Power inverter vs generator

MOguy

Explorer
I understand if you only need a small amount of power an inverter is fine but if you needs/wants are greater (microwave, coffee pot, AC or heat...) when would want a Generator vs an inverter?

I have can take a generator for comfy camping if wanted, why would somebody choose a one over the other?
 

luthj

Engineer In Residence
It really depends on how much energy (runtime) you need. For example running a hairdryer for 5 minutes, VS an electric oven for an hour. Microwaves are a great example, as they are usually only run for a couple minutes a day.

If the battery bank, and wiring are sized appropriately, you can run a 2kw inverter form them for a few minutes to a couple hours depending on size. I have a toaster oven I use for making frozen pizzas. It takes about 10 minutes to do its thing, and consumes about 1500W on average. Thats ~125A from my 12V battery bank, and about 150W-hours or 12.5A-hrs. A 250AH battery bank should have no trouble supplying 125A for 10 minutes.

Another example is my small rice cooker. I can use it for pasta, grains, etc. It uses around 20ADC from my inverter, and uses less than 100watt-hours to cook 4 cups of rice etc.

Its a complex equation to consider your charging, and needs, but if possible I avoid the generator if at all possible.
 

MOguy

Explorer
It really depends on how much energy (runtime) you need. For example running a hairdryer for 5 minutes, VS an electric oven for an hour. Microwaves are a great example, as they are usually only run for a couple minutes a day.

If the battery bank, and wiring are sized appropriately, you can run a 2kw inverter form them for a few minutes to a couple hours depending on size. I have a toaster oven I use for making frozen pizzas. It takes about 10 minutes to do its thing, and consumes about 1500W on average. Thats ~125A from my 12V battery bank, and about 150W-hours or 12.5A-hrs. A 250AH battery bank should have no trouble supplying 125A for 10 minutes.

Another example is my small rice cooker. I can use it for pasta, grains, etc. It uses around 20ADC from my inverter, and uses less than 100watt-hours to cook 4 cups of rice etc.

Its a complex equation to consider your charging, and needs, but if possible I avoid the generator if at all possible.
Could you run an AC or heater for hours with the battery inverter setup? How does you battery bank recharge, solar or the vehicle? How big is the battery bank?

Why do you avoid using a generator?
 

dreadlocks

Well-known member
I got both, started with Generator but I hated firing it up at crack of dawn to make my coffee.. GenSet is primarily used as a battery charge source, sun dont always shine and I dont want to have to drive for hours every few days.. I also have it so I can run AirCon in the summer but thats only a few days a year max.. I'm working to become independent from the GenSet by installing a large solar setup, but even then we frequently visit woodlands so dense that even a massive solar setup wont be worth its weight.. even if I almost never needa run GenSet anymore, I'll still be bringing it with me.

You cant run AC or an Electric heater without an insanely large battery bank, for most of us the'd drain the batteries completely flat before they even changed the temp a few degrees... If I want heating I use LP, and if I want cooling I use a DC Fan, if I want AirCon I fire up Generator.

Right now the Inverter just lets me defer running of Generator.. and less, crockpot needs to run for hours but only takes 8A of power.. my charger can do ~25A of charge, so I can run off inverter for 4h to cook food and run genset for only an hour to recharge it.
 

Happy Joe

Apprentice Geezer
I run a small, compact, very portable, battery (30-35 AH) & inverter mostly for tent lighting and tunes... It works well for 4-5 day trips , is silent , and requires no fuel/oil/hassles and it works very well with 110 volt LED bulbs in table lamps during power failures. ...charges from 110 VAC at home , solar on longer trips or in a pinch the vehicle.
Tried camping with a fridge; too much hassle for the few benefits, for me.
I cook, including coffee, over the camp fire or a propane stove.. no interest in hauling a microwave/induction hobb or other electric appliances (wore that T-shirt to rags during the 20th century)....
The same goes for heaters (propane or electric; have a collection of both (including most of the Mr. Heater catalog) none work well enough to bother hauling along while camping (few have a thermostat), IMO)...I have an adequate tent and sleeping bag.
I have several small generators and really, no use for them other than to run grinder with a cutoff wheel while removing parts in the junk yard.

Simple works best for me.

Enjoy!
 
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luthj

Engineer In Residence
Things like an electric heater, or air conditioner use A LOT more energy. Running them of a battery bank in the 200-300AH (2.5-3.6kW-hr) is not possible. That is where a generator comes in. With batteries is not really about power (watts, instantaneous), its about energy (power over time, watt-hours, amp-hours). AC/heaters need lots of energy, while short duration things like coffee pots etc need the high power 1000-1800W, but use little energy because they don't run very long.

I find that forced air heaters fueled by diesel, propane, gasoline are generally quieter than running a generator. Cost is a toss up, especially if you already have a generator.

The batteries need to be charged somehow. For me that is by a solar array and alternator. You obviously need to do some math to figure out if that will work in your case. There is no one-size-fits-most solution.

I have a ~300AH lithium pack in the works for my van. Combined with 100A alternator charging for recovery the next day, this allows me to run my 5,000BTU air conditioner to cool my bed overnight for 5-8 hours.


Why no generator? Well I don't have the space for one, other gear is to important. Second its noisy, and I don't like it. third, I have to set it up, take it down, start it, stop it etc. I often move every day, and live in my van for years at a time. Doing all that gets old, fast.
 

MOguy

Explorer
Then space and set up time would have to be considered.

As crazy as it sounds coffee and coffee maker is one of the items, how about 12 volt coffee makers run from the vehicle? Do those work?
 

luthj

Engineer In Residence
As crazy as it sounds coffee and coffee maker is one of the items, how about 12 volt coffee makers run from the vehicle? Do those work?
They use about the same energy, and are MUCH slower overall. I would look for a 120V coffee maker that only uses about 900W (some smaller units are this way). They will easily run from a 1000W modified sine wave inverter. Thats about 75A at 12VDC, and should run easily from a modest sized battery, or even straight from the vehicle battery (you may need to idle the engine). Most newer vehicles can supply at least 75A at idle from the alternator. Obviously you need appropriate wiring.
 

john61ct

Adventurer
Generator converts fuel to energy, is an actual source, helps get your bank recharged.

Inverter only helps you use it up.

Two completely different functions, not comparable, not either / or.

I avoid using mains-power home style appliances as much as possible.

Sticking to the native DC of the battery bank is much more efficient.

For heat production, use propane.
 

Alloy

Active member
Propane stove for coffee
Both fixed and portable solar
Propane for heat
Inverter/charger
Larger battery bank
System is sized so that the generator is used as a last resort
 

MOguy

Explorer
They use about the same energy, and are MUCH slower overall. I would look for a 120V coffee maker that only uses about 900W (some smaller units are this way). They will easily run from a 1000W modified sine wave inverter. Thats about 75A at 12VDC, and should run easily from a modest sized battery, or even straight from the vehicle battery (you may need to idle the engine). Most newer vehicles can supply at least 75A at idle from the alternator. Obviously you need appropriate wiring.
Generator converts fuel to energy, is an actual source, helps get your bank recharged.

Inverter only helps you use it up.

Two completely different functions, not comparable, not either / or.

I avoid using mains-power home style appliances as much as possible.

Sticking to the native DC of the battery bank is much more efficient.

For heat production, use propane.
The end goal is the same, getting power. The generator is a complete system, the inverter is part of a system.

I don't want to carry around a bunch of batteries, a generator seems a better choice for my needs/wants.
 

luthj

Engineer In Residence
There are some pretty good presses out there. Combine that with a jet-boil, and you can get pretty fast coffee. 2 mins to get the water to boiling, and 2-4 for the coffee to steep. Pour through a filter if you want to polish the fines out.
 

john61ct

Adventurer
The end goal is the same, getting power. The generator is a complete system, the inverter is part of a system.
No, both just convert one type of energy to another, they only have the output type in common, and it isn't even the type you want off grid.

An inverter is useless without a bank, and completely unnecessary in most cases even with one.

Pretty silly to keep a thirsty noisy generator running when you've only got tiny loads running, say under 100W in total?

It's consuming lots of dollars every hour it runs, potentially putting out kilowatts but you're only using 5%?

I can go 4-7 days never turning the genny on, some months only 3 hours runtime.

Not just the fuel cost, but the noise really bothers me, and neighbors if any.

And not cheap to replace either, even the best portable units don't last too many thousand hours.
 
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e60ral

2016 4Runner Trail w/KDSS
Could you run an AC or heater for hours with the battery inverter setup? How does you battery bank recharge, solar or the vehicle? How big is the battery bank?

Why do you avoid using a generator?
in your jeep TJ you could not practically run AC for hours, the battery bank would be too large to realistically fit in a vehicle that size. you could get a small, desktop size electric 200W-ish electric heater if you wanted, it will still need a battery bank but it's more feasible

P=VI, V=IR, P=I^2*R

So for a 200W heater P=200W
your battery voltage will vary but be about 12V, so V=12V
200W = 12V * I -> I = 200W/12V = 16.7 A

Let's assume you use group 31M AGM or gel batteries, they have about 100 Amp-hours of storage. You can't use 100% of the capacity, since this is a non-starter battery you can discharge it down to about 20% so you can use about 80% of the capacity - about 80 Amp-hours.

80 Amp-hours / 16.7A = 4.8 hours (technically the capacity depends on discharge rate and batteries are rated based on a 20 hr discharge, but for the purposes of these kinds of high level calculations you don't need to worry about that. This also doesn't factor in things like voltage loss or efficiency losses from the inverter if you used an AC heater).

So then using that you just need to decide how many batteries you would need. A 31M battery weighs about 75 lbs and is big, about 13"x7"x9.25". Alternatively you could get something like LiFePO4 lithium batteries, an equivalent 100Ah battery would only weight about 30 lbs but would cost a lot (a battle born 100Ah battery is $949).

The next step is figuring out how to charge, you will need to run your engine (ideally with an upgraded alternator) and will need a dc-dc charging system to recharge your batteries. You could use solar, 100W-200W can easily allow you to continuously run something small like a fridge, but for completely discharging a 100A-h battery you would need a lot of sun and a lot of panels.


The reason I said it's not feasible for AC is that even a small portable AC unit is going to be at least twice the wattage, taking a quick look online climate right has a portable 5,000 btu unit rated at 700W. In something like a tent, the duty cycle (the amount of time it's actually running) will be close to 100% if its hot so lets use 100%

700W/12V = 58.3 A ; 80A-h/58.3 A = 1.3 hour. So if you wanted it to run 8 hours you would need at least 7 batteries, which is about 525 lbs if you are using AGM/gel batteries and it's going to take a lot of work to recharge them. Also, at this level you definitely will need to take into account efficiency losses from the inverter. The inverter will draw a small amount of power the entire time it's running, and when converting DC to AC it will also lose a small amount. It could be as low as 50% efficient or maybe up to 90% depending on the load but that's even more losses.

If you have a sailboat, or a really large vehicle you can build a system to run AC on battery but it's not very practical on something the size of your vehicle.
 
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