12 volt questions

[Gypsy Clipper]

I appreciate your opinion. But I am going to probably be driving everyday, all day and only stopping at night. I will not be hooking up to shore power ever. But my bus is a 24 passenger bus so the roof is quite large. But again I do not want to put solar on the bus at this time.
But I am going to ask this question again. And I will try to be clearer. Let's say the 110 appliances I use are the most efficient money can buy and my buses alternator is large enough to recharge a battery bank of enormous proportions would replacing the two batteries that I have for the wheel chair ramp with deep cycle batteries be enough to power what I have or will I need to add more? I know unless I do the math and figure the amp hours of the particular appliances this question can not be answered. Is there a website where I can find this info or do I need to buy the appliances and a kill a watt measuring device then add batteries?

[john61ct]

The size, weight and placement of the bank you will need has nothing to do with the existing setup, for now figure 1200 pounds and 15 cubic feet, costing thousands.

Now, you can cut that in half by giving up on the 110V obsession.

A good Alt setup for that, with installation will cost at least a thousand, I gave the runtimes above with solar, as I said a small genny would make more sense.

Without solar, your bank may only last a year or two. With at least some solar and proper care otherwise, it can easily last 8-10 years or more.

You can get by without solar by going to Firefly Oasis at $500 per 100AH, with the AC appliances you'll need at least ten.

LFP would be even better but at least triple the Firefly cost since you're not technical.

Now, if you were willing to do this with both a lot of solar and DC appliances, a $600 bank may well be enough, each 200+ AH added is ~$180.

And you would need to run your genny (or alt) less than half as much.

[Brad_SwiftFur]

Originally Posted by Gypsy Clipper

OK. Now that you can see why I took offense I would like to clarify the question.
I would like to avoid 12 volt appliances . I am trying to recreate an actual house but on wheels. I do not want to add solar at this particular point because there is so much work I would like to do to the exterior of the bus.
Actually I am a woman and somewhat sensitive to the fact I know absolutely nothing about these things that I should know. But at 51 I am trying to learn. But it is frustrating to realize how little I know.
I know at one point I drive a semi and the company I worked for installed an inverter so I was able to run a microwave and a dorm sized refrigerator with no change to the alternator or the addition if batteries. That being said. I have a large alternator and the additional batteries for the wheel chair ramp.
Now without upsetting anyone. Let's say I would like to run a small refrigerator, a small chest type deep freeze and two large televisions, a game console. My water will be pumped via 12 volt and my water will be heated with propane. I will install a small apartment sized propane stove. I do believe that must also run on 110. If you could point me to a website where I could calculate the energy needs of these appliances I will do the math. Then I will return with a more accurate account if exactly how much energy I need.
But returning to the original question....
Can I change out the batteries, add a larger alternator and an inverter and run these appliances.
I do not know how long I will need to drive to recharge my batteries but I imagine that I will drive or idle my bus however long it takes to recharge. I do not plan to sit stationary for weeks at a time nor even days at a time. The bus is equipped with a roof mounted thermo king air conditioning and heat system which will probably be how I cool it if there is a need. I will heat it with a propane heater if it is necessary.
I will seek professional help to install the electrical system. I just would like to know what I am asking the professional to install.

Alright, now we're getting somewhere. A 1500 watt inverter is fairly common in big trucks, and even running a microwave/fridge will use somewhere between 600-900 (for many microwaves, depends on how powerful it is), and the dorm fridge doesn't use too much. Both easily within a 1500 watt inverter. Typically you don't use a microwave for hours on end (and usually with the engine/genset running).

Now let's adapt this to your bus. A microwave, let's assume 900 watts (for a reasonably powerful one) but typically used for no more than a few minutes a day. A dorm fridge, and a small dorm-sized freezer. A pair of TV's (presumably flat screen) and a game console. Now, chances are, you'll never run all these at once but even if you do, I'd hazard to guess 3000 watts would be fairly close.

If you already have the TVs and gaming console and fridge and such, just read the wattage ratings off each one and add them up. If not, look up similar devices and get the wattage ratings from those.

You may notice I didn't calculate the water pump, water heating and cooking. As memory serves me, propane house stoves do not need electricity at all (or maybe a 9 volt battery), and propane water heating would need minimal power at the most (really, just enough to work the circuits and relays and such). The first 2 don't figure into the 110V needs and the latter should be so low as to be almost negligible (someone correct me if I'm wrong).

[Twigg]

Originally Posted by Gypsy Clipper

OK. Now that you can see why I took offense I would like to clarify the question.
I would like to avoid 12 volt appliances . I am trying to recreate an actual house but on wheels. I do not want to add solar at this particular point because there is so much work I would like to do to the exterior of the bus.
Actually I am a woman and somewhat sensitive to the fact I know absolutely nothing about these things that I should know. But at 51 I am trying to learn. But it is frustrating to realize how little I know.
I know at one point I drive a semi and the company I worked for installed an inverter so I was able to run a microwave and a dorm sized refrigerator with no change to the alternator or the addition if batteries. That being said. I have a large alternator and the additional batteries for the wheel chair ramp.
Now without upsetting anyone. Let's say I would like to run a small refrigerator, a small chest type deep freeze and two large televisions, a game console. My water will be pumped via 12 volt and my water will be heated with propane. I will install a small apartment sized propane stove. I do believe that must also run on 110. If you could point me to a website where I could calculate the energy needs of these appliances I will do the math. Then I will return with a more accurate account if exactly how much energy I need.
But returning to the original question....
Can I change out the batteries, add a larger alternator and an inverter and run these appliances.
I do not know how long I will need to drive to recharge my batteries but I imagine that I will drive or idle my bus however long it takes to recharge. I do not plan to sit stationary for weeks at a time nor even days at a time. The bus is equipped with a roof mounted thermo king air conditioning and heat system which will probably be how I cool it if there is a need. I will heat it with a propane heater if it is necessary.
I will seek professional help to install the electrical system. I just would like to know what I am asking the professional to install.

This site will help you understand the basics, and help you plan for what you can use, and for how long:

Electrical System Design | FarOutRide

Generally, 12V appliances, especially fridge and freezer consume much more total power than 110V domestic equivalents. You would use maybe 150W for an apartment sized fridge/freezer, and about three times that much for an RV equivalent. So you would run that from an inverter connected to your batteries.

You would have to check the wattage of TVs, etc and add them in. Allow something for lighting and anything else you need.

Once you have worked out your average power consumption you can convert that to Amp hours. Remember the fridge only runs about 30% of the time, not 100%.

The Amp hour number will tell you how many Amp hours you will be able to be off-grid for 24 hours.

After that it's simply a case of deciding how many Amp Hours you need in your batteries, and double that number so you don't discharge them more than 50%.

Keeping it economical .... Pick a sensible number for your Amp Hour storage, and get a small inverter generator A 2000W peak/1600W constant unit can be had for a few hundred dollars. Run a few hours a day it would allow you to remain "unplugged" almost indefinitely.

That's the cheapest way to build a sensible, modest output power system and it's flexible enough to build on in future by adding storage, solar power, etc.

Solar power is attractive in many ways, but it is expensive for occasional use but very effective for longer, off-grid, stays.

[PNW_Steve]

Originally Posted by Twigg

This site will help you understand the basics, and help you plan for what you can use, and for how long:

Electrical System Design | FarOutRide

Generally, 12V appliances, especially fridge and freezer consume much more total power than 110V domestic equivalents. You would use maybe 150W for an apartment sized fridge/freezer, and about three times that much for an RV equivalent. So you would run that from an inverter connected to your batteries.

You would have to check the wattage of TVs, etc and add them in. Allow something for lighting and anything else you need.

Once you have worked out your average power consumption you can convert that to Amp hours. Remember the fridge only runs about 30% of the time, not 100%.

The Amp hour number will tell you how many Amp hours you will be able to be off-grid for 24 hours.

After that it's simply a case of deciding how many Amp Hours you need in your batteries, and double that number so you don't discharge them more than 50%.

Keeping it economical .... Pick a sensible number for your Amp Hour storage, and get a small inverter generator A 2000W peak/1600W constant unit can be had for a few hundred dollars. Run a few hours a day it would allow you to remain "unplugged" almost indefinitely.

That's the cheapest way to build a sensible, modest output power system and it's flexible enough to build on in future by adding storage, solar power, etc.

Solar power is attractive in many ways, but it is expensive for occasional use but very effective for longer, off-grid, stays.

Good info.

One item I would call attention to. "Conventional" 12v RV refrigerators are absorption refrigerators. They are horribly inefficient. I did a comparison on power consumption between a 6.8 cf absorption and a 10.8cf home fridge. The RV fridge use 3-4x they power, held less food and did not stay as cold.

There are however, 12v refrigerators that use a high efficiency 12v compressor. The are the most efficient of the bunch. Unfortunately they are quite expensive. They are generally marketed to off grid and marine folks.

[john61ct]

Originally Posted by Twigg

Generally, 12V appliances, especially fridge and freezer consume much more total power than 110V domestic equivalents.

That is the exact opposite of my experience.

Originally Posted by Twigg

RV equivalent.

Aha! Yes USA RV appliances are woefully inefficient, because they are designed for parking at campsites with shore power.

But appliances designed for off-grid homes and camping, and especially boats at sea are **much** more efficient than those designed for 110V.

Originally Posted by Twigg

especially fridge and freezer consume much more total power than 110V domestic equivalents. You would use maybe 150W for an apartment sized fridge/freezer

Absolutely nothing beats 12V Danfoss style compressor fridges and freezers like Engel and Waeco/Dometic.

Depending on the temp differential and how often they're opened, we're talking 20-50 AH per day at 12V.

3-5A, cycling 7-25 minutes per hour. Some larger units have variable power compressors rather than on/off control.

Even the most efficient 110V "dorm style" unit running off an inverter would likely burn around double that.

On boats it is very common to custom-build the box and add a kit for the 'guts'. Good ones with custom design help run a couple grand, but less efficient OTS kits are about a thousand.

The real key to high efficiency is lots of insulation (4" minimum) and active ventilation of the hot condensor/electronics area.

So it is possible to get a large size unit without increasing electricity consumption by very much.

[john61ct]

Originally Posted by PNW_Steve

There are however, 12v refrigerators that use a high efficiency 12v compressor. The are the most efficient of the bunch. Unfortunately they are quite expensive. They are generally marketed to off grid and marine folks.

Engel's a great brand, currently having a sale, usually $8-900 now maybe $650.

Lesser brands can be found for much less.

[Twigg]

Originally Posted by john61ct

That is the exact opposite of my experience.

Aha! Yes USA RV appliances are woefully inefficient, because they are designed for parking at campsites with shore power.

But appliances designed for off-grid homes and camping, and especially boats at sea are **much** more efficient than those designed for 110V.

Absolutely nothing beats 12V Danfoss style compressor fridges and freezers like Engel and Waeco/Dometic.

Depending on the temp differential and how often they're opened, we're talking 20-50 AH per day at 12V.

3-5A, cycling 7-25 minutes per hour. Some larger units have variable power compressors rather than on/off control.

Even the most efficient 110V "dorm style" unit running off an inverter would likely burn around double that.

On boats it is very common to custom-build the box and add a kit for the 'guts'. Good ones with custom design help run a couple grand, but less efficient OTS kits are about a thousand.

The real key to high efficiency is lots of insulation (4" minimum) and active ventilation of the hot condensor/electronics area.

So it is possible to get a large size unit without increasing electricity consumption by very much.

I don't think we are answering questions from someone with a "marine" budget.

[Greatestrr]

Originally Posted by Gypsy Clipper

Seriously quit it. If you don't have an answer then don't reply. What is it to you if I spend a million dollars? You my mom?

Hmmm... I'm wondering if shes looking for a mom or just doesn't know who her mom is?!?. I could be your daddy tho

[john61ct]

Ahem. . .

From the OP:

>> What is it to you if I spend a million dollars? You my mom?

[Greatestrr]

Haha i know leaves alot of open questions

[Twigg]

Originally Posted by john61ct

Ahem. . .

From the OP:

>> What is it to you if I spend a million dollars? You my mom?

I'm guessing we have moved past that post. Her latest was rather more conciliatory

[john61ct]

But never any indication of a desire to save money.

Sometimes investing more up front makes a lot of sense from a purely financial POV if it saves more over time.

For example if she were able to make an LFP bank last twenty years, plus the fact that there's no need to get to 100% Full, so no need for solar, just run dino juice an hour or two a day and run all the mains power devices you like!

But you of course need to have the upfront, and be willing to risk blowing it all up out of ignorance + stubborn arrogance.

[Greatestrr]

The bank of batteries would be to big for the alternator to charge running a 5000k inverter. Not to mention the strain it would put on it. After running like that some solar panels will sound sweet. Even a small generator with a decent battery charger would be better than trying to charge the battery bank off the alternator.