2008 Ram 3500 diesel: batteries going dead

[A_Harman]

I have been having a problem over the last few months that if the truck sits for 2-3 days, the batteries will go dead. It doesn't happen every time that I let it sit for a couple of days, but it's happened a few times, about 2 times a month. And sometimes even if it has just sat overnight, it will crank slowly, like the batteries are low.

I have had the batteries tested, and they are OK. They are less than a year old, being installed in the truck before I bought it last October.

I have had the alternator replaced, thinking that the old one had a short in it, but the batteries still go dead. I tried to start the truck yesterday, and the batteries were so flat, they only registered about 3 volts on a voltmeter. I had started the truck last friday, and it was fine, but after sitting through saturday and sunday, the batteries were dead. So something is drawing a lot of current when the ignition is off, but it doesn't do it all the time. Chasing down an intermittent problem like this can be difficult. I have thought of buying an inductive current probe to check for current on the battery cables every time I shut the truck down, and if I detect current, restart and shut down again to see if the current goes away. Or if I detect current, start pulling fuses until I find the circuit that is drawing.

Has anybody out there had a problem like this, and what was the solution?

 

[OVERKILL]

I diagnosed a similar issue on a VW a few years back, did it via pulling fuses and watching for change in draw, ended up being the circuit for the interior lights, even though they weren't staying on, something on it was pulling a load.

Edit to add: Car was a beater and once I told them where the issue was they opted not to pursue it further, just left the fuse out.

 

[Rob_Roy]

I diagnosed a similar issue on a VW a few years back, did it via pulling fuses and watching for change in draw, ended up being the circuit for the interior lights, even though they weren't staying on, something on it was pulling a load.

Same thing happened to me with a Lincoln Navigator. I hooked up a multimeter in series with the ground cable, and monitored the draw as I pulled fuses. Ended up being the radio.

Had a similar problem with my F350, turned out to be an aftermarket trailer brake controller.

 

[JHZR2]

Do your parking lights stay on dimly by chance? The PCB on the backside of the fuse box underhood can corrode and drain the battery.

 

[A_Harman]

How much current draw do you measure? I hooked up one battery after giving it a complete charge overnight, connected my voltmeter in series to measure current on the ground terminal, and got 40 milliamps. This doesn't seem to be enough to be a worry.

I haven't looked at the parking lights closely when I shut down, but will do.

 

[OVERKILL]

How much current draw do you measure? I hooked up one battery after giving it a complete charge overnight, connected my voltmeter in series to measure current on the ground terminal, and got 40 milliamps. This doesn't seem to be enough to be a worry.

I haven't looked at the parking lights closely when I shut down, but will do.

Yes, that doesn't sound like a concerning level so you may have to do it a few times until you get an abnormal reading. It's also possible that the phantom draw isn't immediate so you may have to give it a bit and keep an eye on it.

 

[02SE]

Deeply discharging a battery will shorten its lifespan. 10.5 volts is considered completely discharged, so going down to 3 volts will really shorten the life of the battery. Definitely determine if there is a parasitic draw which is beyond the norm, but then replace the batteries.

 

[A_Harman]

It's inconvenient on the truck because of the dual batteries. I have to disconnect both to be sure that I'm reading all the current through one meter.

 

[A_Harman]

Deeply discharging a battery will shorten its lifespan. 10.5 volts is considered completely discharged, so going down to 3 volts will really shorten the life of the battery. Definitely determine if there is a parasitic draw which is beyond the norm, but then replace the batteries.

Yes. I really hate that this has happened to batteries that were only about 6 months old. I'm used to batteries lasting at least 5 years.

 

[wrcsixeight]

DC amp clamps do not always do well at reading low currents, but current that can drain two batteries overnight should show up.

It is very hard on the battery to be brought below 10.5 volts, which is considered 100% discharged as there is very little energy stored when battery reads lesser voltage than this, less watt hours than your cell phone has.

A lot of times when there is a mystery parasitic draw, the owner jumps the vehicle, drives it for a short period, stops it and restarts it, and it starts easily enough, but the battery(s) are nowhere near even 50% charged, much less 100%.

when a battery is drained to 3v, it takes a good period of time for small amperages to bring it upto 10.5ish volts, at which point it is able to accept more and more amperage, upto the limits of the charging source.

if one jumpstarts, ad thinks the alternator is going to quickly recharge them anywhere near full, they are uninformed.

If the batteries are still healthy, they will accept so much amperage the alternator will heat up quickly to unsafe levels and usually lower the voltage to reduce the amperage required to maintain it.

Dead batteries should be plugged in on a large enough charger that has no less than 12 hours to complete the task. relying on the alternator , even one with a large rated capacity, is unwise, and can be very hard on the alternator if it is not told to throttle back voltage when it gets too hot.

Newish batteries can survive being discharged to 3v, if they are promptly put on a charger and brought back to a true full state of charge, not just 70% or 90%, but a true 100%, which is not easy to accomplish and takes a long time to achieve, holding the battery at high voltages, and this time of year one must be weary of it getting too hot while held at those higher voltages.

Many/most smart chargers will not try to charge a 3v battery. it will have to be parallelled with a good battery and the charger put on the good battery until the bad battery is brought above 10.5v.

 

[tiger862]

Unplug the glow plug
This was common. Check current before and after being unplugged

 

[Trav]

How much current draw do you measure? I hooked up one battery after giving it a complete charge overnight, connected my voltmeter in series to measure current on the ground terminal, and got 40 milliamps. This doesn't seem to be enough to be a worry.

I haven't looked at the parking lights closely when I shut down, but will do.

Are the conditions the same every time this happens eg raining? I did a Ford one time that had a phantom drain, when it rained the door number keypad would turn on the park lights in the middle of the night. I caught it just by luck.
This is a helpful article..

Diagnosing A Car Battery That Runs Down

Why Your Car Battery Runs Down

www.aa1car.com

For dual batteries this may be of interest to you..

Painless Wiring

Painless Performance 250 Amp Dual Battery Control System, Part Number 40102.

www.painlessperformance.com

 

[mattd]

Unplug the glow plug
This was common. Check current before and after being unplugged

Cummins use grid heaters, not glow plugs.

OP, you need to check parasitic draw with a meter on low amperage setting. You need to connect the meter inline with the battery ground cable and the battery negative post.

 

[IndyIan]

My buddy has a pair of those trucks and one had an interior item draw killing the batteries. I forget exactly what it was, but he put on a battery disconnect to get through the busy season and then found the draw later.

 

[NewtonPulsifer]

I’ve rescued batteries with this

Amazon.com: BatteryMINDer 2012: 12 Volt-2 Amp Battery Charger, Battery Maintainer, and Battery Desulfator - Designed for Cars, Trucks, Motorcycles, ATV, Boats, RV : Automotive

Buy BatteryMINDer 2012: 12 Volt-2 Amp Battery Charger, Battery Maintainer, and Battery Desulfator - Designed for Cars, Trucks, Motorcycles, ATV, Boats, RV: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Last time I had this exact scenario it was an intermittently sticking relay.

 

[tiger862]

Cummins use grid heaters, not glow plugs.

OP, you need to check parasitic draw with a meter on low amperage setting. You need to connect the meter inline with the battery ground cable and the battery negative post.

You are correct
I was thinking about a different system. The grid heater circuit needs to be checked.

 

[A_Harman]

DC amp clamps do not always do well at reading low currents, but current that can drain two batteries overnight should show up.

It is very hard on the battery to be brought below 10.5 volts, which is considered 100% discharged as there is very little energy stored when battery reads lesser voltage than this, less watt hours than your cell phone has.

A lot of times when there is a mystery parasitic draw, the owner jumps the vehicle, drives it for a short period, stops it and restarts it, and it starts easily enough, but the battery(s) are nowhere near even 50% charged, much less 100%.

when a battery is drained to 3v, it takes a good period of time for small amperages to bring it upto 10.5ish volts, at which point it is able to accept more and more amperage, upto the limits of the charging source.

if one jumpstarts, ad thinks the alternator is going to quickly recharge them anywhere near full, they are uninformed.

If the batteries are still healthy, they will accept so much amperage the alternator will heat up quickly to unsafe levels and usually lower the voltage to reduce the amperage required to maintain it.

Dead batteries should be plugged in on a large enough charger that has no less than 12 hours to complete the task. relying on the alternator , even one with a large rated capacity, is unwise, and can be very hard on the alternator if it is not told to throttle back voltage when it gets too hot.

Newish batteries can survive being discharged to 3v, if they are promptly put on a charger and brought back to a true full state of charge, not just 70% or 90%, but a true 100%, which is not easy to accomplish and takes a long time to achieve, holding the battery at high voltages, and this time of year one must be weary of it getting too hot while held at those higher voltages.

Many/most smart chargers will not try to charge a 3v battery. it will have to be parallelled with a good battery and the charger put on the good battery until the bad battery is brought above 10.5v.

Yes, there is a lot to battery maintenance. I completely disconnected both batteries, and connected my charger to the primary one at about 5 pm, and I checked it every 3 hours through the night. It wasn't full until 4 am. Then I put the charger on the other battery. It still wasn't done when I took the charger off at 11 am to attempt a start. But the voltmeter read 13.4 volts, so I thought it was pretty close. The truck started OK.

 

[MattPersman]

Have seen tipm do this. Obviously it’s best to do a draw test and see if you can pinpoint a different item if it’s that before blindly replacing stuff. No one thing is always the problem

 

[meep]

A two day drain would size at about 2 amps. You’ve got about 100amp-hour capacity there, so for a completely flattening discharge in that amount of time it’d need about 2 amps load per hour. That’s not insignificant, but it’s not huge either. thats a dome light, a really blown diode in the alternator, an energized ecu/bc, or other piece of electronics turned on, not in standby. It’s Slightly more than just a glovebox light.

 

[JHZR2]

Cummins use grid heaters, not glow plugs.

OP, you need to check parasitic draw with a meter on low amperage setting. You need to connect the meter inline with the battery ground cable and the battery negative post.

Agree.
Not sure if this model has the fuel heater at the prefilter/lift pump, but if so, they can stick on too. Getting hot also causes air leaks.