Electric- Steps to Solar

[Savkemp]

Hi all,

First time poster. I’ve got a 30ft 2001 International with a Dt466e and Allison trans. I’m about to the point of starting my electric, which is far over my head.

I have a hook up to plug into on land I live on, so complete solar is not needed immediately. I have a tight deadline and need my bus livable by the end of the year (electric for mini split). Basically, I won’t be getting solar immediately due to no need and tight $$, but still need to build it into my system for later attachment.

Any tips or thoughts that may be helpful? I know I need to determine amount of power, etc..

In addition- what’s the average size converter and inverter amounts typically needed so I have even just a general ballpark of what numbers to look at. Lol

Thanks in advance!

[john61ct]

The key questions:

How many days off grid, between the availability of overnight recharging from shore power?

How many Ah per day does your average usage consume at 12V. What would your "peak days" consumption be.

What sources other than solar will you have for energy input while off grid?

Frequent long distance driving might make it worth optimizing charging off you alternator.

If many days off-grid per year, then really the biggest payoff comes from reducing your consumption of electricity..

Heat production, cooking etc should be propane or direct burning the fuel your vehicle uses.

AC inverter genset give more flexibility, same with LFP lithium House banks rather than lead, maybe even allowing aircon use off grid.

[dzl_]

Originally Posted by Savkemp

In addition- what’s the average size converter and inverter amounts typically needed so I have even just a general ballpark of what numbers to look at. Lol

Inverter size:
I understand what you are looking for, but I don't think average size is very useful. There are too many variables and too much variance in needs and system size and system design. Some people want every creature comfort and then some, and are more comfortable with household wiring and consumer appliances so they design everything around AC. Some people pay more attention to efficiency or just have more modest power needs or more modest budgets. So instead of guessing at an overall average, maybe I'll try something different:


Small to Medium
<2000W

Medium
2000W to 4000W

Medium-Large:
4000W to 6000W


If I were to guess at an average inverter size for Skoolies/RVs I would say 2-5kW

What size inverter is right for you depends on more than just how much power you will consume at any one time. Battery bank size and battery bank voltage are other factors.

My thinking is once you get to a medium sized system you should start thinking more seriously about 24V or even 48V, and once you get to Medium-Large you should only be thinking about 24V to 48V.

-----------------

On to the question of building solar into your system.

I think it is helpful remember that solar is just a charge source, one of a few sources in most situations. For an off-grid mobile electrical system, the battery bank is the center and the heart of your design. Peripheral to the battery bank, you have multiple charge circuits (for instance solar, alternator, AC-charger/shorepower) and load circuits (Inverter/AC distribution, DC distribution).

So in thinking through how to add solar at a later date, you just have to design your system so that circuit can be hooked into the system later on.

The basic pathway for PV is:
PV Array --> Charge Controller --> Battery Bank

Ideally the charge controller will be located near your battery bank.

You could pre-wire between the PV array/roof and the location where the charge controller will be. This is what many RV manufacturers call "solar ready." But its best you have some idea of the characteristics of your PV array before you do this (or just substantially oversize the wiring)