Newbie electrical question

[Dmarcian]

When plugged into 110 shore power do I need to have the batteries turned on for them to receive a charge? After driving for a few hours and then immediately plugging into shore power my inverter reads 14.1 volts. When plugged in for a days (storage) with the batteries turned off the inverter only reads 13.0 volts when I turn them on. Why the difference and what is that telling me? Thanks.

[pconroy]

Originally Posted by Dmarcian

When plugged into 110 shore power do I need to have the batteries turned on for them to receive a charge? After driving for a few hours and then immediately plugging into shore power my inverter reads 14.1 volts. When plugged in for a days (storage) with the batteries turned off the inverter only reads 13.0 volts when I turn them on. Why the difference and what is that telling me? Thanks.

No - the charge is flowing to the house batteries as soon as you plug in, assuming everything is working.

When driving, the alternator is also charging both house and chassis batteries. The alternator puts out 14ish volts. That's probably why your readings are higher.

As for readings over time, you'd need to read up about "Boosting" and "Floating" modes for chargers. In a nutshell, when your battery is very low, the converter pumps 14ish volts in. As the batteries charge, that tapers off to 13ish and then 12ish. Read up on this as its important.

When you flip the master power switch on, everything 12V in the coach that needs power starts to draw from the battery. My inverter often shows 12.4V or around there.

Once you plug into shore power, or start the engine, or start the geneartor (or in my case, get some sun on the solar panels) the house battery should start charging and you'll see a voltage of 13.2V ish.

Again, read up on this to get the nuances.

[SmokeyBear]

Originally Posted by pconroy

Again, read up on this to get the nuances.

Warning newbie Dmarcian, you may also get completely confused. pconroy always assumes all here understand the nuances of electronics and electricity as well as he does.

[LuckyDuck]

Originally Posted by SmokeyBear

Warning newbie Dmarcian, you may also get completely confused. pconroy always assumes all here understand the nuances of electronics and electricity as well as he does.

Actually, he explained it quite clearly and succinctly. If you find it hard to understand, you probably should seek other more elementary sources of information like YouTube vids or an RVs for Dummies book.

[Vicr]

I should mention that the inverter is not the Converter. The converter takes 120v AC and converts it to 12v DC. An inverter takes 12v DC from the battery and inverts it to 120v AC. Also, no charge to the batteries will be present without the coach power switch turning the control relay to the closed position. I'm not going to go into the whole electrical system of an RV which I am most qualified to do (licensed electrician and RV owner of 20+ years) this thread already has some testyness to it. There are numerous youtube videos on RV electrical systems that are done by very qualified individuals.

[pconroy]

Originally Posted by Vicr

I should mention that the inverter is not the Converter. The converter takes 120v AC and converts it to 12v DC. An inverter takes 12v DC from the battery and inverts it to 120v AC. Also, no charge to the batteries will be present without the coach power switch turning the control relay to the closed position. I'm not going to go into the whole electrical system of an RV which I am most qualified to do (licensed electrician and RV owner of 20+ years) this thread already has some testyness to it. There are numerous youtube videos on RV electrical systems that are done by very qualified individuals.

Yeah - I'm not sure why it got testy, but, well, that's the internet.

I said 'inverter" farther down in my post simply because the remote panel for the inverter has a battery voltage display. I use it to see whether I'm in float, boost mode, etc.

You are right - the converter is doing the work here.

[pconroy]

Originally Posted by SmokeyBear

Warning newbie Dmarcian, you may also get completely confused. pconroy always assumes all here understand the nuances of electronics and electricity as well as he does.

That's not my intent. I recall vividly being totally confused by the electrical systems in our first RV.

It took a lot of reading and watching Youtube videos to grasp even the basics. I'm far, far from an expert. Far from...

[Ann-Marie]

I just checked our Greyhawk 30. With the main DC switch off and shore power on the batteries were charging.

What did confuse me is the Ford dashboard radio also shut off when the main DC was off. I thought it was powered from the start battery.

[Vicr]

Originally Posted by Ann-Marie

I just checked our Greyhawk 30. With the main DC switch off and shore power on the batteries were charging.

What did confuse me is the Ford dashboard radio also shut off when the main DC was off. I thought it was powered from the start battery.

If your DC system is shut off (the converter) while on shore power what device is charging your batteries?

[pconroy]

Originally Posted by Ann-Marie

What did confuse me is the Ford dashboard radio also shut off when the main DC was off. I thought it was powered from the start battery.

Mine does too. But my headunit - the Jensen is also connected to both house and chassis batteries. Flip the main switch on, and the radio comes on. Flip it off and it goes off.

[Dmarcian]

Pconroy - you were a big help. Thanks, Dmarcian

[Ann-Marie]

Originally Posted by Vicr

If your DC system is shut off (the converter) while on shore power what device is charging your batteries?

Apparently the charging output from the converter goes straight to the battery positive and by-passes the main on/off switch.

[JimD]

Originally Posted by Ann-Marie

I just checked our Greyhawk 30. With the main DC switch off and shore power on the batteries were charging.

What did confuse me is the Ford dashboard radio also shut off when the main DC was off. I thought it was powered from the start battery.

The radio should be powered by either the house or chassis battery. There are diodes in the circuit that isolates one power feed from the other. To get power from the house battery the master switch needs to be on. To get power from the chassis battery the key needs to be on.

[JimD]

It is very easy to determine whether any battery is being charged. Simply put a voltmeter across it. If it reads mid 13s to mid 14s, you are being charged.

Do this test with the rig plugged in. Typically the converter (the charge source) will be wired directly to the battery and not through the power disconnect switch. Easy to prove with a voltmeter with switch on and off.

Unplug from shore power and start your engine. Measure the voltage at your house battery. Should show a charge voltage. If it doesn't, you may have a problem with the relay/solenoid that connects the engine charge system with the house battery.

[Scoutmaster253]

Originally Posted by Ann-Marie

I just checked our Greyhawk 30. With the main DC switch off and shore power on the batteries were charging.

What did confuse me is the Ford dashboard radio also shut off when the main DC was off. I thought it was powered from the start battery.

Is the Key turned ON, or to ACC? If the ignition Key is OFF the radio will turn off (unless the main DC switch is off).

[pconroy]

Originally Posted by Ann-Marie

Apparently the charging output from the converter goes straight to the battery positive and by-passes the main on/off switch.

Interesting! Good to know.
Thanks Ann-Marie!

[bucko]

I'm one of those who removed the diode power lead from the radio. This way I avoid the coach/house battery from draining if I forget to shut off the coach/house master switch. It happened to me twice.

The chassis/cab radio plays only if the ignition key is in ACC or start/run with my removal of that second diode lead. I have an outside radio if I want tunes when sitting outside. I wired the inside speakers to a plug that connects to the TV; this way I have a poor persons TV surround sound.

I also keep battery tenders connected to the coach/house and chassis batteries when the RV is not in use for a period of time.

[Johnynorthland]

I had the same question a while back. I was told some charge and some don’t while plugged in without the main coach switch on.

So I took my meter and tested at the battery plugged in and unplugged, switch on/off and my 2019 Redhawk 25R charges as soon as it’s plugged in to shore power weather or not coach switch is on. Which is a real plus since I use my solar Gen the night before a trip to run my 12V fridge. I know it’s charging my house battery at the same time but it will run like that for about 60hrs, then hopefully my 190ah AGM would take over if necessary.

[TomC_AZ]

Just a curiosity question what model RV and what model/make inverter is on it?

Some of the inverters do have chargers on them for the batteries. These are or can be separate from the converter which will convert 120v AC power to 12v DC power.

It can get confusing on some of the more complex setups.

[SmokeyBear]

But related.

Often in this thread the term "turn on (or off) the batteries" is used. What does that mean? Is there a switch of some kind? Does this really refer to turning on or off) the circuit(s) the battery(s) support?