Battery dying - portable jump starter question

[dougg3]

I have a 2009 Dodge Ram 1500 with the 4.7. The battery has died a few times when I don't drive it for 4 weeks or so during the winter. At one point the TIPM was replaced because a mechanic found a problem inside it that was drawing excessive current, but it still won't last 4 weeks. I had a dead battery again this month because I've been working from home. It's happened enough that I need to replace the battery, it's 3-4 years old anyway. Here's my problem/question...

I have a portable jump starter, one of the small ones with a lithium battery. When the Ram's battery is dead, the jump starter is able to start the engine, but then the engine immediately dies when the jump starter shuts itself off (which it does automatically). If I jump start the truck using another actual vehicle, this doesn't happen. Should I be worried that maybe my alternator is having issues? I know that the alternator at least sort of works...because if I regularly drive the truck, the battery never dies.

I was just wondering...is this normal? I was under the impression that once the engine starts, the alternator should be able to keep it alive, but maybe it's more complicated than that? The portable jump starter works fine on other vehicles I've used it on. Is there more I should be worried about than simply buying a new battery and making sure I run it regularly? I'd hate to ruin a brand new one. Thanks for any advice!

 

[Brandon-w]

Charge your battery fully. Then take the main charge wire off of the alternator (one that goes to battery) then disconnect the plug on the alternator bacisallynany electrical going to it gets dis connected. That way if you have an Alt killing your battery you'll know. If you don't hook it up and keep hunting. If you are using the ultra start booster they sometomes shut themselves off if the battery has a dead short to preserve its self.

 

[Brandon-w]

That said maybe yank the battery and get it tested first.

 

[MarineBSP]

Conventionally you can get a good idea of alternator performance by measuring the voltage at the battery terminals while the engine is at idle and separately measuring the battery an hour or more after charging is removed

Alternator output to the battery should be at about 13.5 - 14 V while running / charging. When you come back to the truck after the battery is at rest a while, the battery should have 12.3 V (nominal, maybe a little more) if it is good. A battery that is 'charged' but sits at 12.0V or less soon after charging is a sign that the battery itself has issues, and modern vehicles get finicky at that level.

I put the "conventionally" in there, because I know few details about my 2018's alternator control other than there is now "Eco" logic in the TIPM (ECU) that controls energizing the alternator coils so that it doesn't load the motor when the system thinks no charging is needed - this is the penny-wise dime-foolish engineering game that makes maintaining newer vehicles so hard, and the fuel savings are not noticeable.

 

[GhostCost]

My guess is like the others. Dead battery or dead alternator. The battery can short between cells inside and cause a slow drain or weak charge. |The alternator is a finicky beast sometimes. It'll charge one minute just fine, the cut off if the regulator is going out.

For a jump starter, I prefer clore brand chargers. They're almost a full battery in a box - in fact, I've used them as a battery replacement for up to 4 months while a needy friend saved money for a battery. You can't hardly kill them.

These are full size boxes though with lots of power. Not one of those little toys that you get and hold in your hand.

https://www.amazon.com/gp/product/B0002SQTYG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Wild one]

I like the little Noco GB70 I have.

https://www.amazon.com/NOCO-GB70-12...j6g&hsa_cr_id=6001433300401&ref_=sb_s_sparkle

 

[dougg3]

Thank you all for your input! I really appreciate everyone's advice. Sounds like I have some testing to do.

That said maybe yank the battery and get it tested first.

Agreed...maybe the alternator too? Do the car part shops do deeper testing than just checking the voltages? Forgive me for my ignorance on this stuff...I'm more of a computer/electronics nerd than a car guy!

I put the "conventionally" in there, because I know few details about my 2018's alternator control other than there is now "Eco" logic in the TIPM (ECU) that controls energizing the alternator coils so that it doesn't load the motor when the system thinks no charging is needed - this is the penny-wise dime-foolish engineering game that makes maintaining newer vehicles so hard, and the fuel savings are not noticeable.

This is exactly the kind of thing I was wondering about...is it possible that the 2009 has any similar "smarts"? I guess I could graph the voltage at the battery terminals with my oscilloscope while trying to jump it to see if the alternator is even kicking in...but I will have to wait for the battery to drain again if I want to do that test.

For a jump starter, I prefer clore brand chargers. They're almost a full battery in a box - in fact, I've used them as a battery replacement for up to 4 months while a needy friend saved money for a battery. You can't hardly kill them.

That's impressive! Mine was a gift, it's called the HALO Bolt. It's tiny, but it does the trick on every other vehicle, but for some reason the Ram never stays running when I try to jump it, which is why I'm nervous about buying a brand new battery until I figure out exactly what's going on.

I like the little Noco GB70 I have.

That looks like a really nice portable starter! I've been really happy with my Noco charger.

 

[WilliamS]

It takes longer for you to get the cables off another car vs a small jump pack. That tiny amount of time is where the alt picks up and takes over. The computer controls the output. I have a set of cables for my lithium pack that doesn't have the protection module on it and that one will keep the truck running