Some Basic Charge and Discharge Q's

[Instinctz]

I have been trying to read over all of the data to see if my poor algebra skills could figure these Q's out.. but I guess I have been to side tracked since school to remember much of it it.

Basicly lets say I am runnin an avgerage for the day 200 Watts/Hour.  With my math so far that is about 16.5 Amps of constant charging power into the battery bank.  About how much would a 1,000 Watt 120 inverter pull at 25,50,100% usage out of the battery bank? Would the full 1,000w be near 10 amps of draw/hour?

Is it 'hard' or tuff on batteries if there is a constant load on them?  For example your pulling basicly the same as your putting in, other than the resitance heat created from the transfer there shouldnt be anything wrong currect?

I would love to go tottally off grid but as I am informed by now, the expense of a system that would allow me to do that is an extreme ammount more than if I just was to run 90% of my vitals off my system.  So that is what my goal is by the end of this year to be 90% off grid.  Only then perhaps moving 100% by the next year.

[Nando]

The question is basic but not understandable.

You have assumed that we can read your mind since the info lacks a lot of parameters to be able to offer a practical and real response to your question.

You are running 200 watts/hour though you do not indicate the voltage of your battery, I assumed is a 12 volts bank and for 200 watts one needs to think that the battery voltage may go up to 14 volts.

If You assumed 12 volts then is 16.5 amps times divided by the efficiency, let's assume 0.85 for a total of 19.4 amps to keep the battery charged and supplying the power to the 200 watts inverter at full 200 watts load.

For a 1000 watts and 100 %, the current would be 19.4 * 1000/200 = 19.4 * 5 = 97 amps

For 50 % , 48.5 amps

For 25 % , 24.25 amps

It is hard and tough for the batteries to draw such current if the battery is not charged continuously and allowed to be discharged below its minimum of 50 % charge

If you going to draw 100 amps continuously, the battery needs to have a lot of amp hour capability .

NOW can you re-list your question in detail and clearly ?.

Nando

[Titantornado]

By your watt and amp numbers, it appears you have a 12 volt system.  So, for the inverter, and figuring 95% efficiency, it will draw 1053 watts for 1000 watts output.

So, 25% capacity is 263 watts, or 22 amps

and 50% capacity is 527 watts, or 44 amps

and 75% capacity is 790 watts, or 66 amps

and max capacity is 1053 watts, at 88 amps

If you were generating as much power as you are using, there is no load on the batteries.  Power flows directly from generation to load.  Therefore, it isn't hard on the batteries.  About the only things that are, is over discharging it's capacity, or drawing excessive amperage above it's operating limits.

[Instinctz]

Yeah I suppose the voltage of the system would be important to know and yes, cant everyone read minds now a days? I mean come one catch up with technology... nando.

Now.. if I understand my old learning with "order of math" the following equation would be..

"For a 1000 watts and 100 %, the current would be 19.4 * 1000/200 = 19.4 * 5 = 97 amps"

so in a more readable formate your math is [(19.4 * 1000) / 200] = 19.4   how ever I dont understand how you get that since obviously the answer is 97 before multipling by 5.. so what ever logic your using is not in a readable format.. my appoligies for being behind the times and not just reading YOUR mind.

Of course I cant read your mind so.. I can definatly not read your equations nando.

Thank you..

----

How ever,  My 'basic' question is how many amps are pulled out of a 12 volt bank system powering a (per) 1000 watt 120 volt converter at full load? Disregarding any charging ammount from the genny.

My problem is I am not see'ing the 1000watt rating as being for the 12volt side, as it is for the 120 volt side.. dunno if that makes since but anyways.  Dats the question.

Or atleast was, so im guessings from your hiroglyphic equations nando; that the current pulled per 1000 watt is close to 100 amp/hour.

[RP]

See if this helps:

1 watt = 1 volt * 1 amp  

watts =volts * amps

watts/volts=amps

watts/amps=volts

1000watts/12volt system=83amps

Assuming 85% efficiency of the invertor then 1000watts of output (120volts) will require 1176 watts of input from your battery (1000/0.85).  1176watts/12volts=98amps which is pretty close to what Nando suggested.

[Instinctz]

All right finaly a wall broke lose..  it took me awhile to understand how about the efficiency of the Inverter to understand how much more amps it would take verse just the 12volt side.

Dont ask me why, I knew it would be different (the power lost in converting) but didnt click as to why it would be heh, till now.  Perhaps its because I also do all my hobbies after work.. which means I'm drinking hehe.

All right thanks for all the replies, helped further my understanding yet again.

[dinges]

One little, important detail:

You talk about 200 Watt/hour (watt PER hour). This is INCORRECT!

It is 200 Watt-hour; that is, 200 Watt TIMES hours.

When you express the units correctly, you suddenly find that that old highschool math is all you really need...

An ENERGY of 200 Watt-hours equals using a load of a POWER of 200 watt  DURING 1 hour

or

the POWER of a load of 20W load DURING 10 hours

or

a 1W load DURING 200 hours.

I.e, wattage times hours equals Watt-hours.

(POWER * time = ENERGY)

(CURRENT * time = CAPACITY (of a battery))

Suddenly, kWhr (kiloWatt-hours) makes sense too

The same goes for the capacity of a battery, in Ahr (ampere-times-hours; NOT ampere/hour); a battery with a CAPACITY of 7Ahr  can deliver a CURRENT of 1A during 7 hours; or a CURRENT of 7 amp during 1 hour; etc.etc., ad nauseam.

No worries, the mistake you've made (watt-per-hour) is a very common one. And it obscures a real understanding of this unit and its proper application.

Start applying the correct units, and you'll find that those high-school physics are actually useful in the real world too

[commanda]

Watts is watts; minus losses.

In a perfect world without losses; if your generator makes 200 watts, your inverter can only deliver 200 watts continuously.

Now, watt hours. (watts times hours).

If you generator makes 200 watts constantly, that is, 24 hours a day, 7 days a week, 52 weeks a year;

and still in that perfect, lossless world;

You can draw off 400 watts for half the time (12 hours a day)

800. watts for a quarter of the time (6 hours a day)
     
1600. watts for an eigth of the time (3 hours a day)
      
      

Now, 200 watts times 24 hours equals 4800 watt-hours;

So, your 1000 watt inverter can deliver 4800 watt-hrs, or 1000 watts for 4.8 hrs per day.

In the real world we have losses. Nothing is perfect. What you put into your batteries versus what you can later draw back out incurs losses. Lets pick a rule of thumb number and say 85%. Inverters are also not perfect. Their efficiency varies generally as a function of what percentage of their rated output you're running at. They will generally (another rule of thumb here) peak at about 90% at about 80 or 90% rated output. So lets guess that your 1000 watt inverter will run 85% at 1000 watts output.

So, in the real world, that 4.8 hours per day gets reduced by 85% x 85%; about 3 1/2 hrs a day.

Hope that helps.

Amanda

[elvin1949]

Don't forget that without a charge OR drain

your batteries will go dead.[Self Discharge]

another loss in the system.

later

elvin