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johnny-nova avatar image
johnny-nova asked

Will solar power be enough? Newbie here

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Hi,

Does anyone know if this idea below will work? (note: I am a newbie to 12V electrics)

I want to power off JUST SOLAR for a small camper van. That is build a system with 1x solar panel and 1x leisure battery only to power a small fridge (30L), some LED lights, MaxAir fan, 12V cigarette & USB sockets plus an inverter (1000W).

I figured if I oversize our battery and go for a 150-200Ah plus the largest wattage fixed panel to match and see if we can travel and power most of our appliances using just solar. If solar charging is not enough then I will add a DCDC charger later to this system.

I have chosen to go with the Lynx distributor (incl fuses) to make wiring more compact instead of separate positive and negative busbars and circuit breakers.

Have I missed anything in my attached wiring diagram?

The sizing of wires, fuses, Solar charger are still to be finalized but initial calcs indicate a 130-150Ah battery would be enough for our camping needs.

Thanks in advance for any comments




wiring diagram
sketch-a.png (34.9 KiB)
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8 Answers
cargol66 avatar image
cargol66 answered ·

Hi Johnny,

Your schematic is quit good.

Take care to choose the right devices for 12V battery system.

Without information of your solar panel power and your location, it's hard to know your solar energy potential. You can use https://re.jrc.ec.europa.eu/pvg_tools/en/#HR to simulate your system.

Located in center of france (Bourges), a 300 Wp horizontal panel without mask with 900 Wh daily consumption will give you 9 to 24 % days with battery empty between may to august

pvbattery-47095-2411-undefined-300wp-1800wh-50-900.png

About the leisure battery, 150 Ah will give you about 900Wh usable energy.

I suppose your leisure battery is VRLA type, to preserve it, DO NOT discharge it below 50% SOC !

Most important things about batteries are : never discharge it more than 50%, charge it asap when discharged, Never overcharge it. Check if your battery handles equalization charge (VRLA batteries do not handle it) keep it in a dry and 20°C place as long as possible.

To know more about batteries have a look to https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

As you don't have power gen or mains available any time, my advice is: add a smart switch related to BMV to disconnect your leisure battery when 50% SOC is reached.

Take care, some device like battery protect are electronic one and current flow direction is important (not just an electromachanical relay). They do not support DC current flow to inverter. Carfully read Victron battery protect user manual.

As battery capacity is temperature sensitive, use temperature sensor with your BMV and share the information to charger.

And most important : enjoy camping while respecting Nature.

Best regards.

Bruno.


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johnny-nova avatar image
johnny-nova answered ·

Hi Bruno,

Thanks for your reply

The battery when I purchase will be a Lithium type which I understand you can discharge close to 100%. Several brands on the market have built in BMS which protect against overcharging, over discharging, short circuit, temperature and over current. My travels will be in Australia mainly during the spring, summer and autumn months of the year which if I can get 4-5 days of battery power a week to run devices I will be happy.

This website below I found useful in getting an idea of what size solar panel to go for depending on what size battery I choose. The calculator allows you to nominate the no of peak sun hours against a % discharge of battery and then you can quickly read what size panel would suit.

https://footprinthero.com/solar-panel-size-calculator

Regards JN

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cargol66 avatar image
cargol66 answered ·

Hi Johnny,

OK. li-ion batteries are more efficient than lead acid one. it's the right choice.

Choose one with active BMS and don't forget to setup your MPPT and charger according to battery specs (Imax during bulk and charged voltage).

a battery protect relay controled by BMS remains useful with Li-ion batteries vhen you are off-grid into the wild with no alternative supply (may be this disconnection fonction is included in the battery.)

Regards.

Bruno.


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Sarah avatar image
Sarah answered ·

Hi @Johnny Nova your design looks like you have most of the basics covered and the solar panel is probably the cheapest component in the system. Measure up the largest panel that you can put on the roof - if you can exceed 300 watts you should be pretty good given your battery, type, size and load. If possible keeping a common manufacturer across all products can be beneficial.

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johnny-nova avatar image johnny-nova commented ·

Is there a reason why you see multiple small powered panels (wired in series or parallel) on RVs or camper vans versus just one larger powered panel?

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kevgermany avatar image kevgermany ♦♦ johnny-nova commented ·
One reason is getting the panel voltage high enough. Another is fitting into available space. Also panel availability. I have 2x300W on mine. Chosen for dimensions and getting enough power.

Watch the fridge. If it's not a compressor version, power consumption will be high.


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johnny-nova avatar image
johnny-nova answered ·

Hi Sarah

Thanks for your reply.

Yes I hope to use the Victron brand for things like the shunt, solar charge controller, DCDC charger (later if required) and Lynx distributor.

For the solar panels I have been checking out the Trina brand that sell a 425W panel.

Cheers JN

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Sarah avatar image Sarah commented ·
It may also be worth upgrading the inverter to an inverter/charger, you may not use it very often but it can be beneficial for overnight charging or if the camper has been garaged for a while, and cell balancing should it be necessary.
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johnny-nova avatar image
johnny-nova answered ·

Is there a reason why you see multiple small powered panels (wired in series or parallel) on RVs or camper vans versus just one larger powered panel?

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jordan-de-geus avatar image jordan-de-geus commented ·
This may be for a number of reasons - they bought a kit that included panels, or its what they could afford and added to the system. Maybe they didn't have a good way to fit a single large 350w panel, or it was more space efficient to have a bunch of panels
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jordan-de-geus avatar image
jordan-de-geus answered ·

Your diagram is pretty good - one thing i would note is your running everything off that blade fuse block. Thats okay, but you might want to look at a breaker panel instead of the fuse block and size your breakers accordingly.

This would give you a way to individually turn on/off circuits - for example power is low, you might want to shut down the fridge and reduce its run time.

What sort of loads does your camper have on a daily basis, where are you located? Not sure what type of fridge you have. I have a small chest freezer thats about 30L, it burns about 35-40ah per 24/hours. My ice box is probably 100 or so L, it burns around 40-45ah per 24hours. Winter time the freezer is off, summer time it is on.

I live full time off grid on a sailboat - 2 x 350w panels - 440AH firefly batteries that i discharge down to about 30% remaining capacity(try to stay at 50% but sometimes go lower). Having breakers is very useful considering i do like to be able to keep things off(parasitic loads) unless I'm using them.

Just food for thought

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johnny-nova avatar image johnny-nova commented ·

Hi jordan-de-geus

Thanks for your suggestion re: breaker panel versus fuse block.

Do the breaker panels have replaceable fuses or does it just trip during an overload and then you just flip a switch ?

How does it work if you have varying fuse sizes like you might set up on a blade fuse block?

I only plan to run a small 30L fridge, some LED lights, ceiling fan and 12v sockets......plus small inverter (maybe up to 1000w)

cheers

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jordan-de-geus avatar image jordan-de-geus johnny-nova commented ·
This is strictly based on my experience on board a much more complex system so it's harder for me to gauge smaller stuff.


I would look over your fan specs & fridge spec and get their wattage or amp rating, from there you can determine 24hr loads - your inverter usage will also need to be considered.


I run multiple caframo fans 24/7 in winter to help circulate heat through the boat. Each one draws roughly 0.5ah. that's 12amps per fan(2 run non stop) per 24 hours. This alone is 24ah. My fridge consumes roughly 42ah per 24hours. Between these three devices that's 66ah per 24 hours.


If you run lead acid batts, your going to probably want 200ah if your anywhere close to these daily numbers imo as you only have 100 usable. This would give you 1 day of usable capacity with zero charging (solar shaded for example). Lithium 200ah battery would be good as it'd give you 2 or so days with no intake of power. Think being at a camp site in a forest - solar isn't going to produce much


As for breakers, if you exceed the capacity of the breaker they just trip - just like a fuse - except you don't need to replace them. There's cheap ones on Amazon, or you can buy quality ones(blue seas for example).

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kevgermany avatar image
kevgermany answered ·

You can also add a link from starter battery to smart shunt to monitor its voltage.

Also consider a reverse flow trickle charger from leisure to starter if the van will stand for long periods.

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jordan-de-geus avatar image jordan-de-geus commented ·
I would suggest doing this as well. Do it with an ACR that way when the house is full/high voltage you then charge the starter. Have to look into how ACRs work when you have lithium though
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