kausie avatar image
kausie asked

Simple campervan setup help with system build

Hay everyone ive done lots of searching but the information seems to get lost sorry if i appear lazy.

Im building a solar system for my campervan and just need to confirm or help with the build as im unsure but heres what ive figured out so far.

I have 1x 300watt 12v flexi mono panel. Using supplied c4 cable and 5m c4 cable extension (no fuses do i need??)

*Im thinking i need battery isolator switch here red turny knob one to cut off solar panels if needed? Can i live without?

That runs down to victron mppt 100/30 smart solar. (And directly terminates to it with bare wire no fitting?)

From the mppt i directly connect my battery with 8mm/awg wire (again no fuses?)

My battery is a 100ah lifepo4 solarking battery with a built in battery management system enclosed. (So no need for battery monitor right?)

Then directly connected to battery ill wire a 12 way blade fuse block with negative terminals Input rated voltage: max. DC32v
*Input rated current: max.100A
*Max current:30AMP/way
(what wire size this to battery? )

Then from that ill connect max air fan and strip lighting

I want to add a dometic crx40 fridge to system but i dont know if i connect it directly to battery or it gets connected to the fuse block? The fridge has usb ports on it to charge my phone. But i also believe it has its own fuses.

I would really apreciate the help.

Thank you very much

MPPT ControllersLithium Batterysmart solar set-up helpfusesdc system
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5 Answers
dazey77 avatar image
dazey77 answered ·

You shouldn't have any lines coming off your battery that are unfused. If the link from MPPT to battery has no fuse and goes direct to battery you need to add one.

I have no idea if the solarking has a sufficient BMS. It should protect the battery against deep discharge or over charge (the latter may not be a problem for you as your MPPT will do this)

Do you have no alternator charging planned? Winter use?

Nothing ever connects direct to the battery without a nearby fuse. You are protecting the lines not just the kit itself. If you have a 12-way fuse box that is more than big enough.

Battery isolators are to disconnect a battery in storage, not to disconnect solar. If you have solar and the van gets daylight when not in use then you don't need to disconnect the batt, will be kept charged.

A battery monitor helps you understand your state of charge. Battery voltage is a poor indicator as it depends on load, when your fridge cycles on the voltage will drop. A battery monitor will give you a proper indication of % left. If your generation always exceeds your usage then you don't really need a monitor, if it doesnt then a monitor helps you keep tabs on the state of play.

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JohnC avatar image
JohnC answered ·

Take a look here Kausie. Nice'n'new, and suggestions welcome for improvement:

Download the link, then come back with the bits you still need help with.

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kausie avatar image
kausie answered ·

Thanks dazey great help

So 300 watt solar to mppt then wired and fused 8mm to battery then from battery 8mm wire to isolator switch then 8mm wire to 12 way neg pos blade fuse block then my fridge light and fan wired to that fuse block.

Cool how hard can it be :D

1 comment
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esteban avatar image esteban commented ·

Hope you see my answer. I know you want it to be simple, but it does take some attention to detail to wire up this kind of system so it works well and you can manage it so you always have power for your fridge. You can definitely skip the battery monitor, but I strongly suggest that you wire your loads off the MPPT's load output, not the battery itself. This gives you many advantages.

I also suggest that you use a flip reset breaker as noted above, not a burnout and replace fuse so that you can disconnect when desired. Also never need fuses, which are expensive. Very helpful.

Also, especially if you don't use a battery monitor, get the bluetooth adapter for the MPPT if it does not come with BT built in. Depends on the model. That way, you can use the Victron phone app to see how much power is going into the battery and how much is going out. You will congratulate yourself every day you use it that you have a way to see power in and power out for the battery. You will have a voltage reading too. Monitoring the MPPT with the app will help aiming the solar and troubleshooting. All of this will give you control, more dependable power and help you maintain the life of your expensive lithium. The built-in BMS should keep you from ruining the battery but some hands-on monitoring will allow you to keep it operating in the sweet spot for longer life.

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esteban avatar image
esteban answered ·

Yes, you want to connect everything to your battery by fuse. I am using a 12V circuit breaker as both a disconnect switch and fused protection. Mine is 100 amp as I do charge my house battery via the alternator/starter battery. If you are not charging via alternator, you could probably do better with a lower rated breaker, perhaps 50 amps.

I prefer name brand for main battery connection, but there are also cheaper off-brand ones if you want to gamble and/or for less critical uses

Bussmann (BP/CB185-100) 100 Amp Circuit Breaker

KUMEED 12V DC -Car Audio Inline Circuit Breaker Fuse for System Protection (40A)

I would add any decently rated DC switch for solar panel (does not have to be a heavy duty battery disconnect) or another breaker (safer place to use cheap low rated Chinese breaker) between the input of the charge controller and the solar panels in case of shorting and to disconnect panels for long term vehicle storage. You do not want to store your lithium at full charge so best to drain to 50-60% of full charge and disconnect from everything else but battery monitor when stored.

Connect your house fuse block to the load output of the Solar controller. This will allow you to monitor the loads via the Charge controller as well a provide protection from over draining battery.

I also recommend a battery monitor: the BMV 712 is great.

Also you will want something to disconnect the starter battery from the house battery if you do use your alternator to charge. Cyrix Li-connect is one.

Run thick wires from your fuse block to a good marine quality 12V outlet for your fridge. The fridge uses some power and will run better if you minimize voltage drop. Or you can install Anderson connectors or other types if you want to get fancy. The fridge will not be unplugged very often so as long as the mating components are top quality, the common cigarette lighter outlet should be fine.

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dazey77 avatar image
dazey77 answered ·

I will also offer some slight amendments to previous poster on fridge connections.

a- Cigarette lighter sockets are awful connectors and don't lock. They are designed as cigarette lighters not power outlets so only use them where you have to for consumer devices.

b-for back of house connections use automotive grade connections of a suitable grade. Anderson connectors are not suitable for fridges really (too big). For a fridge I suggest these:

for smaller loads you can use the smaller 2.8

These are all simple to crimp. Do buy a crimp tool, don't use pliers!

The wiring guide posted is a good place to start.

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