Electrical issues

[Byron Kinnaman]

Originally Posted by Francesca Knowles

Byron,

Is it OR ???

I can't tell if you really don't know or if you're just being a Mr. Smarty Pants.

I'll explain it as simply and thoroughly as possible, thereby addressing both possibilities:
The battery is a 12v power supply, happily exactly the voltage needed by a 12v fixture.
Shorepower ("hookups") is 120v, which is 10 times more voltage than a 12v fixture needs unless one is trying to set it afire.
Barring that intention, it's necessary to reduce 120v power to 12v, which is ordinarily accomplished by running it through a converter.
What happens to all the leftover voltage after this process (120 minus 12 = 108) I cannot say...
Perhaps it just lies around waiting to be vacuumed up by an inverter, which accomplishes exactly the opposite function: the transformation of 12v power to 120v.

Hope this helps!

Francesca

I guess you really don't understand. That's OK, I'll try to help a bit. Your 12 volt system runs primarily off the battery. Therefore if you keep your battery charged by other means you don't need a converter. Most converters are not very good battery chargers, therefore a few of us prefer to charge our batteries using other methods.

As for how a converter works and what happens to the approx. 108 volts. The simple answer is it gets converted to heat and dissipated. How much heat depends on the efficiency of the converter and amount of current being drawn by the 12 system. It changes with every light you turn on or off.

I can go into detail if anybody would like.

Byron
Electronic Engineer, retired

[Clankster]

Byron,
Thanks for the input on the solar panels. I appreciate it!

Clint

[Byron Kinnaman]

Originally Posted by Clankster

Byron,
Thanks for the input on the solar panels. I appreciate it!

Clint

If need any more information, let me know.

[Francesca Knowles]

Originally Posted by Byron Kinnaman

OK, I'll try to help a bit. Your 12 volt system runs primarily off the battery.
Byron
Electronic Engineer, retired

YES!

Operative word being "primarily"-EXCEPT when hooked up to shorepower, in which case the converter "switches" from battery power to "converting" the 120v power to 12v power. Try to think of it as like the "adapter" on your home answering machine- it works the same way. While that's going on, the power that's stored in the battery STAYS THERE, all ready to be used when hookups aren't available.
PLUS- if the converter has a charging function like the millions of those in use in RV's, it'll very efficiently charge the trailer battery while you're hooked up!

Is that any clearer?

Francesca

[Byron Kinnaman]

Originally Posted by Francesca Knowles

YES!

Operative word being "primarily"-EXCEPT when hooked up to shorepower, in which case the converter "switches" from battery power to "converting" the 120v power to 12v power. Try to think of it as like the "adapter" on your home answering machine- it works the same way. While that's going on, the power that's stored in the battery STAYS THERE, all ready to be used when hookups aren't available.
PLUS- if the converter has a charging function like the millions of those in use in RV's, it'll very efficiently charge the trailer battery while you're hooked up!

Is that any clearer?

Francesca

It works the opposite of what you're thinking. It draws off the battery until the battery voltage drops below some voltage then the converter kicks in to keep the battery charged at that point. The cut off on my converter is 12.2 volts. Fully charged after settling is 12.7 to 12.9.
That's the same way your "Wall Wart" works on your electronic devices with a few exception. I have an hand held Ham Radio that works like described, but that the first item I've seen that works that way.

That's part of the reason converters are not generally good battery chargers. The battery is never fully charged always undercharged. When my trailer is sitting a long period of time (2 week or more) I connect and external charger to the battery even though the trailer is connected to "shore power". I understand some of the more expensive converters have a better charging circuit, but for the difference I can buy a device designed just for battery charging and the battery gets fully charged without overcharging.

I hope this is clear, if you have question I'll be happy to answer them.

Byron
Electronic Engineer, retired

[Carol H]

Originally Posted by Francesca Knowles

YES!

Operative word being "primarily"-EXCEPT when hooked up to shorepower, in which case the converter "switches" from battery power to "converting" the 120v power to 12v power. Try to think of it as like the "adapter" on your home answering machine- it works the same way. While that's going on, the power that's stored in the battery STAYS THERE, all ready to be used when hookups aren't available.
PLUS- if the converter has a charging function like the millions of those in use in RV's, it'll very efficiently charge the trailer battery while you're hooked up!

Is that any clearer?

Francesca

Francesca on my Scamp there are only a few things that run straight off the 120V system and thats the fluorescent light and 2 120V electrical receptacles (if I had an AC that would be probable be off the 120V as well), everything else (furnace, interior lights, fan, water pump etc) is running straight off the 12V battery - even when plugged into 120V. The fridge will run straight off the 12V as well but has the option of running off the 120V system - but it needs to be manually switched over to 120V. When plugged into shore power all the items that run off the 12V keep running off the 12V - even when plugged into 120V and the converter is only keeping the battery charged up.

If you download a Scamp owners manual for the full wiring diagram it will become a lot clearer as to how it all works. When camping without a 120V hook up the only thing I can not use is the fluorescent light and 120V receptacles as they are not connected back to the battery so therefore are not running off the battery at any time. When camping without shore power I can use pretty well everything I own such as my phone charger, computer etc. by using an automotive plug in converter to the 12V receptacle. When dry camping for more than a day I use a solar panel to recharge the battery. So as has been suggested there is no big loss if one decides to go without a converter as long as you have another option for charging the battery.

[Byron Kinnaman]

Originally Posted by Carol H

Francesca on my Scamp there are only a few things that run straight off the 120V system and thats the fluorescent light and 2 120V electrical receptacles (if I had an AC that would be probable be off the 120V as well), everything else (furnace, interior lights, fan, water pump etc) is running straight off the 12V battery - even when plugged into 120V. The fridge will run straight off the 12V as well but has the option of running off the 120V system - but it needs to be manually switched over to 120V. When plugged into shore power all the items that run off the 12V keep running off the 12V - even when plugged into 120V and the converter is only keeping the battery charged up.

If you download a Scamp owners manual for the full wiring diagram it will become a lot clearer as to how it all works. When camping without a 120V hook up the only thing I can not use is the fluorescent light and 120V receptacles as they are not connected back to the battery so therefore are not running off the battery at any time. When camping without shore power I can use pretty well everything I own such as my phone charger, computer etc. by using an automotive plug in converter to the 12V receptacle. When dry camping for more than a day I use a solar panel to recharge the battery. So as has been suggested there is no big loss if one decides to go without a converter as long as you have another option for charging the battery.

I think stated earlier that I too use a solar panel. It depends on the weather on how long I can go without recharging. If I have to run the furnace a lot then daily, it goes down from there. Most of the time the tow charges the battery between stops.
We just got back from 97 day and were plugged less that a week total. I had to use the solar panel 5 or 6 times.
When sitting at home the battery charge is maintained with one of trickle chargers/battery maintainers. There's several brands.
The converter doesn't do much for me.

Byron

[Andy B]

Originally Posted by Byron Kinnaman

As for how a converter works and what happens to the approx. 108 volts. The simple answer is it gets converted to heat and dissipated. How much heat depends on the efficiency of the converter and amount of current being drawn by the 12 system. It changes with every light you turn on or off.
Byron
Electronic Engineer, retired

This statement is misleading. With most converters the entire 120 volts AC gets converted to 12 volts AC (alternating current) with a transformer and then changed to DC (direct current) to charge the battery. The first 12 volts does not charge the battery with 108 volts left over that is turned into heat. There is an efficiency loss for the conversion that will vary with the converter design and load and most of that loss ends up as heat, but that loss comes equally from every one of those volts and is relatively small, certainly not 108/120 or 90% as was implied.
I am sure you know that Byron, and you did offer to explain in more detail, but some people do not have a very good understanding of electricity and might take it the wrong way.

[GeorgeR]

Originally Posted by Andy B

This statement is misleading. With most converters the entire 120 volts AC gets converted to 12 volts AC (alternating current) with a transformer and then changed to DC (direct current) to charge the battery. The first 12 volts does not charge the battery with 108 volts left over that is turned into heat. There is an efficiency loss for the conversion that will vary with the converter design and load and most of that loss ends up as heat, but that loss comes equally from every one of those volts and is relatively small, certainly not 108/120 or 90% as was implied.
I am sure you know that Byron, and you did offer to explain in more detail, but some people do not have a very good understanding of electricity and might take it the wrong way.

Ditto,
George.

[Francesca Knowles]

Originally Posted by Clankster

Hello,
I have a 1995 13' Scamp that I just bought. Everything seems to be in good condition. However, there is a problem that I just recently noticed. The battery will not charge off the 120v power source. It will only charge when hooked up to the car. .

Originally Posted by Francesca Knowles

Are you sure that you have a converter? Not all trailers of that vintage came equipped with one. Without one, 110 power won't operate your 12v lights. If you DO have one, it may require that you manually switch between battery and 110 power.
Also, even if you have a converter, if it has no charging function it won't charge your battery.


Francesca

Originally Posted by Clankster

It very well may be the case that I don't have a converter. That's what I'm beginning to think. I have looked everywhere and this is the only electrical box I can find.

Is a converter a separate unit?

Thanks for your help.

Originally Posted by Francesca Knowles

Looks like shorepower to me! I think that's your 110v circuit breaker.
A converter is a separate unit that "converts" 110v AC power to 12v DC. Your 12v lights/pump/whatever-you-have won't work off shorepower without one.
Some, but not all, converters also charge the trailer battery. I think you can buy a combined converter-charger for less than $200.00.
My Trillium came to me with a converter only- I had to add a charging module to it.

Francesca

Originally Posted by Byron Kinnaman

If my Scamp didn't already have a converter I wouldn't pay for one.
From my experience and a couple others on Yahoo Groups it's felt that a converter probably isn't worth the cost.

Originally Posted by Francesca Knowles

You can't run 12v fixtures off shorepower without a converter.

Francesca

Originally Posted by Byron Kinnaman

Why not?
You run them off the battery.

Originally Posted by Byron Kinnaman

It works the opposite of what you're thinking. It draws off the battery until the battery voltage drops below some voltage then the converter kicks in to keep the battery charged at that point. The cut off on my converter is 12.2 volts.

I hope this is clear, if you have question I'll be happy to answer them.

Byron
Electronic Engineer, retired

Originally Posted by Carol H

So as has been suggested there is no big loss if one decides to go without a converter as long as you have another option for charging the battery.

I realize that this thread has turned to a discussion of solar panels instead (?) of shorepower, BUT
If there's anybody out there that's still interested please take a moment to review the above excerpts from the thread, beginning with the Original Problem, which was, and I quote:
" THE BATTERY WILL NOT CHARGE OFF THE 110v POWER SOURCE "
It appears that our friend "the Clankster" would like for his battery to charge off 110v power. A discussion ensues. It's established that Clint doesn't have the equipment to CHARGE THE BATTERY OFF THE 110v POWER SOURCE, perhaps the one at the RV park that he's paying $30.00 or more a night for. Those of us sympathetic to the notion that one ought to be able to Get One's Money's Worth when paying to park describe the systems we have that enable us to do so. Early Trilliums didn't come from the factory with batteries unless specially ordered. Their 12v systems ran from the car battery when connected to the car. And each was supplied with a converter whose sole function was to convert 110v power to 12v power for the use of the trailer's systems. Many new trailers today come with a similar setup, a battery being an option only necessary for storage of power.
In point of fact, one can (and many do) camp ONLY with shorepower, no battery at all. But since most RV electricals (pump, heater fan etc) are 12v, they must have a converter to do so, hence my (controversial?) observation that "you can't run 12v fixtures off shorepower without a converter".
And if, like Clint, one wants to CHARGE THE BATTERY OFF THE 110v POWER SOURCE , the converter must be equipped with a charging function, also 12v.

Whew!

Francesca

[Carol H]

No need to yell Francesca dont think the discussion has become about solar panels although they have been offered up to Clint as an option to purchasing a converter. I dont recall him actually stating that he wanted/must be able to charge off the 110V system - although he obviously tried to - he only asked why it was not charging.

I am also pretty sure that anyone following the topic has been clear all along as to what the orginal question was and the debate that developed as a result of the answers given. Clint was correctly advised that if he wanted to charge his battery off his 110V power source he needs a converter.

I suspect the confusion within this thread comes from the following statements:

"The battery is a 12v power supply, happily exactly the voltage needed by a 12v fixture. Shorepower ("hookups") is 120v, which is 10 times more voltage than a 12v fixture needs unless one is trying to set it afire. Barring that intention, it's necessary to reduce 120v power to 12v, which is ordinarily accomplished by running it through a converter." and this "the power in the battery STAYS THERE, all ready to be used when hookups aren't available." and "you can't run 12v fixtures off shorepower without a converter".

I suspect I was not the only one who came away with the impression from the above that you felt that when his trailer was plugged into power, that a converter was necessary to be able to use the 12V system. As Clint indicated he had a battery and a seperate 120V box it was correctly pointed out that his 12V system will contiune to work off the battery regardless of whether or not he was plugged in. As the 12V system is drawing off the battery so the power will not as indicated just "stay there" in the battery regardless of whether or not he is plugged into shore power - this would be the case even if he had a converter that was recharging his battery. As he does not have a converter connecting his 120V system to his 12V system nothing will fry up when he plugs in. The only issue is how do you keep the battery charged up without a converter which brought the topic around to alternatives to converters.

Sorry if you felt we were not listening to you.

[Greg H]

I'm not touching this one.

[Carol H]

Chicken!

[GeorgeR]

Originally Posted by Carol H

Chicken!

Me too,
George.

[Frederick L. Simson]

I think this discussion has run it's course.