt 600 and 48V 500Ah bank.. this is the field you should be playing in.

[Ironhead72hd]

My reasoning for the one hundred amp hour 12 volt AGM batteries was I Found A supplier where I can get them for less than $100 each and thy're new batteries. and if I run them all in series that would be a total of 144 volts DC and the charge controller I'm talking about says the max volt DC input is 150. like some others on here I'm also trying to work on a budget. so some of the Lithium-ion batteries are going to be out of my price range at the moment. I will do some more research on the posts on this board as suggested by old smokey. I have played around with a harbor freight solar kit 45 watt model and a couple of tired d8 battery. But that's my total experience with solar up to this point. thanks for the input and I'll be doing some more research.

[Sunking]

Stop what you are doing right now. Get 12 volt and AGM off your mind right now, there is no such thing as 12 volt forget 12 volt.

Did I forget to say forget 12 volt? You are stuck inside a 12 volt box, there is no such thing as 12 volt batteries. What you are going to need is a lot of cash today, and a lot more in your future if you insist on off-grid.

OK with 2025 watts of panels requires you to use 48 volt battery system, and the minimum battery size is going to be 500 AH. A 48 Volt 500 AH Flooded Lead Acid battery is going to cost you roughly $4500 and weigh in around 1700 pounds. You will be replacing them in less than 5 years. You will not use 12 volt batteries you would be using 6 volt 500 AH batteries like a Rolls 6CS17P a 6-volt 546 AH battery. Now you could use AGM if you have cash heavy pockets. A 48 volt AGM 500 AH battery will cost you roughly $8000 and you get to replace them every 2 or 3 years so they end up costing you 400% more than FLA. Keep in mind your system will generate about 50-cents worth of electricity per day, and just in battery cost alone is going to be 5 to 10 times more than the Power Company will charge you. That is what you get when you ask to go off grid. Did you know that?

At 2025 watt panel wattage operating into a 48 bolt battery will require a minimum 50 Amp MPPT charge controller. That will cost you roughly $500. A good one to look into is a Morningstar TS-MPPT-60. You need to loose one of your panels or buy 2 more because 10 cannot be used. For 48 volt battery requires strings of 3 or 4 panels in series and no way to use 10 panels. If anything buy 2 more panels for a total of 12, but 10 is not going to work. You can make 8,9, or 12 work for 48 volts. 10 will not cut the mustard. That is what you get when you fail to research.

As for an Inverter, no larger than your panel wattage around 2000 watts max. Do not forget you must have a good generator, at least 4 Kw and a good 48 volt 100 amp charger for those rainy days and monthly battery maintenance.

So dig deep in your pockets, you are going to need a lot of cash now and in the future to maintain and replace batteries.

Good luck with that.

[littleharbor]

My reasoning for the one hundred amp hour 12 volt AGM batteries was I Found A supplier where I can get them for less than $100 each and thy're new batteries. and if I run them all in series that would be a total of 144 volts DC and the charge controller I'm talking about says the max volt DC input is 150.

You have a lot more learning to do.

[Sunking]

You have a lot more learning to do.

Ditto, your learning has not even began yet. So far your education has cost big and you got a lot more money and learning required.

To start that 150 volt controller you are talking about is the Voc input voltage from the panels and has nothing to do with battery voltage. Battery voltages for solar are 12, 24, 36, and 48 volts. Some models can do 60 volts, but not yours. So stop everything and start over before you loose more money.

[Mike90250]

There is no better teacher than experience. Your 12V lesson will be an expensive experience if you go forward with it. Please continue your research before you spend any money.

[Ironhead72hd]

I am not that far in yet. Only the panels at 200 buck each. Have not purchased anything else yet. I appreciate all the input. I do not plan on purchasing anything else until I better understand the sizing requirements and you guys have started me in the direction I need to go. Thanks for that.

[Sunking]

I am not that far in yet. Only the panels at 200 buck each.

Well good then because $2000 is pocket change to you and only a small down payment toward $10,000 plus with $4000 battery replacement every few years. At this point you can only use 9 of those panels, and what is scary you do not know why.

You are heading for disaster. You have no idea what your daily electrical needs are and no one can tell you what they are. Right now you have 2550 watts of panels which come with minimum requirements. Example a 65 Amp MPPT Controller, 48 volt 500 AH battery. That at best will only supply you with 6 to 7 Kwh per day of electricity. Less than a dollars worth of electricity, and you had better live like a hermit alone with no wifey or kids around, or you are going to go dark day 2 and destroy your batteries. You are talking bare bones living with no air conditioning, electric cooking, electric hot water. Just lights, a fridge, and very few luxuries. So if what you have will not meet your requirements, you are going to learn a very expensive lesson.

Lesson 1. Anything you take off grid is going to cost you 5 to 10 times more than just buying it from the POCO for the rest of your life all up front in cash every few years with each battery replacement. You got that kind of cash to spare and waste needlessly?

[zamboni]

The information is in here, but you will need a thick skin to harvest it. Several people on here really know their $hit, and they want you to be safe,
and to protect you from spending money with inaccurate expectations. They aren't into hand-holding though.

Your original post asked for suggestions, so: Start with a good, honest energy audit. System design is a process and if you start in the middle it won't end well.

From there...more research...then figure out your battery needs. Hint: this is the hardest part. Once you've done that, do a rough financial sanity check: Add up costs on that battery...along with the recurring replacement costs for the next 25 years: Sunking is definitely right that off-grid batteries are more expensive than most people expect. This is not a "real" number, just a decision-making tool. Compare that number with the cost of paying for a power line run out to your property. I'd say if it's within 50% of the cost of the power line, then off-grid probably doesn't have a business case.


- Jerud
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1220W array / 1000Ah LFP house bank
MidniteSolar Classic, Magnum MS2812
ME-RC, Trimetric, and JLD404
Yep, made some bad decisions but learned my lesson and now making the best of it
Full-time 100% electric boondocking (no propane, no genny) since 2015
2001 Fleetwood Prowler 5th wheel 25 foot, self-rebuilt

https://www.livesmallridefree.com