Folks, solar panels that work, and a controller that works without creating issues, are not cheap.
But then you need to add storage for that juice you are making, that's going to add cost, and the battery is not going to last as long as the panel. Going easy on a good battery and you still NEED to replace in 5 years.
I've done a bit of this. Currently running a 400 watt on my trailer and adding a 700 watt new generation panel that's 26"X4' and bendable stick to curved surface as soon as I get a slider made to place 2 8D Batts under my trailer.
I constantly see people chasing the sun with cheap panels and barely putting out a trickle charge.
Solar will also bring out the weakness of a battery, even with a good controller. Have a panel that's been bounced around or an old battery, that controller is going to try and push out juice creating a top popping off. Yeah, it's a mess and have seen it a couple times too many.
Cheap and solar doesn't mix.
The 700 watt cost a moderate house payment, but the best you can get in a stick on bendable panel at this current time, the 400 watt wasn't cheap either but still 1/3 of the 700.

Yes and no. Just like anything, you can either pay a lot of money for a turnkey solution, or save a ton of money and get cheap stuff, and everywhere in between.

Sealed Lead Acid is a dying technology. Another issue is charge controllers need to be programmed for their planned usage. Buying a controller and just putting it in with incorrect settings will absolutely lead to damaged batteries and possibly equipment. Cheap controllers can do that too.

Sealed lead acid batteries also can't accept as high of a charge rate as lifepo4. SLA shouldn't be routinely charged higher than .2/c, meaning, for a 100AH battery, no more than 20A charging current. A single 100W panel will put out ~8A at full tilt. Lifepo4 can be charged at 1/c if needed, meaning 100AH battery can accept 100A, at a cost of reduced battery life. General suggested charge rate is .3/C, or 30A for 100AH.

Lifepo4 batteries are dirt cheap right now, even rivaling SLA in cost per usable watt hour.

Right now, as it sits, I currently spent ...for my planned 24V system..

$1000- 2,160W in panels (Ja solar, 540W x 4)
$200 - 2x 60A MPPT charge controller (Powmr)


(still need to purchase)
~$50 MC4/QC4 connectors
~$200 wire/fuses
BATTERIES!

Batteries are a huge topic.

Right now, basic El cheapo 12V 100AH lifepo4 batteries, which can be configured in 4s/4p (48v, 400ah) are about $250 ea. Now, since it would be 24v, it would be 2s4p, or 24V@400AH, or 9,600Wh... at a cost of $2k.

Those batteries generally have no low temp shutoff, or built in heater. And questionable quality. A good quality lifepo4 battery should last 10 years even if drained completely and recharged every day.

Pluses are, if a battery fails, it can be replaced. Down side is they're dumb, other than the BMS, and there are no protections other than what the charge controller offers(the one I got offers low/hi temp shutoff). Also, since the batteries are only rated as 4P, any add'l batteries aren't technically supported and may cause issues.

On the opposite side of the spectrum are rack mount batteries. They're more compact, much higher quality, and offer advanced features like built in heaters, higher quality BMSs, and modularity. You can add virtually as much storage as you want. Down side is primarily cost. They START at about $1400 for 24V@200AH, so the comparison with the above 2s4p setup would mean $2800 VS $2k. For me, I think it's worth the extra money.

For someone setting up a fridge and lights emergency setup, it may not make a difference.

All told, I'll be into a 2kW setup with 10kwh battery for less than $5k, which would run the weeniewagun for the next 10-15 years, with virtually no maintenance.

Solar is absolutely scalable.

You can start with a used 240w panel, a single 12V 100ah battery, a basic Mppt solar charge controller, for less than $500, that would run a small chest fridge or dorm fridge virtually indefinitely while providing power for basic lights and phone charging kinda stuff..

All the way up to completely off grid, 100% energy provided by sun and batteries.

I like cheap but most efficient while keeping it simple and cheap.
Flooded batteries are a dying technology because something bigger and better has come along, yet flooded are so much cheaper and nobody that sells the expensive Batts are willing to cost compare over 20 years, because they will lose a sale. New gen batteries are good, and efficient, but to compare cost over 20 years flooded wins that argument. Albeit there's higher maintenance and mess.
Running a bank of 10 grp 31, good panel putting out clean amps and a high end clean ac power just plain works. Lose a battery in your bank, buy a new one for $75-80 and keep going.
There's always a downside, sometimes it's because the end user is stuck on what they've been using for years and not interested in learning something new, why fix something that is already working fine and is inherently cheaper. Starting from scratch might be different when you have nothing to minimize starting cost.
Technology is great, if it wasn't so damned expensive! I'd give up a nut to have 6-8 spendy hi output new gen batteries to slide under the trailer. But I have well over a dozen flooded batteries from a few 8D to a dozen grp65 and a few grp31 at home that gets used during camping/hunting trips and there's no reason to change now.

How do you figure?

SLA batteries can only be discharged to 50% capacity....in routine use. 2 GC2s is 12v @200AH, only 100AH is usable. Those GC2s are about $130ea at bare minimum. So, $260, and average is 800-1000 cycles before dead.

A lifepo4 100ah 12v battery is 100% usable with no damage, costs about $260, and lasts 3000-5000 cycles before needing to be replaced. They also weigh half as much and can charge must faster.

There is no cost benefit to SLA. The only advantage to SLA is for starting batteries, and even then, that's quickly changing as well.

$80 for a deep cycle Group 31? This isn't 1998...


That's one of the great things about the newer batteries - they have built in BMS... Battery Management System. Think of it as a mini charge controller. It will shut off charging when full, and disconnect if overloaded....

My bank is all 200ah cell tower batts. used ones are available that are 1-3 years old. They can be gotten for about $100 each or less.

I have 16 of them in my bank at our other property.

Plus when they finally die in 6-15 years, I can get SCRAP lead $ for them.

Its not in a camper so I could care less about the weight and they are sealed = no mantainy!

A little OT, TW, but I'm getting a little curious about this stuff. A buddy of mine and I are having an argument since one of my plans for the inheritance is to try to set up an offgrid live-aboard Class C, but it needs to have enough power to run a high-end gamer-grade desktop rig, a small server AND my work laptop. He insists it can't be done fully offgrid--as a techie with liveaboard experience, what say you?

I'm also starting to think about once we finish probate and start refurbing the current house, trying to gut the old greenhouse (only southern exposure we have for PV's) and turn it into a utility shed hosting a solar system, but that may be a question for another time.

Couple years ago, $80 something each, with core and tax. Shopping around and you can find deka's for under 150. Batteries aren't that expensive if you look around.
Might want to price FMP new gen batteries, they are the only distributer in WA as of a year ago, will be price mark-up for each buyer transfer.
Make friends with an Interstate distributor that services the RV dealers. The dealers won't charge dead batteries, you can find new to newer deep cycle 6 and 12v for core exchange prices too. Ran new used 6volts for a dozen years, replacing the batteries with other new dead batteries every spring.

That's a good score, for sure.

A good quality gaming setup could easily push 1KW. That's almost as much juice as air conditioning. That's a lot.

Is it possible? Depends on how much real estate you have for panels. Depends on how much real estate for batteries you have for when solar isn't producing.


It's all a juggling act.

1. Figure out your loads.
2. Figure out how long you need to supply those loads, without solar, plus overhead, which will tell you how large of a battery bank you need.
3. Figure out how quickly you want to be able to recharge your battery bank, and run your loads in #1 - that will tell you how much solar you need.

The hardest thing for me was to stop thinking volts/amps, as that's what I was trained in and used throughout my career/life, and start thinking watts. W=V*A so it's an easy calculation to make... but much like transitioning from 12hr time to 24hr time it takes a bit before you stop doing the calculations in your to convert it and just accept 'it's 1500' and not try to do the math to figure it's 1pm.


As an example, let's say, per day.... you use..

Lights. 20W, 8 hours
Computer, 500W, 4 hours
Router, 10W, 24 hrs
Fridge 60W, 24hrs

(20*8) + (500*4) + (10*24) + (60*24)


That's 3,840W

So, how many days do you want to run with little or no solar power? Let's say 5 days.... so that's (3840*5) 19,200 kw.

Assuming a 12V battery bank, we can convert watts to volts and amps to find how many Ah of battery you need.

Since we know V*A=W, we can reverse the equation W/V=A. So, 19,200 /12 = 1600. So you'd need 1600ah of 12v batteries to have that load for 5 days with zero backup.

Now the question comes into play... how much of those loads are in day time VS night time? How much of those loads will be powered by solar?

Also, how long do you want it to take to recharge your battery bank from the usage of the night before?

If you're using less than 4kw/day and you have 2kw of solar, then your loads are low enough that your battery bank will be getting charged using excess power from the panels.

The idea is to use high current stuff during the day so solar is used to it's max, because batteries can only hold so much.

However, if you're a night owl, that might flip, where your heavy loads are at night and you have almost no loads during the day, allowing your battery bank to recharge that much faster.

Get too much solar and not enough battery and all that energy is wasted. Get too much battery and not enough solar and your batteries will always be dead. It's a juggling act.

The above doesn't take into account efficiency, conversion loss, etc etc. Generally, everything should be given at least a 10% margin of error. Eg if you think you're gonna use 100W, calculate 110w. If you think you need 1000w of solar, go 1100, etc etc. That way you've covered for any miscalculations, so if everything is perfect, you actually get a bonus.

Don't forget motor start up. Takes more to get it to turn, then to keep it turning. If you are planning to use battery/inverter, get a QUALITY soft start kit, or build your own for the 1/4 of cost.

There is that, but I was thinking completely isolate the "residence" vs "vehicle/cab" electrical systems. Maybe have a breaker I can throw to cross-tie in an emergency where I need to use the engine as a genset for some reason or use the residence battery bank for a jump, but I was also considering a small gas generator or if I can figure one out a knockdown wind-farm for auxiliaries.

This is a normal configuration.

If voltages are the same, you can use a simple switch or battery isolator (one of the reasons I want a 24V battery bank in my 24V truck). Otherwise you can get a DC->DC converter/charger, that will regulate voltage and current going to the battery bank.

With the juice I will have available, I will be able to boost the front battery and start the truck from the house battery bank, or use the alternator to charge the house batteries, should I have no solar for 2 weeks.

There are dual circuit cutoff switches. Both banks are wired to the switch, and you can select either Bank 1, Bank 2, or BOTH to be connected to the alternator. So, you can use your house batteries (if SLA, or a substantial amount of LiFepo4) to start and completely bypass the starter batteries, or divert all power to house bank to charge it quicker.

This is what I did in my last 5 ton. Switch has - from 12 o'clock to 9 o'clcok - OFF - BANK 2 ONLY - BOTH - BANK 1 ONLY - Which allows the electrical system to be completely disconnected from the truck - a great option if it's going to be sitting for a bit, as it prevents any possible drains coming from the vehicle itself, and acts as a quasi theft deterrent, since it won't start unless it's in the right position, and in my case, the switch was not readily observable.