Solar setup on a bus conversion

[MambaJack]

Hi Everybody, new to the forum, looking for some advice on system sizing.
I am from the Missouri Ozarks, and plan to use the bus as an rv on 3 to 4 day trips
Also like the idea of using as a backup when my house electrical goes out
I appreciate you allowing me on the forum and thanks for any advice that you can provide.

Not sure if i did this right, but here is an estimate of my appliances

v	qty	hrs	device	watts	amps	total amps
110	1	4	ps4	110	1.00	4
12	1	9	fan 12v	15	2.00	18
12	1	1	water pump	85	8.00	8
12	4	3	phone	12	1.00	12
110	2	3	computer	45	1.00	6
12	12	4	lights	3	0.25	12
110	1	4	refrigerator	500	8.00	32
110	2	4	Monitor	18	0.50	4
	1	0.5	Coffee Pot		8.00	4
						100

Was thinking 4 @ 300w 24v panels, a 60 amp mppt charge controller, and 8 @ 6V gc2 230ah batteries,
Not sure what size of inverter to get. was originally looking at a combination inverter charger as the bus will just be a tripper for now, not fulltime.so wanted the potential to charge from shore.
I was also originally looking at running the system 12v, since i have several 12v devices, but not sure on that now.
Anyhow, thanks for any thoughts.

dave

[bcroe]

Your last column of TOTAL AMPS is useless, since the devices do not all run on the same voltage.
Upgrade the last column to WATT HOURS by multiplying the voltage X the current X the running
time on each line. Compare that to your battery watt hour storage capacity, however you will
only be able to use a fraction of that number in the real world. Bruce Roe

[MambaJack]

Thanks Fanatic,

I have updated the chart to what I think the wattage would be.

v	qty	hrs	device	watts	amps	total amps	total watts
110	1	4	ps4	140	1.00	4	140
12	1	9	fan 12v	15	2.00	18	15
12	1	1	water pump	85	8.00	8	85
12	4	3	phone	12	1.00	12	48
110	2	3	computer	45	1.00	6	90
12	12	4	lights	3	0.25	12	36
110	1	4	refrigerator	1000	8.00	32	1000
110	2	4	Monitor	18	0.50	4	36
	1	0.5	Coffee Pot	1000	8.00	4	1000
						100	2450

[J.P.M.]

Thanks Fanatic,

I have updated the chart to what I think the wattage would be.

v	qty	hrs	device	watts	amps	total amps	total watts
110	1	4	ps4	140	1.00	4	140
12	1	9	fan 12v	15	2.00	18	15
12	1	1	water pump	85	8.00	8	85
12	4	3	phone	12	1.00	12	48
110	2	3	computer	45	1.00	6	90
12	12	4	lights	3	0.25	12	36
110	1	4	refrigerator	1000	8.00	32	1000
110	2	4	Monitor	18	0.50	4	36
	1	0.5	Coffee Pot	1000	8.00	4	1000
						100	2450

Start by scrapping the electric coffee pot and use something other than electricity to heat water. If nothing else, your system will get about 40 % smaller.

[Sunking]

Was thinking 4 @ 300w 24v panels, a 60 amp mppt charge controller, 12 volt toys.

You need to stop right now because you do not have a clue what you are doing. Here is an example of how much you do not know. 1200 watts of panels into a 12 volt battery requires requires 2 x 50 Amp Controllers. With a 60 amp controller, you just as well throw half the panels in the garbage with the rest of your ideas because that is where it is all going to end up.

[MambaJack]

Thanks. I wondered if it might take 2. I had figured 300 watts at 24 volts to be 12.5 amps x 4 = 50 amps. Did I do that incorrectly. Or the issue with not having enough padding?

[littleharbor]

If you are planning on running a 12 volt system then you can double those 50 amps. Controllers are rated by output, not input. MPPT controllers will basically double your current into a 12 volt battery bank. That being said 100 amps of charging current would typically want a 1000 ah. battery..

[MambaJack]

Thanks littleharbor. What if I want to setup my battery bank at 24v?

[PNW_Steve]

Hey Mamba,

You are off to a better start than many newbies to the solar realm by recognizing that you need to start by identifying the load that you need to support and trying to design a system to support it.

I have seen quite a number of "I bought all the wrong stuff, now help me make it work " threads. Glad to see that you are avoiding that pitfall .

Keep asking good questions and don't be offended by direct answers.

Take care .

S.

[PNW_Steve]

Regarding the coffee maker, anything with an electric heating element is going to be an energy pig.

If you will have propane on board you can eliminate a significant load by making coffee on your propane cooktop. Or, middle ground, use a coffee maker that brews into a thermos. Still a big load but it runs for less than five minutes a day.

[MambaJack]

Thanks Steve for the encouragement.

[littleharbor]

Thanks littleharbor. What if I want to setup my battery bank at 24v?

Then you should be fine with a 60 amp MPPT controller , Series wire your panels into two strings then combine the two strings. 2S2P is what your configuration will be noted as. That should be a comfortable charging current for your 460 amp hour battery bank.

[Sunking]

Thanks. I wondered if it might take 2. I had figured 300 watts at 24 volts to be 12.5 amps x 4 = 50 amps. Did I do that incorrectly.

Make believe math.

MPPT Output Current = Panel Wattage / Battery Voltage

1200 watts / 12 volts = 100 Amps
1200 watts / 24 volts = 50 Amps
1200 watts / 48 volts = 25 amps.

Controllers get less expensive with fewer amps. You can spend $1000 buying 2 x 50 amps controllers to make it work if you do not know what you are doing. I make more money selling it to you that way. I would not dare insult you and save you any money.

[MambaJack]

Make believe math.

MPPT Output Current = Panel Wattage / Battery Voltage

1200 watts / 12 volts = 100 Amps
1200 watts / 24 volts = 50 Amps
1200 watts / 48 volts = 25 amps.

Controllers get less expensive with fewer amps. You can spend $1000 buying 2 x 50 amps controllers to make it work if you do not know what you are doing. I make more money selling it to you that way. I would not dare insult you and save you any money.

SunKing, Thanks for the info. Seems like cost is a great reason to run dual controllers, I didn't realize they were priced like that.

Sorry if I got off on the wrong foot here, didn't mean to. I am definitely here to learn, not to give the answers.
After reading thru the forum, I thought it might be more courteous to propose a solution to my problem instead of just asking what would be recommended,
but maybe that is a better approach, so here goes.

I would like to put some solar electricity on my bus conversion.
I estimate the use at around 2000 to 2500 watts per day, and would like to have enough battery coverage to sustain 4 to 5 days of cloud cover.
Much of what i am using is 110v but i do have several items, lights, fan, water pump that run on 12v dc.
Thanks so much for your time and help.
dave

[MambaJack]

Regarding the coffee maker, anything with an electric heating element is going to be an energy pig.

If you will have propane on board you can eliminate a significant load by making coffee on your propane cooktop. Or, middle ground, use a coffee maker that brews into a thermos. Still a big load but it runs for less than five minutes a day.

Thanks Steve, I plan to install a propane cook top, so that sounds great!
dave