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Coach Batteries Not Charging on Shore AC

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I have a 1999 Four Winds Windsport RV. The coach batteries are not being charged when I'm connected to shore power. I've verified this by measuring the voltage at the battery terminals when on shore power. There is no change in voltage when I connect to shore power.

I have checked the 120VAC to 12VDC inverter that I assume is supposed to charge the coach batteries. It produces 13.5 VDC (with no load) and powers all of the 12V components in the RV.

The RV uses an Intellitec battery disconnect system. Inside the door are two switches to disconnect the chassis and coach batteries (see photo below). Also below photos of the Intellic disconnect relays inside the power distribution box that's in the engine compartment.

I'm an mechanical engineer and I have spent a huge amount of time trying to fix this. So I will be immensely grateful if anyone has suggestions.

Best regards,

Frank

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post-37376-0-74249000-1397582010_thumb.j

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Frank,

Welcome to the FMCA forum!

Could you post he model and make of your charger / inverter for the group.

Do the batteries charge while running the generator?

That will aid in pinning down the electrical wiring and charging circuits.

Rich.

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Thanks Rich

The Inverter is a PowerSource PC50 producing up to 50A at 12VDC.

The alternator is charging the chassis battery just fine, and I've verified the output of the alternator. But I don't think the coach batteries are charged by the alternator... is that correct?

Does anyone know if the Battery Disconnect system also disconnects the coach batteries from the PowerSource charger? I've had problems with the Battery Disconnect for the coach batteries.

Thanks!

Frank

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Frank,

Alternator should charge BOTH battery banks-- chassis and house. Easy to verify with a voltmeter. Check with engine off and then at each battery bank with engine running and at high idle. Both should be 14-14.2 VDC with engine running.

On many coaches, the charger or converter (120 VAC to 12 VDC) only charges the house battery bank, not the chassis bank. Which bank is not being charged?

And your mention of an inverter may not be the correct item-- an inverter takes 12 VDC and "inverts" it to 120 VAC. A converter, charger or inverter/charger takes 120 VAC and produces 12 VDC.

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Thanks for the thoughts Wolfe10

I measured voltage across both chassis and coach batteries with the engine off, and both are at 13.3 V. I started the engine and let it idle at ~900 rpm. The voltage across the chassis battery was 14.9 V. The voltage across the coach batteries dropped to 12.1 V.

I'm perplexed. Why would the coach batteries drop from 13.3 V to 12.1 V when I start the engine? It's almost like a load is applied to the coach batteries when the engine is started.

When the engine is off and I'm connected to shore power, there is no power applied to the coach batteries.

Sorry about my confusion of invert/convert. The Powersource PC50 takes 120VAC and converts to 12VDC.

Any thoughts appreciated.

Frank

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Frank, thanks for the information.

Looking at the pictures you posted, are they of your coach system? The right hand relay labeled Chassis. There is a copper link / strap with nothing connected. Below it looks like there might be 2 gray wires connected to it.

That should be a ground.

The coach batteries should be connected at this point, positive on the left

The other relay labeled chassis has a red wire on the left and a black wire on the right. What is the voltage reading from ground to the 2 red wires on the left side of them?

Get a reading when connected to shore power and when disconnect from shore power and post the readings.

Rich.

See you got a reading with the engine running. at the relays with the engine running and the engine stopped, what reading do you get?

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Frank,

A drop in the house battery bank voltage from 13.3 to 12.1 in just a couple of minutes indicates either a MASSIVE draw or much more likely one or more bad batteries. So, I would start by fully charging them and have them load tested. A bad battery can give all kinds of weird symptoms.

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Wolfe10, Thanks again for helping me troubleshoot this!

All of the batteries are new. They've been on a float charger and were at 13.3 V today before I connected them to the RV two hours ago.

Now the batteries are at 12.4 V. Seems like something is drawing current from them. And they are not being recharged by shore AC.

I will pull out the batteries and test them, but I doubt that they are bad. if they are bad, somethnig made a new battery go back very quickly.

I'm starting to think that something is broken (a disconnect relay, heater element, etc) and is shorting to ground and draining the coach batteries. But no fuses are blown.

I remain bemused.

Thanks,

Frank

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What size and how many batteries make up your house battery bank (in amp-hrs best)? Basically want to see how many amp-hrs "disappeared" in those couple of minutes. 13.2 shows a totally charged battery bank (actually 12.7 is a fully charged 12 volt battery-- anything over about 12.7 is just surface charge). 12.2 VDC is a 50% discharged battery bank.

Guess my point is if you have 200 amp hrs of house battery bank and within a few minutes 100 amp-hrs went somewhere, that is a HUGE amount. As an example, a 1500 watt microwave would need to run for over 40 minutes on the battery (with inverter) to use that much power. Something is wrong here-- that is why I mentioned fully charging and then load testing the batteries.

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Frank, thanks for the information.

Looking at the pictures you posted, are they of your coach system? The right hand relay labeled Chassis. There is a copper link / strap with nothing connected. Below it looks like there might be 2 gray wires connected to it.

That should be a ground.

The coach batteries should be connected at this point, positive on the left

The other relay labeled chassis has a red wire on the left and a black wire on the right. What is the voltage reading from ground to the 2 red wires on the left side of them?

Get a reading when connected to shore power and when disconnect from shore power and post the readings.

Rich.

See you got a reading with the engine running. at the relays with the engine running and the engine stopped, what reading do you get?

Rich,

The photo is of the power dist box that has a disconnect relay for the coach batteries and a disconnect relay for the chassis battery. Power from the batteries enters through the two copper bars in the center (see red arrows pointing up). The cables labled S and I are from the rocker switches inside the RV that activate the disconnect relays. When activated, the relays connect coach and chassis power to the RV.

The voltage in and out of each relay was 12.3V, the same with and without shore power.

I'm still trying to figure out why the coach batteries are not being charged by shore AC. That might solve the problem, even if there's a large load on the coach batteries.

Thanks,

Frank

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What size and how many batteries make up your house battery bank (in amp-hrs best)? Basically want to see how many amp-hrs "disappeared" in those couple of minutes. 13.2 shows a totally charged battery bank (actually 12.7 is a fully charged 12 volt battery-- anything over about 12.7 is just surface charge). 12.2 VDC is a 50% discharged battery bank.

Guess my point is if you have 200 amp hrs of house battery bank and within a few minutes 100 amp-hrs went somewhere, that is a HUGE amount. As an example, a 1500 watt microwave would need to run for over 40 minutes on the battery (with inverter) to use that much power. Something is wrong here-- that is why I mentioned fully charging and then load testing the batteries.

Wolfe10,

I have one 12V auto battery for the engine/chassis and two 12V deep cycle batteries connected in parallel for the coach. I will get the specs for you later (it's cold and dark in Pittsburgh now), but they're typical 12V chassis and coach batteries.

I am going to do some tests to try to find the large load that's draining the coach batteries. I will charge the coach batteries, then remove fuses from certain 12V circuits, and then connect the batteries. When the coach batteries stop draining, that should track down the load.

However, I am still faced with the problem that my coach batteries are not being charged when shore AC is connected.

Thanks,

Frank

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Frank, look in your AC circuit breaker panel and see if you have a tripped 15 Amp breaker.

From the information I have, it looks like most of if not all the convertors are fuse at 15 amps AC.

Regarding the Charging from shore power it should read very close to the same reading you are getting from the alternator.

You should have a 12 volt fuse box that is power from the batteries and the convertor when things are working properly.

How many fuses does your panel have and what is the total amperage when you add the fuse size numbers up?

If the relays are always drawing current, that will be part of the load always present, if they are latching relays then that load is only temporary, until the relays latch in the on or off position..

The switches on the inside control panel, look like rocker switchs.

Rich.

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Frank, look in your AC circuit breaker panel and see if you have a tripped 15 Amp breaker.

From the information I have, it looks like most of if not all the convertors are fuse at 15 amps AC.

Regarding the Charging from shore power it should read very close to the same reading you are getting from the alternator.

You should have a 12 volt fuse box that is power from the batteries and the convertor when things are working properly.

How many fuses does your panel have and what is the total amperage when you add the fuse size numbers up?

If the relays are always drawing current, that will be part of the load always present, if they are latching relays then that load is only temporary, until the relays latch in the on or off position..

The switches on the inside control panel, look like rocker switchs.

Rich.

Rich,

There are more fuses and breakers in this RV than I can shake a stick at! There's a fuse box under the rear bed, a fuse box under the dash, a fuse box inside the power dist box, and two more high amp breaker boxes in the engine compartment.

I think I need to systematically remove fuses and see if the batteries stop draining, until I isolate the load that's draining the batteries.

In addition, I need to understand why the coach batteries are not being charged.

The Intellic disconnect switches are not always working, so I'll start by replacing them.

I've helped to solve some national level crises, but this one has me pulling my hair out!

Frank

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Frank,

If its electrical then its a head scratcher. I had the same problem with my inverter. No charging of the Batteries. Took the inverter to a shop that is noted for repairing inverters. "Mr. Mullins, I have bench tested this inverter up, down, in & out over and under, there is nothing wrong with the unit." I asked if a loose ground could be the problem? His response was possible. When I was removing the unit I noticed one ground connection where the wire nut was very loose. When I replaced the unit I made sure all connections were tight. It works like a dream now.

My point is that you may just have a loose connection in your unit. Like Chicken Soup for a dead man, it may not help but it can't hurt.

Herman

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Frank, welcome to the new owners learning curve !

Good post regarding the location of the fuse panels !

Could you post the chassis make and I will see if I have some fuse panel info.

The one on the firewall / dash is for fusing the chassis items, lights, dash AC and heater motor ext.

The ones in the engine compartment are the primary panels for the engine and the fuel pump, ignition, ECM, Most likely the entry power steps, ext.

The one under the bed , slide out power, leveling jacks and holding tank monitor power, and power for activating the relay(s) in question.

The one next to the AC breaker panel would power all the 12volt lights, roof fans, water pump, plus.

I was thinking of suggesting removing the fuses to find the phantom loads this A M before I opened your post. Pull one fuse at a time from the panel. then use a test light across the fuse gap. if it lights that circuit is drawing power.

The charging voltage, should be present on one side chassis and coach relay. reading from ground to all the large terminals of the relays. That voltage should be close to the same from both the engine alternator and shore powered convertor.

Rich.

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Frank, welcome to the new owners learning curve !

Good post regarding the location of the fuse panels !

Could you post the chassis make and I will see if I have some fuse panel info.

The one on the firewall / dash is for fusing the chassis items, lights, dash AC and heater motor ext.

The ones in the engine compartment are the primary panels for the engine and the fuel pump, ignition, ECM, Most likely the entry power steps, ext.

The one under the bed , slide out power, leveling jacks and holding tank monitor power, and power for activating the relay(s) in question.

The one next to the AC breaker panel would power all the 12volt lights, roof fans, water pump, plus.

I was thinking of suggesting removing the fuses to find the phantom loads this A M before I opened your post. Pull one fuse at a time from the panel. then use a test light across the fuse gap. if it lights that circuit is drawing power.

The charging voltage, should be present on one side chassis and coach relay. reading from ground to all the large terminals of the relays. That voltage should be close to the same from both the engine alternator and shore powered convertor.

Rich.

All,

My RV is a 1998 Thor Four Winds Windsport. The metal sticker under the dash says the vehicle ID number is 3FCMF53G4VJA22935 and the Model Number is WA04698.

I had AutoZone test my batteries today. All are at 12.5 V and producing 550 CCA. They are rated at 875 CCA. So they are somewhat weakened. I am pretty sure there is a large parasitic load. The parasitic load drained the batteries a few times. That's probably why they are weakened. I need to find the parasitic load before I replace the batteries.

This evening I will put a volt meter across each fuse to try to detect the parasitic load. I have a good multimeter that should detect small millivolt drops across a fuse.

I think i should also replace the Powersource PC50 converter. It's output is rated at 12VDC at up to 50A. This converter is no longer made. Can anyone suggest a good replacement?

Thanks to everyone for the excellent advice!

Frank

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YES! Thanks to the advice from this forum, I found the parasitic load that was draining my coach batteries!

I removed the negative cable from the coach batteries, then connected my multimeter between the negative cable and the negative terminal of a coach battery. It showed that 1.5 A was being drained from the coach batteries.

I then measured the voltage drop across each fuse. One fuse had a 200 mV drop across it!. I removed that fuse, and that completely stopped the parasitic current drain from the coach batteries. The fuse is labeled "Body Builder Access Feed (run only)" Does anyone know what that is???

Now I just need to get the coach batteries to be charged when I'm connected to shore AC. When connected to shore AC, no charging power is delivered to the coach batteries.

vielen veilen Danke!!!

Frank :)

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A bit more info about my coach batteries not being charged when I'm plugged into shore AC.

I took the DC output leads off of my PowerSource PC 50 converter, and connected the leads to a high current 12V battery charger.

But still no power reached the coach batteries. So the link between the AC-to-DC converter and the coach batteries is broken somewhere...

Thanks,

Frank

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Have you looked for a battery isolator, maybe diode based, or relay operative. Most coaches have one, and yours may have gone bad. Just a thought, since you have now tested using a known good battery charger.

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Have you looked for a battery isolater, maybe diode based, or relay operative. Most coaches have one, and yours may have gone bad. Just a thought, since you have now tested using a known good battery charger.

There is an Intellic relay based battery disconnect system. Just inside the door are two rocker switches that activate battery disconnect relays. Is that what you're referring to?

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Frank,

The fuse labeled "Body Builder Access Feed (run only)" Thinking it powers the monitoring system / the battery disconnect circuits and LP detector plus a few others.

Looking for item(s) that do not operate. is one way too narrow it down.

The other tool you could look into is a circuit tracer.

They work well for finding where the wires run between too points.

They come in a wide price range. The tone generator, puts a tone on the wire and the level needs to be adjusted lower to narrow down the exact wire; by using the receiver portion.

Lowe's has them and you can search the web for circuit tracers to get an idea of the price range and even look at a user manual(s) on line (with Make and model)to find one you feel will work.

It takes time and a learning curve, but one can get very good at finding circuits with practice.

Rich.

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When I'm searching for a break, short or open, I use the Power Probe with a 20 foot lead. If you ever use one of these you will never go back to a test light.

http://www.rakuten.com/prod/power-probe-ppr319ftc-power-probe-iii/212940171.html?listingId=331619458&scid=pla_google_SynergyDataInc&adid=18172&gclid=CO6-wKDl570CFQWTfgodiH8AqA

manufacture link

http://www.powerprobe.com/pp3.php

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Frank,

The fuse labeled "Body Builder Access Feed (run only)" Thinking it powers the monitoring system / the battery disconnect circuits and LP detector plus a few others.

Looking for item(s) that do not operate. is one way too narrow it down.

The other tool you could look into is a circuit tracer.

They work well for finding where the wires run between too points.

They come in a wide price range. The tone generator, puts a tone on the wire and the level needs to be adjusted lower to narrow down the exact wire; by using the receiver portion.

Lowe's has them and you can search the web for circuit tracers to get an idea of the price range and even look at a user manual(s) on line (with Make and model)to find one you feel will work.

It takes time and a learning curve, but one can get very good at finding circuits with practice.

Rich.

The fuse labeled "Body Builder Accessory Feed (Run Only)" is in the chassis fuse box under the dash. So the fuse is for a chassis accessory. I think Ford called it's electrical chassis system "Body Builder" for RV's. I cannot find anything that stops working when I start the RV and pull out the Body Builder Access fuse. The engine runs. The lights, AC, windshield wipers all work.

What other chassis accessory could there be that is only turned on when the engine is running?

Thanks,

Frank

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Frank, got to say that is strange, you mentioned removing the Body Builder fuse removed the parasitic load from the Coach batteries. Even thought the fuse is in a fuse box under the dash.

1.5 amps is going somewhere! The fact that it is loading the coach batteries, would make one think something related to the coach circuits..

Do you have power operated steps / and do the coach and chassis disconnect relays still work?

Rich.

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