Help! How many batteries do I need?

[CuriosityBus]

Okay, I need a crash course in batteries/solar.

Basically, I have no idea how many batteries or how much solar I'll need. I've never worked with electrical before.

The things I'm going to have in my bus requiring power are as followed:

1. Dual Zone Mini Split AC/Heater
18000 BTU's total. Roughly 8 hours/day without shore power.
Will run all night with shore power if it's hot enough out.
(I honestly have no idea what it will take to power this system. Any
advice would be much appreciated).

2. Hamilton Beach 0.7 CU FT Microwave.
Walmart lists wattage as 700W.
Would I leave this plugged in 24/7 or only plug it in while using?
5-10 minute usage (not daily but for calculating's sake, we'll say
daily).

3. Stove that will run off propane.
I'm not sure whether this needs any power. I haven't researched it
yet).

4. 9.9 CU FT Magic Chef Fridge
Will run 24/7.
Energy Consumption listed as 329 kWh/year.
329/365 = 0.901. 900W/day? I'm not sure how to calculate it.

5. Water Pump and Heater
I have no idea for this as I haven't planned my water system yet.
Any suggestions?

6. Laptop Charger
90W, roughly 2 hours/day.

7. Backup camera and GPS System.
Two things I'm not sure how they work yet, if you have either,
please let me know your average usage.

8. iPad and iPhone charging.
Roughly 1-2 hour increments, once or twice daily.
5 Watts for iPhone, 10 Watts for iPad.

9. LED Puck Lights.
Maybe 20 Max, depending on the size and placement.

10. 32" Westinghouse Smart TV. (1-3 hours/day)
I don't know the watts on this.

11. Carbon Monoxide Detector. (24/7)

I believe that's everything that'll be plugged in and used on average. I plan on having a battery bank inside the bus, a generator (ideally as a backup only), and around 1600-2000W worth of solar on the roof.

If I'm missing anything that'll require power please let me know, and if anyone could help me calculate how much I'll need, that'd be great. I want to be able to go off the grid as much as possible, but on hot/really cold nights I'll plug in somewhere to run the mini split during the night.

[john61ct]

Your generator will be needed many hours per day.

The purpose of your battery bank and solar will be to help reduce the runtime a bit in good conditions.

Getting your consumption a **lot** lower will save you a **lot** of money.

1600W of solar implies 800-1000Ah of lead bank, 500-600 if LFP.

[CuriosityBus]

As I said, I have no idea what I'm doing when it comes to electrical. Honestly I'm still learning all of the terms, and I'm not even sure how it all works together.

My priority is making the bus as comfortable and livable as possible, without having to worry too much about not having enough power. Phone charging, the fridge, and the stove are all things that will for sure be used daily. AC/Heat, only when necessary if not plugged in, and everything else is only an estimate and may not be used every day. As for solar, I don't know what is realistic and what is not yet since I'm still in the gutting phase.

I'm prepared for it to be expensive, but I'm looking for how much watts I can expect to use in a day on average.

[Brad_SwiftFur]

Originally Posted by CuriosityBus

1. Dual Zone Mini Split AC/Heater
18000 BTU's total. Roughly 8 hours/day without shore power.
Will run all night with shore power if it's hot enough out.
(I honestly have no idea what it will take to power this system. Any
advice would be much appreciated).

2. Hamilton Beach 0.7 CU FT Microwave.
Walmart lists wattage as 700W.
Would I leave this plugged in 24/7 or only plug it in while using?
5-10 minute usage (not daily but for calculating's sake, we'll say
daily).

3. Stove that will run off propane.
I'm not sure whether this needs any power. I haven't researched it
yet).

4. 9.9 CU FT Magic Chef Fridge
Will run 24/7.
Energy Consumption listed as 329 kWh/year.
329/365 = 0.901. 900W/day? I'm not sure how to calculate it.

5. Water Pump and Heater
I have no idea for this as I haven't planned my water system yet.
Any suggestions?

6. Laptop Charger
90W, roughly 2 hours/day.

7. Backup camera and GPS System.
Two things I'm not sure how they work yet, if you have either,
please let me know your average usage.

8. iPad and iPhone charging.
Roughly 1-2 hour increments, once or twice daily.
5 Watts for iPhone, 10 Watts for iPad.

9. LED Puck Lights.
Maybe 20 Max, depending on the size and placement.

10. 32" Westinghouse Smart TV. (1-3 hours/day)
I don't know the watts on this.

11. Carbon Monoxide Detector. (24/7)

1. I'm going to let someone more knowledgeable and experienced than myself answer this one.


2. Plugged in, but not running, will use minimal power. Most have a clock and display that is always on, using very little power. The actual cooking will use the most power.


3. Some do, some don't. The ones that do use little power, for clocks, timers, igniters (some use batteries), temperature sensors ... If it were me, I'd look for one that needs no power.


4. It seems to me you are mixing up "Watts" and KWH, which while they are related, are two totally separate things. Watts is "How Much Energy the Thing uses to actually run", such as a 40 watt light bulb, which uses 40 watts to light up. KWH is "How much energy it uses per hour", or in many cases, how many hours it takes to use 1 Kilowatt for an hour. A 1,000 watt load running for an hour equals one KWH. A 100 watt light bulb will run for 10 hours on the same KWH, or a 40 watt bulb will go for 25 hours. In terms of "how thick a wire and what size breaker do I need", you look at wattage and amperage, but in terms of "how much will my power bill be", or in our case, "how much battery capacity do I need", we need KWH. Dividing the annual KWH by 365 gives 0.901 KWH, which is not necessarily the wattage while running. Doing a little checking around, a similar 'fridge uses 120 watts (or 1.4 amps, not sure why the discrepancy in the math unless it's accounting for start-up surge) though that particular model was not recommended for use with an inverter. That calculates out to around 7.5 hours of run time per day.


5. I'll let someone else answer this.


6. I think 90W will be a maximum current usage. But sounds reasonable.


7. These will probably run off your engine/alternator power while driving, and won't need to run off batteries while parked. Unless I am mistaken?


8. Same as #6.



9. Aren't these typically battery operated? Like a pair of Double-A's or 9V's? If so, they are self contained and won't factor into your electrical system requirements.


10. A quick search finds one Westinghouse 32" TV that uses 70 watts "operational" and 0.5 watt on standby. I'd imagine many others are fairly close.



11. See #9. I'd opt for a 9V battery powered version.

[somewhereinusa]

That mini split is going to be 220 VAC. Unless something has changed in the last year or so you won't find a dual zone one in 120VAC.

[david.dgeorge07]

Originally Posted by CuriosityBus

Okay, I need a crash course in batteries/solar.



Basically, I have no idea how many batteries or how much solar I'll need. I've never worked with electrical before.



The things I'm going to have in my bus requiring power are as followed:



1. Dual Zone Mini Split AC/Heater

18000 BTU's total. Roughly 8 hours/day without shore power.

Will run all night with shore power if it's hot enough out.

(I honestly have no idea what it will take to power this system. Any

advice would be much appreciated).

I would strongly suggest 2x 12000 units to keep everything on 120V and to simplify line set routing. Every other load on your list will be negligible compared to your AC demands.
[QUOTE/]

2. Hamilton Beach 0.7 CU FT Microwave.

Walmart lists wattage as 700W.

Would I leave this plugged in 24/7 or only plug it in while using?

5-10 minute usage (not daily but for calculating's sake, we'll say

daily).



3. Stove that will run off propane.

I'm not sure whether this needs any power. I haven't researched it

yet).


[/QUOTE]
Stove will not take anything really, but if the oven uses an electrical thermal igniter it will use quite a bit when oven is in use. Check the model
[QUOTE/]

4. 9.9 CU FT Magic Chef Fridge

Will run 24/7.

Energy Consumption listed as 329 kWh/year.

329/365 = 0.901. 900W/day? I'm not sure how to calculate it.



[/QUOTE]
I have a similar one and it uses about 100W when running. I have observed about 40 AH/day at 12V in cool weather.
[QUOTE/]


5. Water Pump and Heater

I have no idea for this as I haven't planned my water system yet.

Any suggestions?



[/QUOTE]
Pump will be negligible. Water heater should be propane. On demand is nice imo.
[QUOTE/]


6. Laptop Charger

90W, roughly 2 hours/day.



7. Backup camera and GPS System.

Two things I'm not sure how they work yet, if you have either,

please let me know your average usage.


[/QUOTE]
Should not be on your house system. Keep on chassis 12V system.
[QUOTE/]

8. iPad and iPhone charging.

Roughly 1-2 hour increments, once or twice daily.

5 Watts for iPhone, 10 Watts for iPad.

[/QUOTE]
Negligible.
[QUOTE/]




9. LED Puck Lights.

Maybe 20 Max, depending on the size and placement.


[/QUOTE]
Depends on what size, but if you are working with a decently sized bank, LEDs don’t make much of a dent.

[QUOTE/]


10. 32" Westinghouse Smart TV. (1-3 hours/day)

I don't know the watts on this.

[/QUOTE]
I run a smaller color reference monitor and I don’t even really notice the load.
[QUOTE/]




11. Carbon Monoxide Detector. (24/7)
[/QUOTE]
Nada
[QUOTE/]




I believe that's everything that'll be plugged in and used on average. I plan on having a battery bank inside the bus, a generator (ideally as a backup only), and around 1600-2000W worth of solar on the roof.



If I'm missing anything that'll require power please let me know, and if anyone could help me calculate how much I'll need, that'd be great. I want to be able to go off the grid as much as possible, but on hot/really cold nights I'll plug in somewhere to run the mini split during the night.[/QUOTE]



If you have a propane furnace that takes a bit to run the blower.

My biggest notes are that it is near impossible to power AC with solar/batteries. If you are very well insulated, your chances go up. The reality is that you will probably need a generator for your AC. The cost and weight of batteries and panels will be huge for AC unless you are crazy well insulated.

I have a 400ah 12v bank and I can run 1 ton of mini split AC for a couple hours or so...

[brokedown]

It's straightforward enough to calculate power needs, if you have the data just remember that watts=amps*volts, conversely amps=watts/volts and volts=watts/amps. The watt is the unit of work, and your volts can be raised or lowered pretty efficiently as long as you stick to DC power. In a perfect world everything would be rated in WH but in reality most things aren't. Batteries tend to be rated in AH, appliances tend to just give you max amperes, but it's most simple if you reduce everything to watts. Batteries will have limits of how many amps you can draw safely which is why 24 and 48v banks are popular. Doubling the volts halves the amps.

Second, remember that solar panel ratings are maximums and generally require conditions you may never see in the wild. Most of the time you will be far far below those maximums and the goal of generation electricity is at odds with the goal of being in the shade to stay cooler. if you get 80% of your maximum for more than 3 hours per day you're quite lucky, and for fully half of the day you're generating nothing.

1. Air conditioner. THis is going to be your biggest power draw and your biggest complication. I don't know how many watts it actually consumes but if you estimate at 2000 you're going to be pulling serious amperage from your batteries running it. Enough to throw out the idea of running it 12v and maybe jump right to 48v. That complicates the DC side if you were intending to save some power by using DC where possible. because of this, I don't typically suggest trying to run AC off of solar unless you've fully considered the difference in cost and complexity. Some people here have one it successfully, it's much cheaper and less complicated to use a generator especially if you intended to have and maintain one anyway.

2. Microwave. Doable in short bursts but questionable if you get #3 anyway. Simple math says if you run a 700 watt microwave for 6 minutes you've consumed 70WH, or just under 6AH from a 12v battery.

3. Propane stove. Likely doesn't use electricity at all. We (and most people) use this one: https://amzn.to/2HLAkB7 which is 2 burners plus an oven and don't feel that we need a microwave.

4. Refrigerator. Likely your second highest power draw behind air conditioning. Use a good PSW inverter to waste less power in the inversion process.

5. Water pump and heater. Pump only uses electricity when building pressure. Heat should be propane of course. We use the Ecotemp L5 (https://amzn.to/2sMkjpK) instant propane water heater and a Flojet 12v water pump (https://amzn.to/2IwHkYc) which is rated at 50PSI and 2.9 GPM. It will use around 75 watts max when running.

6. Laptop charger. Laptops charge from DC so you save a ton of power using a DC charger instead of unnecessary inverting and regulating. I use this universal one: https://amzn.to/2NNPWYm with my 17" i7 4k laptop and its great. it can charge from AC or DC outlets so you don't need to dig out another charger when you're at starbucks. Power usage of 90 watt max but usually more like 60 watts when charging, much much less when the battery is full but that will depend on the laptop. Get in the habit of closing your lid when you aren't using your laptop!

7. Backup camera. I use this wireless one: https://amzn.to/2LFAIDH and love it. It has IR LEDs for night time visibility and signal is great on my 32 foot Bluebird. Runs from the bus, not from the solar, so power isn't a concern. For GPS we use our phones.

8.Tablet/phone. Anything USB is charging from DC so you just need a good USB outlet. I run these outlet panels: https://amzn.to/2JUxSdk Not a huge draw, 25 watts or so while charging.

9. LED puck lights. These are usually a watt or two each at full brightness, You likely want dimmable ones. I'm using led marine lamps instead of pucks mostly for aesthetics. If you plan for 2W each while in use that should be close enough, 20 of them seems like a lot though.

10. Television. TV power usage can really vary. I'd first look to see if it has a power brick, if so I'd convert the power input to DC. If not, a good PSW inverter will waste less power than a MSW inverter. We kept a TV for a while but found that we never used it and it took too much valuable space, so we use laptops instead. Measure with a kill-a-watt meter to see how much it eats.

11. Smoke/CO detector. We use a battery powered unit. A couple AA batteries simplifies the setup and lasts 6 months or so. We use this one: https://amzn.to/2Lz32Y4

12: You didn't mention heat, so I will. Electric heaters are as bad as air conditioners, maybe worse. I suggest using wood or diesel as your primary heat source, maybe have a little propane heater as a backup since you've got propane anyway. A fairly small electric heater will be 1200 watts and will struggle to keep a sectioned off bedroom warm on a frigid day. Of course, the best way to heat your bus is to drive to a warmer place.


I hope this helps more than it confuses!

[john61ct]

I stand by my #2 response.

And once you decide running a genset for many hours a day for aircon and appliances designed for shore power, then

a charger capable of being appropriately de-rated will keep the bank full, handling all the lower-Ah per day needs with no trouble at all.

Have a look at the Victron line of combi charger-inverters' power boost feature.

You can even rig genny auto-start based on user configured criteria.

Then keep adding solar if you want to reduce genny runtime.

Or, choose your load devices for max efficiency if you want to strive for "mostly solar", but

regular aircon usage requires the genset in all but **very** exceptional and expensive setups.