Watt to Ah

[wyb2]

Originally Posted by Xavierp

400Ah is 1/2 of my 800Ah battery bank

let's say the appliance is on all day. How long would it take to empty the bank?
2 hours or 2 days?

You’ve already answered the question. 400Ah is 1/2 of your 800Ah battery bank (unless it’s actually a 400Ah bank like your OP says). If something is using 400 Ah per day it will use half of your bank per day. Two halves is a whole. 2 days.

There are about a hundred reasons why it won’t be that simple in practice, but that’s the direct basic math answer to the question.

[JustMurph]

Just to avoid any confusion for people in this thread, in DC systems (like we're talking about here), watts is the correct unit for power. VA is only relevant in AC systems.

[Xavierp]

Originally Posted by ohgary

Is your appliance really on all day?

I used an example. The subject of the posting was converting.

Thx for the info

[Xavierp]

Originally Posted by wyb2

You’ve already answered the question. 400Ah is 1/2 of your 800Ah battery bank (unless it’s actually a 400Ah bank like your OP says). If something is using 400 Ah per day it will use half of your bank per day. Two halves is a whole. 2 days.
.

so 400Ah means in fact 400Ah for 24h?.... It will take 24 hours to empty the battery if 400A are drawn every hour?

[JustMurph]

No. 400Ah = 400 A for 1 hour.
Or 200A for 2 hours
Or 800A for half an hour
Or 40A for 10 hours

[Baronkrak]

Originally Posted by JustMurph

Just to avoid any confusion for people in this thread, in DC systems (like we're talking about here), watts is the correct unit for power. VA is only relevant in AC systems.

Back to harping
You must have missed that post.

Originally Posted by Baronkrak

give you VA

Are you able to make the difference between True and Apparent wind?

[Xavierp]

Originally Posted by deblen

Here is one online-there may be more.
Start with Basic DC
https://www.electronics-tutorials.ws/sitemap

Thx!!!!

[Xavierp]

Originally Posted by ohgary

Is your appliance really on all day? .

not the subject of the post.
I am trying to understand the math / conversion.

[Xavierp]

Originally Posted by deblen

OHMS Law and the Power(Watts) formulae.
https://www.electronics-tutorials.ws...its/dcp_2.html


Plus-as said by others-you must determine how long that you draw how much current per hour (Amp Hrs).

thx for the Link.

[SailingHarmonie]

Originally Posted by Baronkrak

Back to harping
You must have missed that post.


Are you able to make the difference between True and Apparent wind?

I certainly can tell the difference between AWA and TWA, but you will have to explain to me what power factor has to do with a DC system. How amps can be out of phase with volts in a system with a frequency of exactly zero.

Kind of like calculating true wind on a stationary vessel.

[Xavierp]

Originally Posted by SV_FlyingTigress

Google Search [Watts to amp hour conversion]
First hit:
"How do you convert watt hours to amp hours?

MY POINT!!!!!
I am NOT trying to convert watt HOURS to amp hours.
I am trying to understand how to go from Watt to Amp h.

Now try that search again and you'll see that they are no hits. Hence coming to this forum.

[SailingHarmonie]

Originally Posted by Xavierp

MY POINT!!!!!
I am NOT trying to convert watt HOURS to amp hours.
I am trying to understand how to go from Watt to Amp h.

Now try that search again and you'll see that they are no hits. Hence coming to this forum.

There s no conversation possible. The measure different things. Here is very similar example: I drove 50 miles per hour. Can you convert that to how many miles I drove?

[Xavierp]

Originally Posted by SailingHarmonie

There s no conversation possible. The measure different things.

then this was the answer I was looking for and the Google search didn't help.
This forum did. You did. And could have done it w/o the comment about Google search.
Remember that nobody forces you to answers the posts. Especially when they come from people like me, who are eager to learn from peers, and not just from "google searches'.

[thinwater]

Originally Posted by Xavierp

then this was the answer I was looking for and the Google search didn't help.
This forum did. You did. And could have done it w/o the comment about Google search.
Remember that nobody forces you to answers the posts. Especially when they come from people like me, who are eager to learn from peers, and not just from "google searches'.

The difference between W and VA is a "measuring" contest in this thread context. It's about simple DC on a boat.



---

The thing to understand is that watts is a unit of energy per time, just as knots is a unit of distance per time. Ah is a unit of energy (assuming the volts are known) and miles is a unit of distance. Thus, you need to convert either the watts to current and multiply by time, or convert the battery Ah to Wh and divide by watts used.



200 W at 12 V results in 200/12=16.7 A current draw. You know this.


800 Ah is a measure of how many amps the battery can supply over time. Really, it is bastardized unit of energy storage, because Ah x V = Watt-hours. You battery bank can supply about 400 x 12 = 4800 Wh. As a practical matter, if you draw more than 1/2 of that you will damamge battery a little bit every time.



The appliance will use 16.7 Ah every hour it is on. It will draw 8.3 Ah in 30 minutes. It will draw the battery down to 50% (200 Ah) in 12 hours.


The same math works with watts. 2400 Wh usable / 200 W = 12 hours.

[Xavierp]

Originally Posted by thinwater

The thing to understand is that watts is a unit of energy per time,

would it be correct to say then that W = Wh?
If I see on my charger 30W I should in fact read "30W will be used every hour"?