Amp vs amp hours

[cpe.wolf]

Hi all,

I am new to all this, learning so that we can use solar and wind in our future house.

I’m having trouble finding information that explains the difference between a 200 amp Service compare two solar system. Does amp hours equivalent the same thing as a 200 amp grid service? Are there any videos that showThing connecting a solar system into a 2 phase 200 amp breaker box? Would I have two separate breaker boxes one for 12v such as LED lights etc and one for outlets/fan etc?

thank you for the assistance and knowledge!!!

 

[HighTechLab]

Amp hours is a measurement of power over time. An amp-hour is one amp for one hour, or 10 amps for 1/10 of an hour and so forth. It is amps multiplied by hours. If you have something that pulls 10 amps, and you use it for 10 minutes, then the amp-hours used would be 10 (amps) X .167 (hours), or 1.67 AH.

On the other hand, amps is an instantaneous measurement (at only one given point in time). In terms of the service on your house, if that is a 200 amp service it can provide your house with 200 amps at any given time (or continuously for that matter)...There is no capacity involved in that.

Think of Amp Hours like measuring Kilowatt Hours on your house - The difference is that batteries aren't measured in KWH like your house's consumption is.

The accepted AH rating time period for batteries used in solar electric and backup power systems is the "20 hour rate". This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.

It's tricky because the voltage supplied to your house by the utility is more-less constant, whereas batteries drop in voltage and have different capacity at different charge rates (c ratings).

 

[fat_old_sun]

Amp hours is a measurement of power over time.

Think of Amp Hours like measuring Kilowatt Hours on your house - The difference is that batteries aren't measured in KWH like your house's consumption is.

An Amp-hour is *not* a measure of power! It is a measure of electrical charge. 1 Amp = 1 Coulomb per second. 1 Amp-hour = 1 Amp current flowing for 1 hr (3600 seconds) = 3600 Coulombs.

Amp-hr multiplied by the electrical potential difference that drives that current equals the energy delivered by that current in Watt-hrs. 1 Watt-hr = 3600 Joules.

Battery capacity can be (& often is) measured in kWh. A typical 100 Amp-hr '12 Volt' LFP battery stores about 1.3 kWh

 

[Deleted member 783]

Volts X Amp Hours = Watt Hours. A 12 volt, 100 amp hour battery is 1200 watt hours, or 1.2 kWh.

 

[fat_old_sun]

a "12 Volt" LFP battery usually operates in the mid 13's Volts during its entire charge state. So, the math is 100 Ah x 13.x V or about 1.3 kWh

 

[Deleted member 783]

a "12 Volt" LFP battery usually operates in the mid 13's Volts during its entire charge state. So, the math is 100 Ah x 13.x V or about 1.3 kWh

Sorry, I wasn't trying to correct you, just laying out the formula for the OP.

 

[nosys70]

you can make an analogy with passing people trough a door.
with a small door, (low Amp) you can pass a lot of people , but it will takes time.
with a big door, all the people will pass at once, fast.
Your TV set is in that case, because it suck a few amps at a time, but if you let it on all the day, at the end, the bill is high.
On the other end, you have device like the fridge that sucks a lot of amps, mainly to start the motor, but usually the fridge works for a few minutes and shut off until the temperature raise again.
At the end of the day, it is possible that your TV set has eaten more amps/hours than your fridge because even if it needs less amps, it used them more hours.
The exception is usually the AC or devices that require a lot of power for long periodes. They are difficult to integrate into an off-grid scheme because they inflate the capacity needed as well instantly than on the duration.
this is the two extreme of capacity balancing and what make planning difficult.
small power (under 500W) for a long time require small sized (and usually cheap) equipment. While big instant power (over 3000W) require costly equipement, because like car, the more instant power you need , the more expensive it will.

 

[ghostwriter66]

I am a EE and NOW even I am confused ... CPE.WOLF -- this is right out of one of my digital textbooks ... hopefully this helps

Amps
Current is the amount of electrical charge flowing in a circuit. Static electricity is charge that sits still on an object; when charge moves, it produces a current. Scientists measure charge in units of coulombs, and an amp is a coulomb of charge flowing past a given point in a circuit in one second. Low-power devices, such as digital watches, use millionths of an amp of current. A hair dryer or toaster might use ten amps. The starter motor in your car draws hundreds of amps, but only for a few seconds.
Amp-Hours
Technicians use amp-hours to express current produced or consumed, or the capacity of something to produce or consume current. A starter motor that draws 400 amps for 10 seconds uses 400 * 10 / 3,600 = 1.1 AH of capacity. A flashlight that consumes 400 milliamps for 4 hours uses .4 * 4 = 1.6 AH of capacity. Though the starter motor is a more powerful device than a flashlight, it consumes current for only a short amount of time

 

[electric]

Very common confusion because people don't distinguish Power from Energy. Amps/Volts/Watts all describe Power, which is a timeless property, it is only valid for the instance it's measured at. Energy is something that includes a time factor, or a stored property, something that is accumulated or expended over a time period, hence Ah and Wh describe Energy.
Good analogy is water in pipes and containers. Water in the tank is Energy, water flow in the pipe is Power. Thicker pipe allows more water at any instant, analogy with Amps. Water pressure analogy is Voltage. Pressurized or elevated tank has energy and potential ( Voltage ), but if the valve is closed there is no flow ( no current, no power ) and energy is not changing. Flow is a rate of change, high flow ( high Amps ) means Power is expended faster and Energy will run out sooner.
Hope this helps. I always use water analogy when explaining electricity, because it obeys similar laws of physics.

 

[nosys70]

usually real electrician are saying that this analogy is the worst you can use, because it seems so close and at the same time so wrong.
there even people writing books about that

GEORGIA STATE UNIVERSITY HYPERPHYSICS How Newtonian Mechanics is Incorrectly being Applied to Explain the Laws of Electricity and Magnetism

GEORGIA STATE UNIVERSITY HYPERPHYSICS How Newtonian Mechanics is Incorrectly being Applied to Explain the Laws of Electricity and Magnetism - Download as a PDF or view online for free

www.slideshare.net

 

[electric]

Maybe for AC power and magnetism it's not a good analogy, but for plain DC circuits and pure resistive loads it is quite good analogy to illustrate simple concepts of power and energy.

 

[Supervstech]

Hi all,

I am new to all this, learning so that we can use solar and wind in our future house.

I’m having trouble finding information that explains the difference between a 200 amp Service compare two solar system. Does amp hours equivalent the same thing as a 200 amp grid service? Are there any videos that showThing connecting a solar system into a 2 phase 200 amp breaker box? Would I have two separate breaker boxes one for 12v such as LED lights etc and one for outlets/fan etc?

thank you for the assistance and knowledge!!!

My $.02

a 200A service is capable of supplying 48000 watt loads continuous in 24 hours that is... 1,152,000Wh... at 240v common NA split phase voltage.

A 200Ah battery can support varying loads depending on battery voltage... 14v would be 2800Wh, 24v would be 5600Wh, 48v would be 11200Wh ...

So, the utility is a VERY big battery...

 

[JeepHammer]

Hi all,

I am new to all this, learning so that we can use solar and wind in our future house.

I’m having trouble finding information that explains the difference between a 200 amp Service compare two solar system. Does amp hours equivalent the same thing as a 200 amp grid service? Are there any videos that showThing connecting a solar system into a 2 phase 200 amp breaker box? Would I have two separate breaker boxes one for 12v such as LED lights etc and one for outlets/fan etc?

thank you for the assistance and knowledge!!!

You are confusing terms from different disciplines in electricity...

First, the utility grid has TWO 120 Volt AC (Vac) conductors ('Hot' Wires Called 'Line 1' & 'Line 2' that when Combined produce 240 VAC.
The inside of a breaker panel looks something like this, Gray & Red represent the 120Vac 'Line 1' & 'Line 2' from the power grid.
The breakers in the drawing show how two stacked breakers provide the 240Vac to any particular device.
While a single breaker provides power to any 120Vac device.



In AC, your meter reads Watt Hours (Wh), or more often Kilo (thousand) Watt Hours (kWh).
For example, every AC appliance is *Supposed* to have a CONSUMPTION sticker, as in showing '1,500 Watts' (1.500 Watts/Hour) or it may be expressed as 1.5kWh, same consumption just a different way to express it.

A Watt is a unit of measure of energy.
1 Watt of electricity can be directly converted into 3.12 BTU of heat (British Thermal Unit) through electrical resistance.
745.7 Watts is one 'Horsepower' of mechanical energy.

So Watt Hours (Wh), often expressed as just Watts (W) is the baseline you break everything down to because it is the base measurement.

------------------------

Now you will need to break down things that are rated in Watts & Amps, or Watts & Volts.

An example:
2,000 Watt Inverter @ 120 Volts AC, Watts Divided By Volts = Amps (Amp Hours or Ah)
2,000Wh / 120Vac = 16.66Ah, or Amps per Hour.
2,000Wh / 16.66Ah = 120 Vac

The other way around,
120Vac x 16.66Ah = 1,999.2Wh
16.66Ah x 120Vac = 1,999.2Wh

Now you can figure the load on any particular circuit and convert it to Wh...

----------------------------------

When dealing with batteries it's not much different, same rules apply.
A 12 Volt DC (Vdc) that's rated for say 100Ah, 12 Volt, 100Ah
100Ah x 12 Vdc = 1,200Wh (12kWh)
12,000Wh / 12Vdc = 100Ah
1,200Wh / 100Ah = 12Vdc

Since a Watt is a Watt, from the panels to battery to inverter, it's direct measuring when reduced to Watts.

This doesn't account for conversion losses, from solar panels through charge controller,
From charge controller into batteries, and the power you must leave in the batteries so they aren't damaged.
A lead/acid 100Ah RATED battery will only provide about 25Ah without being damaged.
A LFP 100Ah RATED battery will produce about 80Ah without being damaged.
From batteries through inverter, all have losses in the conversion process from volts to amps, from DC to AC.

---------------------------------------------

Panels in SERIES drives up Voltage. (amperage remains the same base number)
Example would be 100Wh, 12Vdc panels.
100Wh / 12Vdc = 8.33 Amps

In SERIES, this would produce 48 Volts, but the Ah would stay at 8.33

Panels in PARALLEL drives up Amperage. (Voltage remains the same base number)
100Wh / 12Vdc = 8.33 Amps

In PARALLEL, this would produce 12 Volts, but the Amperage would jump to 33.32.

You can also split the difference, 2 panels in Series for 24 Volts x2 (4 panels total),
Then Parallel the two Series strings for 16.66 Amps.
An Example:
Panels that use MC4 connectors that are rated for 20 Amps, this keeps you under the 20 Amp limit with exactly the same power being conducted.
Two panels in Series for 24 Volts, Two Parallel sets of lines into the charge controller.

The 2 batteries are in Parallel.

 

[electric]

A Watt is a unit of measure of energy POWER
1 Watt of electricity can be directly converted into 3.12 BTU of heat (British Thermal Unit) through electrical resistance.
745.7 Watts is one 'Horsepower' of mechanical energy POWER

I fixed this part for you
Watt is power, Watt-Hour is energy. Energy is power over time.

 

[JeepHammer]

I fixed this part for you
Watt is power, Watt-Hour is energy. Energy is power over time.

And all this time EVERYONE was wrong thinking moving electrons were energetic particles...

 

[nosys70]

you can easily make an anlogy with tokens (or cookies) (1 token=1 Amps) and a box.
a 200A battery is a box containing 200 tokens. you can empty it slowly ( one token every hours, so it will takes 200 hours to empty it at 1A/hour)
or you can empty it fast (remove 20 token every 10 minutes, so it will take 100 minutes to empty the box, an equivalent of 120Amps/hour)

the AC wire delivering the power at home is like having somebody delivering a new full box to you every hour.
The good thing is you can have has much token you need because when the box is empty, a new one will be delivered soon.
I f you do not have a way to store the unused token, they are taken back when the new box is delivered, so at best you will never get more than 200 token at a time.
the bad thing, is if you empty the box in less than one hours, you will get no token left until a new hour start (and a new box is delivered, it is called "blowing a fuse").

so capacity in Amps is usefull when you need to plan the size of a battery.
imagine i tell you that a fride when starting with request 120 tokens from the box the first second, but then when running, ask only 2 token ever 15 min (8 tokens per hour, so 8amps/hours).
If you connect your fridge to an 10 amps battery, in theory you could run it for at least one hours, since it needs only 8 amps/hour.
but in reality it will not even start because it is missing the 120Amps "kick" at start that a 10 amps battery can hardly deliver.

The is why a battery has a C discharge rate, that is the maximum Amps you can get for a very short period.
for example many car batteries are 60 Amps/hour battery (meaning they can deliver 60 amps over an hour, or 30 amps over 2 hours , or 20 amps over 3 hours), but they can deliver up to 500Amps for a short periode (usually less than 10 sec).

 

[electric]

And all this time EVERYONE was wrong thinking moving electrons were energetic particles...

In the world of batteries mixing power and energy creates a lot of confusion, so the distinction is very important.
An open circuit battery has no power, but has energy, which is potential for power.
Moving electron has power, but stored electron ( or ion ) has no power, only energy, which is potential for power.
I am not a pedantic person, in fact the opposite, I can't stand pedants. But I feel this subject is important enough to point out as it's not obvious for most newbies.

 

[Deleted member 4428]

There is enough brain power on this thread to put a man on the moon. This is a DIY forum. KISS (keep it simple silly) will help beginners understand how all of this works. I'm sure many beginners get the deer in the headlights effect when reading all of this.

 

[Deleted member 783]

Cookies, deer...am I the only one getting hungry?

 

[Deleted member 4428]

I am not trying to call anyone out on this thread, because this is all through the forum.