Overcharging?

[NNethers]

I’ve done a little searching on here but haven’t found the exact answer to my question…maybe you guys can help out.



What is the MAX charging voltage I should see? I suspect that my rig may be overcharging. I measured it at the passenger side battery last weekend and it was over 15 volts but at the driver’s side battery it was high 13’s or low 14’s (can’t remember). Furthermore, I’ve had some events happen in the last few months that now lead me to believe it may be overcharging. Here’s a brief description of the “events”:



1. While coming back from a weekend at Pismo Beach in November I was towing my rockcrawler and camping gear (GVW somewhere around 17k) I started smelling sulfur. Didn’t think much of it but when I got home I found out the passenger side battery (still the stock one) had blown off the access ports and lost all of it’s fluid by puking it up all over the engine compartment. I figured the battery had finally just decided to die as in the weeks leading up to this my truck had been hard to start (it’s no longer my daily driver so it only gets driven on the weekends) or it wouldn’t even turn over. So, I replaced both batteries with new red top optima’s and it has been fine since. During the whole “battery death” incident I got no warning lights, and the volt gauge didn’t move out of it’s normal range.



2. Two weekends ago I was driving the rig to the auto parts store when the “check gauges” dummy light came on. The volt gauge was buried all the way to the left (reading 0). The truck ran fine and I noticed no issues. I went inside the store, came back out and it started right up and I drove it home no problems (no “check gauges” light and the volt gauge reading normal). When I got home I took the voltage readings posted above (measured at idle at the battery posts) and I noticed what possibly could’ve been battery fluids/electrolytes on top of the passenger side battery. Not 100% sure if that’s what it was because it had been raining that weekend. This past weekend I took it out for a spin and it ran fine (no dummy lights and gauge was fine). However I did notice some fluid on top of the passenger battery and this time after the rig was shut off I could hear fluids moving around inside the passenger side battery.



So my questions are:



1. What is the max charging voltage I should see?

2. Is the charging voltage controlled by the alternator? If so, maybe my alternator is going bad?

3. Think it’s possible I could simply have a bad Optima battery?

4. Is this even a problem?



I haven’t thrown my OBD scanner on it, I’ll do that in the next few days to see if any codes come up.



Thanks in advance for any help.

 

[NNethers]

Sorry it wasn't clear in my first post. I replaced both batteries with Optima's so I haven't mixed the two types and I also didn't replace them till AFTER my trip to Pismo.



Is the PCM the same as the ECM which is mounted on the side of the engine?

 

[Allnew2Me]

You should never mix battery types, a flooded lead acid and an AGM, as they have different charging needs and very different charge acceptence rates. Your voltage regulator is part of the PCM and is not repairable, short of changing the PCM. It is possible that you drained your batteries while at Pismo and the regulator "saw" the low resistance of the Optima (AGM) and increased the charge rate resulting in an over-charge of the flooded lead acid stock battery. My charging voltage is usually around 14. 2-14. 4 while driving. AGM batteries are dry in the sense that they have no free acid in them, all the acid is in the absorbed glass mats. They are advertised as safe even if the case is broken open so I doubt that you would have any acid on the battery tops.

What is your voltage at the battery at idle? You should check it with a good VOM not the truck gauge.

 

[Allnew2Me]

Okay I misunderstood your post sorry about that. The ECM controls fueling and the PCM controls transmission functions and some electrical such as charging. It sounds like you were overcharging the batteries but you should check the voltage at idle if you can. Also, there is a battery temperature sensor that varies charge rate that could be reading wrong. Over 15 volts is too high and you need to find out why it is so high. From what I have read about our charging systems the regulators rarely go out but anything is possible.

 

[NNethers]

I tested the voltage with a hand held multimeter at the battery posts while at idle. I'll test them again later this week and post up the EXACT results. I'll also test it at the alternator itself.



Where is the battery temperature sensor located? Is there a way I can test that?



I didn't think it was possible to leak fluids from AGM batteries as well that's why I wasn't too sure it was battery fluid. I've run a yellow top OPtima in my rockcrawler for the last 7 years (mounted on it's side) and I've had ZERO problems with it... even after complete discharges several times. So I'd be surprised if I got a bad battery.



What's even weirder is that I'm only getting the hi voltage reading at the passenger side battery and not at the driver's side. Is there a battery isolator in this system (typically in dual battery set ups there is)? Possibly that could've gone south?

 

[Allnew2Me]

The battery temp sensor is under one of the batteries, I don't remember which one. It is a black disc that is spring-loaded in the bottom of the battery tray to contact the bottom of the battery. The PCM sends a 5 volt signal to it and as the temp increases resistance decreases and varies the charge rate. I don't know how to test it, my manual does not say what the proper resistance is. If your truck is stock (electrically) you don't have an isolator, our batteries are just wired in parallel and voltage should be the same at both positive posts. Did you ever have a frozen battery? If your battery goes dead it can freeze in cold weather and then do what yours is doing when a charge is applied to it. Also, as simple as it sounds, clean and tighten all battery post connections, including the grounds to make sure there is no resistance to charge on either battery. You might also check the grounds on the engine block to make sure they are tight.

 

[NNethers]

Yes, my charging wiring/system is 100% stock... so I guess there's not isolator.



I'm going to remove the passenger side battery and clean and redo all connections to it as when the old battery died it spewed it's contents EVERYWHERE in the engine compartment and for all I know it might've corroded some connections, the batt temp sensor or a wire and that's what's throwing off the charging. My guess is if it was a bad voltage regulator it would have high voltage at both batteries and not just one. So it's probably a bad connection or corrosion somewhere.

 

[ENafziger]

I'm using a digital voltmeter in the cab. At an idle, I'm around 14. 5 - 14. 9 volts. Driving down the road, it's always 15. 1 - 15. 4. It's been like this for 3 years and 63k miles, and no issues yet.

--Eric

 

[Duc]

the ecm engine control mod is on the drivers side of the motor

 

[sweeda]

passenger side is where the sensor is. with the red top optima batteries when I installed mine I needed to add a layer of mud flap between the battery and the tray to keep it from siding around. If the sensor is not in contact with the battery it will not know that the battery is getting hot or even warm. just a thought.

 

[Hercules130]

Drove home to NH from Baltimore today. Truck started acting funny and i smelled sulphur. Thought it was my dog but when i pulled in my Mothers driveway the passenger side battery was hissing and spewing gas and leaking acid real bad. I doused it in baking soda and then rinsed it with the hose. These Die Hard Platinums were just replaced under warranty a few months ago (for not holding a charge) and now this. I was under the impression they were made by Oddessey. I'm damn lucky i didnt stall on the GW bridge. Now if i could only figure out if i have a battery problem or a truck problem.

 

[p-Bar]

Mine is 14. 4 reading off my Escort radar detector which I trust and scangaugeII which reads . 1 volt higher

 

[TCDiesel]

Sensor in under driver side battery... system charges Passenger side 1st... System has Max valve 14. 5-9 ... is control by drivers side battery Temp... VERY POOR SETUP and is known to blow up the Passenger side Battery when poorly connected to driver side battery.

 

[cerberusiam]

Now if i could only figure out if i have a battery problem or a truck problem.

Usually its a cable problem. If the ends were not scraped and cleaned good enough when installed, corrosion starting on the inside of the cable end, etc, can cause the pssenger battery to blow up becuase it overcharges and the voltage at the driver side battery does not read correctly.



If there is any question about continuity on the cables, replace them with new.

 

[bladehauler]

I have tested my cables by unhooking 1 battery and trying to start the truck off of the other, found I had a bad ground cable this way.