Please review my solar system assumptions

Life on the Road Electrical: Batteries, Generators, Solar, etc...
1

Would you please review my solar system plan and let me know if I’m making incorrect assumptions?

I’d like to power the following in the van every day, and be able to survive one cloudy day without shore power:

  • LED Lights ~10 ah
  • Laptop, phone, etc chargers ~10 ah (AC)
  • Dometic CFX 65W Powered Cooler: ~10-15 ah
  • MaxxFan Deluxe 7500: ~12-15 ah
  • Water Pump and other minor loads: ~5 ah
  • Bosch Electric Mini-Tank Water Heater Tronic 3000: ~50 ah? (AC)
    –> total = 105 ah

I’d like to install the following:

  • 2 x 100 ah BattleBorn LiFePO4 batteries, (in parallel: 12v 200ah)
  • 3 x 100 watt 12 Volt Renogy Monocrystalline Solar Panels (in series: 12v 300 watt)
  • Renogy 3000W Pure Sine Wave Inverter Charger
  • Rover Li 40 Amp MPPT Solar Charge Controller
  • Some battery monitor: I haven’t picked one yet
  1. Will this solar setup be adequate for charging the 200 ah battery? Is 200 ah too optimistic for the above mentioned loads?

Product specific questions:
2. Why is the Renogy 3000W Pure Sine Wave Inverter Charger so much cheaper than the seemingly similar product (VICTRON MULTIPLUS INVERTER/CHARGER 3000W 12V) by Victron? What does the Victron do or allow for that the former does not?

  1. Is a 40 Amp MPPT controller needed, or would 30 Amps be sufficient?

I chose this by dividing the wattage of the panels (300 watts) by 12 volts = 25 Amps, and considering a 125% safety factor (25 x 1.25 = 31.25 Amps which is just over 30 Amps). I thought one advantage of the 40 Amp MPPT would be to allow for adding one or more solar panels in the future if need be.

Are there any disadvantages to the 40 Amp vs the 30 Amp aside from a small price difference?

  1. Is the 3k watt inverter overkill? Aside from price, does it have major disadvantages compared to a 1k or 2k inverter?

We are thinking that on bright sunny days we might plug in an induction cooktop (~1k-1.8k watts) if propane is low, or plug in a microwave oven or toaster every once in a while.

2

Greetings!

You’ve got lots of problems here…

10ah (AC) =120ah DC

50ah (AC) =600ah DC

Maxx fan probably 40 ah per day in summer. (~2a x 24 hours each)

Dometic CFX 65W Powered Cooler: closer to 80-100ah per day in summer. (personal experience, 40-50ah per day in mild winter) 12v only fridges/freezers are extremely overpriced energy hogs. Propane fridges are much more energy efficient and reliable.

Inverters typically consume 20%-25% more power than whatever you’re running, the top two numbers reflect that, whenever possible it’s better to get the car cords for your electronics. Inverters are VERY inefficient and should be avoided all together if at all possible.

Those batteries aren’t worth the money, go with typical lead acid deep cycle batteries for the best bang for your buck.

If you’re going to have 200ah worth of batteries, you want AT LEAST 600 watts of solar, and in Seattle that might not even be enough, but in all seriousness, solar is usually the worst and most expensive choice anyway. Charging via an isolator, relay, or solenoid while driving is always the best choice, and should be your first choice. A cheapie generator or shore power combined with a cheapie battery charger comes in as #2, but should be included, and solar comes in dead last. None of the real experts that aren’t trying to make money by giving bad advice use solar, not to mention that parking in the sun during the summer is a really dumb idea. 99% of the time, just charging while driving keeps my batteries full, the other 1% of the time, I have my $99 generator and my $29 battery charger. My generator will run for 8+ hours on a gallon of gas.

Heat, heating water, an induction cooker, or a microwave are best run on either shore power or a generator, if you INSIST on using electricity. Fuel powered appliances are much more energy efficient.

As an example, my entire power system cost about $200. $99 generator, $29 battery charger, 110ah deep cycle battery installed, with the isolator $80 at a battery shop. No solar or controller, and no inverter. The generator and battery charger can charge either my house battery or my starter battery, but most often gets used charging other peoples batteries that are foolishly relying on solar. If you are going to use an inverter, you want the smallest one possible PLUS 25% over the maximum load. Batteries are typically spec’d at a 20 hour rate, meaning that if you have 200ah of batteries, they don’t want a load of like more than 200/20hrs =10ah draw at any one time. Anything higher will seriously shorten the battery(s) life. Also keep in mind that if you have 200ah of batteries, only half or less of that is usable without damaging the battery(s).

I try to be power smart, and charge my electronics while driving. This is a free charge, that doesn’t effect my house battery, which is also charging simultaneously.

I do know a couple of people who love their roof full of solar, but for each of them, I know hundreds who have learned to hate it, just like I have. Over the years I’ve wasted probably $10k between several attempts to make solar work for me, (and my needs are minimal), and it never worked as advertised for me. Solar hot water is doable though, just have a back up plan for when the sun isn’t shining. Anywhere in the country, you can go a week or more without seeing any sunshine, especially in the winter. The better options don’t rely on sunshine…

As much as solar powered house battery charging has failed me, I do have individual solar powered items that I use daily. Unlike the roof solar, they seem to charge just fine in only daylight by sitting them in a window or outside. Among them are lanterns, flashlights, headlamps, a bug zapper, a radio, and a battery charger for AA/AAA/C/D/9v batteries, and it also has several USB ports on it. I also have water jugs and spray bottles painted black for solar hot water and showers.

Our systems don’t need to be expensive to be good, convenient, and efficient.

Cheers!

"Be the reason someone smiles today!" ~ Van_Dweller



3

Thank you for your reply. I had already converted the AC loads to DC aH. And your assumptions regarding 50% DoD for batteries and price are correct about AGM batteries but not LiFePO4 batteries like BattleBorn.

  • I understand that the BattleBorn batteries can be discharged fully. They’ve simply spec’d the batteries at 120 ah and the BMS stops discharging when it reaches 20 to avoid harming the longevity. They are more expensive upfront but if they actually last the 3k-5k cycles that they claim they’ll be cheaper than AGM over time. Lastly, they weigh a lot less.

  • I won’t run a generator, for all sorts of reasons. But I’ll research the alternator and B2B chargers for charging when the van is being driven. Unfortunately our van is a Diesel Sprinter so idling in it will quickly harm the DPF system but it’s a good option for when driving.

  • Yes our cooking will be with propane, but it’s good to have redundancy with the microwave/etc if possible. That’s why I’m keeping that in mind.

  • I hear you about minimizing electric loads, looking at alternatives and considering the price and reliability aspects and will continue the research.

Thanks!

4

Greetings!

I’m not ready to buy into the marketing hype of any of the lithium batteries just yet. Everybody who has used them disappears from the forums and gatherings shortly after, and I know of at least one case where they had solar and lithium and it burned their roadtrek down. When I see someone other than a promoter sharing how long their lithium batteries have lasted and how great they are, then and only then would I even consider them. To date, it’s only promoters pushing them.

I’ve actually been buying ~$20 junkyard deep cycle batteries and have been getting 5-7 years out of them. I get ones that are almost new to start with. They might weigh more, but they’re cheap, reliable, and plentiful. A tip passed on to me by other old timers.

Those B2B chargers have no advantages over a simple isolator, relay, or solenoid. It’s all marketing hype. Your vehicle is already designed to charge 12v batteries.

I practically never need to run my generator for myself. I can go a week on my house battery, and a second week on my starter battery which is also a deep cycle battery, before my low voltage shut offs will disconnect them. That still leaves me plenty of starting power after it disconnects. I highly recommend those cut off devices too. So my generator is actually a backup plan, not something I use normally for myself.

You are correct that idling is never a good idea for any vehicle.

Cheers!

"Be the reason someone smiles today!" ~ Van_Dweller



5

Hey and welcome. In short a 30amp solar charge controller would be fine. If you are looking at increasing your batteries amp hour storage and are thinking 2 batteries a good option is also to connect 2 x 6v batteries in series to make a 12v battery. Connect this to in parallel to your first battery via a continuous duty solenoid so that your battery will charge while driving but will not drain your starter battery when you have pulled up for the day and night. Solar is expensive and if used exclusively without the above method mentioned in overall very ineffective. It is great when used in conjunction with the above method as the alternator does not have the ability to fully charge the battery the solar provides a constant trickle charge thy will increase the life of your batteries. As for the inverter, if you are only charging phones and computers a 300w pure sine wave inverter would be sufficient. As mentioned in other comments, inverters are not very efficient. Using a 12v socket to charge phones, cameras and laptops in a much more efficient option. Good luck with the set up and look forward to hearing how it all goes.

6

Greetings!

Alternators are totally capable of fully charging your house battery(s). I ditched solar long ago, and solely charge my house battery via alternator, and even when doing very little city driving, I never run out of power unless parked for over a week without driving.

My power needs are minimal, mainly a laptop and a fan, and a very low power, under 2 amp @ 12v swamp cooler when it’s hot.

Cheers!

"Be the reason someone smiles today!" ~ Van_Dweller



7

Hi…solar is usually the worst and most expensive choice anyway. Charging via an isolator, relay, or solenoid while driving is always the best choice, and should be your first choice. A cheapie generator or shore power combined with a cheapie battery charger comes in as #2, but should be included, and solar comes in dead last.

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8

I use lithium batteries in all my motorcycles and they work awesome. They are a bit more pricy than an normal acid batteries but also way smaller, lighter, have a ton of power and a way longer lifetime. Can’t speak about how they work as a home battery but until now i only can recommend them. I still use a normal acid in my camper though just because it’s cheaper.

9

Greetings!

I was talking to an electric wheelchair/scooter tech a little while back, and he said they typically got 3+ years longer lifespan out of lead acid batteries than they did the more expensive lithium ones. Not a good recommendation in my book.

Luckily 1 or 2 heavy lead acid batteries in a camper van or larger aren’t much of an issue.

Cheers!

"Beat the heat with an energy efficient 12v DIY swamp cooler.
Indirect swamp coolers work great even in high humidity areas." ~ Rubber Tramp



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10

I ended up getting the 2 LiFePO4 batteries listed above and added a 4th 100 watt solar panel because they are cheap. So far (warm summer months) the system is charged all the time and the MaxxAir fan, Dometic fridge and other loads are all drawing as much power as I had assumed.

I have hooked up the 2000 watt version of the Renogy inverter charger listed in the OP and it is able to power 10-15 Amp 120 VAC table saws and such just fine.

I have no idea what some folks have against solar, lithium batteries but so far things are working well for us.

I’d urge future readers to learn about voltage drop calculations and size their wires for a ~1% loss when possible.

Here is my wiring diagram in case it is useful to folks later:

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