DIY Solar Power station question for truck bed

[cmhmh]

I am looking to build my own solar generator for my truck bed to power my Truma C60 fridge, some lights, and re-charge phones. I have a 12v DC outlet in the bed I'd like to be able to slow charge from while doing long drives. I do not currently want to install an alternator charger.

I do not currently have a need for an AC inverter, but will leave space in the Rigid tool box I plan to build the battery in case an inverter becomes a need at a later time.

I have drawn a wiring diagram linked below and put together a parts list, but am struggling to sort out what gauge wire I need to use and would be grateful for some guidance here.

Wiring diagram:



Parts list:

• Renogy - Core Mini - 12.8V 100Ah Lithium Iron Phosphate Battery
• 6 gauge wire
• Victron Energy Blue Smart IP65 Smart Car Battery Charger 12V 15A
• 2pk: 12V USB DC 65W USB-C PD3.0 and 18W QC3.0
• 2 Pack Car Cigarette Lighter Socket DC 12V Waterproof Power Outlet
• Battery Power Cut Master Switch Disconnect Isolator
• Blue Sea Systems 6 circuit fuse block
• 2x - Blue Sea Systems Terminal Fuses - 50a
• Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP
• Renogy - Rover Li 30 Amp MPPT Solar Charge Controller w/ BT module]()
• Renogy 100W N-type compact Suitcase. Not married to this panel. just added to parts list.
• Etekcity Infrared Thermometer Laser Temperature Gun - check wire temps before use

 

[robbob2112]

First - if you haven't already purchased anything you have made a wise choice...

Second - friends don't let friends by Renogy products -- when they work they are fine --- when they don't and you need to claim a warranty they are painful at best and impossible at worst... They are also over priced for what they are -- they spend their money on marketing and advertising instead of customer care.

If you have already purchased it and returns aren't free work with what you have and when it goes bad decide if you want to deal with it.


For wire size - https://learnmetrics.com/calculate-wire-size-dc-awg-wire-gauge-calculator/

But as for deciding how much current you will need --- from the battery assuming you have a 12.8v100ah battery with a 100amp BMS inside

100amps * 1.25 = 125amps --- this is the size MRBF fuse you could use on the battery post to protect from shorts there --- Use wire to match -- The chart says 1/0 --- if you use welding or battery wire with a 105c rated sheath you can use 2awg. If you really only want to ever use 50amps you can downsize according to the chart -- but if you add an AC inverter later it will make you go higher which means you will have to re-run the wire --- doing larger now is easier than re-running later.....

Batterycableusa.com will cut and make cables to length with the ends of your choice for a good price --- this saves having to buy a hydraulic crimper to make just a few cables .... you can sometimes go to a welding shop and get cables made with welding wire. Either way you want to use pure copper fine battery or welding wire for the battery lines.


The switch you linked isn't great - this would be better instead - it only goes in the positive line

https://www.amazon.com/Blue-Sea-Systems-Battery-Switch/dp/B00445KFZ2/

Adding a shunt based battery monitor is a good choice

Amazon.com

There is a free program called drawio -- takes about 20 minutes to learn to use --- you can find various examples in my answer thread --- makes designing this sort of thing easier and beats an eraser

What questions did I miss?

 

[cmhmh]

First - if you haven't already purchased anything you have made a wise choice...

Second - friends don't let friends by Renogy products -- when they work they are fine --- when they don't and you need to claim a warranty they are painful at best and impossible at worst... They are also over priced for what they are -- they spend their money on marketing and advertising instead of customer care.

If you have already purchased it and returns aren't free work with what you have and when it goes bad decide if you want to deal with it.


For wire size - https://learnmetrics.com/calculate-wire-size-dc-awg-wire-gauge-calculator/

But as for deciding how much current you will need --- from the battery assuming you have a 12.8v100ah battery with a 100amp BMS inside

100amps * 1.25 = 125amps --- this is the size MRBF fuse you could use on the battery post to protect from shorts there --- Use wire to match -- The chart says 1/0 --- if you use welding or battery wire with a 105c rated sheath you can use 2awg. If you really only want to ever use 50amps you can downsize according to the chart -- but if you add an AC inverter later it will make you go higher which means you will have to re-run the wire --- doing larger now is easier than re-running later.....

Batterycableusa.com will cut and make cables to length with the ends of your choice for a good price --- this saves having to buy a hydraulic crimper to make just a few cables .... you can sometimes go to a welding shop and get cables made with welding wire. Either way you want to use pure copper fine battery or welding wire for the battery lines.


The switch you linked isn't great - this would be better instead - it only goes in the positive line

https://www.amazon.com/Blue-Sea-Systems-Battery-Switch/dp/B00445KFZ2/

Adding a shunt based battery monitor is a good choice

Amazon.com

There is a free program called drawio -- takes about 20 minutes to learn to use --- you can find various examples in my answer thread --- makes designing this sort of thing easier and beats an eraser

What questions did I miss?

Thanks for your detailed reply here.

I have not made any purchases yet!

I had continued doing research after posting and have updated my parts list to remove Renogy and replace with a Victrom MPPT Charge Controller and, likely, a LiTime LiPo4 battery.

I spent more time watching Will Prowse's YT videos about wiring choices, etc and that has been instructive. I'll check out Batterycableusa.com as well since I had not yet come across that.

I'll try to get an updated wiring schematic in drawio.

Questions/Next steps:
- wire size. For the 12.8v 100aH battery... I follow your math here, but does this mean I would only have to use the 1/0 wire from the battery terminals --> fuse --> switch? Then, for the rest of the system I can use device-specific wire size? Likely 8 AWG between the Victron ACDC charger and Victron Solar MPPT Charge Controller?
- Fuse size: I just stole that 50A fuse from a number of YT videos I watched, but was struggling to see if that was actually an appropriate size. The Victron 100/20 MPPT requires, I believe, a max 30A fuse. Is it correct that I'd need to use your suggested fuse off the battery's positive terminal and just ensure that I have an appropriate fuse in the fuse block for the other devices?

Thank you.

 

[Enketchum]

Good choice on ditching the renogy crap.

You don't need huge wire coming off the battery. You only need big wire if you are going to draw big loads. If something shorts, that wire will only see the full amperage for a fraction of a second. That voltage drop turns into heat and heat for a fraction of a second can be handled by a smaller wire. Big wire in the 0awg size usually goes between battery and inverter because the inverter takes sustained high amperage loads.

Fuses go by max amperage draw x 1.25

Question to everyone else: I've never seen anyone wire the solar controller to the fuse block. Is that normal / safe?

 

[robbob2112]

Looking at the fuse panel you linked I would use a 125amp MRBF on the fuse block --- then the 1/0 wire to the fuse block. Then you can just stick to 30amp or less blade fuses for the individual devices....

In the product description for the fuse panel

• Max Amps: 100A per block, 30A per circuit, Max Volts: 32V DC, Mounting :#8 (M4) Screw, Negative bus: #10-32 stud, Positive bus: #10-32 stud, Recommended Stud torque: 24 in-lb, Screw Terminal Torque: 18in-lb, Screw terminal type: #8-32 screws with captive star lock washer

For DC current - 10awg is good to 40amps if in free air and if enclosed it is 30amps. For 12awg you can go to 30amps in free air and 20amps in a closed space. 14awg is good to 20amps free air and 15amps in a close space.... I wouldn't run less than 14awg for anything that doesn't come with its own wires.... The small stuff will come with an inline fuse holder a lot of times.

Good choice on ditching the renogy crap.

You don't need huge wire coming off the battery. You only need big wire if you are going to draw big loads. If something shorts, that wire will only see the full amperage for a fraction of a second. That voltage drop turns into heat and heat for a fraction of a second can be handled by a smaller wire. Big wire in the 0awg size usually goes between battery and inverter because the inverter takes sustained high amperage loads.

Fuses go by max amperage draw x 1.25

If he is fusing the 100amps the block supports the wire size needs to match. If he fuses at 50amps then the wire size can be bigger, but not smaller than what will support it. If this is what you are saying great--- if you are saying run a small wire, but fuse to 125amps that would be incorrect.

Question to everyone else: I've never seen anyone wire the solar controller to the fuse block. Is that normal / safe?

It works fine, especially for a small system. The fuse block supports up to 30amps per fuse and the MPPT puts out less than that. Placement wise I would put whichever devices have the most continuous output/input nearest the the battery attachment. Basically he will be using the fuse panel as a bus bar that has a fuse at the bus bar for each connection.... and at least with Blue sea verse a no-name brand I would trust it to run to the full rated current in short bursts and lower continuously