Service 4WD and Batteries

[surfbeetle]

For about a month or so, the truck has a message of Service 4wd System showing when starting the truck. Over the last couple of weeks, twice, I have moved the truck, (2016 2500 4WD) around the property and also had it in both 4wd high and low. Total run time each time was 10 to 15 minutes before parking, leaving it in 2wd and turning off the truck, the truck wasn't driven at all until the next day. After each of these two times, the battery was dead the next day and the truck had to be jumped started. The first time, it was fine afterwards with no dead batteries. This was days apart and on the other days we have driven the truck normally with no issues or dead batteries. Yesterday was one of those days where I drove it for a few minutes in 4wd. Today, I had to jump start the truck. We went up to the local mountains and drove quite a bit in 4wd high, at least an hour at around 30 mph in the snow and then back to 2wd and drove 30 minutes home. The truck was on for about 2 hours so that was definitely enough to charge the batteries.

I've read some threads where guys are saying that their factory batteries are junk after a short time. My truck is 2 1/2 years old and has 40,000 miles. My question: is it possible that the Service 4wd system message has something to do with running down the batteries?

Thanks in Advance

 

[jhenderson]

It’s far more likely your bad batteries are the cause of the service light. Remove or totally disconnect both batteries before doing a load test. Not just voltage. Load test and record available amps vs what they’re rated for. 12 volts but 2/3rds the amps means a bad battery.

 

[Larry Sciblo]

I had a similar experience in my 2016 RAM 2500 with 38K miles. After load test had one bad battery, but everyone said if one is bad, to replace them both.

 

[seafish]

I had a similar experience in my 2016 RAM 2500 with 38K miles. After load test had one bad battery, but everyone said if one is bad, to replace them both.

The reason to replace BOTH batteries at the same time in a dual battery system where one battery has already failed is to keep the charge potential of each battery roughly equal so that the ECM continues to charge them equally through the crossover cable.

Charge potential is determined by the internal chemical state of the battery plates and fluid which changes with temperature, type of battery, age of battery and also use and/or abuse of the battery.

In short, if one battery has already gone bad, it is more then likely that the other battery has already been overcharged by the ECM/alternstor at least for awhile and this leads to it having a different and lower charge potential then the new battery.

If the older battery cannot accept a charge at the same rate as the new one, then the newer battery will be overcharged as well, thus leading to its eventual failure and the cycle repeats itself unless both are replaced with equivalent batteries.

Just my .02

 

[JR]

I'll also add that depending on the state of discharge 2 hours may or may not be enough to completely charge your batteries. It is always best to throw a slow charge on them after being discharged to fully recover.

Here's a chart to give you a rough idea of the required time to charge based on amps. This is not all inclusive and there are many factors involved but gives you a starting point. Remember this is assuming a single battery. Generally speaking the slower you can charge (less amps) the better for the batteries.

 

[surfbeetle]

Thank you all for the replies. 11 volts on the gauge today but it started since I didn’t wait for the diesel preheat. I’m going to throw the battery charger on it for now.

 

[kthaxton]

The reason to replace BOTH batteries at the same time in a dual battery system where one battery has already failed is to keep the charge potential of each battery roughly equal so that the ECM continues to charge them equally through the crossover cable.

Charge potential is determined by the internal chemical state of the battery plates and fluid which changes with temperature, type of battery, age of battery and also use and/or abuse of the battery.

In short, if one battery has already gone bad, it is more then likely that the other battery has already been overcharged by the ECM/alternstor at least for awhile and this leads to it having a different and lower charge potential then the new battery.

If the older battery cannot accept a charge at the same rate as the new one, then the newer battery will be overcharged as well, thus leading to its eventual failure and the cycle repeats itself unless both are replaced with equivalent batteries.

Just my .02

Overcharge is actually the result of too much voltage, not amperage. If one battery is bad, it is going to call for more amperage, not voltage, the computer will not up the voltage in this scenario. Voltage is tightly controlled based on temperature and a couple other factors.

The issue with dual batteries with one being bad (or older, or different model etc.) is the difference in internal resistance. If there is no isolation device (i.e. wired directly together like our trucks) the two batteries slowly drain each other when sitting with the engine off. The battery with lower resistance will draw from the better one, but it will draw a little too much....then that one gets drawn down to meet it...but it also overshoots, and the cycle continues until they are both dead.

 

[jhenderson]

Then please explain the common problem of the pass side battery overcharging to the point of explosion Or at least a swollen battery case because of a bad crossover cable. More resistance in the bad battery because of a shorted cell combined with low voltage detected by the truck results in the same effect. It’s happened to me twice.

 

[Newsa]

Then please explain the common problem of the pass side battery overcharging to the point of explosion Or at least a swollen battery case because of a bad crossover cable. More resistance in the bad battery because of a shorted cell combined with low voltage detected by the truck results in the same effect. It’s happened to me twice.

I would also like to hear this explanation.

 

[kthaxton]

Then please explain the common problem of the pass side battery overcharging to the point of explosion Or at least a swollen battery case because of a bad crossover cable. More resistance in the bad battery because of a shorted cell combined with low voltage detected by the truck results in the same effect. It’s happened to me twice.

While I can't say for certain because I am not familiar with the problem, logic tells me if there was resistance in the crossover cable, this would result in inadequate charging of that battery. In a constant state of low charge, more sulfation happens on the plates which means more sulfates shed and sink to the bottom of the battery eventually shorting out the bottoms of the plates. When the plates become shorted, this creates heat and boils out the electrolyte, which would appear like an over charge condition. Just a swag however.

What I can say for sure is that there is no way one battery could get "over" charged and the other not. The alternator does not send a specific voltage to each battery, they get the same voltage. If one gets overcharged (again, from too much voltage) they both get overcharged.

Think about it, how would the battery with resistance in its charge cable get MORE voltage than the other one? It can't.

 

[jhenderson]

That’s not the problem. The crossover cable was fine in both instances. A bad battery doesn’t fully charge. The truck recognizes the low battery and sends more juice. The charge goes through the pass side first. If the bad battery doesn’t accept the charge the pass side gets overcharged. Hence the swollen case in my experience and an exploded battery in those who don’t notice the smell of the cooking battery in some others.

 

[seafish]

KThaxton,

The problem of a bad crossover cable resulting in overcharging of the passenger side battery on our trucks is both common and well documented!!!

It works like this--

The ECM measures and adjusts charging voltage based on battery temp and battery voltage of the DRIVERS SIDE battery.
While charging voltage of the alternator is controlled by the ECM , the alternator is hooked up ONLY to the PASSENGER SIDE battery.
The large crossover cable connecting the two batteries then transfers and equalizes voltage between them.

If the crossover cable itself and all connections are in GOOD CONDITION, the voltage passes from the PS battery, through the crossover cable and to the DS battery and the dual battery system works as designed.

BUT if the crossover cable is failing (internal resistance increases due to corrosion) or connections are bad (loose and/or dirty)
then the drivers side battery continues to fall in voltage through use and since the ECM monitors charging voltage through the DS battery, it continues to INCREASE voltage up to max parameters in order to charge the DS battery which will continue to lag behind the PS battery due to increased resistance in the crossover cable. This eventually results in the overheating and boiling over the PS battery leading to failure of the PS battery.

You can read MANY threads documenting this unfortunate process on any of the Ram/Cummins forums.

 

[seafish]

And in fact JUST like JHenderson says, a bad cell in the drivers side battery will cause the exact same symptoms of the PS battery overheating and overcharging even if the XO cable is good. Again, this is due to the design of the charging system -- ECM reads voltage and monitors temp on the DS battery, but charges first through the PS battery, If the DS battery reads low, due to a bad cell, then the ECM will continue to ramp up charge until the PS battery fails.

 

[kthaxton]

KThaxton,

The problem of a bad crossover cable resulting in overcharging of the passenger side battery on our trucks is both common and well documented!!!

It works like this--

The ECM measures and adjusts charging voltage based on battery temp and battery voltage of the DRIVERS SIDE battery.
While charging voltage of the alternator is controlled by the ECM , the alternator is hooked up ONLY to the PASSENGER SIDE battery.
The large crossover cable connecting the two batteries then transfers and equalizes voltage between them.

If the crossover cable itself and all connections are in GOOD CONDITION, the voltage passes from the PS battery, through the crossover cable and to the DS battery and the dual battery system works as designed.

BUT if the crossover cable is failing (internal resistance increases due to corrosion) or connections are bad (loose and/or dirty)
then the drivers side battery continues to fall in voltage through use and since the ECM monitors charging voltage through the DS battery, it continues to INCREASE voltage up to max parameters in order to charge the DS battery which will continue to lag behind the PS battery due to increased resistance in the crossover cable. This eventually results in the overheating and boiling over the PS battery leading to failure of the PS battery.

You can read MANY threads documenting this unfortunate process on any of the Ram/Cummins forums.

Ahhh! That makes sense! I had assumed the alternator went to the DS battery or at least a PDC on the DS and that the PS battery was only connected to the DS battery (and nothing else). I have yet to have to mess with electrical on my 2015 nor do I own an FSM for it so I had never traced the alternator output. That being the case I can see how that would happen. That's kind of a dumb way to route the alternator output....I guess it reduces wire length.

My mistake.

 

[surfbeetle]

I spent the money and replaced both batteries on Sunday. I wasn't happy having to do this on such a young truck. The original batteries on my '95 were 5 years old when they went out. Everything seems to be okay now.

 

[Newsa]

My original batteries lasted about a month and a half shy of 4 years.

At 2 1/2 years, you were 6 months out of the 2 year warranty for the batteries

 

[TomBrady]

I spent the money and replaced both batteries on Sunday. I wasn't happy having to do this on such a young truck. The original batteries on my '95 were 5 years old when they went out. Everything seems to be okay now.

I’m glad I read this thread! It helped me figure out was was going on with my truck. I replaced my batteries on Monday. It too was behaving strangely for the last couple of weeks. It’s back to normal now. 97,476 miles and 26 1/2 months of ownership. Really ticks me off. I replaced them with a pair of Northstar AGM’s.
There is a wealth of information and knowledge here. Great reading in hotel rooms on the road!

 

[Road Dog]

The battery life doesn't start when you buy the truck. It starts when the battery is manufactured. Then the truck is manufactured and the truck may sit in factory or dealer lot for a long time (discharging all the while) before you buy it.

It means that a new truck may have worn out batteries when you buy it. It used to be that lead-acid batteries were shipped dry and the acid added when purchased. Then you have a new battery.

 

[surfbeetle]

The battery life doesn't start when you buy the truck. It starts when the battery is manufactured. Then the truck is manufactured and the truck may sit in factory or dealer lot for a long time (discharging all the while) before you buy it.

It means that a new truck may have worn out batteries when you buy it. It used to be that lead-acid batteries were shipped dry and the acid added when purchased. Then you have a new battery.

While that is correct for battery life, it may not be true with regard to the warranty life. I spoke to my service writer because I have an extended warranty with the dealer, not a Chrysler warranty. He said that since I'm at 40,000 miles and out of the 3 year/36,000 mile warranty, he wouldn't be able to swap it under warranty. If I'd been under on the mileage, then at 2 1/2 years I would have been okay. I was more irritated with the fact that my Challenger has gone 5 years so far with the battery and as I said before, my other truck was also 5 years on the original batteries. We did however have a 2012 Flex and when it was new, the battery only lasted a couple of years as well. So it's a crap shoot if you're going to get a decent amount of use on it.

 

[EDankievitch]

My 2013 was throwing all kinds of very strange codes when my batts were failing. It would start up fine on warm 40 degree days and on cold 20 degree days the **** would hit the fan code wise as it would crank slowly. I had thought the factory batts were AMG was I wrong they were sealed wet cells and one had almost No water left in it with No way to refill it. I think when my Alt burned up two years ago it damaged the batts? Who knows for sure. Rock Auto had by far the best price on AMG batts.