Battery drain

[arboldt]

What should I check to solve house batteries draining? Yesterday morning batteries were at 12.8 VDC, MH left unused for 30 hours, and batteries were at 12.0 VDC this afternoon. We are at my sister's, where we can pull the MH into her driveway and plug it in when needed but we can't block her driveway overnight. More importantly, this may discourage our intended dry camping / boondocking.

2004 Newmar Mountain Aire gasser. 2 - 6V deep-cycle batteries are 10 months old. The controller/charger has an add-on iQ4 adapter. I've installed a solar panel controller that's hooked up to the battery, but the panel is stored and not connected.

I've checked that there are no lights on in any bays, no lights in the MH itself, and inverter is off. The only things obviously drawing power are the refrigerator control circuit (the refrigerator itself is running on propane), the LP warning sensor, and the control circuit to extend the steps when I open the door. I don't want to switch the batteries to 'store' because I do want to keep the 'fridge going.

I tried another test: had the MH on shore power for 48 hours, then disconnected for 1 hour. Battery level was 13.1 VDC, then I checked each DC circuit, removing each fuse, measuring at 20mA scale with the common lead on the ground, the other lead where the circuit connected for each circuit. Here are the results:

Circuit / reading on 20mA Scale

TV/Stereo                0
Kitchen                  0
Bedroom                  0
Security                 0
Wrap Lights              0
Slideout lights          0
Refrigerator             0.54
Furnace                  0
Living Rm/Entry          0
Bath                     0
Monitor Panel/Water Pump 1.33
Slideout Motor          16.00
Fantastic/Water Heater    .80
AC Controls              0
Satellite                0

I was expecting a reading for the refrigerator control (it's powered by propane when off shore power but still needs controls active). I also expected a slight draw from the monitor panel. Although there is a satellite dome on the roof, the previous owner took the control box; we don't know if there is a dish up there or not. The TV BOMB (box of many buttons) is off. The inverter is off so both TVs are off. The thermostat is off, so furnace and AC circuits are all off. The water heater is off (both propane and shore power switches). The fantastic vent fan is off. The water pump is turned off.

For the Fantastic Vent, when I put the meter probes on the leads with the fuse removed, I could hear the vent motor cranking the vent open. With the fuse in place, the motor was off and silent. Can't understand why using the Amp meter would activate the vent motor.
The biggest draw is the slideout motor circuit. I tested with the bedroom slide all the way out (easier to get to the fuse panel). I put the slide back in, waited 4 hours, and tested again with the same result. So with slide motors off, why would they be drawing so much power?

What should be my next step?

Thanks.

[Yarome]

Have you checked your break-away switch?

[SCClockDr]

If the break away switch is OK. Then the slide circuit it's the culprit. If it has a control board I would suspect it, if not I would suspect the switch.

16 amps will drain 2 GC batteries in short order.

As a temp workaround pull the offending fuse till you need to move the slide.

I'd suspect the slide motor to be warm or hot to the touch as well.

[Kirk W]

The first thing that I'd do would be to make sure that the batteries are not the problem by first checking to make sure the electrolyte is at the proper level and then lift the negative cable to be sure that nothing is getting power from them. Once that cable is off, check the voltage, then wait 1 hour and check, then wait 8 or more hours and check again. It should not drop appreciably between the 1 hr. and the 8+ hour checks. Use a meter that reads voltage to 3 decimal places if possible and no less than 2 decimal points. If the batteries were fully charged, you should start with more than 13.5V but you may have a converter that isn't fully charging your batteries and that may be part of the problem. Check voltage across the pair and also across each one individually to see if the voltage is actually half from each battery as one much lower means a weak battery. 

If you don't check the electrolyte levels frequently, 10 months could be enough to cause it to be low and low electrolyte will mean the batteries will not fully charge. While you have the negative cable lifted, measure voltage between the negative and the positive to see what voltage is being supplied by your converter with the battery open. The only way to be sure that nothing is drawing power from your batteries is to lift the cables since it is very common for RVs to have some things powered by fuses not located on the fuse panel. 

[lenp]

When you say you tested each circuit "with the common lead on the ground", are you saying you connected one lead to chassis ground (negative side of the battery)?  If so, that is NOT the way to measure the current in each circuit.  Rather you should (1) remove the fuse, (2) connect the meter across the fuse terminals and (3) read the current.

If you actually measured each circuit the correct way, your total current drain is less than 20 MILLIAMPS (per your readings) which would take weeks to drain a battery.  

To measure TOTAL drain, disconnect the negative terminal on your battery (the ground connection) and insert your meter (on the 10 amp scale to begin with - you may have to connect your leads to a different socket on your meter for the 10 amp scale - depends on your meter) between the battery and the disconnected lead.  This will tell you if there really is a big draw.  If you don't get a reading on the 10 amp scale, try a lower scale.  With everything in the MH turned OFF except the frig and other monitors you should be drawing less than 2-3 amps.

I carry a clamp on amp meter that allows me to simply clamp around the battery cable (or any wire)  and take a measurement without disconnecting anything.  Very handy and they are available on Amazon (just make sure you get one capable of both AC AND DC current measurements - most of the cheap ones will not measure DC accurately (if at all).  https://www.amazon.com/Craftsman-Digital-400A-Clamp-Ammeter/dp/B003TXUZDM/ref=sr_1_1?ie=UTF8&qid=1504325787&sr=8-1&keywords=clamp+on+amp+meter+%2Bcraftsman

As Kirk indicated, you could have a bad battery.  Do the tests he suggested.

Lenp

[SCClockDr]

Quote

Slideout Motor          16.00

 

[arboldt]

1) The measurements above were mA (milliamps) so the slide circuit was 16 mA.

2) I took the measurements at the fuse block inside the MH. In-wires from each circuit had connectors to the fuse panel, then the fuse, then all went to a common ground. Because I wasn't sure if the meter probes would make good contact at the terminals grasping each side of the spade-shaped fuse, I tested from the input connector to the common just above the fuse panel.Electrically it's the same as the two spade-fuse contacts, just easier to get at.

3) I felt one of the slide-out motors. It was cold.(What's a breakaway switch on a motor home?)

4) I followed Kirk's suggested tests this afternoon. Here are the details:

• I disconnected the MH from shore power last evening at 5:45 pm. At 7:30 pm I tested: 13.1 on the monitor in the MH, 12.91 VDC with a meter at the battery.
• Today I checked the batteries -  fluid levels were 1/2 -3/4 the way from the top of the plates to the bottom of each cell cap opening (the bottom of the 'tube seen when the cap is removed -- don't know its formal name)
• 12:45 the batteries were at 12.55 VDC by meter.
• 12:55 I disconnected the negative cables and tested the batteries. They were 12.63. One battery was 6.31, the other 6.32.
• at 7:53 pm, the batteries tested at 12.69. I reconnected the negative cable; the inside monitor showed 12.9 VDC.

I don't understand why the batteries might have gained slightly after 8 hours, although the amount was very minimal. The primary take-away is that they were not drained over that time.

So the question remains: What do I do next to diagnose what my problem is? And the ultimate question is what can I do about it?

Thanks.

 

[lenp]

A fully charged battery at rest (after hour or so of no load or charge - disconnected) will read 12.66 to 12.9 volts.  You may read more or less when first disconnecting the battery due to surface charge or recent drain.  At 12:45 before you disconnected the batteries and they read 12.55 volts they were connected and a small drain was causing them to read slightly below full charge of 12.63.  After they were disconnected they returned to the fully charged reading of 12.63 (very close to fully charged).  I suspect the slight increase you saw at 7:53 was simply a more "at rest" condition.

Have you measured the total drain by connecting your amp meter between the negative battery terminal and and the lead going to that terminal?  

When you say "In-wires from each circuit had connectors to the fuse panel, then the fuse, then all went to a common ground" do you really mean a to a common HOT terminal?  Your circuits ARE NOT fed from a common GROUND - that is the negative side of the battery.  If indeed you were measuring from a common HOT terminal, I think all of your readings are well within reason and you need to go to the next step and measure the total drain at the batteries.

In your post you say the batteries were at 12.0 volts after 30 hours.  Was anything running besides the frig ( a light or two)?  If there was a significant load (10-20 amps) at that 30 hour point your batteries WILL read a lower voltage but may not be  significantly discharged.  The ONLY way to accurately measure state of charge is with an "at rest" battery.  Before you get to wrapped around this issue run the same test you did above when they reach 12.0 volts (i.e., disconnect the batteries and let them rest for an hour or so and measure them again to confirm you do or do not have a problem.

Good luck,

Lenp

[Kirk W]

11 hours ago, lenp said:

A fully charged battery at rest (after hour or so of no load or charge - disconnected) will read 12.66 to 12.9 volts.  You may read more or less when first disconnecting the battery due to surface charge or recent drain.  At 12:45 before you disconnected the batteries and they read 12.55 volts they were connected and a small drain was causing them to read slightly below full charge of 12.63.  After they were disconnected they returned to the fully charged reading of 12.63 (very close to fully charged).  I suspect the slight increase you saw at 7:53 was simply a more "at rest" condition.

Agree. The electrolyte level is proper as you don't want to put it much higher or the extra will boil out. This does show that your batteries are holding a charge and that the two are as nearly equal as you are likely to see. What none of this does prove is the amount of charge that our batteries will take as only a load test can do that. But at this point, I tend to believe that your batteries are not the problem.  If I read your post right, you measured 16 mA to the side and that is only 0.016 A and that should not drain your batteries in so short a time. 

12 hours ago, arboldt said:

So the question remains: What do I do next to diagnose what my problem is? And the ultimate question is what can I do about it?

If I were trouble shooting your problem, the next thing that I would do is to remove all of the fuses from the fuse block, then put my ammeter in series between the negative battery post and the negative cable. I am suspicious that you will see some significant current draw. It is not uncommon for RVs to have what we tech folks call "phantom loads" and those are things which are not connected via the fuse block and often they also stay connected when the battery disconnect is open. It is very common to wire an electric step so that it will operate even with the battery isolator off and there are other things as well. The only way to know for sure what is coming from your battery is with the post to cable measurement.

[ms60ocb]

On 8/31/2017 at 10:08 PM, arboldt said:

I've installed a solar panel controller that's hooked up to the battery, but the panel is stored and not connected.

Did I miss something, did you test the leakage to the solar controller. I missed that number.

I have a 2016 Fifth Wheel that now has 4 DC switches to turn off and yet have 2 devices with 24/7 power. I still looking for a convenient place to install a bigger DC switch.

[arboldt]

I've followed the suggested tests and here are my results:

1. I had the MH plugged in for 24 hours.
2. At 3:10 I unplugged it
3. At 4:20 I disconnected the cable from the negative battery post
4. I tested voltages in the batteries: 6.56 VDC, 6.56 VDC, 13.13 VDC across both
5. Amperage between the neg cable and neg post = 178.8 mA
   1. note cable to solar panel controller was disconnected, hanging loose
6. I removed all the fuses from the house fuse block
7. Amperage between the neg cable and neg post = 141.0 mA (slowly declining)
8. Amperage between the solar panel controller cable and neg post = 37.0 mA
9. Fuses were replaced, the battery cables reconnected, and the MH plugged back in.

Questions:

• Is it merely coincidental that the difference in mAmps between with and without fuses is the same as the draw to the solar panel controller? (37.0 mA)
  • Although that draw is not too significant, should I put a disconnect switch in the cables between the batteries and the solar controller?
• (primary question) What should be my next step to identify / resolve the 141 mA draw from the battery when all fuses are removed?

I deeply appreciate everyone's help and guidance, making fellow Escapees a most valuable resource. Thanks.

[Al F]

The 0.14 amp drain you see with all fuses removed sounds about what the propane detector pulls.  To be sure you will have to pull the detector off of the wall and remove one of the wires. 

The 0.18 amp drain you see with all fuses installed, should not cause a problem with your batteries draining down to 12.0V in just a few days.  The 0.18 amp rounded up to 0.2 amp times 24 hours gives about 4.8 amp hour (AH) per day of battery drain.  Assuming ~200AH of battery, it would take about 20 days for that to bring the batteries down to 50% SOC.

 

[Yarome]

Finally sat down and read through this today. My mistake on the break-away switch remark. I wasn't paying attention to your rig.

That being said... I'm not sure why you're taking readings at 20mA scale, but regardless... all of your load measurments to date do not indicate anything out of the ordinary. In fact, your "phantom load" is actually on the low side.

Referencing: "Amperage between the neg cable and neg post = 178.8 mA"

With regard to a your controller, yes... it's a good idea to have a disconnect between your controller and battery bank. But that's moot to your problem.

As far as the issue at hand I'm mainly leaning in only one direction. Your batteries are shot.

From your readings under your post:

"4) I followed Kirk's suggested tests this afternoon. Here are the details:"

Lenp said, "You may read more or less when first disconnecting the battery due to surface charge or recent drain". He is correct, however, the load measurements you've been reporting are not significant enough to actually "dip" your voltages like that. It's important to note that "voltage" does not equate to "capacity". Your batteries appear to lack the capacity to "back" even small loads.

My advice... before doing anything else, you need to have your batteries load tested.

[Yarome]

50 minutes ago, Al F said:

The 0.18 amp drain you see with all fuses installed, should not cause a problem with your batteries draining down to 12.0V in just a few days.  The 0.18 amp rounded up to 0.2 amp times 24 hours gives about 4.8 amp hour (AH) per day of battery drain.  Assuming ~200AH of battery, it would take about 20 days for that to bring the batteries down to 50% SOC.

Spot on. Your loads are not the issue. Any "phantom loads" up to around .5 amp would be considered perfectly normal.

[Kirk W]

1 hour ago, arboldt said:

1. Amperage between the neg cable and neg post = 141.0 mA (slowly declining)
2. Amperage between the solar panel controller cable and neg post = 37.0 mA
3. Fuses were replaced, the battery cables reconnected, and the MH plugged back in.

Questions:

• Is it merely coincidental that the difference in mAmps between with and without fuses is the same as the draw to the solar panel controller? (37.0 mA)
  • Although that draw is not too significant, should I put a disconnect switch in the cables between the batteries and the solar controller?
• (primary question) What should be my next step to identify / resolve the 141 mA draw from the battery when all fuses are removed?

Since your phantom load is only .14a, it really should not drain the batteries very quickly. I highly suspect that the 37 mA readings is just a coincidence.  I suggest one of two possible next steps. I would either leave the negative cables all off for 48 hours, checking voltage before and after that period to see if the voltage drops that way and if it doesn't the next step is to take the batteries and have them load tested. At this point I consider the batteries suspect as a load of less than less than .5a should not drain a pair of batteries in one or two days. 

[lenp]

x3 on getting the batteries tested.  Agree the load your reading IS NOT a problem.

Lenp

[Yarome]

4 hours ago, arboldt said:

(primary question) What should be my next step to identify / resolve the 141 mA draw from the battery when all fuses are removed?

I apologize for ignoring your "primary question". The .14mA you're seeing with all fuses pulled and your battery still connected can be attributed to "line loss" (simply energizing the wiring) , possibly a device connected to ground that is not tied to your PD panel, and/or simply to "acceptable" deviation in the meter you're using. (Ie., +/- 1.2%-1.5% when testing DC current)

IMO, that small of a draw it's not even remotely worth the effort to try to identify or affect any type of correction.

[ms60ocb]

3 hours ago, Al F said:

The 0.18 amp drain you see with all fuses installed, should not cause a problem with your batteries draining down to 12.0V in just a few days.  The 0.18 amp rounded up to 0.2 amp times 24 hours gives about 4.8 amp hour (AH) per day of battery drain.  Assuming ~200AH of battery, it would take about 20 days for that to bring the batteries down to 50% SOC.

 

Having a battery drain does  not have a place of semi full timer or any seasonally RV user.  How many people can park for a month or so with back up electrical. Several years ago I parked in a secure storage area planing two months storage. Some expected surgery made that 4 1/2 months. I arrived at the fifth wheel, turned on the kill switch and started the furnace before even connecting the truck. Now I have a difference RV and know that that batteries have a drain so if I had to park for an extended time I would have to remove battery cables.

Like wise when we leave for the winter the newer vehicles have a constant drain but being in the Garage rather than disconnecting battery. We connect a Battery minder.

 

8 minutes ago, Yarome said:

IMO, that small of a draw it's not even remotely worth the effort to try to identify or affect any type of correction.

So I'm on the side of saying "Even The Small Drain Is Worthy Of Locating"

I'm betting arboldt will find some added device to the 13 year old RV that has not noted yet. That device may fused with a hidden fuse under the dash.

Clay

[Yarome]

45 minutes ago, ms60ocb said:

Having a battery drain does  not have a place of semi full timer or any seasonally RV user.

You're talking about two different situations though. In storage you hit your kill switch so your wiring is no longer energized. There is little to no "sympathetic/phantom loss". At that point your only concern is self discharge (for wet cells... ~10%-15%/30 days).

If your kill switch is installed in the proper location it doesn't matter if a load passed through the DP or wired to the chassis. No current will pass.

With an energized system, as his was (and as yours is when you turn "on" your kill switch), some amount of loss is inherent.

[ms60ocb]

11 hours ago, Yarome said:

If your kill switch is installed in the proper location it doesn't matter if a load passed through the DP or wired to the chassis. No current will pass.

 

I agree 100% IF the Kill Switch is Installed ________________. That is my case, arboldt has a 13 year old RV  (things added or modified) and I have unit I bought new that has a drain when all systems are turned off. My Kill Switch does not kill 100% of the circuits. The Kill switch only kills the Main DC Fuse panel. There are other battery connected circuits that have fuses which either must be pulled (I added 2 switches as DRV said adding a switch at the factory would be a design change) or lead lifted. I'm not the DRV owner that wants to pull fuses. I suspect other MFG have some drains especially in a Class A or Class C with any alarm systems.

Clay

[arboldt]

I've followed the suggestions and this morning did a load test:

1. I disconnected the negative cable from the batteries (2 6-volt batteries in series). I left them connected together, along with the positive cable. I tested them individually, though.
2. The load tester directions said to connect the test cables, note the voltage, then switch on the load for at least 5 seconds. Following those instructions, each battery tested the same when connected = 6.8 VDC then under load = 6.2 VDC. According to the load tester dial (and directions), the batteries are good.

So now what?

I don't want to use the battery Store ('kill') switch because I need the control circuits for the refrigerator etc. But when not on shore power and with everything else off, the MH system will loose approx 0.5 V per day (e.g. from 12.6 in the morning to 12.1 or 12.0 V the next morning, so I have to connect to shore power or run the generator to recharge the batteries. This severely impedes our desire to boondock / dry camp.

All the testing I've done (reported above) indicated there should not be that significant a drain. So what should be my next step?

I deeply appreciate everyone's help and guidance. Thanks.

[Al F]

So far so good on your load testing. 

Was the load only on for about 5 seconds?  Try leaving the load tester on for 60 seconds to 3-4 minutes, unless the load tester says to shorten the length of the testing. 

If these load test don't show a problem, then start your checking all over.  It could be the problem has gone away. 

That is, set your RV up as it was when you had the problem, and then check your battery voltage every hour or two, extending the time between testing if no problem seen.  If no battery drain is found after 24-36 hours, then just check the voltage every 24 hours or as often as is convenient.

If/when you see a fairly rapid drop from the 12.6V starting voltage (that is the voltage the batteries should be at after the surface charge is dissipated) Then disconnect the ground side cable, put your meter on the highest current scale and measure the current draw.

I wonder if the problem has gone away.  Or maybe the batteries start to die when they are discharged down to some point.  Maybe 25% discharge level and one of then dies??. 

[Al F]

One additional thought.  You mention you have plans to boondock/dry camp.  A must have item for anyone planning on using their batteries to dry camp is a battery monitor such as a Trimetric.  You can tell at an instant, just by glancing at the monitor how many amps are being discharged (or charged) to/from your battery.  It also tells you the percent of charge and the number of amp hours used.  This is extremely important to know so you don't drain the batteries more than 50%, even better don't drain them beyond 75% full (use only 25% of the total capacity) for longest battery life.

In fact if you had one of these installed it would have made your diagnosing of the problem much easier.  Just turn on/turn off each load, or remove each fuse, and just a quick look at the monitor would give you the results of the action you took.

 

[arboldt]

I may have inadvertently identified the problem while creating a new one.

We'd had the MH on shore power for a couple days, then had to disconnect it. The next day, the battery level was 12.7 (per the control monitor). Another day, and it was 12.5. Sounded good. However, the backup camera was no longer working. This leads me to believe the backup camera was the culprit. Don't necessarily understand it, but... The camera was coming on automatically when I put it in reverse; the power switch had no effect.

Now I need to find the fuse for the backup camera. It's not on the 12 V fuse panel. Assuming that's what the problem is, then I should put an in-line switch to turn if off when we're dry camping in one place for more than a day. I'm also assuming the several times I disconnected the battery cables is what created the issue.

Yesterday we drove a couple hours, then parked at my brother's, not connected. A couple hours after we stopped (approx 4 pm), I checked the monitor and the battery was at 13.1!. This morning (11-ish) it was 12.7. So I don't know if the 13.1 was accurate and it actually dropped 0.4 V or if it just returned to 'normal'. Since then I did get shore power out to the MH, so should be good.

[Chad Heiser]

On my last 5th wheel, the factory wired the back up camera to direct power.  In other words it was always on.  I couldn't believe they did this, but they did.  I quickly rectified this problem by putting a switch in the line.  It is a good possibility your camera was wired the same way and that would definitely create a draw on the batteries.