Help me evaluate my electrical needs for full-timing

[jaross]

I am ordering a Ford Transit High Roof and will be doing a custom conversion. Here are what I evaluate to be my electrical needs. This is the extreme high end of what I estimate my usage to be! For instance, this is running my Webasto heater full blast for 24/7. I plan on insulating very well but I also plan on boondocking in the middle of the mountains during the winter! Even so, it is my understanding that the Webasto won't need to run 24/7. I am getting the 230A alternator and the dual 70A batteries, but needless to say I am going to need more. Is this realistic, or is it likely I am over-estimating with these numbers?

Appliance------------DC Amps--Hours----Amp Hours
Webasto Air Top-----2.45--------24-------58.8
Stereo----------------0.8---------4---------3.2
water pump----------4.5---------0.15-----0.675
fridge-----------------6-----------8---------48
induction cooktop----150--------0.6-------90
microwave-----------50---------0.068----3.4
laptop-----------------5.6--------4---------22.4
cellphone-------------1.2---------2---------2.4
Led lighting-----------2-----------3--------6
maxxair fan-----------2.3--------4--------9.2


TOTAL AMP HOURS: 244.075

What might you suggest for a house battery or solar panel solution? So far, I think I want to connect the house battery to the alternator with a battery isolator/automatic charge relay. Assuming my numbers are realistic, I will need about 490 amp hours of battery. That sounds like a lot! Maybe I should forget the induction cooktop?

 

[dwh]

Yes, you probably should forget the induction cooktop. Besides, I think your estimate of .6 hours a day is too low unless you don't really plan to do much cooking, and if that's the case, you should definitely delete it.

Cooking 3 squares a day, plus hot water a couple times a day for coffee and tea, I get around 10 weeks out of a 5 gallon propane tank. At today's prices, that's a little over a dollar a week for fuel, plus the stove probably weighs less, and the propane is lighter than lead.


Figure flat mounted solar and getting 4 hours a day of "good sun". Batteries are not 100% efficient, the usual number for doing estimates is 80%. So you have to supply 1.2 times what you took out.

235 ah x 1.2 = 282 ah
282 ah ÷ 4 hours = 70.5 amps/hour
70.5a x 14v = 987 watts

The 14v is just a rough estimate, actually the voltage would move from around 12v (if battery at 50%) to around 14.5v during bulk stage charging, but then it'll still need to absorb for some hours.

So figure roughly 1,000 watts of solar would be the bare minimum you'd need. You got room on the roof for that?

With buildings you start by figuring out the power budget you need to supply, and calculate the size of the battery you'll need to store it, and that also tells you how much solar you need.

But for a mobile installation, you work it the other way. How much solar can you fit, which determines the battery size, which then dictates your energy budget.

 

[dwh]

Hey! No fair changing the numbers!

Oh well, just plug in the new total and recalc.

 

[jaross]

Hey! No fair changing the numbers!

Oh well, just plug in the new total and recalc.

yeah I have it all automated in a nice spreadsheet on my computer

Yes, you probably should forget the induction cooktop. Besides, I think your estimate of .6 hours a day is too low unless you don't really plan to do much cooking, and if that's the case, you should definitely delete it.

Cooking 3 squares a day, plus hot water a couple times a day for coffee and tea, I get around 10 weeks out of a 5 gallon propane tank. At today's prices, that's a little over a dollar a week for fuel, plus the stove probably weighs less, and the propane is lighter than lead.


Figure flat mounted solar and getting 4 hours a day of "good sun". Batteries are not 100% efficient, the usual number for doing estimates is 80%. So you have to supply 1.2 times what you took out.

235 ah x 1.2 = 282 ah
282 ah ÷ 4 hours = 70.5 amps/hour
70.5a x 14v = 987 watts

The 14v is just a rough estimate, actually the voltage would move from around 12v (if battery at 50%) to around 14.5v during bulk stage charging, but then it'll still need to absorb for some hours.

So figure roughly 1,000 watts of solar would be the bare minimum you'd need. You got room on the roof for that?

With buildings you start by figuring out the power budget you need to supply, and calculate the size of the battery you'll need to store it, and that also tells you how much solar you need.

But for a mobile installation, you work it the other way. How much solar can you fit, which determines the battery size, which then dictates your energy budget.

Yeah I am having trouble juggling all the different fuel/electrical options. On face-value, I like keeping everything as simple as possible (as few sources as possible) and was trying to avoid propane for that reason. But then you account for roof space and cost, and propane is looking more and more like a viable option! I was thinking about a Webasto Dual Top, but then I decided the only thing I really need hot water for is the occasional shower. A propane flash hot water heater is only $130. But if I am adding propane to my rig, then maybe I should just forget the Webasto heater all together and go with a Camco Wave Gas Catalytic Heater or something similar. Then there are the propane fridges. I wonder how much propane I would need if I went full propane!

 

[java]

I just went through all this. Your heater wont run nearly that much, if your insulated well anyway.

Everything else seems decent estimate wise. Remember you really don't want to take your batteries less than 50 SOC ideally, so double your AH needed.

Definitely do a house battery with a isolation unit/relay. Gives you peace of mind that you can run your house batteries flat if needed and still start up in the morning and leave. I had 300W of solar on my old truck, yeah it helped a little, but if it snows they are nearly useless. I went bigger battery bank this time around. I can always add them later on.

Im running propane for hot water and cooking, kerosene for the Webasto. I stayed webasto as finding a small non catalytic heater is hard. I dont want the extra moisture form burning propane for heat inside. The webasto is too much heat still (its the 3500W model), so even the smallest RV propane heater would have been more. There is the propex for a small option but it wasn't in my budget, I was just looking at RV style ones.

 

[dwh]

My camper has a Norcold 323 - I think it's 1.7cu.' On low (good enough most of the time) plus cooking as mentioned above, the 5g propane tank lasts 5-6 weeks. Fridge on high (summer) + cooking, 3 weeks.

I don't use the furnace, Suburban 12,000 btu, because I don't need that much heat in a camper van, and it's a horrible pig for both propane and power. If I really needed a heating system, I think I'd go with the Webasto running from the vehicle's fuel tank.

Or propane...either the Camco you mentioned, or a Platinum Cat vented, or a Propex. (Keeping in mind that the Camco uses internal cabin air for combustion, so you have to keep a window or vent open to supply oxygen. But humans burn a lot of oxygen too, so I always have fresh air regardless.)

I mostly just use a stovetop heat diffuser to take the chill off in the morning. The burners on my Wedgewood stove are, I think, 9k btu and I'm making coffee anyway:

I only fire up the water heater, Suburban 3 gallon, when needed. Not sure what it consumes, but it's not much. It's an older unit with pilot light, not electronic ignition and I don't like leaving the pilot running. But building new, I'd likely go with on-demand as well.

Propane has 91,000 BTU per gallon, btw.

 

[jaross]

I just went through all this. Your heater wont run nearly that much, if your insulated well anyway.

Everything else seems decent estimate wise. Remember you really don't want to take your batteries less than 50 SOC ideally, so double your AH needed.

Definitely do a house battery with a isolation unit/relay. Gives you peace of mind that you can run your house batteries flat if needed and still start up in the morning and leave. I had 300W of solar on my old truck, yeah it helped a little, but if it snows they are nearly useless. I went bigger battery bank this time around. I can always add them later on.

Im running propane for hot water and cooking, kerosene for the Webasto. I stayed webasto as finding a small non catalytic heater is hard. I dont want the extra moisture form burning propane for heat inside. The webasto is too much heat still (its the 3500W model), so even the smallest RV propane heater would have been more. There is the propex for a small option but it wasn't in my budget, I was just looking at RV style ones.

Yeah I was concerned about the moisture too. Maybe thats a reason to go with the Webasto in itself.

As for windows open, I didn't want to do that in the dead of winter, but I guess I need to

 

[java]

I usually leave at least one of the roof vents open, even in -10 degree weather, just too much moisture otherwise....

 

[Bbasso]

Does your Transit run on gas or diesel? If it's diesel strongly consider the Espar D4. It's made van life awesome for me. It hardly uses any fuel and even less electric.

I decided to go with propane for my cooking needs, stove and oven. The typical 20 pound BBQ tank will last me 3 months and that's including my water heater. It's an Eccotemp L5 .

 

[SoCal Tom]

For heating the interior I'd look at something like this that takes advantadge of the hot water heater. http://www.tnttt.com/viewtopic.php?f=54&t=62327&start=15
If you need that many amps, I'd also look at a pair of golf cart batteries.
Tom

 

[jaross]

Does your Transit run on gas or diesel? If it's diesel strongly consider the Espar D4. It's made van life awesome for me. It hardly uses any fuel and even less electric.

I decided to go with propane for my cooking needs, stove and oven. The typical 20 pound BBQ tank will last me 3 months and that's including my water heater. It's an Eccotemp L5 .

Thats the water heater I was looking at. 3 months is pretty livable

Its going to be the 3.5L gas twin turbo. I want the possibility of taking it to S. America, plus I am not too keen on all the modern diesel emissions b.s. (not that I am not an environmentalist, its just extra complication and stuff to break)

But both Espar and Webasto make petrol (gasoline) versions of many of their heaters. Not sure if I should go Espar or Webasto. Webasto seems to have more support here in the United States

 

[DiploStrat]

FWIW

Everyone differs a bit, but here are some real world numbers:

Two adults and one cat. Cold weather, heat on 24/7, refrigerator on 24/7. The biggest drain is the refrigerator, followed by the heat/hot water.

Heat from a Webasto Dual Top, cooking with True Induction and microwave. Assuming engine stop at about 5 PM, cooking dinner inside, cabin heated to 65F, espresso after dinner, computer charge, music, etc. Breakfast coffee, toast, etc. We guesstimate that a meal takes 30 minutes, 15 minutes of induction and 15 minutes of microwave.

We use between 100Ah and 150Ah, the big variable being hot breakfast or cold cereal and toast. The long term average has been 125Ah overnight.

Battery bank is 600Ah, solar is 500w, connection to engine alternators is properly sized. We are typically full recharged by noon in good weather.

YMMV.

 

[jaross]

Everyone differs a bit, but here are some real world numbers:

Two adults and one cat. Cold weather, heat on 24/7, refrigerator on 24/7. The biggest drain is the refrigerator, followed by the heat/hot water.

Heat from a Webasto Dual Top, cooking with True Induction and microwave. Assuming engine stop at about 5 PM, cooking dinner inside, cabin heated to 65F, espresso after dinner, computer charge, music, etc. Breakfast coffee, toast, etc. We guesstimate that a meal takes 30 minutes, 15 minutes of induction and 15 minutes of microwave.

We use between 100Ah and 150Ah, the big variable being hot breakfast or cold cereal and toast. The long term average has been 125Ah overnight.

Battery bank is 600Ah, solar is 500w, connection to engine alternators is properly sized. We are typically full recharged by noon in good weather.

YMMV.

Humm, thats good to know. So what made you choose induction? I assume you hook that up to an inverter? Can you give me some more details on your electric system? Maybe I am missing something but it sounds like your solar and battery setup are overkill for your needs?? Is this with driving every day until 5pm and running anything during the day off of the alternator directly-thus not running down the batteries?

 

[luthj]

Everyone differs a bit, but here are some real world numbers:

Two adults and one cat. Cold weather, heat on 24/7, refrigerator on 24/7. The biggest drain is the refrigerator, followed by the heat/hot water.

Heat from a Webasto Dual Top, cooking with True Induction and microwave. Assuming engine stop at about 5 PM, cooking dinner inside, cabin heated to 65F, espresso after dinner, computer charge, music, etc. Breakfast coffee, toast, etc. We guesstimate that a meal takes 30 minutes, 15 minutes of induction and 15 minutes of microwave.

We use between 100Ah and 150Ah, the big variable being hot breakfast or cold cereal and toast. The long term average has been 125Ah overnight.

Battery bank is 600Ah, solar is 500w, connection to engine alternators is properly sized. We are typically full recharged by noon in good weather.

YMMV.

This is fairly representative of our experience. Our rig has similar solar, battery bank, induction, etc (see build thread). We live in our van full time. I can go through our system logs if you want a monthly average of usage. In the winter solar charging is limited, you may need tiltable panels, or a dc-dc charger from the alternator. Alternatively, a lithium bank doesn't need to be fully charged regularly, and will accept charge rapidly from lower alternator voltages without a dc-dc charger.

 

[jaross]

With buildings you start by figuring out the power budget you need to supply, and calculate the size of the battery you'll need to store it, and that also tells you how much solar you need.

But for a mobile installation, you work it the other way. How much solar can you fit, which determines the battery size, which then dictates your energy budget.

Sounds like one way to do it would be to figure out the largest system that will fit, and through trial and error, figure out what needs to be run on what fuel/power source from there. Solar systems are expensive though.