Batteries

[randye]

Hi I have a question, about the system of the converter. Does it not only charge the Batteries, but also converts 115 volts to 12 volts. Then that means while hooked up to shore power our onboard batteries are not really doing anything except discharging and charging? The only time the fifth wheel is using the onboard batteries is when the power goes out, or you are boon docking? Am I on the right track thanks for the help.

[DQDick]

You are correct.

[1retired06]

And you should still check the water levels occasionally.

[DarMar]

x2 on checking the water levels frequently!

[dieselguy]

I may have read the article wrong, but the converter doesn't exactly put out the cleanest power, so the battery(s) absorb the irregularities in power production going from AC to DC. With battery(s) installed, the 12V is primarily pulled off them while the converter keeps them charged.

[Tom S.]

quote:Originally posted by dieselguy

I may have read the article wrong, but the converter doesn't exactly put out the cleanest power, so the battery(s) absorb the irregularities in power production going from AC to DC. With battery(s) installed, the 12V is primarily pulled off them while the converter keeps them charged.

DC power from a battery is constant. DC power from the convertor is AC power stepped down via a transformer to 13 volts and converted via a rectifier from AC to DC. The rectification process takes an AC sine wave that goes from 0 to approximately 180 volts positive, then back 0 volts, down to approximately 180 volts negative, then back to 0 again in each cycle. Your standard AC performs 60 of these cycles every second. You may be saying something to the effect that your AC voltage is only 120 volts, but that measurement is an average of the voltage in the cycle from 0 volts through the cycle mentioned above and back to 0 again, which is about 120. The rectifier takes the positive side of the cycle that the transformer has stepped down to 13 volts and then reverses the other side of cycle (that would have been a negative 13 volts) to make it positive, and adds them both together. Keep in mind, that as I said at the beginning, DC power is constant. But 120v AC power converted to 13v DC still has the cycles, so the power is rising from 0 to 13 volts, and then dropping back down again. Because the inverter has the ability to reverse the negative side of the cycle and make it positive, instead of AC cycle going from 0 to 120+ to 0 to -120 and back to 0 sixty times a second, the rectified DC goes from 0 to 13+ to 0 to 13+ to 0 one hundred and twenty times a second.

Although that is very fast, it still leaves very tiny fractions of times where there is less than 13 volts, in fact almost no volts at all. I say almost no volts, and you might wonder why it doesn't actually drop all the way to zero, but it would require another lengthy post to describe it, so please just trust me that it gets close but doesn't actually hit the zero mark. At any rate, this is why DC power is considered "cleaner" than AC converted power. Things like light bulbs can't tell the difference, but more complex electronic items like computers can.

So, once again, someone has asked "What time is it?" and I've told them how to build a watch! For those who wanted to know and learned something from this post, I'm happy and for those who are saying to themselves "I wasted 5 minutes reading this crap", I apologize!!

[K0LCB]

Good explanation, Tom! I'm glad you never got to root mean squared

[Tom S.]

quote:Originally posted by K0LCB

Good explanation, Tom! I'm glad you never got to root mean squared

Yeah, I was avoiding going into RMS for fear of having everyone go to sleep when their eyes glazed over.

[Bigboomer]

I knew I should have gotten a beer before I read Tom's post...well explained!

[CORattler]

Tom,
Great explanation. You made my head hurt (but in a good way).

[paulinbaja]

You did not say why the question. But removing the battery is not a good choice. You refrig works on DC so if the AC goes out you need the battery. Do keep an eye on the water!

[Ozz]

Tom, you are scaring me...

[Tom S.]

quote:Originally posted by Ozz

Tom, you are scaring me...

You say that like it's a bad thing....

[Ozz]

Hey Tom, I found the Avitars! It is amazing no one told me when I brought it up with a question.
BTW, thank you for 'splaining it to me.

[jlb27537]

Not being a engineer, but I agree with Tom IF you only have a diode bridge. However those little round things called capacitors smooth out the bump's and when you look at a DC voltage line on a scope, if you have a decent converter you will see very little variance in the voltage.

Now, what Tom described is exactly what you will see if you look at the output of a $30 battery charger from Walmart with no Caps in the output ckt.

To see how much A/C is on the line from your converter, go to the frig, and using the A/C scale on your meter see what you read on the DC input to the ckt board there. Now turn the battery disconnect off and see if the A/C reading changes.

With a good converter you will read "0"vac with the battery disconnected. If you read some A/C that is called ripple and the battery will absorb it, sometimes. Our ckt boards do not like ripple.

Jim

[Tom S.]

quote:Originally posted by jlb27537

Not being a engineer, but I agree with Tom IF you only have a diode bridge. However those little round things called capacitors smooth out the bump's and when you look at a DC voltage line on a scope, if you have a decent converter you will see very little variance in the voltage.

Now, what Tom described is exactly what you will see if you look at the output of a $30 battery charger from Walmart with no Caps in the output ckt.

To see how much A/C is on the line from your converter, go to the frig, and using the A/C scale on your meter see what you read on the DC input to the ckt board there. Now turn the battery disconnect off and see if the A/C reading changes.

With a good converter you will read "0"vac with the battery disconnected. If you read some A/C that is called ripple and the battery will absorb it, sometimes. Our ckt boards do not like ripple.

Jim

Even 'decent' convertors will show ripples in the DC output on an oscilloscope.

[jlb27537]

Agree, we are not working on main frame computers with "perfect" DC. I have a PD4590 converter which shows less than 100 millivolts RMS ripple, which is pretty decent.

When I was working on electronics we used a scope daily, but never seen one in a RV shop or Car dealership...now I need to take that back. In the 60/70's's Sun had a piece of test equipment that we could look at voltages from alternators and spark plugs.

Tom, remember the good ole days when we had the Heath Kit voltage regulator tester and we repaired alternators instead of just replacing them?

http://www.progressivedyn.com/all_in_one_pd4500_1.html

Jim

[Tom S.]

quote:Originally posted by jlb27537

Agree, we are not working on main frame computers with "perfect" DC. I have a PD4590 converter which shows less than 100 millivolts RMS ripple, which is pretty decent.

When I was working on electronics we used a scope daily, but never seen one in a RV shop or Car dealership...now I need to take that back. In the 60/70's's Sun had a piece of test equipment that we could look at voltages from alternators and spark plugs.

Tom, remember the good ole days when we had the Heath Kit voltage regulator tester and we repaired alternators instead of just replacing them?

http://www.progressivedyn.com/all_in_one_pd4500_1.html

Jim

Alternators, generators and starters. Brushes and bearings. And you could repair the Ford fender mounted solenoids by drilling out the rivets, cleaning the contacts with a file, turning the copper washer over and bolt everything back together.

[jlb27537]

Yea, the good ole days....

[mhs4771]

Next you Guys will be talking about the manual spark advance lever on the steering column