Very high charge voltage 16+ at battery, normal 14.4 V on volt guage?

[MichaelOverfield]

So I go to drive the truck today.. dead batteries.. which is weird, they are about 1 year old Oddesy performance AGM batteries, kept on an Odessy approved Minn Kota on board charger, which was plugged in... I read up on restoring discharged AGMs, involving a high charge rate, each at 55amps! That is over 100 for both, only way I get there is alternator. So after charging with an additional charger, I had enough to get it started. All seemed well at first, I was monitoring voltage at the battery, since over 15V is not good for AGM. It was normal at first, but kept going up, up, passing 15 V and got just above 16, STILL going up, but I shut down the truck to avoid further battery damage.. meanwhile the volt guage was reading about 14.4, as was a separate meter connected to the accessory outlet. So I have distribution voltage off significantly for battery charge voltage, BOTH​ batteries were within .1 of each and over 16v, I could feel them getting warm. Something is seriously wrong.. please help if you have ideas. Thank you.

 

[Wayne M.]

Dual battery systems can be tricky to diagnose. Take them both out, or separate them and charge/ test each.
Is this a limited use truck? Do you use the charger as a maintainer?

 

[lpennock]

What was the temperature at the time? These trucks do temperature compensated charging. As Wayne said the only way to properly diagnosis batteries in a parallel system is to pull them. They will charge fine on a standard 15-25 amp charger; however, you might need a parallel attached battery for about 10m to get enough change the charger doesn't think it is a shot battery and refuse to change.

 

[MichaelOverfield]

Dual battery systems can be tricky to diagnose. Take them both out, or separate them and charge/ test each.
Is this a limited use truck? Do you use the charger as a maintainer?

Thanks, will be trying that. Yes, limited use, and yes the Minn Kota is a maintainer that has been on most of the winter.

 

[MichaelOverfield]

What was the temperature at the time? These trucks do temperature compensated charging. As Wayne said the only way to properly diagnosis batteries in a parallel system is to pull them. They will charge fine on a standard 15-25 amp charger; however, you might need a parallel attached battery for about 10m to get enough change the charger doesn't think it is a shot battery and refuse to change.

Temperature was about 45 degrees. When I shut down at 16volts and climbing, I could feel the batteries were beginning to warm up. In any case, I don't think the charging should ever go above 15volts, the Haynes manual says above 15, you have a problem. I'm definitely there. With the normal reading in truck, this could have been the case for some time and has perhaps damaged the AGM batteries to the point they don't want to hold a charge? I still don't know how it's wired to have 16v at the batteries, yet 14.4 v at the guage and accessories.. that would require a separate regulator or some high resistance connection, the latter unlikely to be so stable.. it's very odd.

 

[lpennock]

At 45 degrees, normal charging would be very close to 15.0 volts or very slightly above on good batteries. I do agree that 16v is high but if they are low they will get warm even at 15v.

I'm not sure why the two meters read that much different unless one is bad. Take a real meter to the power outlet and verify the plug in one is actually reading the same as a real meter.

I have a Minn Kota on my boat and every so often it will boil out a battery. I believe the MK is a constant V charger which works fine until the battery starts to fail. Once it starts to fail a constant V charger will keep driving more current to try and keep the V constant and that causes cascade failure of the battery. Bottom line is you need to:
1. pull the batteries
2. charge each separately
3. load test each separately
4. if they both test good you can reinstall otherwise replace both and save the good one as a spare for other things.

When storing the truck it is better to just disconnect the batteries unless you know for sure your charger does a periodic top rather than just a constant float charge.

 

[MichaelOverfield]

At 45 degrees, normal charging would be very close to 15.0 volts or very slightly above on good batteries. I do agree that 16v is high but if they are low they will get warm even at 15v.

I'm not sure why the two meters read that much different unless one is bad. Take a real meter to the power outlet and verify the plug in one is actually reading the same as a real meter.

I have a Minn Kota on my boat and every so often it will boil out a battery. I believe the MK is a constant V charger which works fine until the battery starts to fail. Once it starts to fail a constant V charger will keep driving more current to try and keep the V constant and that causes cascade failure of the battery. Bottom line is you need to:
1. pull the batteries
2. charge each separately
3. load test each separately
4. if they both test good you can reinstall otherwise replace both and save the good one as a spare for other things.

When storing the truck it is better to just disconnect the batteries unless you know for sure your charger does a periodic top rather than just a constant float charge.

This is the charger I have, Odessy approved, and charges AGM. It goes to float when charged. This issue of high voltage is not coming from Minn Kota, it's unplugged. It's the truck driving excessive voltage. The instrument meter, and the extra accessory meter track, I'll check with a third. All that said, I'm sure one or both batteries are bad. The 6 amp charger on all night and the voltage has gone down.. 12.14v seems that can only be a Battery issue unless there is a significant short somewhere.. my Friday night Battery party awaits!
http://www.minnkotamotors.com/Products/MK-106PC/

 

[Wayne M.]

Please be careful at your party! I've seen a battery explode. Make sure you have good ventilation, and always (-) first off and last to go on.
I agree that modern charging systems have an unconventional alogorithm and can do strange things at times to maintain a temp and state of charge.

 

[phantomusa]

Best bet is take your battery to any big box auto store and have them load test it that will determine the condition of that battery

 

[MichaelOverfield]

Thank you all for the replies, I got these less about 14 months ago, AutoZone, and they have a 3 year free replacement warranty. I'll be taking them there this eve to test and claim that warranty if they prove bad.. but I'm concerned that they failed because the truck has been overcharging them. Above 15V is bad, and that will damage an AGM battery (and 16V ANY battery), there is no reason under any conceivable condition the voltage should go to 16V and certainly not above that which is where it was going. Concur on the battery explosion concern, that's precisely what I shut the truck off at 16 and still going. These are AGMs, so only if there is a problem (like 16v) would there be any gassing, and there was a sulfur smell to the reliefs must have lifted. I think it is safe to say these batteries are toast, but WHY they are is what has me seriously concerned. The OEM batteries were preemptively replaced at 7 years, but were trouble free, and I did not even have a maintainer on them during that time, so for the first 7 years the charging system was working without issue.

 

[Bob4x4]

If one battery has failed the truck will charge till they blow.I've seen it too many times.I doubt very much your truck caused a batt failure.The odds are much higher your small batt maintainer does not work so good for a dual batt in parallel system

 

[MichaelOverfield]

If one battery has failed the truck will charge till they blow.I've seen it too many times.I doubt very much your truck caused a batt failure.The odds are much higher your small batt maintainer does not work so good for a dual batt in parallel system

Thanks, but that still makes it hard to understand how even one battery would fail, only a year old. I had no maintainer on the OEM batteries, and they were still OK after 7 years service. I can see one battery dragging down voltage, and the system continuing to charge at a higher voltage than the other battery needs, and that doing as you have seen, but even then, it should really never go above 15V, and definitely not above 16V. The Haynes manual for what its worth, says if you have above 15V, you have a charging system problem. I'm concerned I put in new batteries, and it kills them with this excessive voltage. Can't be good for the other electronics either.

Odyssey battery has a list of approved chargers, they are not the cheap ones, and I got the Minn-Kota 106PC from that list. It's set up specifically for AGM, and it's the lowest amperage, because it's purpose is to maintian a charge... 6 amps should be plenty for that, other batteries do fine with only 1.5Amps. I have a tractor with 2 batteries parallel and a 1.5A maintainer, and it's got one battery that is 12 years old and still working well..

 

[phantomusa]

As others have stated if they are hooked up in parallel if one battery is bad it can cause over charging and it will kill the other battery too the bad battery needs to drag the good battery down to equalizer voltage in both batteries
Take both battery's out and get them load checked
After you have installed two equally charged battery's then recheck your charging voltage if it's still too high then the voltage regulatory is bad or the alternator has gone bad
If you use a float charger use one on each battery to maintain that battery preferrably have them disconnected from each other

 

[seafish]

No one here has yet mentioned that a fairly common problem leading to overcharging in these dual battery trucks is that the CROSSOVER cable (i.e. the large wire that connects to BOTH batteries POSITIVE post) corrodes and/or degrades beneath the insulation near the battery posts and causes increased resistance and decreased charging to the battery that is NOT hooked up directly to the charger. In the case of these trucks, the alternator is hooked up to the passenger side, but the ECM reads voltage on the drivers side battery, so if the crossover cable is not properly distributing voltage from the alternator to the drivers side battery, then the passengers side battery WILL overcharge as the ECM continues to try to charge to the low reading of the drivers side battery.

In short (no pun intended) check the voltage condition of each battery when it is unhooked from the truck and I also recommend checking resistance of the XO cable or simply inspect for corrosion by slicing the insulation of the XO cable lengthwise for about 4" from each battery post and and then peeling it open so that you can inspect the actual wire(s) underneath. If there is green and/or white corrosion visible, then you have likely found the source of your overcharging problem and simply replacing the cable will likely fix your problem (if your battery has not yet been damaged by the overcharging) If there is no corrosion present on the cable, then you can simply close the insulation around the wire and tape it shut with several layers of electrical tape. Remember I am not saying to entirely remove the insulation from he cable, but simply to slice it parallel with the wire so that you can spread it open to inspect the wire...resealing the insulation around the wire with electrical tape is then relatively easy and effective.

Just my .02

 

[lpennock]

FYI. Haynes is wrong about max voyage with temperature compensated charging. . 15.2v@32f is normal.

 

[MichaelOverfield]

No one here has yet mentioned that a fairly common problem leading to overcharging in these dual battery trucks is that the CROSSOVER cable (i.e. the large wire that connects to BOTH batteries POSITIVE post) corrodes and/or degrades beneath the insulation near the battery posts and causes increased resistance and decreased charging to the battery that is NOT hooked up directly to the charger. In the case of these trucks, the alternator is hooked up to the passenger side, but the ECM reads voltage on the drivers side battery, so if the crossover cable is not properly distributing voltage from the alternator to the drivers side battery, then the passengers side battery WILL overcharge as the ECM continues to try to charge to the low reading of the drivers side battery.



Just my .02

Good suggestion, I was concerned about same, which is why I measured voltage on both batteries, on the posts themselves.. and they both were 16V, that said, I'll check this also when I pull the batteries out tonight. Seems the crossover cable problem would see higher voltage on the pass side, than the driver's side, and I was not seeing that.

 

[MichaelOverfield]

FYI. Haynes is wrong about max voyage with temperature compensated charging. . 15.2v@32f is normal.

Thanks, good point. Makes me wonder if the system is really suitable for AGM, which documentation says, stay below 15V. In any case, can't find over 16V good no matter how I try.

 

[Wayne M.]

Good point on the cross over cable. I never knew them to give trouble. The only real way to check it is to do a second load test through it. If it passes- say- 75 amps, I'd say it's good. You need to check its potential.

 

[MichaelOverfield]

Ok, batteries out. One definitely dead, confirmed by AutoZone. Charging and testing the other, but I'm going to insist on 2 new ones. Bad Battery was on sense side, driver side. It was warm when taken out with only a 6 amp charger. Now I'm putting in on of the old, but charged batteries, plus another with is serviceable as Temp batteries to verify that the vehicle charging system is working correctly.

 

[Wayne M.]

I would hold off for the new batts unless you need the truck. IMHO.