Problem with battery voltage for T@B slowly dropping

ChrisandAlexis · December 2017

Hi,
Our T@B is having a problem with the voltage on the less than 1 year old, group 24 battery slowly dropping. When I first noticed this problem I took the battery out and fully charged it and it measured 12.6 volts out of the T@B with no load with a voltmeter. I installed the battery back into the T@B and after turning on the cut off switch I can see that the voltage slowly drops using a voltmeter. We've had our T@B since April so the battery is not that old. I also took the battery into an auto parts store and had them use their equipment to check it out. I am assuming that the equipment the auto parts store used puts a load on the battery and the battery tested good.

Our last trip with the trailer was in mid-October and we had full hook ups. I noticed the problem recently because I installed an antenna booster for our inside television and was checking the battery voltage as a habit. That was when the meter inside the T@B measured 11.9 volts and I became concerned. I have since disconnected the antenna booster and also unplugged the televisions. Any ideas on what the next troubleshooting step I should take? The trailer is in a storage yard so I do not have access to electricity but might be my next step to hook up to shore power. I'm not sure what that would eliminate as possible causes if it works or doesn't work.

FishDoctor · December 2017

Are you saying that the voltage drops when the cutoff switch is turned to ON? If so, it is normal that there are various small loads draining the battery anytime the switch is turned on (electricity going to trailer). If the green light on the converter box is on and you are not plugged into shore power, there is a load on the battery. The only way to prevent that is to turn the battery cutoff switch to the OFF position (no green light on at the converter). If the battery switch is turned to off and the battery is draining over a short period (e.g., a matter of hours or days), either the battery is faulty or there is an electrical short somewhere. Or am I misunderstanding what you are saying?

ChrisandAlexis · December 2017

@FishDoctor. Thank you for replying. Yes, I understand about the small drain on the battery once the cutoff switch is turned on as we have had about 6 dry camping trips and constantly monitor the SeaLevel meter inside the T@B.

I have not looked at the converter to see if the green light is on. I first thought the easiest thing to do was to check out the battery and I took it to the auto parts store. Not knowing what that little black box actually does that the person at the auto parts store used to test the battery, I am assuming that it does put a load on the battery during the test.

When I had the voltmeter on the battery while it was in the T@B and I had the cutoff switch to on, the voltage was definitely dropping and I would have been well below 12 and maybe 11 volts within an hour. The SeaLevel meter has been reading at 12 volts and below which it has never done prior to this problem.

FishDoctor · December 2017

That is a pretty quick drop in voltage and suggests to me that there is 1) something with a pretty significant electrical draw turned on, 2) a faulty battery, or 3) a short somewhere. Are you sure the refrigerator and the Alde heater are completely turned off? No fan or lights turned on? (I know you have probably already thought of all these things!). If the cutoff switch is set to OFF and the green light on the converter is on, then the switch might have a short. It can be a real pain to track down electrical faults!

ScottG · December 2017

@ChrisandAlex, when the battery is completely disconnected does it hold its charge over time?

I've had failing batteries that will do exactly what you described just sitting on a bench. The test you had at the auto parts store should have determined this if they did an actual load test as you correctly described.

In addition to those things FishDoctor described, you might also check to make sure the breakaway brake pin is fully seated. If you electric brakes were inadvertently activated I'm expect that would drain your battery in a hurry!

Sharon_is_SAM · January 2018

Something else to consider, batteries last longer if you make sure they are fully charged before storing. Also, I assume you have checked the water level. Is the voltage dropping when the battery is isolated or is it maintaining a charge after a full recharge?

ChrisandAlexis · January 2018

A little background info that I have not mentioned. I pull the group 24 battery out after every trip and store it in the garage where I regularly check the battery with a voltmeter and the battery has been holding the voltage with a little drop from 12.6 to 12.5 after a month of sitting. I have not checked the water in the battery so I need to do that. I did not check to see if the fridge, Alde heater, lights or fans are on but even if one of them are on I would not expect the SeaLevel meter in the T@B to show 11.9 or 12 volts that quickly with a fully charged battery.

I measured the battery after charging it this morning at home and it measured 12.9 volts. I went to the storage yard and installed the battery in the tub and connected the battery cables (cables are labelled positive and negative) but did not turn on the cutoff switch. I measured the voltage and it showed 12.9 volts. I turned on the cutoff switch and measured again and voltage dropped to 12.6. I went inside and read the SeaLevel meter and it showed 12.0 volts. I went back outside to the tub and monitored the battery voltage and watched it slowly drop. I turned off the cutoff switch and watch the battery voltage slowly start to go back up.

@SAM, I know about the break-a-way pin because I inadvertently left the cable hooked up one day to my TV and pulled forward with the TV and it popped out. I don't think that would cause the problem because I pull out the battery each time and the voltage drop problem I am having is within a couple of minutes.

Thank you @FishDoctor, @ScottG and @SAM, I have some more troubleshooting to do. I was thinking of pulling fuses to see if I could isolate the circuitry or area that may be pulling my voltage down.

Sharon_is_SAM · January 2018

So, full battery that sounds like it is holding a charge at home. It was never discharged below 12.2? When open to the trailer the voltmeter drops - which it should under load - even if only parasitic load. But, that is a big discrepancy between the voltmeter at the battery and the SeeLevel even for under load. Then the voltmeter continues to drop without additional load. Did the antenna booster require any wiring? As you said, pull the DC fuses one at a time and see if you can stop the drop.

ScottG · January 2018

@ChrisandAlex, 12.6V to 12.5V when sitting disconnected for a month sounds normal for a healthy battery.

The 12.9V to 12.6V when you flipped the switch is also probably normal, since the 12.9V was almost certainly some residual surface charge left over from the charging.

It is curious why your reading at the battery was 12.6V when the SeeLevel read 12V, but I don't have a whole lot of faith in the accuracy of most of that cheap electronic gee-gaw.

The abrupt drop in voltage (measured at the battery) combined with the recovering voltage upon disconnect does suggest that your battery is probably ok (though I would still advise checking the fluid level).

That brings us back to the trailer. Before your next test, do make sure everything is turned off. While I agree with you that most items should not draw that much power that quickly, a fridge inadvertently left on DC might.

If that checks out, you are up to pulling fuses to isolate the offending circuit. As FishDoctor noted, don't rule out the possibility of a short somewhere.

ChanW · January 2018

@ChrisandAlexis,
The three-way fridge could drain your battery pretty fast. I think I measured it at 11A once. That's really the only high power thing (12V) in the Tab.
I'd start by pulling that fuse.
The Alde pump can run continuously if your controls are on, but I don't think it takes that much power. And you'd probably hear it.

ChrisandAlexis · January 2018

Happy New Year everyone and thank you for all the suggestions. I went back out to the trailer this morning and the first thing I did was check if anything was still on...starting with the fridge. I played with the setting knob and it was at 0 or so I thought. Once I determined I was turning in the right direction I turned a little harder and it went click. I went back to check the voltage reading on the SeaLevel and it showed 12.5 volts. Nothing wrong with the T@B, just operator error. It makes sense now because our last trip was with shore power and we used the fridge while the 5 previous trips were dry camping.

I am really surprised that our 2 way fridge sucks up that much juice even when set to almost 0. And kind of surprised as @ScottG stated that the Fluke multimeter read 12.65 at the battery and the SeaLevel was giving me a reading of 12.0 volts. After turning off the fridge, the SeaLevel reading matched my multimeter reading at the battery.

Thank you @FishDoctor, @ScottG, @SAM and @ChanW for your suggestions and troubleshooting tips.

ChanW · January 2018

Huh, a two way fridge sucks that much power... surprised.

The difference in voltage readings sounds like voltage drop in the power supply line to the SeaLevel. Might be a not-tight or dirty connection, or too many connectors, or too small a wire gauge.

Unhelpful in any case, and I'd want to find the cause, in order to be able to trust the SeaLevel! (Or can the SeaLevel be calibrated?)

Glad you found the cause! Happy New Year.

Sharon_is_SAM · January 2018

Good call Chan and Scott! Although the DC draw on the 2 way Norcold is less than the 3 way Norcold, it is still a relatively high user of power, especially when it is in active cooling mode.

ChrisandAlexis · February 2018

Well, I guess we still have a problem. I visited the trailer this morning in preparation for a trip starting tomorrow. I put some fresh water into the tank and ran the pump to prime it and noticed the SeaLevel reading drop again...from 12.5 volts with the pump off and down to 11.7 volts with the pump on. I know this is not normal as I constantly monitor the voltage on the SeaLevel when we are on our trips. I did not have time to check out the voltage at the battery with a voltmeter this time. I may try another battery even though the battery checked out okay at the auto parts store.

ScottG · February 2018

I notice when something is running--particularly a high draw device like your water pump--the voltage will drop just as you describe. Once you disconnect the load, the voltage should return to at or near what it was. This is why it's important to assess your battery health in a no-load situation.

Of course a weaker battery will show a deeper discharge under load, and will not "bounce back" as readily. This is usually a gradual effect as the battery ages.

ChrisandAlexis · February 2018

Thanks @ScottG . that makes sense. I can't remember if I ever checked the SeaLevel voltage while I had the pump running while on one of our trips. I know I am always pushing the SeaLevel battery button or asking Alexis to do it to check to see how the battery is doing. In addition, I usually have the solar panel connected so that may mask the reading on the SeaLevel while using the pump.

ScottG · February 2018

Yep, the SeaLevel (or any other basic voltage monitor) will reflect any 12V input into the the camper. If you are hooked up to a solar panel or to shore power, the voltage you see will reflect the input from those sources and not necessarily tell you the state of your battery.

Problem with battery voltage for T@B slowly dropping

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