Best Batteries and Parts

[XFILE36]

There is no such thing as a 1000 watt battery. 1000 watt hours. So since it is lithium, when brand new, call it 800 WH usable.

So 800 watts divided by 1,800 watt hours is .44 or maybe half an hour of usage.

As time goes by, capacity shrinks. It will last longer, maybe even years if it's good quality, but only if you stop drawing down before it's completely empty, and don't charge it all the way full, ideally at less than 14V (13.8 is ideal), assuming it's LiFePO4.

But likely the included battery is not great quality, so with hard use it may die within six months. So make sure to confirm replacement batteries are available.

And also verify how long it takes to recharge, what, on shore power every night?

A 20A charger would take 3-4 hours, as fast as an hour at 80A, don't go bigger than that. The built in POS one may take over 12 hours, and probably charges at too high a voltage.

If you're driving at least an hour every day, rigging a high-amp DC-DC charge connection off your vehicle alternator will be a good way to go.

Are you debatin this with DLTooley or me?  I'm even MORE confused.

 

[XFILE36]

There is no such thing as a 1000 watt battery. 1000 watt hours. So since it is lithium, when brand new, call it 800 WH usable.

So 800 watts divided by 1,800 watt hours is .44 or maybe half an hour of usage.

As time goes by, capacity shrinks. It will last longer, maybe even years if it's good quality, but only if you stop drawing down before it's completely empty, and don't charge it all the way full, ideally at less than 14V (13.8 is ideal), assuming it's LiFePO4.

But likely the included battery is not great quality, so with hard use it may die within six months. So make sure to confirm replacement batteries are available.

And also verify how long it takes to recharge, what, on shore power every night?

A 20A charger would take 3-4 hours, as fast as an hour at 80A, don't go bigger than that. The built in POS one may take over 12 hours, and probably charges at too high a voltage.

If you're driving at least an hour every day, rigging a high-amp DC-DC charge connection off your vehicle alternator will be a good way to go.

I just get more and MORE confused about this subject.

 

[John61CT]

Break it down, ignore the "other bits" for now, focus on the basic math, units definitions, and ask specific clarifying questions.

 

[John61CT]

Are you debatin this with DLTooley or me?  I'm even MORE confused.

I'm not debating anything, just stating information relevant to your questions and the decisions you're facing. In some cases if you're looking at specific potential purchased, you may need to track down the specifications for the device in question.

Note these specs are usually "generous" in the vendors' favor, and many outright lie.

 

[akrvbob]

You haven't even started to discuss if it is 100 watts at 110 volt or 100 watts at 12 volt even though they are 10 times different from each other. Then the confusion will increase exponentially.

This is why it is nearly universal in the RV world to convert everything to 12 volt amps and work with amp hours. The simple act of dividing by 12 to go from watts to ah, or, dividing by 10 to go from 110 volt to 12 volt amps allows everyone to be on the same wavelength when discussing watts and amps.

 

[Optimistic Paranoid]

I just get more and MORE confused about this subject.

John61CT is essentially right, he really knows his stuff, he's just not expressing it as simply as possible.  Think of him as a really good engineer, but not much of a teacher.

The capacity of a battery is not measured in amps or watts, it's measured in amp hours or watt hours.  A battery with 1,000 watt hours is capable of supplying one watt for 1,000 hours, or 1,000 watts for one hour, or 500 watts for two hours, or any similar combination.  It's like the difference between miles and miles per hour.  If you want to know how far you've traveled, you need to know more than just how fast you were driving, you also need to know how long you were driving that speed.

Bob is also correct when he says we mostly just use amps and amp hours, I'm not at all used to thinking in terms of watts and watt hours.

Lets see, if you've got an 1800 watt hair dryer - presumably running on 120 volt ac - then 1800 watts divided by 120 volts = 15 amps.

Now, you'll need to plug that in to an inverter to run it off 12 volt dc.  So 1800 watts divided by 12 volts = 150 amps is how much current the inverter will pull from the battery to provide 15 amps of power at 120 volts.

(Notice the ten to one ratio between the 120 volts and the 12 volts and how that carries over to the amps.  15 amps at 120 volts becomes 150 amps at 12 volts.  Both 120x15 and 12x150 = 1800.  Watts is power and doesn't change whether ac or dc, 120 volts or 12 volts.)

A battery pack containing 1,000 watt hours at 12 volts has an amp hour capacity of 83 and a fraction amp hours.  So MATHEMATICLY  you might have enough power to run it for half an hour.  But in the real world, trying to pull 1800 watts (or 15 amps) through the inverter is probably more than it was designed to handle.  In all probability, such a heavy load would probably cause built in safeties to shut it down and you wouldn't be able to run the hair dryer at all.  You would need a bigger inverter, hooked up to a bigger battery, to power it.  Or that's my best guess, anyway.

 

[John61CT]

Yes on usually 12V as lingua franca.

But these portable power packs (sometimes "generators", hate that misuse of the term) are all over the map, USB outlets @5V, laptop socket @19V, 12V and then inverter outlet 115V AC. Then some even pocket size, can jumpstart even a big diesel engine, lots of amps but only for a few seconds at a time.

So in this one topic area, watt hours works well to compare apples to apples.

They're also usually well below usual House bank sizes, definitely can't think about fridges, even a decent gaming laptop or editing video even the bigger ones would only last a few hours.

Heavy usage like that you want hundreds of AH, fancy lithium a couple grand just for bare cells, good lead around a grand, basic GC2s maybe $500. But not in a sleek portable box. . .

 

[caretaker]

isn't 1800 w for a hair dryer kinda big,,,i mean 1800 w is throwin a bunch of heat

 

[John61CT]

I assumed he just chose that as a large-load example in order to learn how to do the calculations.

 

[caretaker]

Dang one would hope so,,,,

 

[MikeRuth]

FYI a lot of Hair dryers are rated to 1500 Watts. Most all have three heat levels, no heat, low, and high.

 

[tx2sturgis]

Watts and amps are real-time "flow rates", not measure of capacity.

Amp hours and watt hours are capacity.

It's nice to see when someone gets it right!

The complex relationship between volts, amps, watts, and time is a mystery to so many, but you expressed it well. I made an attempt to explain this on another thread but it probably got lost in the noise...

 

[XFILE36]

You haven't even started to discuss if it is 100 watts at 110 volt or 100 watts at 12 volt even though they are 10 times different from each other. Then the confusion will increase exponentially.

This is why it is nearly universal in the RV world to convert everything to 12 volt amps and work with amp hours. The simple act of dividing by 12 to go from watts to ah, or, dividing by 10 to go from 110 volt to 12 volt amps allows everyone to be on the same wavelength when discussing watts and amps.

Dear Bob,

You lost me at the bakery.  If I understood what you said, I probably wouldn't be here asking questions.  Just so everyone knows, I have an above average I.Q., graduated always at the top of my class in several occupations, and am self-taught in MANY subjects. I also grew up without parents, so I am street smart too.  I just was never taught anything at all about THIS subject.  At this point, I would like direction from anyone to a beginner's class (quick - I have an emergency and need to learn now!) to learn what I need to learn in order to understand batteries, solar, electric in a motor home, doing it MYSELF.  Either way, I may just have to learn from MUCH trial an error, but that is what I thought I could avoid by asking here.  Thank you. :heart:

 

[XFILE36]

" I would like direction from anyone to a beginner's class "

Have you read the solar and electrical topics on this site? There are links at the top of the page. Good place to start.

Lots of "beginners classes" online.
https://www.google.com/webhp?ie=utf-8&oe=utf-8#q=basic+12v+solar+primer

Or videos.
https://www.youtube.com/results?search_query=12+volt+solar+basics

It all breaks down into very basic math and understanding the relationship of power to volts, amps and time.

BTW, congrats on the IQ, I'm a little challenged in that area.

Thank you for the links and I will check them out.  I only included my comment on I.Q. because some people have called me handicapped.

 

[mayble]

Thank you for the links and I will check them out.  I only included my comment on I.Q. because some people have called me handicapped.

"some people" need to STFU
it's all greek to those of us just learning, and not everyone with knowledge can communicate across the gap
keep plugging away (no pun intended ) and you'll figure out enough to do what you need to do

 

[DLTooley]

Watts, Amps, Volts.

My examples were based on simpler conversions. I left time out for simplicity.

Any 120v device will require an inverter to run from a 12v source. There is a loss of efficiency in the use of an inverter and one's that can handle a hair dryer are spendy.

Amps, or Amp hours, are calculated based on voltage and aren't good for apple to apple comparisons. You will see low voltage batteries with very high ah. The 120v conversion would make that a very low ah battery. In RV world 12v is common and used as a standard. Watts, or watt hours, are a single measure of energy.

A 50 watt device draws the same amount of power regardless of whether it is 120v, 12v, or 3.2v - less the conversion losses.

Running a hair dryer for a short period of time is doable.

Here's the math: 1500 watts for 5 min is going to take 125 watt hours. That can be deducted from the 1000 watt hour battery. 1500 watts at 120v = 12.5 amps. The 1000 watt hour battery at **12v** is 83.33 amp hours. In the RV World this is roughly the capacity of a very good AGM deep cycle battery. How much of that 1000 watt hour capacity is actually usable is another question.

Personally, I started doing everything in 12v volts to make the math easier and avoiding the conversion losses.

 

[XFILE36]

Running a hair dryer for a short period of time is doable.

Here's the math:  1500 watts for 5 min is going to take 125 watt hours.  That can be deducted from the 1000 watt hour battery.  1500 watts at 120v = 12.5 amps.   The 1000 watt hour battery at **12v**  is 83.33 amp hours.  In the RV World this is roughly the capacity of a very good AGM deep cycle battery.  How much of that 1000 watt hour capacity is actually usable is another question.

Personally, I started doing everything in 12v volts to make the math easier and avoiding the conversion losses.

DLTooley,

Actually, I have a 1850 watt hair dryer, but see it will probably be a power burden, even though I might only use it once a week for 10 minutes.  Thanks for pointing out that I will need to convert everything to 12 volts, even though I haven't made it that far yet in my education!