Electrical mathmatical frustrations.

[AutumnB]

We want everything in our bus. Trying to add up numbers to get a clue for electrical needs but feeling overwhelmed. Is there a simple mathmatical equation for this???

We can guess on average how long power will be used daily for the appliance or electric device. Things like fridge, freezer, and other things will be 24 hrs a day. But dishwasher and the washing machine along with AC and heaters and other on demand needs will not be a constant thing.

I want to do this right the first time. I hate having to redo or upgrade later. It's a pain and a frustration. Any insight would be appreciated.

Thanks in advance!

Autumn!

[CHEESE_WAGON]

Originally Posted by AutumnB

I want to do this right the first time. I hate having to redo or upgrade later. It's a pain and a frustration. Any insight would be appreciated.

Thanks in advance!

Autumn!

Always easier to do it right the first time, I say, especially with electrical. I am NOT an electrician, mind you, but I do understand some basic concepts. What you'll need, and how much of it depends on a big question -- how will you be using your bus? Full-timing? Boondocking? Both will require a serious electrical system.

And keep in mind, this will be a two-sided system, DC on the supply side, AC for certain appliances and devices, which you will need an inverter for, and I highly recommend a pure sine wave inverter, nothing less, especially if expensive electronics are in play here. Anything less will fry certain devices over time.

TOO MUCH OR TOO LITTLE RESISTANCE = BAD. A certain amount of resistance is needed in any electric circuit, but outside of a certain range, things can heat up and cause a fire. Too small a gauge wire is also a no-no, for the same reason.

Current flow is rated in amperage. Battery bank storage capacity is generally referred to as amp-hours, meaning the amount of time the batteries can last at a certain amperage load.

Deep-cycle batteries are designed to put out consistent voltage until they have nothing, and then it's lights out. One trick some members use here is to wire two 6-volt golf cart batteries in series to emulate a larger 12-volt battery, and for most, it works well.

However, you are suggesting a desire for a lot of bells and whistles, and all that takes more amp-hour capacity. Sounds like you really need a large battery bank, I'd say about 600-1200 amp-hours if you're boondocking, as well as solar and a solid generator for cloudy days. But I seem to remember something about a 600-amp hour capacity is actually about 300 amp-hours unless using deep cycle batteries. Remember, more batteries = more weight, and you don't want to overload your bus.

And don't forget, an isolator will be necessary to allow your alternator to charge your 'house' batteries with the engine running, but prevent your electrical usage from draining your starting batteries.

Here are some YouTube videos on electrical concepts I found, hopefully they will help.

https://www.youtube.com/watch?v=UOzbcXMJ8K4

https://www.youtube.com/watch?v=OGa_b26eK2c

[AutumnB]

Thanks for the info!
Definitely wanting to be able to live off grid as much as possible. My wife and l are not really into campground after campground. The idea of where you park is exciting every day is us. We want to roam all over.

[CHEESE_WAGON]

Originally Posted by AutumnB

Thanks for the info!
Definitely wanting to be able to live off grid as much as possible. My wife and l are not really into campground after campground. The idea of where you park is exciting every day is us. We want to roam all over.

Sounds nice, but choose wisely. Compromises are necessary in a lot of situations such as this. Use LED lighting when possible, and any laptops, etc. are best used with a proper 12V charger for power. If you can get 12V versions of appliances, their decreased energy needs in comparison to their 110V AC-powered counterparts on your inverter can help stretch the charge cycles of your battery bank. A certain amount of energy is lost through inverters, and the less loss through your inverter, the better.

BTW, an inverter's 'rated' capacity is usually its PEAK, or surge, not what it can deliver sustained. So a 2000 watt inverter will likely be rated for a 2000-watt surge, or momentary load. Your sustained capacity will usually be aorund 55-75% of that, depending on efficiency.

Refrigeration (both for air-conditioning and keeping foods cold / frozen will be your biggest loads. Mini-splits are getting popular for their efficiency both in power usage and in space used. A lot of older RV refrigerators / freezers used to be a dual system, capable of working by ammonia or by electric, but ammonia has pretty much a thing of the past, as it is unreliable on anything but a perfectly level surface.

Use LED lighting and 12V appliances when possible, and while you don't mention a washer or dryer, I would HIGHLY recommend those sorts of devices be run off of a generator, not your inverter. And research any candidates considered for use and installation. Not all AC power is the same. And if you can get more energy-efficient devices by spending a little more, by all means, do it. It's no fun sitting in the dark with no power wondering when your groceries are going to go bad.

Your inverter will deliver 110V, 120V single-phase electricity, and most washers and dryers use 220-240V three-phase, and will not work properly (if at all) on an inverter. Washers and dryers that can run on 110-120VAC can be found, but I do not recommend running them off of an inverter -- the inverter can easily overheat and catch fire from that extreme of a load. Not that it can't be done, I just don't recommend it.

Besides, the more load thrown to your inverter, the quicker it drains your batteries -- which, if you didn't catch my edit on my first post here, install an isolator on your main engine start batteries. This will allow your engine's alternator to charge your house batteries without allowing your house load to deplete your starting batteries.

UPDATE: You might research the Broccoli Bus, their electrical system was adapted from or based on the battery system of a Nissan Leaf. They even have a video tour on YouTube.

Hope all that helps. Good luck!

[AutumnB]

I had actually planned on sealed LED lights inside and outside. Much less draw and headaches. As for inverters l currently have 3- 3000 watt sine inverters and a 10,000 watt 110/220 gas generator. The idea of using it for the washer and other short use times is a good idea! I had planned on using it for my pull behind trailer for the air compressor, lights and welding machine.
I hope to keep myself busy with projects over long stops. We really dont plan to be high milers.

[CHEESE_WAGON]

With inverters, you have sine, full sine, pure sine. The first two of which are fine for anything but sensitive electronics. Make sure you know what is safe to use with what. ;)

Also, with refrigeration, the first seconds of startup are a surge load, so insulation is a must, a constantly cycling air-conditioning system is wasted energy. I would also tint windows or use curtains / shade to reduce the amount of heat generated by sunlight in the interest of helping to keep temps down in the summer. Another thing, you might consider propane heat and cooking to reduce your electrical load, which will also help stretch your charge cycles.

[dzl_]

Here is a useful spreadsheet for planning your electrical


A device like this is super useful for finding out the hourly or daily or weekly power consumption of appliances in your home



It can feel like an overwhelming task to plan everything out when there are so many unknowns, I feel your pain. Take it step by step, little bits at a time, don't get too stressed out by the big picture, ask question as they arise (but also use google and youtube, there is an answer to pretty much every basic question you have out there already)

[AutumnB]

Originally Posted by dzl_

Here is a useful spreadsheet for planning your electrical


A device like this is super useful for finding out the hourly or daily or weekly power consumption of appliances in your home



It can feel like an overwhelming task to plan everything out when there are so many unknowns, I feel your pain. Take it step by step, little bits at a time, don't get too stressed out by the big picture, ask question as they arise (but also use google and youtube, there is an answer to pretty much every basic question you have out there already)

Thanks DZL...
I've been a diesel mechanic for a long time. Electrical in heavy duty was never a problem but l agree this does feel a bit over whelming. I will take your advice though. Thanks again.

Autumn!

[john61ct]

Guesstimating is difficult and inaccurate.

Actually measuring is the way to go.

First question

what proportion of your time will be off grid?

[AutumnB]

Originally Posted by john61ct

Guesstimating is difficult and inaccurate.

Actually measuring is the way to go.

First question

what proportion of your time will be off grid?

I believe 90 to 95% of the time.

[TheArgobus]

I made a post about my planning "process" here: https://www.skoolie.net/forums/f27/t...tml#post382066


Basically, for those big appliances, find their manual and their annual/daily kwh usage and use that for planning. If you're trying to get an hourly estimate, then you'll have to divide the daily kWh rating by 24 and so on. It isn't exact, but it works for planning.

[AutumnB]

Originally Posted by TheArgobus

I made a post about my planning "process" here: https://www.skoolie.net/forums/f27/t...tml#post382066


Basically, for those big appliances, find their manual and their annual/daily kwh usage and use that for planning. If you're trying to get an hourly estimate, then you'll have to divide the daily kWh rating by 24 and so on. It isn't exact, but it works for planning.

Basically what l have started out with doing. The numbers are crazy.

[kazetsukai]

Originally Posted by AutumnB

I believe 90 to 95% of the time.

The biggest loads are typically going to be consistent drains. Running your 1200W microwave for ten minutes a day will cost you about 200Wh for the day. Running a 50W load (our bus computer + security system) 24/7 will cost you 1200Wh per day.


Our biggest electrical challenge has been climate control. Running the split AC during the day for heat has cost us around 7kWh over night, or around 15kWh per day if run 24/7. If you want to be off grid most of the time like we do, you need a large PV array.



Do you have your panels yet? I was able to get mine (305w) for $110 each, with about $450 shipping. They're new panels, but are a bit on the larger side, see my build thread. If you're interested I can dig up the link.

[john61ct]

Originally Posted by AutumnB

I believe 90 to 95% of the time.

Well then, that makes the issue of energy efficiency your top priority.

You should invest up front in appropriate appliances

designed as much as possible to run natively on DC off grid power

Propane or your vehicle's fuel wherever possible.

AC powered devices only if absolutely necessary.

In the US where efficiency requirements are very slack, it is hard to find AC appliances that run efficiently enough.

But since you will be running off stored bank energy + inverter 95% of the time, you can look at units targeted to the 240Vac Euro market which often use a small fraction, many times more efficient.

All this assuming you'd rather not be running a genset many hours every day and paying lots of fuel expenses, shooting for your solar covering your needs as much as possible.

[john61ct]

For a given device, you should put a coulomb-counter, aka wattmeter on it over a 24-hour period.

Include the inverter inefficiency, so measure the actual draw from the storage bank.

Get the Ah per 24hrs used when you're using it "normally", if something like a powerful computer that varies a lot, push it a bit harder to be conservative.

If the Ah per hour consumption is pretty constant then you can extrapolate by estimating your hours usage per 24hours.

The goal is to assemble a complete energy consumption budget in

Ah per 24hrs.

Extremely thirsty devices, anything involving cooking or other heat production from electricity, schedule that usage for while you're running the genset

and you can take it out of the "stored energy consumption" budget, get those done while you're Bulk charging up the bank in the morning.

Aircon is always going to be nearly impossible, or at least impractically expensive unless shore power is available.

Following the 60's a much better approach.

[AutumnB]

Originally Posted by kazetsukai

The biggest loads are typically going to be consistent drains. Running your 1200W microwave for ten minutes a day will cost you about 200Wh for the day. Running a 50W load (our bus computer + security system) 24/7 will cost you 1200Wh per day.


Our biggest electrical challenge has been climate control. Running the split AC during the day for heat has cost us around 7kWh over night, or around 15kWh per day if run 24/7. If you want to be off grid most of the time like we do, you need a large PV array.




Do you have your panels yet? I was able to get mine (305w) for $110 each, with about $450 shipping. They're new panels, but are a bit on the larger side, see my build thread. If you're interested I can dig up the link.

Yes please l would like the link! No l haven't bought anything yet. The numbers l keep coming up with are crazy insane when l look and see the average home runs on a 10 kwh system there is no way a bus could be this bad of a load. Heating and AC numbers are crazy. We plan on being in the USA in the winter months while bouncing from the west coast to the east coast of Canada every other winter. Definitely following the 70 degree weather systems.

I am not crazy about the idea of wood heat. It might be nice during the cooler days but night time.... no it's just too much of a risk.

I kinda wanted to stay away from propane but now I am thinking with stove and fridge loads... it could save alot as well as the power load on the electric with a on demand water heater. I didn't want to get into plumbing gas as l know very little about it.

Looks like it will be a full size bus if anything to carry the monolith of the solar array! Sighhh.

[kazetsukai]

PMed you the link.

[Drew Bru]

Originally Posted by AutumnB

I kinda wanted to stay away from propane but now I am thinking with stove and fridge loads... it could save alot as well as the power load on the electric with a on demand water heater. I didn't want to get into plumbing gas as l know very little about it.

Looks like it will be a full size bus if anything to carry the monolith of the solar array! Sighhh.

Just some random, disorganized thoughts:
Propane for cooking, space heater and hot water is how we're rolling. We've also got a diesel air heater that we use on cold nights. Space heater is for cold mornings to take the chill off. Heating during the day is mostly accomplished with solar gain.

Piping the propane wasn't all that hard, we used regular black steel gas piping for the main runs. Takes a few minutes to check with an electronic gas leak detector when we set up camp. When you're talking about heating and cooking with electric you start getting into some big numbers.
Our water heater is a 6gal tank that can run on electric or propane. We use electric on sunny days as we've usually filled the batteries pretty early in the day so it would otherwise be wasted sunshine.

We've got 6 golf cart batteries (~700ah) and 1100w of solar. Probably our biggest regular draw is the fridge/freezer.
We don't use air conditioning, dish washer, or clothes washer so your use case will be different than ours. IMO solar panels are cheap enough that it's better to overbuild. Keep a generator handy for intense electrical demand.

[kazetsukai]

Originally Posted by Drew Bru

Propane for cooking, space heater and hot water is how we're rolling. We've also got a diesel air heater that we use on cold nights. Space heater is for cold mornings to take the chill off. Heating during the day is mostly accomplished with solar gain.

The problem I've found with electric water heat is that instant/on demand requires an insane inverter. I have an 8kW inverter, I think I'd have needed a 15kW to run most on demand water heaters. Tanked heaters have less draw but would be near-constant consumers of electricity, expanding solar requirements prohibitively.

All in all, electric water heat didn't seem practical from my research. I'd definitely be rooting for anyone who /does go that way, though. I'd love to avoid the hassle of dealing with gas/fuel...


We went with a Girard propane on demand heater made for RVs. Its the sole propane appliance we have. Its quirky- it has a hard time dealing with variable loads. If you turn on the sink to full or half and leave it there, it will deliver nice hot water. If you play with the lever / alter the flow rate, it has to adjust and will often under or over deliver hot water. It is pretty efficient, I imagine a 25lb tank will last us around two months at least.

[john61ct]

Electricity for HWS is insane except when on shore power.

Off grid living needs to completely get away from the stupid and sinfully wasteful practices and habits of the average USian living in a S&B home.

Think of it as camping, but with added conveniences and comforts. But definitely needs to involve some compromises

which end of being very minor, at least once you've adjusted.