Charging problem... 2009 Navion iQ (Sprinter 3.0 V6).

[MyGplante]

Hi, I'm having trouble diagnosing the charging problem on my 2009 Navion iQ (Sprinter 3.0 V6). While driving on the highway, the RV batteries (2 x 6 volts Trojan T-105) started to drain slowly. I have a display on my iPhone that allows me to see the RV's Victron Shunt in real time. It's as if the alternator can't supply enough current to compensate for the electricity demand (air conditioning fan and Sprinter compressor plus RV fridge). Everything worked fine before. The motor's 12-volt gel battery is about 5 years old, and I've been having a bit of trouble recharging it lately.
If the Sprinter is stationary and the engine is running, the alternator's charge reading is 13.2 volts. The Sprinter's battery is holding at 12.8 or 12.9 volts. The Cole Hersee 24213 solenoid (200A) seems to work fine, it clicks on start-up but is it enough to check? In short, I don't know whether I have an alternator problem (180A OEM and 14.4 volts normally) or a problem with the engine's 12-volt gel battery (4 years old) or something else.

On a 5-hour highway trip, I got down to 12.3 volts everywhere (RV batteries and motor battery).

1- When I'm driving and everything's off, I get 40 watts going to the RV batteries (photo 1) for a while, then it gets worse.
2- When I turn on the RV's fan speed, air-conditioning compressor and 12-volt fridge, I'm down to -28 watts, and it can go as low as -80 watts (photo 2).
3- Photo 3 shows the Sprinter's battery Volts on my Garmin GPS ODB2 connector.

What can I do to find my trouble (12-volt engine gel battery, alternator or Cole Hersee 24213 200A solenoid)?

Thank you for your help. ;-)

[Morich]

Some testing will be needed but there are some first thoughts that may ease your mind a bit?
One is that the RV alternator is sized so big that is is not likely you will ever overwork it to the point that the output voltage will actually go down.
Second point is that if there were such a large short to ground and you did begin to reach the top level of current the alternator would provide, there are fuses or breakers to protect it from failure. No blown fuses/tripped breakers? Alternator probably okay!

But the two most likely causes are bad batteries or the even more common dirty/corroded connections.
I would not try to do any repair work using the monitor panel as they are just too unreliable and isolated in such a way that they can actually not be reading the true battery voltage if they are out on a dirty connection!

How to go with testing can depend on how difficult to reach different points like the two battery groups versus getting under the seat to test at the solenoid? I might like to start at the batteries as there are several things to look at and test there.

First step might be to let the RV set for six hours or so to let the battery chemicals get stable without charging or significant drains. For this, it is best to turn off any battery disconnect, etc to reduce any drains. There will still be some but not enough to mess the readings if you do them in the same time frame.

Starting at the batteries, check the voltage right on the positive post, then the clamp on that post and they should be very near the same if they are clean and making good contact.
If the batteries are difficult, take the same readings at the large posts on each side of the solenoid before starting the engine and you would expect some difference in the two battery voltages.

If you have tested at the batteries first, compare the readings from both points. This chart is handy if there is tape still on the cable ends to ID them.


The main point is that the point on th esolenoid and the battery posts should be only slightly different due to the length of cable between the points. May a half volt? But if there is any big difference, it is saying the cables are corroded at some point between the battery and solenoid!
If you find this, look all along the cable as there are often big "mega fuses" that have connections on each end to corrode!
Sometimes easy to spot in the battery box but also may be out on the frame and covered in dirt and tar??

Once you have the readings before starting, look at the chassis battery voltage and it is handy to have a second person start the engine???
You should first see the chassis battery voltage drop as it cranks but then once running the alternator puts out power and the voltage will often be around 13+ and may go to 14 if revving the engine.
Seeing that proves the alternator, etc and cable to the solenoid or battery is good, so next check the coach batteries and you should see very near the same and jump up and down as you rev the engine!

If it does that, the charge voltage is getting to both sets of batteries okay. Any trouble with charging or holding that charge will likely be a question of bad batteries.
Keep in mind that the readings at the posts is not a true picture of what is going on all down through the battery lead and chemicals but what we call "surface charge". It can be reading higher than actual if charging has been going on or lower if the Rv has been using power, so letting things settle is critical to get good voltage readings.

What the monitor says? If it is not getting near the same readings, it may have dirty cables between it and the batteries! But that is a second question to work out, so I would first want to know the batteries are good and fully charged as well as able to hold that charge.
Fully charged can only be near 12.7, any higher is left over charging.
It should stand up near that for at LEAST several days with only minor change. If it has dropped down to 12 overnight, suspect bad batteries!

Run through a bit of that and see what you might find and we can go further if okay to that point!

[MyGplante]

Originally Posted by Morich

Some testing will be needed but there are some first thoughts that may ease your mind a bit?

Thank you very much for your detailed answer. I will test each step to try to find the problem. I'm really impressed by all your knowledge. Thank you so much.

[Morich]

Thanks for the comment---but before being too impressed, I should admit that I left out one of the easy things to check that can happen?
Be sure to look at the negative battery cable where it often goes down behind the battery to the frame!
Being under the RV, it can get lots of wet, dirt and corrode easy!

[MyGplante]

Originally Posted by Morich

Thanks for the comment---but before being too impressed, I should admit that I left out one of the easy things to check that can happen?
Be sure to look at the negative battery cable where it often goes down behind the battery to the frame!
Being under the RV, it can get lots of wet, dirt and corrode easy!

Hi Morich, here's a collection of data to analyze. I removed the passenger seat to read the data with a multimeter on the 4-year-old Cole Hersee 200A solenoid (replacement for the faulty 80A Trombetta, four years ago).

BEFORE to start tests:
- Fuses or breakers blown: I checked the accessible fuses I could see, and found nothing wrong.
- Dirty/Corroded connections: I lay down under the RV to look for bad, dirty or corroded connections, but everything is healthy and clean (never been out in winter in salt and snow).

Before taking a reading of the battery values: Sprinter chassis (AGM 12 volts) and Coach/House (2 Trojan T-105 6 volt batteries for 12 volts), I disconnected everything so that the batteries could rest without any demand, even the big positive cable under the Sprinter dashboard. I waited 9 hours of rest before taking all these readings.

1. First start reading without rest: Chassis 12.83V and House 13.36V
2. After 9 hours of rest: Chassis 12.81V and House 13.07V

When the problem appeared on our 5-hour return trip, I had to turn off the A/C and speed ventilation to save power, and even so, we dropped to 12.3 volts (Chassis and House batteries).

Engine idling during readings
- 1. ENGINE RUNNING
- A/C:ON and SPEED VENT: MAX. Alternator 13,45V - Battery (Sprinter) 12,78V - Solenoid (Chassis side) 12,80V - Solenoid (House side) 12,80V

- 2. ENGINE RUNNING AFTER 15 minutes
- A/C:ON and SPEED VENT: MAX: Alternator 13,15V - Battery (Sprinter) 12,64V - Solenoid (Chassis side) 12,62V - Solenoid (House side) 12,61V

- 3. ENGINE RUNNING AFTER 30 minutes
- A/C:ON and SPEED VENT: MAX: Alternator 13.06V - Battery (Sprinter) 12.43V - Solenoid (Chassis side) 12.37V - Solenoid (House side) 12.37V

- 4. ENGINE RUNNING AFTER 45 minutes
- A/C:ON and SPEED VENT: MAX: Alternator 12,90V - Battery (Sprinter) 12,37V - Solenoid (Chassis side) 12,32V - Solenoid (House side) 12,31V

- 5. ENGINE RUNNING AFTER 1 hour
- A/C:OFF and SPEED VENT: OFF: Alternator 13,08V - Battery (Sprinter) 12,63V - Solenoid (Chassis side) 12,68V - Solenoid (House side) 12,68V

After this hour, I also took a reading from the HOUSE batteries, which were at 13.07 volts and then went to 12.68 volts, the same value as on the Sprinter chassis 12,68 volts.

Does the chassis battery, even with a good voltage, no longer have much reserve and create this significant drop?
I've also been thinking about the 4-year-old Cole Hersee 200A solenoid, which, as it heats up, becomes defective because the Victron Shunt on the batteries house after 15 minutes says it's no longer receiving current from the engine, like when I'm camping in the wild with the engine off. For example, on the road from a reading of +3A to +4A, after about 15 minutes, it drops to -2A to -3A. And the house batteries start to run down.

Any suggestions?

THANK YOU FOR YOUR SUPPORT.

[Morich]

With the two voltages on coach and chassis reading the same at 12.68, it is almost certain that the solenoid is good as it looks like they are connected together and that's really all it can do. It's just like a big light switch only it operates electrically when the ignition is on. They call it "ignition hot" on some places I've read.

So it is likely what is holding the voltage on both at 12. 68 after an hour of idle.
But I would expect the voltage coming out of the alternator to be plenty to hold all the batteries at that level or a bit more, even if we are running lots of stuff.
The alternator is kind of like a battery charger that adjusts the output higher as it is needed or backs off to lower if the batteries are full and that let's it keep running without overcharging them.
Kind of like a really good charger that puts out a lot when a battery is really low and what we call bulk charge, then has several different stages, for just the normal use and finally backs down to a level we call float charge or just enough to keep the battery neither running down nor over charged.
We want the battery full but not boil off the water by charging it too much!

But one thing to look at is what happens if we speed up the engine? If the fan belt that drives the alternator is good and all normal, we expect to see the battery first get a drop as we crank the engine as power is taken out of the battery but then when the engine gets going, the alternator "knows" that and puts out a little bit higher to "refill" the battery.
That voltage coming out is often set by how fast the engine is turning the alternator, so if we rev the engine, we expect to see a meter go up to around 13+ before it backs down if the battery gets full.

I don't know exactly what to expect with the engine at idle for a long time as that is not the way we expect to drive a car. What we need to see is that the voltage at both batteries flies up real quick as we rev up the engine.

It sounds like it is getting there right, higher voltage to both batteries but good to check that?
It "could" be something wierd like a fan belt slipping or something so that the alternator is not picking up speed when it should but that often squeals or something that lets us know.
The solenoid should not be a problem as it heats up because it is a pretty simple thing.
It has a magnetic coil that has a metal rod in the center. When power moves through the coil, it moves the metal rod and on the end is something pretty close to like a cheap silver dollar (big washer?) that slaps up against the two big lugs to make contact between them. You can often hear or feel it move as it kind of thumps!
Big enough to last a good long time but they do eventually get burned and corroded. But if they are passing the power from the chassis to the coach batteries, we usually can say they are good.

The more likely problem is the battery is not holding that charge it is getting long enough. Sometimes it is like the difference in pouring water on a sponge and we come back six hours later and it is still wet but if we do the same on a rock, it's dry when we come back!
If the alternator seems to be getting the higher voltage to both batteries and it shows full but goes down way too fast, it may need to be load tested at a car parts place to let them check if it is holding that charge okay.
They need to charged pretty well to do a good check but that might be where I would look next.

[MyGplante]

As I have to go for regular maintenance for my Sprinter, I will have the belt and alternator checked. I'll keep an eye on my old Sprinter AGM battery, which is almost 5 years old. It will probably be replaced next spring. Thank you Morich (Richard), I am very grateful for your quick follow up and very accurate support. Merci beaucoup de la ville de Québec (Canada). ;-)

[bigb]

A couple of things are confusing here, what do you mean by this? "2- When I turn on the RV's fan speed, air-conditioning compressor and 12-volt fridge, I'm down to -28 watts, and it can go as low as -80 watts"

Are you referring to the House rooftop AC fan or the dash air fan and compressor? Also is your inverter on? This will use some wattage too. Is the fridge 12 volt absorption or compressor?

It would help to know the total wattage of the loads that are running off the house batteries. You don't say how old they are but it's possible they are weak and you are losing ground. There is going to be a limit to how much the Sprinter alternator can charge the house batteries by design (usually 40 amps or 480 watts at 12V & 576 watts at 14.4 volts), then there are the house batteries themselves and how much current they will accept at any given time and at any given SOC. If they are failing they may not be accepting the charge current they once did.

You can get an idea of the total wattage you are demanding of the house batteries by running everything with the engine off and seeing how many watts the Smart Shunt says you are using. But if the batteries are getting older that may be your issue. With battery capacity lower you're going to see a lower system voltage when power is being consumed.

The system voltage while driving can show the same at the house and the chassis because your solenoid has them linked together when the engine is running. What happens when you are parked and plugged in, what voltage do you see on the house batteries while charging and what voltage do you see on them after leaving the charger and all loads disconnected overnight after you have fully charged them? (You won't be able to go by the Smart Shunt as that is just a bean counter, it doesn't actually monitor voltage and current to get the SOC)

If wanting to test alternator output try disconnecting the solenoid to the house batteries then see what the alternator output is, and if the chassis battery charges fully. Remember to let batteries rest at least 3 hours with no charging and no load to get a true resting voltage.

[MyGplante]

Sorry for the confusion. For the a/c, it's the one from the Sprinter motor (dashboard) with the dashboard fan too. When I drive, the House section only consumes a few watts (Fridge 3-way including the 12 volt absorption) normally maybe 20 watts. Of course, the house batteries are 5 years old, as is the Sprinter battery too. And when I'm not driving, the house batteries are charged by 200-watt solar panels and reach over 13 volts. But as you say, the age of the batteries doesn't help. I've never had such problems like that since I've owned my Navion iQ. So I'm going to plan to replace the batteries gradually, but also have the belt and alternator checked. Thank you for your post Brian.

[bigb]

Got it. Just to point out, my Dometic RML 8555 consumes 175 watts on 12 volts which is 14.6 amps at 12 volts and 13.5 at 13 volts. If you are seeing only 20 watts on the shunt that is the sum of what you are using minus what the charge current is putting back. Everything runs off the batteries which are in turn charged by the alternator, the batteries are kind of a buffer between the alternator and the loads. If the batteries are weak and not accepting enough of a charge you are losing ground. Since a Sprinter alternator is not cheap, a pair of new GC-2s is probably a good plan, or have them tested although to properly test deep cycle batteries is more involved than the simple hand held load testers are capable of, although some of the hand held battery analyzers can do much more than a load test.
A true load test of a deep cycle bank is done with a measured load over a timed period that matches the spec on the batteries. (It has to be done when the batteries have been fully charged first)

[MyGplante]

Thank you Brian for your point. If I understand correctly, when the solenoid is open, the batteries adjust to the same voltage (for the three batteries)? And the alternator works to fill the entire energy demand for all the batteries?
But, one thing I don't understand. When I recharge the RV (house) batteries with other power sources such as the propane generator, solar panels or a 120-volt cable, my Victron Shunt always indicates that it's receiving power from these various power sources. However, when the engine is running, the first few minutes of alternator work are recognized by the Shunt, but after about 15 minutes, it doesn't see it.

[bigb]

Originally Posted by MyGplante

Thank you Brian for your point. If I understand correctly, when the solenoid is open, the batteries adjust to the same voltage (for the three batteries)? And the alternator works to fill the entire energy demand for all the batteries?
But, one thing I don't understand. When I recharge the RV (house) batteries with other power sources such as the propane generator, solar panels or a 120-volt cable, my Victron Shunt always indicates that it's receiving power from these various power sources. However, when the engine is running, the first few minutes of alternator work are recognized by the Shunt, but after about 15 minutes, it doesn't see it.

When the solenoid is closed everything is charging. If the shunt does not see a charge from the alternator after awhile it means either the charge is insufficient (or interrupted), the batteries are already full and will not accept a charge (batteries near end of life will do this as I mentioned) or you are running loads equal to or greater than what the charge current is.

If you are seeing good charging from the converter while plugged in then it's possible your alternator is not doing it job.

Have you looked at your history in the shunt software? This could give you an idea of the condition of the house batteries. If the batteries are low yet they reach float voltage in a short time this could mean the batteries are near the end of their useful life.

Various charging methods will also be different, smarter charging methods tend to ramp down the charge current to near zero as the battery nears a full charge while dumb chargers tend to keep charging.

[MyGplante]

In short, my batteries are old (4 or 5 years) and they're starting to give me problems I've never had before. So, I'll plan to replace them.
Thanks again Brian.