Overcharging...Battery fire

[pwerwagn]

Ive read through a lot of posts on here and am not sure I found my answer yet.



~3 weekends ago I was prerunning in my 04 for the Cinco De Baja. I got about 5 miles into the track and started to smell something not right. I was a ways ahead of everyone else with us, so I pulled over. My passenger side battery had broke the hold down. The bolt that passes through the battery cable terminal was melted off. This bolt has the alternator fusible link attached to it, as well as the power to the 2 relays next to the passenger batt.



I took the battery out and finished the lap with the alternator disconnected (we had to race the race truck about an hour later... I didnt have time to mess with the dodge). About half way into the loop (40 mile loop) my volt gauge dropped to nothing (I had the race radio on so it was draining the battery).



When I got back I didnt get any time to look at it at all. The next day, I went to start it and it actually started (barely). I tried to hook the alt wire back up and it sparked like crazy, so I figured it shorted something out. So I drove it back home with the 5th wheel with no alt. I charged the battery off the 5th wheel generator for a while so i had trailer brakes. The alt fusible link was still fine.



Anyhow... when I got home i hooked everything back up, started it, and I see ~15V at the passenger batt (which I replaced after the race with a known good one). I disconnected the alt to check, and it full fields at ~50V not hooked to any load. Is that normal-ish? My passenger batt was staying around 15-15. 3 volts every time i checked it (with a fluke, not the dash gauge). So I figured all was well since that seems to be what a lot of people report.



Fast forward to this past friday. I had to use the truck to go rescue my sister/brother in law. He rolled his 05 cummins/5th/jeep on the way to the mtns (everyone is fine), and I had to use my truck to haul his jeep home. I had to sit in traffic for a while because they had the freeway shut down because of the accident. I started to smell another "not right" smell... popped the hood... battery on fire!! I keep fire ext's everywhere so I had it out in 1/2 second.



I do have an optima on the drivers side and a lead-acid on the passenger side. But Ive had a lead acid on the pax side for like 2 years now. The optima is getting bad however... maybe thats part of my problem? Perhaps the alt is trying to charge the optima too hard, and getting the passenger side too hot? Maybe me running the optima dead at the race/trip home did it in?



I would like to say if I replace both battery's I should be ok. But I also dont want to buy 200$ worth of batt's only to burn one up again.



Any suggestions on something to check? Has anyone ever checked alt voltage with no load? The fusible link from the alt didnt seem to "fuse". The very end is melted off now from the fire, but I dont think its melted from excessive amperage.

 

[cerberusiam]

Replace BOTH batteries with new or weird things can happen. The alternator charges the batteries thru the passenger side battery and reads voltage from the driver side one, IIRC. The low reading on the driver side will overcharge the passenger side and you see the results.



The other to do for safety sake is replace the cross over cable between batteries. As hot as you got the one with a fire you could have a bad connection internally on the cable. That will result in the same charge imblanace.



The other possibility is the fire and shorting out the battery has damaged the circuit in charge of reading battery system voltage. Not positive if that circuit is actually in the ECM or the FCM and how it really works. Damage on either of those 2 will result in bizarre behaviour.



Dead shorts, battery fires, welding, etc, are almost a death sentence for the electrical system at times. There is no telling what got screwed up with all the integrated circuits controlling things.

 

[pwerwagn]

Oddly, Ive never had a matched pair of batt's in this truck. The optima on the drivers side has always been weak, but fine for summer. The winter its a little iffy, so I pull the batt out of my boat (dont need it in the winter), and put that in the truck. Ive been doing that for ~4 years now.



BUT... I think the optima on the drivers side is totally trashed now. Even if I charge it, it wont start the truck. I think for starters, Im going to put a new batt on the drivers side and nothing on the passengers side (but a new crossover cable between the two). I think you are right... I think the alt was trying so hard to charge the optima it overcharged the lead/acid.



Does that alternator full fielding at ~50V seem right? It never does it with any load on it, and I never saw more than like 15. 4 volts at the passenger battery (which Eric N said his truck regularly sees).



Thanks for the help.

 

[cerberusiam]

Not sure what the full filed specs are on that alternator. Your battery voltage sounds right though.



The Optimas have been an issue. They are not as good as once thought. The fact it is getting weak is probably the source of the problem.



These trucks have a huge load on the batteries and they need a good clean signal to get all the electronics to operate correctly. Mis-matchig batteries has always been crap shoot. Every problem traced back to the batteries I have solved has been in a mismatch or a bad battery. Not saying other issues won't contribute, but, rule of thumb is replace both at the same with good units, don't share and mismatch, don't jump start another vehicle with engine running, and if in doubt replace the cross over cable.



Maybe not the only answer but it works for me.

 

[pwerwagn]

Thanks Cerb. I hope its the only answer... as it seems logical!! And decently cheap!! haha.



My brother in law totaled his 05 friday (only 9K miles on new motor!), so I was going to go jack all of the electronics in case mine are fried. But I will try this first.



Thanks again!

 

[K5IP]

pwerwagn.

When you measure the open circuit voltage output of your charging system, your Fluke meter is sensing the high transient spikes that occur when the diodes (there are six of them) in your alternator begin to conduct. This is a normal condition and it is usually filtered by the battery itself. Keep in mind that other electronic devices in your truck do not like this and that is why at least one battery should always be connected.

That said, voltages of 15. 4 VDC seem kinda high, especially on a warm day, and may be the reason for the fire.

I agree that batteries need to be changed in pairs. I just did this on my truck with a pair from Costco for $85 each. They are made by Johnson controls, same folks that make Di-Hard, Interstate, and other high quality batteries. I got 10 years on my last set. (but not at charging levels above 15V).

Rog

 

[pwerwagn]

Thanks Rog. That makes sense. Fortunately I never had both batts removed with the alt hooked up. I was checking the alt from it's output, so my electronics never saw those spikes.

I'm going to recheck the 15. 4 number. That reading came when the drivers side optima was totally dead, and the passenger side wasn't at full charge. I will double check with the new battery today.

Thanks!

 

[K5IP]

I just checked my system:

Batteries are new and fully charged and the battery charge voltage is 14. 3Vdc (also a Fluke meter)

With the ambient temperature at 60 deg F.

There is a sensor in the battery tray (BTS) on the drivers side battery which provides temperature information to the ECM to establish the charging voltage for different temperature conditions. This sensor (a thermistor) might be worth checking if you get good batteries and the charging voltage is still above 15VDC.

Rog

 

[Road Dog]

There's three things in play: the batteries, the alternator & the voltage regulator. The first two can be bench tested at most auto/battery supply stores. Measuring the voltage doesn't tell you much. The voltage regulator is built into the ECM so if it's not working then you need a new ECM or you have to wire in an external voltage regulator. I'm sure there's a thread around here showing how it's done.

15. 4V is a little high and batteries in parallel should be identical. With batteries in parallel the weaker battery sees a higher load which weakens it even more. It's a little counterintuitive but that how the physical world works.

 

[pwerwagn]

I also wondered about the thermistor. I need to check it and make sure it still looks intact. I dont have inner fenders on this truck, so it could have gotten damaged. The truck doesnt have an easy life...



I will put in a new battery tonight and see what happens. I am assuming my charge voltage was high because I had one bad battery (the drivers side). I have noticed over the past year or so my volt gauge in the dash has gone up a bit. When I had new batt's in it, it was usually right at 14V. Its recently been 2-3 needle widths or so past 14V.

 

[K5IP]

Dodge, in it's infinate wisdom, chose to make the volemeter simply a go-no go indicator.

Keep using your fluke.

You seem to lead a vedry interesting life.

keep us informed.

 

[pwerwagn]

Dodge, in it's infinate wisdom, chose to make the volemeter simply a go-no go indicator.

Keep using your fluke.

You seem to lead a vedry interesting life.

keep us informed.

Go No-Go meaning it only reads voltage or not? My dash gauge always reads *close* to my fluke... hard to tell exactly. It does however seem to just drop to 0 (or 8 as the gauge says) as soon as batt voltage gets to ~10. 5V or so.



Haha... I dont know about interesting life. But its always fun filled! And I like it that way.

 

[cerberusiam]

The gauge is set based on what the ECU tells it. In a normal range of 10-14 volts it seems representative, outside that range it just goes to pegs when something is really wrong.

 

[Got HO?]

My truck has always shown higher voltage in cold weather as opposed to summer time. Is this normal? I've never had any charging issues but have replaced the batteries twice in 250k miles.

 

[K5IP]

pwerwagn and Cerb,

You are both right and I am wrong. My apologies to Dodge. Don't know what I was think about, maybe the oil gauge?

Rog

 

[pwerwagn]

pwerwagn and Cerb,

You are both right and I am wrong. My apologies to Dodge. Don't know what I was think about, maybe the oil gauge?

Rog

Its still a pos!! Haha. But yeah, the oil pressure gauge on my 98 was that way. it either had pressure or it didnt. The water temp was a pos too, it worked up to like 220, then it pegged.

 

[cerberusiam]

Don't know what I was think about, maybe the oil gauge?

The oil gauge IS a joke for sure. Dodge really needs to be slapped around for cheaping out in that area.

 

[pwerwagn]

Just to revisit this...



I put a new battery in the drivers side tray. I checked the resistance of the crossover cable, and it was minimal, like 1/10th of an ohm. I checked a few other similar cables I have and got resistance along the same order of magnitude.



So I rewired the end of that cable with a new terminal, and rewired the alternator to that terminal. I didnt put a battery in the passenger side. I am seeing a consistant 14. 3-14. 4 volts now on the drivers battery. I dropped a new battery in the passenger side just to check, and I see the same 14. 3-14. 4. (all with the fluke)



So it looks like my problem was the no-good optima on the drivers side and the good lead acid on the pax side. While trying to charge the bad optima, it overcharged the good lead acid.



Thanks for all the help guys,

Jeff