Duracell AGM not holding solid charge

[ebg18t]

Been using Duracell AGM 34 batteries (East-Penn) for my starting and 2nd batteries for 2years. When off, the starting battery has 12.7v, 2nd battery has 11.51v. The batteries are connected via a BlueSea Isolator. When running The 2nd battery starts charging after 30 sec since the primary is at full charge (13.7v). 2nd battery still reads 11.51v when charging.

I noticed this weekend that when the truck wasn't running my Engel fridge turned off after about 45min. This is the first time I have had issue. Been several months since I used it.

For some reason the battery isn't holding a charge, it did get drained last summer and read 10.4v. Charged it on the charger and hoped for the best, could I have ruined the battery last summer?

Thoughts; suggestions?

 

[4x4junkie]

The 2nd battery remaining at 11.51V would indicate that it is not being charged at all (any current going into it should raise it's voltage, even if it's by only 0.01V).
10.4 volts may not be good for a battery, however one instance of that occurring (and it being recharged right away) shouldn't ruin it.

Have you checked at the output of your isolator to see if you have full alternator voltage there? Are all your fuses intact? Ground cable connected well?

 

[wrcsixeight]

How thick is wiring through the Blue seas ACR and to Aux battery? I don't care what some say about thin wire ampacity being adequate, when this wire is too thin, the depleted Aux battery is not adequately 'seen' by charging source and voltage regulator, and not charged at a good rate, and 10 awg is too thin. even though it is rated for 30+ amps and you never expect to see any more than that, it is too thin to properly feed the depleted battery what it wants, especially an AGM battery which are Notoriously thirsty.

Far too many people act like an alternator is the almighty instant battery charger. Charging a battery requires sufficient current and time. A battery reading 11.4v is simply discharged, and might have a shorted cell if it falls to the 10.5v range after a charging source is removed.

Perhaps your battery is no longer capable of holding a charge, or perhaps the owner is unaware how undercharged it has lived its abbreviated life. Try putting it on an automatic charger in the 15 amp range overnight. If the automatic charger refuses to start, hook battery to known good battery with jumper cables and restart charger. Unhook jumper cables once the charger is going ,so all charging current is fed into depleted battery. Once Charger indicates full charge and stops, put a load on the battery to drop voltage just below 12.8v or 12.6, then restart automatic charger again, at a lower amp setting if available.

You might be able to get it to store some electricity, or its capacity could be so reduced as to be worthless for your needs, other than as a core charge on a new battery.

Any new battery will likely meet the same fate until you figure out how to best get the battery fully charged and keep it at that stage whenever not in use.

Leaving a battery in a partial state of charge is simply abusive. Aim at foot, and shoot, and repeat.

 

[ebg18t]

Answers:
All wires related to the the battery & Bluesea ACR is 2gauge. Ground appears clean and solid.

The 2nd battery was not used/load applied for several months. It remained in the truck connected to the ACR so I assumed it was getting topped off everyday during my 2, 1hr drives daily.

I did not check the batteries voltage before I took the trip last weekend. On Thursday night the fridge was plugged into AC power to get it down to temperature, Friday morning the fridge was loaded and when we left I swapped over to the battery source for the trip. Drove for a few hours, fridge maintained its 36deg temp. Parked for a few hours and when I went to grab meat from the fridge (~4hrs later) it was 48deg which means it wasn't running for quite a while. Luckily our location had AC plugin so I ran an extension cord and plugged the fridge in and the temp dropped.

I put the battery on my regular charger overnight and battery is sitting at 12.50v as of this morning. I will put it on the charger again tonight to finish charging it and then add a load to see what happens to the voltage.

I will get the alternator checked. Could the BlueSea ACR not be allowing enough juice through to allow complete charging if the 2nd battery? It's a simple system, just confused what I could be overlooking.

 

[wrcsixeight]

Sounds like the battery gave up the ghost, but I would confirm that juice is making it through the ACR. Congrats on using 2awg cable through it. if you are taking power from the starter batter for the ACR, consider that the weak point then becomes the original starter battery charging circuit. You can add another fused cable from alt(+) to starter battery or to the starter battery side of ACR to further increase the amps a depleted aux battery will receive from the alternator.

When compressor fridges begins to fail, their amperage draw can increase exponentially. If you've got access to a DC clamp on meter you can check currents easily without opening the circuit.

You should always use a plug in charger after an outing. With AGM batteries, since you cannot check specific gravity, determining full charge is more difficult. Lifeline AGM says when a 100 AH battery can no longer accept more than 0.5 amps at 14.4v, it is fully charged. A similar amp figure can be used for other AGM's at their specific recommended absorption voltage. When you confirm that the charging source has held ABSvoltage for long enough for current to drop below this .5 amp level, then you can check resting voltage 24 hours later, or bring the battery in somewhere for a load test, or just plug in your fridge and see how quick the voltage drops.

Far too many plug in chargers are scared to actually fully charge a battery. The full charge indicator lies, to give you and the lawyers the warm and fuzzies, as it is safer to undercharge a battery than overcharge it, and every battery is different, and different as it ages, so a one size fits all charging algorithm simply cannot fully charge any given battery, unless perhaps it is plugged in for a few days.

 

[ebg18t]

Driving today brought the battery voltage from 12.50v to 12.79v.

I just plugged the fridge in to the dc (put it in freezer mode for max draw) and I will monitor the voltage for the next few hours and see how it drops.

You mention adding a 2nd cable from alternator to starter (battery 1) battery, or from the alternator to the (+) side of the ACR. Will this really help? Is it bad that I linked the (+) side of the ACR to the starter battery (battery 1)?

 

[ebg18t]

Ran the fridge and it kept at 28deg for 22hrs, ambient temp 91deg. At this point the battery was at 11.79v. (Started at 12.78v). Does this sound about right? I just put it back on the charger to recharge the battery.

 

[4x4junkie]

Driving today brought the battery voltage from 12.50v to 12.79v.

I just plugged the fridge in to the dc (put it in freezer mode for max draw) and I will monitor the voltage for the next few hours and see how it drops.

You mention adding a 2nd cable from alternator to starter (battery 1) battery, or from the alternator to the (+) side of the ACR. Will this really help? Is it bad that I linked the (+) side of the ACR to the starter battery (battery 1)?

Was that 12.79V with the engine running or off?

If the engine is running, you should see 14 volts (or a little higher) at your aux battery. If there is more than 0.3-0.5V difference between it and the starting battery means you have an issue somewhere in your cabling and/or connections.

I don't see an answer to whether you checked at your isolator (ACR) if charging voltage (14V) was present... If you have 14V at both it's input and output connections, and your aux battery is sitting at 12.5V, then your problem lies in the cables between the isolator and the aux battery. If the isolator output shows the same voltage as the aux battery (12.5V or so), then most likely it's not engaging the relay to allow charging current to reach your aux battery.

Adding the 2nd cable from the alt I suspect was a suggestion to reduce the overall resistance of the wiring (OEMs often use #6 or even thinner wire from the alt to the OE battery). Bypassing (or better, replacing) it with a #4 or #2 wire could improve somewhat the speed at which it can charge the battery. However the low voltage you found on your aux battery (11.51) tells me your issue is elsewhere.

 

[dwh]

You say driving the truck brought the aux battery to 12.79v. Was that surface charge voltage or resting voltage?

Resting voltage is what the battery will be at when fully charged and has no activity (power in or out) for a while (like a couple hours).

Surface charge is what it will be at after the voltage regulator/alternator (or your other charger in the garage) holds it at 14+ volts for a while. Then you have to wait for that to dissipate to see what the real voltage of the battery is.

12.8v is the proper resting voltage for a fully charged 12v battery.


As a chronic battery abuser, I can tell you that even a heavily sulfated battery can and will charge up to a full 12.8v resting voltage. But due to sulfation, it won't have nearly the same amp*hours of capacity. A 100 amp*hour battery with 25% of the lead plates' surface area covered by sulfation will charge and behave normally (if it's not internally shorted, or low on water), but will only actually be a 75ah battery.

If it's REALLY badly sulfated, it won't hold a full resting voltage of 12.8v for very long.

So say you fully charge the battery and let it rest a couple hours and measure it and you see 12.8v (or close anyway). Then don't touch it and measure again the next day. If it's dropped at all it's on its last legs. If it's dropped a lot in 24 hours, like down to 12.5v or less then it's time to start pricing out a new battery.

 

[ebg18t]

The 12.79v was with the vehicle off. Not really rested, was about 1.5hrs after I returned home.

The led on the isolator unit does light to show it is connected & charging. I positioned the isolator lower than the battery, so the connections are fairly difficult to get to to check the input and output voltage. I suppose I could check the output wire from the primary battery to the ACR and the the input wire to the secondary battery to establish that voltage, right?

I am charging the battery tonight and I will let it sit for a few hours tomorrow to check the resting voltage and also see if it drops overnight.

Guys-- Thanks for the help!

 

[dwh]

After you do a full charge in the garage, then with the engine running, after your 1 hour commute, leave the engine running and use the multimeter to check both batteries. They should be the same. If they are, then the ACR is working. At idle, you might not see a full 14+ volts though. My truck holds 13.5v at idle and 14.5v at higher RPM.

 

[ebg18t]

I took it off the charger this morning and just checked it this afternoon. It Looks like resting voltage is 12.79v. I will check it in the morning to see if there is any drain or voltage drop.

After you do a full charge in the garage, then with the engine running, after your 1 hour commute, leave the engine running and use the multimeter to check both batteries. They should be the same. If they are, then the ACR is working. At idle, you might not see a full 14+ volts though. My truck holds 13.5v at idle and 14.5v at higher RPM.

I'll check that tomorrow. I am going to call BlueSea to see if there is anything in the ACR that might prohibit full charging voltage from going thru the ACR. I checked the input line to the second battery (from ACR) and it seemed to have more voltage than the battery (12.9-13.0v) but less than the line going from the primary battery to ACR which had 13.8v.

Thanks

 

[dwh]

I'll check that tomorrow. I am going to call BlueSea to see if there is anything in the ACR that might prohibit full charging voltage from going thru the ACR. I checked the input line to the second battery (from ACR) and it seemed to have more voltage than the battery (12.9-13.0v) but less than the line going from the primary battery to ACR which had 13.8v.

Thanks

Well, testing with a multimeter can sometimes be a bit deceptive. Basically, when you test with a meter, you are creating and testing a "short" circuit. Not a "dead short", but a circuit that is not the same exact length as whatever it is you are trying to troubleshoot.

So the voltage measured on a "long" circuit - say from the alternator through a wire to the chassis battery, and then through another wire to the ACR terminal, and then through your meter, and then to whatever ground you are using, and then back to the alternator - can (and often will) read a different number than the voltage reading from a "short" circuit, such as battery + through the meter and back to battery -.

But conversely, even if the one circuit is "longer" it can also have a lower resistance - which will allow the meter to read a higher voltage. Since the battery is one big resistor, you can see a lower voltage measuring across its terminals than you might see measuring the voltage at some other point on the "charging loop".


That's why I suggested A) making sure that both batteries really are charged, B) giving the vehicle charging system enough run-time to make sure that both batteries have had time to be topped off to whatever the voltage regulator is holding the "12v bus" at, and then C) measuring both batteries. They should be equal and both equal to the voltage that the voltage regulator is holding the bus at.

If they are, the ACR is working.

Even if one battery is a bit worn out, it should still come up to a surface charge equal to the bus voltage. It just won't stay there long after you remove the supply voltage that holds it there.


Now, the ACR is just a solenoid - a switch with the contacts pulled into position by an electromagnet. An electrician would call it a contactor or a relay. The contacts inside that connect the two large terminals can get damaged or worn out - like the points in an engine ignition system.

The same sort of gizmo used in electrical work:

Is usually designed to be rebuilt. The rebuild kit usually includes new contacts, and sometimes new springs and screws and whatnot:

You can't (or probably can't anyway) rebuild your ACR solenoid.


BUT - even if the contacts are worn or burnt - it ANY power is getting through it, given enough time, the second battery should eventually reach parity with the bus voltage. It'll just take longer to get there.

 

[4x4junkie]

I'll check that tomorrow. I am going to call BlueSea to see if there is anything in the ACR that might prohibit full charging voltage from going thru the ACR. I checked the input line to the second battery (from ACR) and it seemed to have more voltage than the battery (12.9-13.0v) but less than the line going from the primary battery to ACR which had 13.8v.

Thanks

Yeah it definitely sounds as if you've got too much resistance in your wiring or connections somewhere.
Can you check if the voltage is the same both going in and coming out of the ACR? (measure it right at it's terminals) If it's the same coming out as going in, then we should be able to rule out the ACR as the culprit.
Also, feel if any of the connections themselves are getting warm or hot. Heat will indicate right away the connection has a high resistance (is dirty or loose).

 

[ebg18t]

Spoke with BlueSea today, they indicated it didn't seem unusual that there was a 0.5v difference between the input and output voltage on the ACR. I asked why? And he didn't have a good answer. He said he would check on it and call me later this week. Any thoughts?