Is there extra electricity coming out of my generator that is being wasted?

[OlgaAK]

I have a Goalzero Yeti 400Wh battery that I can use to run a few useful things. I also have a small generator that says it is 700 running watts, with a peak of 900 watts.

When I plug the Yeti into the generator, it shows that the input is 65 watts and it takes a full day to charge completely. That uses a bit more than a gallon of gasoline.

Does this sound right? Is there an extra 635 watts coming out of the generator that is being wasted? If so, how can I capture that extra power without buying ten more Yetis? I have heard about having a "house battery bank" but I do not know how to set that up or use the generator to charge it.

Eventually I would like to have a complete electric system in the bus, including an air conditioner, computer screens, lights, an electric hotplate, etc. I would like to install 100 watts of solar on the roof now and increase that over time, as my budget allows. I would also like to get a more powerful generator, but not immediately.

I'd like to have the basic system set up in a way that I can add more to it over time. I would really appreciate any info about how this all works, in simple terms. Thank you very much for any help.

[kazetsukai]

Originally Posted by OlgaAK

When I plug the Yeti into the generator, it shows that the input is 65 watts and it takes a full day to charge completely. That uses a bit more than a gallon of gasoline.

How are you plugging the Yeti in? Pictures may help.


EDIT: It looks like the 65W input is a limit on the Yeti 400's factory AC charger.

[john61ct]

Yes Yeti cripples the C-rate with the BMS, protects the internal cells from owner abuse, make sure they get past warranty.

They aren't great value, DIY a pack for better flexibility.

But going over a .4-5 C-rate does reduce longevity.

[OlgaAK]

Originally Posted by john61ct

Yes Yeti cripples the C-rate with the BMS, protects the internal cells from owner abuse, make sure they get past warranty.

They aren't great value, DIY a pack for better flexibility.

But going over a .4-5 C-rate does reduce longevity.

What does C mean? What parts do I need to make best use of the generator? Is power being wasted with the Yeti?

[john61ct]

Say your nominal 12V bank is 100Ah.

A 1C current rate is 100A, .2C is 20A 3C is 300A.

Find out the maximum amps rate the Yeti BMS allows - it will be slow, and get a tiny genset that puts out around that rate if wasting power is a big deal for you.

Or get a bank that can accept the full rate your existing genset puts out, and use solar to get that expensive Yeti recharged.

[Doktari]

Good question. It sounds like solar only is the way to go for that small prepackaged energy system. Any generator would be wasteful if it only accepts 65 watts in bulk charge mode. And generators are wasteful in general for charging. Yes, there’s lots of power going to waste.
General rule of thumb for bigger house battery energy systems is to run a generator if necessary for a hour or so for the bulk charge and then have plenty of solar to do the absorb charge which can take many hours. The batteries can last years longer doing it this way than consistently undercharging them with a generator or alternator alone.
If the house battery is not cycled deeply then the solar may top it up without a generator. Everyday varies slightly with cloud cover, energy use, condition of batteries, user habits, etc. My plan is to have more than enough solar for 99 out a 100 days.
There are countless ways to fine tune efficiency. You can turn your fridge all the way up while running the generator and charging batteries. Or run a heater or AC. Another thing to consider is a power factor corrected battery charger. These work more efficiently with generators. Most inverter/chargers have a Pfc charger.

[TheHubbardBus]

That's the reality of using a generator. Your load (electricity being used) will have a small effect on the amount of fuel consumed, but by far the bulk of your fuel consumption will depend on how much energy it takes to spin the rotor assembly, regardless of load. So the larger your generator (in terms of horsepower), the more inefficient it's going to be powering small loads, and the more fuel it's going burn no matter what you're using it for.

That's why it's best to try to match your generator size to your expected loads... just enough to power them, but no more. Of course, your needs will vary, so you'll at times find yourself using more generator than you need, particular if you have only one.

A better solution - if doable - is to run two smaller generators with parallel capabilities rather than one large generator. For small loads, use one. For larger loads, hook them together & you get double the output. You'll get the most bang for your fuel dollar, and also some measure of redundancy if one generator fails.

For your specific application, however, I don't think I'd try to downsize your already-small generator. I'm speaking more to your future plans than your current needs. Even the small generators (which yours is) is overkill - and thus inefficient - for charging your battery.

[OlgaAK]

Originally Posted by john61ct

Or get a bank that can accept the full rate your existing genset puts out

How do I figure this out? And put it together? I have a bunch of empty space where I could put batteries but I don't know what kind I need. I've tried reading about this and it gets very complicated very quickly, with lots of things depending on how much power I "need." Right now I'd just like to be able to fully store the power that the generator puts out from one gallon of gasoline, which appears to be 700 Watts x 5 hours = 3500 Wh.

What kind of batteries do I need to store that? How do I connect them to one another? How do I charge them from the generator? How can I then use that battery bank to power something that needs a lot of watts, like a hotplate? Can I simultaneously use the bank to power some 12v appliances?

[Sleddgracer]

Originally Posted by OlgaAK

How do I figure this out? And put it together? I have a bunch of empty space where I could put batteries but I don't know what kind I need. I've tried reading about this and it gets very complicated very quickly, with lots of things depending on how much power I "need." Right now I'd just like to be able to fully store the power that the generator puts out from one gallon of gasoline, which appears to be 700 Watts x 5 hours = 3500 Wh.

What kind of batteries do I need to store that? How do I connect them to one another? How do I charge them from the generator? How can I then use that battery bank to power something that needs a lot of watts, like a hotplate? Can I simultaneously use the bank to power some 12v appliances?

forget about using an electric hotplate in your skoolie - a propane stove top with 3 or 4 burners is much simpler, cheaper and easier to install than the electric power you need for a hot plate, and cooks your breakfast much faster

[john61ct]

Originally Posted by OlgaAK

How do I figure this out? And put it together? I have a bunch of empty space where I could put batteries but I don't know what kind I need. I've tried reading about this and it gets very complicated very quickly, with lots of things depending on how much power I "need."

Well it can take a while to learn how to DIY, but it's not rocket science.

Maybe paying professionals would be a good shortcut, the fact you bought that Yeti is an indicator you maybe can afford that?

Even if going that route, get guidance here, plenty of professional electricians and even EE types have little clue about batteries and DC electrics.

First off, buy tools to measure your electrical realities, volts and amps, never trust mfg ratings nor the readouts on your charge sources or other devices, even super sophisticated pricey ones.

Lots of basic meters that are "good enough" cost well under $100, no need for a super-accurate Fluke.

And don't expect us to hold your hand and dictate every step, get out there and develop your Google-fu, be as self-sufficient as possible.



Including reading past threads here.

[Kubla]

The only "generator" that is small enough to charge that yet I at that slow rate is a solar panel, even the best inverter Honda will use a gallon of gas at that rate since it is essentially idling, you need a bigger battery bank with an inverter/charger setup

[Drew Bru]

Originally Posted by john61ct

And don't expect us to hold your hand and dictate every step, get out there and develop your Google-fu, be as self-sufficient as possible.

Yup. I found this website https://faroutride.com/electrical-system/ extremely helpful when I was completely overwhelmed and had electrical questions.

[kazetsukai]

Originally Posted by OlgaAK

How can I then use that battery bank to power something that needs a lot of watts, like a hotplate? Can I simultaneously use the bank to power some 12v appliances?

Battery chemistry and design determines its discharge capability, and manufacturers will provide these specifications to you..

Originally Posted by OlgaAK

Right now I'd just like to be able to fully store the power that the generator puts out from one gallon of gasoline, which appears to be 700 Watts x 5 hours = 3500 Wh.

If you buy 12V, 100Ah AGM batteries you'll have 1200Wh, or around 600Wh of "usable" energy, you'll need roughly 6 batteries.

[OlgaAK]

Originally Posted by Sleddgracer

forget about using an electric hotplate in your skoolie - a propane stove top with 3 or 4 burners is much simpler, cheaper and easier to install than the electric power you need for a hot plate, and cooks your breakfast much faster

It is just a theoretical example. There are lots of appliances that use high watts. Hot plate is just the first I could think of.

[OlgaAK]

Originally Posted by Drew Bru

Yup. I found this website https://faroutride.com/electrical-system/ extremely helpful when I was completely overwhelmed and had electrical questions.

Thank you very much for this link! That is a lot better than what I was looking at before. I'm perfectly willing to use Google, but it's a bit harder when you don't even know the words to be looking for! This gives a lot info that will help me search more effectively in the future!

[john61ct]

Originally Posted by kazetsukai

if you buy 12V, 100Ah AGM batteries you'll have 1200Wh, or around 600Wh of "usable" energy, you'll need roughly 6 batteries.

Pairs of 6V FLA GCs would be much cheaper and last longer.

The best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

Assuming OP is in the NA market.

[john61ct]

Originally Posted by OlgaAK

It is just a theoretical example. There are lots of appliances that use high watts. Hot plate is just the first I could think of.

If you use high currents for any length of time, you need a very high Ah capacity bank.

Which would make that Yeti look like storage only suitable for keeping your phone topped up when going on a picnic.

[john61ct]

My DC Electrics 101 thread http://www.cheaprvliving.com/forums/....php?tid=28197

If https://faroutride.com/electrical-system/ is not listed there, please add it.

[Iqinsanity]

Can i ask why you only factor in battery charging?

Do you plan on not using any ac while the generator is on? Nothing wrong with that im debating seperating a generator from house ac myself but im still very early in the planning stage. Most people that hook up a generator run the ac and other appliances while they are burning gas precisely because the cost is about the same to run the generator.

But your ideal generator size should max out your charger and handle the full house load.

[kidharris]

Originally Posted by OlgaAK

How do I figure this out? And put it together? I have a bunch of empty space where I could put batteries but I don't know what kind I need. I've tried reading about this and it gets very complicated very quickly, with lots of things depending on how much power I "need." Right now I'd just like to be able to fully store the power that the generator puts out from one gallon of gasoline, which appears to be 700 Watts x 5 hours = 3500 Wh.

What kind of batteries do I need to store that? How do I connect them to one another? How do I charge them from the generator? How can I then use that battery bank to power something that needs a lot of watts, like a hotplate? Can I simultaneously use the bank to power some 12v appliances?

I'm not an expert, but here is my 2 cents.



Don't store the electricity, use it as the gen runs and let the excess go to the battery.


Also use an inverter generator instead of a regular generator. It is quieter and more efficient on fuel. Here is why......


Generators have to put out ac at 60hz to run standard electrical appliances/tools etc here in the USA. To do this a gasoline generator has to run at 3600 rpm (60 cycles/hz per second = 60rpm per second..... 60rpm x 60 seconds per minute = 3600rpm) to make 60hz power no matter whether you are running a light bulb or an air conditioner. It will of course use more fuel while supplying the air conditioner. Diesel generators are usually geared 1:2 to allow the diesel engine to run at 1800rpm to supply the same 60hz power and have a longer lifetime, but are more expensive than gas.


inverter generators work like the alternator on your car and produce more power as they spin faster. The inverter part takes care of 60hz requirement instead of the speed so that you get 60hz at all speeds. This ability to run slower when loads are less is the reason for the fuel economy and the lower noise level. In addition, most brands allow you to connect 2 inverter generators of the same size and brand together for even larger loads. Honda is the most expensive brand.



You could build your own setup with a gas engine, alternator and battery. A voltage regulator may be necessary depending on your alternator. Then use your inverter from the battery to power your 120v stuff or battery 12v to power your 12v stuff. Controlling when to auto turn you generator off/on would be a problem if you didn't want to manually control it.



Hope I made sense.