Battery charging question

[Oneilkeys]

I have a question for all you 12v and battery gurus out there. I am upgrading my WFCO converter/charger to a Progressive Dynamics 4655. We dry camp in the National Parks and Forests a lot and the PD4655 has the capability to manually choose the charging mode. This means I will, hopefully, be able keep the charger in the 55 amp charging mode for the full hour+ that I run my generator and put as many amp hours back into the house batteries as possible in a short period of time.

However, the way the charging system is set up in the Axis (and most - if not all - Thor RVs), when the generator is running the Trombetta is opened and both the chassis and house batteries are charged at the same time. Since the house batteries will be around 12v when I turn on the generator, it is not possible to over charge them in an hour or so of generator time. However, the chassis battery will probably start out in the 12.5v range.

My first question is - should I worry about over charging the chassis battery if I keep the PD4655 in the high charge mode for a hour or so to put the maximum charge on my house batteries.

My second question is - since I want to put the maximum number of amp hours back into the house batteries, is it necessary to put a circuit breaker between the house battery and the Trombetta to keep the chassis battery from being charged when I want all the charging amps to go to the house batteries? I don't really understand how the charger charges the three batteries (two house and one chassis). Does it divide the 55 charging amps among the three batteries equally? Is there someway that it senses the voltage in the batteries and charges the lower voltage batteries at a higher rate? If it charges the batteries equally, it seems to me that unless I isolate the house and chassis batteries, I will only be putting in 2/3 of the charging amps into the house batteries and could overcharge the chassis battery over multiple days of running the generator

My high school physics 50+ years ago leaves this a little fuzzy.

[Buck H]

My 2015 Vegas 25.2 chassis battery has gone completely flat while full timing, connected to shore power. I called Thor tech Support yesterday, and they went through a long troubleshooting process that led to power at the dash. I went to work, and when I came back, there was no power to the dash and the battery was dead again. On today's call (different person), I was told that the chassis battery only gets a milliamp level charge and only when the coach batteries are fully charged.
I'm on my battery charger now, and it shows about 5% charge on the battery after an hour. This had metotally frustrated.

[petew]

I put a knife switch on the positive post of my chassis battery . When the rv is parked I open the knife switch which isolates the chassis battery from Trombettas , Birds or any voltage drains .
For charging I have a disconnect harness wired to the + and - sides of the chassis battery (at the posts) that plugs into my Battery Tender charger , the end of that harness has a weather cap and can extend through the grille for plug in to the charger.

I did this a week or so ago after finding my chassis battery dead and house batteries down on voltage , all while on shore power.

I found a draw on the chassis battery and after searching this forum found a great thread ( Dead chassis battery E350 )that claims the draw is in three (dash) circuits for lighting if I recall correctly.

To me the knife switch is not the "correct" way to solve the problem but isolating the chassis battery Keeps it from overcharging or being drained to nothing.

The switch was easy to install and easy to access/operate. I am no expert ,
Just my 2 cents on the subject

[Oneilkeys]

Originally Posted by Buck H

My 2015 Vegas 25.2 chassis battery has gone completely flat while full timing, connected to shore power. I called Thor tech Support yesterday, and they went through a long troubleshooting process that led to power at the dash. I went to work, and when I came back, there was no power to the dash and the battery was dead again. On today's call (different person), I was told that the chassis battery only gets a milliamp level charge and only when the coach batteries are fully charged.
I'm on my battery charger now, and it shows about 5% charge on the battery after an hour. This had metotally frustrated.

If you put a volt meter on the chassis battery when under shore power or generator, it should read the same charging voltage as the house batteries - at least mine does. That means to me that they are being charged at the same rate. Are you charging using your internal converter charger or an external battery charger? What voltage do you see on both battery banks?

[Oneilkeys]

Originally Posted by petew

I put a knife switch on the positive post of my chassis battery . When the rv is parked I open the knife switch which isolates the chassis battery from Trombettas , Birds or any voltage drains .
For charging I have a disconnect harness wired to the + and - sides of the chassis battery (at the posts) that plugs into my Battery Tender charger , the end of that harness has a weather cap and can extend through the grille for plug in to the charger.

I did this a week or so ago after finding my chassis battery dead and house batteries down on voltage , all while on shore power.

I found a draw on the chassis battery and after searching this forum found a great thread ( Dead chassis battery E350 )that claims the draw is in three (dash) circuits for lighting if I recall correctly.

To me the knife switch is not the "correct" way to solve the problem but isolating the chassis battery Keeps it from overcharging or being drained to nothing.

The switch was easy to install and easy to access/operate. I am no expert ,
Just my 2 cents on the subject

You have something wrong with your charging system. If you are plugged into shore power at all times, both battery banks should stay fully charged. The WFCO converter should charge both battery banks to 12.7 or so volts and then switch to trickle charge mode to keep them charged. The only time you should need to separate the chassis battery is if you are not on shore power. While plugged into shore power, you should not read below 13.1v on either the house or the chassis batteries.

[gmc]

Originally Posted by Oneilkeys

...
However, the way the charging system is set up in the Axis (and most - if not all - Thor RVs), when the generator is running the Trombetta is opened and both the chassis and house batteries are charged at the same time. Since the house batteries will be around 12v when I turn on the generator, it is not possible to over charge them in an hour or so of generator time. However, the chassis battery will probably start out in the 12.5v range.

My first question is - should I worry about over charging the chassis battery if I keep the PD4655 in the high charge mode for a hour or so to put the maximum charge on my house batteries.

My second question is - since I want to put the maximum number of amp hours back into the house batteries, is it necessary to put a circuit breaker between the house battery and the Trombetta to keep the chassis battery from being charged when I want all the charging amps to go to the house batteries? I don't really understand how the charger charges the three batteries (two house and one chassis). Does it divide the 55 charging amps among the three batteries equally? Is there someway that it senses the voltage in the batteries and charges the lower voltage batteries at a higher rate? If it charges the batteries equally, it seems to me that unless I isolate the house and chassis batteries, I will only be putting in 2/3 of the charging amps into the house batteries and could overcharge the chassis battery over multiple days of running the generator

My high school physics 50+ years ago leaves this a little fuzzy.

OK... so it is just a single charger - it has one output - that will be used to charge whatever is connected to it...

Whatever form of battery control - when the chassis and house batteries are tied together (for charging or EMER start) - they are in parallel with each other - and will try to equalize voltage between them.

So actually - if the house voltage is lower than the chassis - the chassis battery will flow current to the house along with the charger until all are equalized - and then all will charge together...

Certainly can disconnect the chassis battery (via breaker or disconnect) if you prefer - but really shouldn't hurt anything to have it in there (unless you are overcharging all three...)

[Oneilkeys]

Thank you gmc. Of course. I didn't think of it that way, but when you tie two batteries together to jump start one, the current flows between the two to try to equalize them. So the same thing should happen when they are charging. The charger does not have to sense anything because the whole system will try to reach equilibrium. That also answers my second question. If the chassis battery is near full charge, then it does not need to be isolated from the house batteries while charging them because the three batteries will equalize and then charge together. While the chassis battery may end up at a lower charge than when you started, basically all the amps will go into the coach batteries until you reach the voltage that the chassis battery was when you started. That makes things much simpler. I knew I was missing something. Thanks for the help.

[bevedfelker]

It doesn't technically charge them both at the same time. The BCC or the BIRD/Trombetta senses the charge state of the battery banks. When it sense 13.1 volts for 2.5 minutes, the BCC isolator or the Trombetta opens and the other battery bank charges. So rather than a simultaneous charging, it is being automatically switched back & forth.

The isolation function of the BCC or the Trombetta keeps the weaker battery bank from drawing g down the fully charged bank if they were both connected at the same time.

[Oneilkeys]

I don't think so Ed. If that were true, the voltage at the two battery banks would not be exactly the same as soon as the Trombetta opens. The BIRD senses the charging voltage, not the state of the battery and as soon as the charging voltage gets above 13.1v at the house batteries for the requisite time, the Trombetta opens and charges both the house and chassis batteries at the same time. You can confirm this by plugging into shore power waiting for the Trombetta to open and then immediately shutting off shore power. The house batteries which read 14.1 or 13.6v charging will immediately fall to the voltage they started at. Because the batteries have not had time to equalize, the chassis battery will read close to where it was when shore power was turned on. The isolator function only works when not on shore power or generator and the voltage at the batteries falls below 12.8v.

[petew]

Originally Posted by Oneilkeys

You have something wrong with your charging system. If you are plugged into shore power at all times, both battery banks should stay fully charged. The WFCO converter should charge both battery banks to 12.7 or so volts and then switch to trickle charge mode to keep them charged. The only time you should need to separate the chassis battery is if you are not on shore power. While plugged into shore power, you should not read below 13.1v on either the house or the chassis batteries.

Well sir I had it checked by my dealer and they claim all is well . The dead chassis battery , even when on shore power ,also seems to be a common occurrence with other Vegas owners , at least that is what I have read here .

Only happened to me once so perhaps I had a relay that got stuck but it won't happen again with that chassis battery isolated when at rest from Thor's top shelf wiring and electronics ....

[camperguy99]

On my Tuscany I simply pull the green wire off the BIRD and this forces the trombetta to open up isolating the two battery banks. So the full charging current of the 100 amp Magnum goes to my bank of 3 series pairs of GC2 batteries. Works well and does not require any extra wiring or devices. The BIRD has a spade lug with the green wire carrying only the coil power of the relay. Incidentally, i replaced the Trombetta with a White Rodgers 200 amp solenoid that has much lower coil current. Nearly an exact replacement for the powe hungry Trombetta.

[bevedfelker]

Attached is the file I received from Thor describing the operation of the BIRD & Trombetta. In reading the description of the Trombetta's isolation function I had interpreted that when a battery was isolated from the other battery only one battery bank at a time was charging. That was I incorrect.

If I would have paid more attention to the BIRD "How It Works" I would have seen it specifically says the batteries are paralleled charging both. Here is the complete description:

How It Works
The BIRD operates in conjunction with a continuous duty solenoid to provide the isolator/battery charging functions of a motor home. It senses voltage on the coach and chassis batteries. If the voltage on either one is above 13.1 volts, indicating the battery is being charged, it closes the isolator relay, paralleling the batteries, charging both. It operates in two directions, charging the batteries from the engine alternator and charging the batteries from the converter. These functions are similar but operate at different thresholds.

Engine Alternator Charging Batteries
When the ignition switch is turned on and the engine is running, the system senses the level of voltage on the chassis 12 volt system. When this voltage goes 13.1 volts for approximately 2.5 minutes, as happens when the engine is running normally (normal alternator output voltage of a cold engine is approximately 14.4 volts), it will close the isolator relay providing charging current to the battery. This delay allows a cold engine an opportunity to start and warm up before having the heavy load of a discharged coach battery placed on it. If the voltage should fall 12 volts for more than about 1 minute, the relay will drop out to feed all the alternators available output to the chassis battery to keep the engine running. This might happen when the alternator is not able to supply sufficient current to all of the loads and charge the coach battery at the same time. When the chassis voltage goes 13.1volts again, the relay will again close in about 2.5 minutes to retry to charge the battery. The resultant flickering of lights would alert the driver of the system overload.

Converter Charging the Batteries
When the coach is plugged into shore power and the ignition is off, the unit senses the voltage on the coach batteries. When this voltage goes 13.1 volts for approximately 2.5 minutes, as happens when the converter isn't heavily loaded, it will close the isolator relay providing charging current to the battery. If the voltage should fall 12.6 volts for more than about 1 minute, the relay will drop out to prevent the coach loads from discharging the chassis battery. This might happen when the converter is heavily loaded by coach loads. When the coach battery voltage goes 13.1 volts again, the relay will again close in about 2.5 minutes to retry to charge the battery.

[gmc]

Originally Posted by petew

Well sir I had it checked by my dealer and they claim all is well . The dead chassis battery , even when on shore power ,also seems to be a common occurrence with other Vegas owners , at least that is what I have read here .

Only happened to me once so perhaps I had a relay that got stuck but it won't happen again with that chassis battery isolated when at rest from Thor's top shelf wiring and electronics ....

Well.. glad it happened only once... maybe it was just something stuck... but it certainly isn't a normal/ok behavior...

What is consistent is that there are varying (inconsistent) experiences with how things actually are wired - ranging from disconnects not disconnecting the complete load, to batteries not charging when they should (usually the chassis)...

From all I have seen in how it is SUPPOSED to work and be wired - the coach disconnect should be absolute... and both batteries should charge from shore/generator/alternator power (when coach disconnect is in 'use' position)... Chassis draw should be very minimal (computer and radio 'keep alive') when in storage...

My 2000 had a chassis disconnect that was also absolute... Seems they have gone away from that - my guess being to avoid the 'relearn' of the computer each time power is cut/re-established...
But it certainly prevented any draw... Of course if parked for long time (extended camping) on shore power which chassis disconnected - you can't forget the chassis battery... Your addition of a battery tender covers that.

In my 2014 hurricane - even camping I use some 12v circuits that are chassis powered (those on dash and in the passenger 'flip out' desk - aka my 'office') - so don't want it disconnected. It has always remained charged on shore power.

[Oneilkeys]

I agree with gmc, while the chassis battery not charging happens, it is not normal. Mine was one if those and it was a miswired BIRD. Others have had problems with their Trombetta sticking (apparently petew's problem) or not functioning correctly or a bad BIRD. In my Axis (at least) the Use/Store switch is not absolute in that it only disconnects the coach batteries from the coach and generator/shore power. On the other side, the alternator is connected directly to both the chassis battery and (thru the Trombetta) to the coach batteries. So the coach batteries will charge with the alternator even with the Use/Store switch in the store position. The system is not simple or transparent and there are many pieces to go wrong or be miswired.

[Oneilkeys]

Originally Posted by camperguy99

On my Tuscany I simply pull the green wire off the BIRD and this forces the trombetta to open up isolating the two battery banks. So the full charging current of the 100 amp Magnum goes to my bank of 3 series pairs of GC2 batteries. Works well and does not require any extra wiring or devices. The BIRD has a spade lug with the green wire carrying only the coil power of the relay. Incidentally, i replaced the Trombetta with a White Rodgers 200 amp solenoid that has much lower coil current. Nearly an exact replacement for the powe hungry Trombetta.

That's basically what I was going to do in my Axis, except put a switch in there, and in your case with a large battery bank and 100 amp charger, I think that is an excellent idea. In my case with two small 29 batteries in my house bank and a 55 amp charger, I don't think that is necessary. Your replacement of the Trombetta with the White Rogers solenoid is an good idea. I will put that in my list.

[petew]

Originally Posted by Oneilkeys

I agree with gmc, while the chassis battery not charging happens, it is not normal. Mine was one if those and it was a miswired BIRD. Others have had problems with their Trombetta sticking (apparently petew's problem) or not functioning correctly or a bad BIRD. In my Axis (at least) the Use/Store switch is not absolute in that it only disconnects the coach batteries from the coach and generator/shore power. On the other side, the alternator is connected directly to both the chassis battery and (thru the Trombetta) to the coach batteries. So the coach batteries will charge with the alternator even with the Use/Store switch in the store position. The system is not simple or transparent and there are many pieces to go wrong or be miswired.

That would make sense (sticking Trombetta) but since it has happened I don't trust those components to do their job correctly.
Is there an upgrade for these components that doesn't require major rewiring .

[Oneilkeys]

I have seen many reports on this forum and others about malfunctioning Trombettas and there are several other solenoids out there which can replace it - see camperguy99's post above for the one he used. That is an easy replacement. I have only seen a couple of BIRD failures. Some Axis/Vegas use a BCC (battery control center) which apparently provides the same capability, but I do not know if that is a better or easy replacement.

[wredman]

admittedly I don't know much about the battery systems, but allowing a single starting battery to charge, or equalize voltage, 2 deep cell batteries every time they are run down is a recipe for short life with the starting battery. That can not be happening by design.

[justjohn57]

Great thread with lots of information here. However, I am an ACE owner and not sure it would apply. I was told at the PDI there is nothing that will charge the chassis battery from the house system, and that putting an exterior trickle charger on the chassis battery would be a good idea during the long winter storage. I'd appreciate knowing if anyone knows for sure so I don't hurt anything if I hook up an external charger.

[Oneilkeys]

Originally Posted by justjohn57

Great thread with lots of information here. However, I am an ACE owner and not sure it would apply. I was told at the PDI there is nothing that will charge the chassis battery from the house system, and that putting an exterior trickle charger on the chassis battery would be a good idea during the long winter storage. I'd appreciate knowing if anyone knows for sure so I don't hurt anything if I hook up an external charger.

Interesting. I cannot believe that Thor would design the charging system in the Axis and Hurricane and others to charge the chassis battery off of shore power and not the ACE. But in all the discussions on this issue over the past year or so, I don't remember any ACE owner entering the fray.