Chassis battery not charging when hooked up to shore power

[BSexton]

I have an issue with my 2016 Axis 25.2 that I’m hoping someone can help me with.

The issue is that when connected to shore power, my chassis battery keeps getting depleted. I had this problem last year. Did a whole bunch of testing. When I got a good charge on the chassis battery everything started to work. I even got paranoid and put a voltmeter/USB Socket on both the chassis and coach sides so that I could keep an eye on it. Everything worked fine until yesterday when I went to run the engine and the generator. The chassis battery was about 6V.

So, it works fine from the engine running, both batteries charge. If I start from a really well charged chassis battery, both batteries will charge from shore power. If the chassis battery is under about 13.1V, the converter wont charge the chassis battery.

I’ve looked at the Trombetta, and it seems to working. I’m assuming it isn’t the issue, because it works from alternator and shore power (some of the times).

One more interesting tidbit. So, today after I ran the engine to get everything charged, I turned off the engine and turned off the shore power. The Trombetta spent the next 10 minutes, or so, opening and closing.

I’m not sure how to proceed with my diagnostics. I’m also not sure why it would work for a while (when the chassis battery has a charge) and not others.

Any advice?

[Bob Denman]

If the Trombetta spent that much time "flapping it's wings": that's where the problem has to lie...
But I don't have any clue as to what might be causing it...

Please let us know what happens next: good luck!

[OldWEB]

I have only seen that name used in Thor Forums and I did a quick search, but all I found out is its a name brand of relay.
Now, trying not to sound stupid, where is it used and what is its duty?
I know of the isolator relay and the coach and chassis disconnect relays and also the transfer relay for a generator application, but a Trombetta?


Please be kind.


Stay cool

[BSexton]

Originally Posted by OldWEB

I have only seen that name used in Thor Forums and I did a quick search, but all I found out is its a name brand of relay.
Now, trying not to sound stupid, where is it used and what is its duty?
I know of the isolator relay and the coach and chassis disconnect relays and also the transfer relay for a generator application, but a Trombetta?


Please be kind.


Stay cool

Trombetta is manufacturer of the isolation relay used in between the coach and chassis batteries. I think it might be my problem, but I’m not sure how to diagnose it. As you can see from my first post, it seems to be working correctly.

[Oneilkeys]

If you search Trombetta and BIRD, you will find lots of posts. Basically, the Trombetta is a solenoid that opens and closes to isolate or connect the chassis battery from the coach batteries. So if you run down your coach batteries you will not run down your chassis battery at the same time and you will be able to still start your engine. In some coaches, like the Axis, a BIRD opens and closes the Trombetta depending on whether you coach is plugged into shore power or on generator or if the engine is running. Basically they are designed to connect the two battery systems when the coach is plugged in or running and disconnect them when not plugged in and turned off. A BCC or battery control center in some Axis models performs the same function. Not all Class C’s or B’s are equipped the same way. Some will only charge the coach batteries and chassis battery when the engine is running. But will not charge the chassis battery when plugged in or the generator is running.

[javelin]

Originally Posted by BSexton

I have an issue with my 2016 Axis 25.2 that I’m hoping someone can help me with.

The issue is that when connected to shore power, my chassis battery keeps getting depleted. I had this problem last year. Did a whole bunch of testing. When I got a good charge on the chassis battery everything started to work. I even got paranoid and put a voltmeter/USB Socket on both the chassis and coach sides so that I could keep an eye on it. Everything worked fine until yesterday when I went to run the engine and the generator. The chassis battery was about 6V.

So, it works fine from the engine running, both batteries charge. If I start from a really well charged chassis battery, both batteries will charge from shore power. If the chassis battery is under about 13.1V, the converter wont charge the chassis battery.

I’ve looked at the Trombetta, and it seems to working. I’m assuming it isn’t the issue, because it works from alternator and shore power (some of the times).

One more interesting tidbit. So, today after I ran the engine to get everything charged, I turned off the engine and turned off the shore power. The Trombetta spent the next 10 minutes, or so, opening and closing.

I’m not sure how to proceed with my diagnostics. I’m also not sure why it would work for a while (when the chassis battery has a charge) and not others.

Any advice?

There is a very good Intellitek document attached which describes the operation of the BIRD and Trombetta very well.....should be useful for many reders who have this system. There is also a trouble shooting segment in this document which states that it is normal for the trombetta (interconnect relay) to oscillate under certain battery voltage conditions. After reading your entry I have to wonder about the status of your chassis battery dropping to 6 volts.......what load is on it that would do that? I would charge it and then have it load tested. The other suggestion for chassis battery does not charge when on shore (but it all workes fine the other way around) is, possibly the Bird is not correctly sensing the coach battery charging voltage when on shore power. So either a bad Bird or check and clean the sensing wires/check fuse etc.

[Bob Denman]

Okay... it's Friday, and this Thread is just begging for some party music!

https://www.youtube.com/watch?v=9Gc4QTqslN4

[OldWEB]

Interconnect relay (my schematic), isolator relay (BIRD typical diagram), Trombetta... Why not call it by its function and not the brand name?

Would it still be a Trombetta if I would replace it with a Chinese knockoff?



My opinion on the OPs problem is a 'dead' chassis battery, one that will hold a charge but die very quickly when a small load is applied. It has one or more dead cells internally



Stay cool

[javelin]

Hi, well when we need to wipe our nose we usually ask for a kleenex......even though the Brand "Kleenex" is competitively in the marketplace with many other brands. That's why companies try to be first on the market with their brand name products. Becoming a defacto brand name is worth a lot of money. I guess Intellitec was first with this style of battery control system and many RVers have come to know the component parts by that brand's component assigned names. The main thing is that everyone knows what a kleenex means, but they don't all use a "Kleenex" brand.

[BSexton]

My opinion on the OPs problem is a 'dead' chassis battery, one that will hold a charge but die very quickly when a small load is applied. It has one or more dead cells internally



Stay cool

I’m not sure its a dead battery. When I put the RV up after our trip out here to Utah, the battery was fine and the charging was working.

This has happened twice, with 2 different batteries. I have replaced the chassis battery after the first instance.

Everything works fine when the engine is running and when I store the RV without hooking up to shore power. There is a voltage drop when I store without shore power, but it what you would expect since I don’t have a battery disconnect.

I’m thinking that my load that is draining the battery is the charging circuit.

Some time this morning, I’m going to go make some more scientific measurements of the Trombetta, rather than my haphazard approach so far.

My understanding is that the Trombetta should have infinite resistance between the two positive posts when open and a nominal resistance when closed. Can anyone verify this?

[Bob Denman]

If you could "load-test" the battery in question: it could answer some of the questions...

[javelin]

Hi, the trombetta (interconnect/isolator relay) main (high current) contacts should have infinite resistance when open and zero ohms when closed. The other way to test it is to actually operate it under the charging conditions that work and then measure the voltage on each main high current contact. If the voltage difference is greater than 0.2 volts, they suggest replacing the relay per the Bird document I attached previously. Excerpt of that in trouble shoot section (last item) attached.

[BSexton]

Originally Posted by javelin

Hi, the trombetta (interconnect/isolator relay) main (high current) contacts should have infinite resistance when open and zero ohms when closed. The other way to test it is to actually operate it under the charging conditions that work and then measure the voltage on each main high current contact. If the voltage difference is greater than 0.2 volts, they suggest replacing the relay per the Bird document I attached previously. Excerpt of that in trouble shoot section (last item) attached.

Ok, it’s amazing what you can learn when you take a scientific approach to a problem.

I tested the system in all of the various states. I’m getting 70 ohms of resistance when the engine is running and between 300 and 1200 ohms when the converter is running on shore power. And that’s just not right.

So, I’m now going to order a replacement for the Trombetta. I’ll post back if this fixes the issue.

This probably explains my battery drain. I was essentially running a little heater in the relay.

[OldWEB]

[javelin]

Well you should never use an ohm meter on a "live voltage" circuit.....or you could be buying a new meter or a fuse for the meter. That's why measuring the voltage drop across the main contacts of the Trombetta when closed is probably a safer and more accurate indication of continuity through the relay. Relay operated and charging is working: Meter - to ground; Meter + to each of the two relay main contacts (two separate measurements) and then see what the voltage difference is between the two readings. Greater than 0.2vdc and replace the relay (suggested by manufacturer).

[16ACE27]

Originally Posted by javelin

Well you should never use an ohm meter on a "live voltage" circuit.....or you could be buying a new meter or a fuse for the meter. That's why measuring the voltage drop across the main contacts of the Trombetta when closed is probably a safer and more accurate indication of continuity through the relay. Relay operated and charging is working: Meter - to ground; Meter + to each of the two relay main contacts (two separate measurements) and then see what the voltage difference is between the two readings. Greater than 0.2vdc and replace the relay (suggested by manufacturer).

We hope he disconnected the main cables to do his resistance test, otherwise, the results are meaningless.

[gmc]

Originally Posted by javelin

Hi, well when we need to wipe our nose we usually ask for a kleenex......even though the Brand "Kleenex" is competitively in the marketplace with many other brands. That's why companies try to be first on the market with their brand name products. Becoming a defacto brand name is worth a lot of money. I guess Intellitec was first with this style of battery control system and many RVers have come to know the component parts by that brand's component assigned names. The main thing is that everyone knows what a kleenex means, but they don't all use a "Kleenex" brand.

Wayyy off topic, but...
While it may sound good... having worked for the company who’s name is still the ‘defacto brand’ when someone wants a photocopy... they don’t like or promote that usage.
They can actually lose their trademark on the name if it is deemed too common... And them promoting that would only help the argument.

[javelin]

Very true. Trademarks can be lost in the eyes of the Law when generically used.....but it is so much easier to use a term that is generically well known by many.

[BSexton]

Originally Posted by 16ACE27

We hope he disconnected the main cables to do his resistance test, otherwise, the results are meaningless.

Thanks to you and Javelin for pointing out my mistake with how to measure the resistance of the Trombetta. I seem to need to measure the resistance of something about every 10 years or so. I always forget that you can’t do that in a live circuit. Apparently, I have to make a measurement that don’t make any sense, be confused for about a day, and then go look up the correct method for measuring resistance.

In my defense, the last formal training on multi-meter use was Computer Engineering 101 in college, 30 years ago!

[BSexton]

Ok, finally, I have this thing working.

After several people pointed out that my method for determining the Trombetta was good was inaccurate, I went out and used the correct way to test it. The voltage drop across the Trombetta was about .05v. So, that wasn’t the issue.

However, in doing the measurements, I noticed that the “coach battery” line for the BIRD seemed to be hooked up to the chassis battery side of the Trombetta, not the coach. I was pretty sure that the extra line with the fuse holder in it was the “coach battery” line in the BIRD documentation. I tested it and, sure enough, it was.

Through my testing, I was able to determine that the chassis battery is on the right of the picture and the coach is on the left. Since there were very different voltages on these two circuits, I was able to confirm which was one was which. So, the BIRD was mis-wired.

So, I turned off shore power, disconnected all of the negative battery terminals, swapped the line with the fuse over to the other terminal at the Trombetta, and reconnected everything.

Viola!

The mis-wiring would explain what I was seeing. The system would work when the engine was on. The system would work for a little while after turning off the engine and connecting shore power (it would work until the chassis battery dropped to 12.6v).

The second picture is what I ended up with.