Sanity Check on skoolie electrical system (help)

[skooolieboi]

Attached is the electrical diagram for the electrical system I plan on installing into my 2008 IC International 53 passenger school bus. I am hoping some of you could check this over to make sure I don't burn down the bus accidently or run out of power.


I am hoping to keep this system very simple and avoid any complicated wiring because this bus will only be used for one summer. The DC to DC charger would act as a battery isolator to make sure the main batteries are always charged up before the alternator charges up the aux batteries. I think it would also prevent the aux batteries from draining the main batteries when the bus is off. After the inverter, I would just use a few power strips and extension cords because I am not familiar with 120V wiring. The system would ideally be able to power a fridge constantly, fans at night, and random things during the daytime as shown in the spreadsheet calculations. In order to suit our needs, I am currently looking at:


four 215 Ah golf cart 6V batteries in parallel and series to form a 430 Ah 12V battery

200W solar panel kit to produce power when camping

20A DC to DC charger to produce power when the bus is on and isolate the main batteries from the aux batteries

500W Pure Sine Wave Inverter and extensions cords/power strips



Spreadsheet: https://docs.google.com/spreadsheets...it?usp=sharing

In the spreadsheet, I made a list of appliances then used simple watt's law calculations to estimate power consumptions. I looked up or estimated real power consumption of each of the things we plan on using and then summed up the power of each appliance for day or night usage. It seems like I would be able to run my preferred day appliances without draining the batteries at all (if the sun is bright and pointing towards the solar panels), since the incoming power would be more than the power consumption. The red appliances aren't being used anymore. The runtimes I calculated assume that there are no sources of power to account for the cloudiest of days or a non running bus. I calculated the usable battery capacity to be roughly half of the deep cycle battery's capacity. The vacant bus power is running a fridge while we are out camping. The far right side of the spreadsheet also shows the links to components.



Is there anything I am overlooking? Are the basic golf cart deep cycle batteries good for skoolie applications? Would the DC to DC charger and Solar Charger be bad to run at the same time to the aux batteries? Would I also ground the Auxiliary batteries to the same chassis as the main batteries? Do I really need a DC to DC charger, or should I use that money to get an additional solar panel?

[Bert06840]

If you plan on driving 100-200 miles a day, charging from the alternator MAY work if your alternator is sufficiently powerful. At idle it will take way too much time.

Forget the A/C. But you figured that out already.

You'll need 2.5-3kWh a day for what you listed. 1.5kWh for the fridge, if it is efficient model, and more than the typical 1kWh because beer will be involved.

Solar panels are so cheap that for a summer installation, that's where you should bulk up from. San Tan solar has used 250W panels for $35. Get 4 of those and you're done.

Charge up your laptops during the day, not from the battery bank.

500W for the inverter is not enough. Double perhaps just about.

[skooolieboi]

Thank you for the advice. I agree that charging off the alternator is not a great option, especially for days off the road. At this point with my budget, I am considering using the generator I have to power up the batteries once a day. I might have to add more batteries if I go that route, but I would have to cancel doing solar to save money. Either way, I am cancelling the DC to DC charger and keeping the battery systems separate.

The beer definitely is important! haha

Using 2500Wh a day does seem like a pretty good guess to me too. With 215 Ah of battery to use, I should have 2580Wh to use, so the generator only option of charging batteries would have to happen daily. And yes, I am looking at small RV 12V/120V fridges that idle around 30W.

I did not realize you could buy used solar panels. To ship $35 solar panels to me (MI) from AZ would be almost $200! I'll look for used solar panels closer to me.

Why is a 500W inverter not enough? My usage will usually be 180W, and my max should be around 580W, but that number is with all devices possible running at the same time, which I would not do obviously.

[Bert06840]

Charging up deep cycle batteries takes HOURS. The ability to generate peak power with a generator isn’t the problem. The ability of the battery to absorb the energy is.

Do you have the fridge already? A recent energy star rated $150 (new) dorm fridge is easy to get, a 12V model costs many times that.

If you plan to run the fridge off 12V you may get away with a light inverter. My super efficient 2020 vintage dorm fridge thing takes almost a kilowatt to start. You need a lot of margin.

But. There is a much better solution for you.

Drop the batteries. Drop the solar panels. The charge controller. The inverter. The whole thing.

Just buy a $790 Harbor Freight inverter generator, and three 100’ extension cords. You were going to buy a generator anyway. Run it for a month 24/7, then sell it for $500 to one very happy guy.

Change the oil every second day.

[skooolieboi]

If I need to charge half of my deep cycle battery setup, that would require 215 Ah. If I use this 60A battery charger off the generator:
https://www.amazon.com/Progressive-D...ustomerReviews
..that would mean 215Ah/60A=3.58 hours to charge from half capacity I think. Although I am not sure if a 3000W generator is enough to power that charger.

I do not have a fridge, but I was looking at this one:
https://www.amazon.com/dp/B088FDTTY4/ref=emc_b_5_t?th=1
I would be using it on 110V, but I am looking at it because the running wattage (38W) seems to be lower than mini fridges (70W) according to the reviews. It is a bit more expensive than a typical mini fridge but not insane.

I like the wildness of your generator solution. That probably would be cheaper than using solar for just one summer. Although after dumping more and more money/TLC into this skoolie, I am not sure if I can let go of it so easily. Might end up future proofing the electrical system. Anyway, would 300' of extension cord make it lose some power? Also, I am not sure if I can always run a generator especially when its far from the bus. I may stay in walmart parking lots some nights or rv camps.