12volt DC vs 120volt AC question

[bfkhome]

I'm new to this RV stuff so bear with me and what is probably a very elementary basic question.

I have many lights in my interior coach that are 12volt DC fixtures. I know when the coach is turned off and not connected to shore power or the generator running, then the lights are working off of my batteries.

But if I have the generator on or am connected to shore power does the battery still get used to power these lights? In other words am I still putting a drain on the battery or does something switch over when it senses the 120volt AC and the battery is temporarily cut out of the loop?

[Golden_HVAC]

Hi,

The battery stays in the "Loop". However it is not typically supplying power while plugged in or running the generator.

What happens is the converter/charger can put out up to about 45 amps (might be a 55 or 60 amp model?). If the battery is really low, it will accept most of that power. If you are running 10 amps of lights (about 9 of them) then the charger will supply all 10 amps + have about 10 more amps to run things like the refrigerator circuit board, furnace, water pump, ect, and still have another 25 - 45 amps available to recharge the battery. The battery might not be in the mood to accept all 25 amps. Once the battery voltage is around 14.0 volts, the amperage into it will drop a lot. So it is like a frog jumping 1/2 way to the end of a log. THe first steps are large ones, but get smaller as the frog is closer to the end. Charging a very dead battery, it will accept a lot of power quickly, but will slow it's charge amperage as it gets up to about 80% full, and might take 1 hour to put in 40 amp hours when 40% full, and take 3 hours to put in 40 amp hours when 85% full.

It is best to keep the battery as full as possible - at least in the 50% to 80% full range. At least once a month recharge by plugging into shore power, or run a generator for 4+ hours to get the capacity up above 95% full. Also check the water level every couple of months if you are using it regularly.

So no- the battery should not be supplying power while plugged in. However it can. Lets say you have a sudden need to run 30 lights, the furnace, and water pump. This 48 amp load is more than a 45 amp converter will supply, so the battery will supply the balance, about 3 amps in this case.

Fred.

[Canadian_Rainbi]

Our 2002 Itasca Horizon had a converter as OE located under the stove. We removed it and added a Xantrex Prosine 2.0 pure sinewave inverter/charger in the shore power and transfer switch compartment.


Its' got about 60,000 more miles on it than yours! Nice coach though isn't it?

[MrWizard]

just like your car
the battery is always connected
but when the charging ciruit is on ( generator or shore power ) powering the converter/charger
the battery is being charged while the 12v power comes from the charging circuit
in our car it comes fom the engine alternator

[Old-Biscuit]

RV AC & AC SYSTEMS With CONVERTER


RV AC &DC SYSTEMS With CONVERTER & INVERTER

[FIRE_UP]

Well,
As many don't, he didn't put his rig type/engine/make in the original post. But, a quick view of his profile shows an early Winnebago Journey Diesel. Now, about 99% of the diesel rigs out there come with an "Inverter". And, many of those are "Inverter/Chargers". I know many Journey owners and all of theirs have inverter chargers. So, without the OP actually stating what came with his particular rig, based on history and the norm, I'd say he's got an inverter/charger, not a converter.

If that's the case, the batteries will remain to power up the lights/water pump/12V gas furnace/ and anything else that's normally 12V powered. When on shore power or generator power, that inverter charger, on the charger side, will be charging the batteries WHILE they're still powering up the lights etc.

Now, some of the 32' Journeys did not come with an inverter so, a form of a converter had to be present in those. But, his appears to be at least a 36' unit which, would make the assumption that it has at least a 1500 watt inverter/charger.
Scott

On edit: I see he's responded with info that was needed to allow for better and more accurate answers. Thank you.

[bfkhome]

Thanks to ALL for the great comments. I think I understand now. For those who mentioned it, I indeed have an inverter/charger so I know its charging the batteries, etc.

Special thanks to Dave Bishop who sent two links to a great article on the way the whole system works. I can see from there how the battery interacts with everything else.

[D_E_Bishop]

The 120 vac siteHere is a site to visit and I will post another. Both sites are great for understanding the electrical systems in your rig. I refer to them on and off, always something I need to know.

12 volt side of life part 1

part two

The above are the 12 vdc story.

Good Reading

[enblethen]

Yes, when connected to shore power the lights will be powered through either a converter or by batteries if your rig is equipped with inverter charger.
Whether you have a converter or an inverter charger should be in your owner's manual.
I beleive your Winnebago will have a converter.

[calamus]

We do not even have a battery in our camper that is permanent. One way to find out is to unhook the batt and see if the lights work.

[wallynm]

I would guess you may have an inverter which is more sophisticated than a converter. I would assume the inverter or converter is charging the batteries and the batteries are powering you 12 volt system. Where is a EE when you need one.

bfkhome wrote:
I'm new to this RV stuff so bear with me and what is probably a very elementary basic question.

I have many lights in my interior coach that are 12volt DC fixtures. I know when the coach is turned off and not connected to shore power or the generator running, then the lights are working off of my batteries.

But if I have the generator on or am connected to shore power does the battery still get used to power these lights? In other words am I still putting a drain on the battery or does something switch over when it senses the 120volt AC and the battery is temporarily cut out of the loop?

[BigSkyBob]

When you are connected to shore power or the generator is running either one will charge the batteries through the convertor. Even though the convertor changes 120VAC to 12VDC the power for the lights still originates at the batteries.

[Matt_Colie]

Barry,

This is somewhat coach specific, but with a look at your profile, my guess would be that the coach has a good converter to keep the house bank charged and as that is what powers the house lights. So the battery is not actually out of the loop (it could be), but it is not actually being used to support any loads.

Matt

[2oldman]

When on shore your converter is charging the battery. It's still in the loop.