Vampires and multimeters - R-pod Owners Forum

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CharlieM

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Joined: 23 Nov 2012
Location: N. Colorado
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Topic: Vampires and multimeters
Posted: 09 Aug 2017 at 8:48pm

As Paul says, until we get some real current measurements we are just shooting in the dark with no sights. Putting the ammeter across the open battery disconnect switch will measure the current drawn from the battery but I'd rather you measure directly at the batteries. Sometimes loads are connected before the disco switch so, to be sure, measurements should be made right at the battery. With two GC2s in series the easiest method is to disconnect the jumper between the two batteries and connect the ammeter in place of the jumper.

Most multimeters have a DC current function. It should be labeled DC Amperes, DC Amps, or DC current. Typical ranges will be 10A or 20A. If you'll tell me the make and model of your multimeter I'll look it up and help you with it.

Charlie
Northern Colorado
OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD
PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD

GLBCamper

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Posted: 09 Aug 2017 at 11:19pm

I am using a CenTech multimeter model 98025. I have it set to DCV 20 and am touching the red lead to the positive on the battery with the positive line connected to it and the negative lead to the negative terminal on the other battery with the ground wire attached. Wrong? Here is my log: I'm not seeing a smoking gun yet.

7/31 @ 10:00am 12.86 w/battery cutoff

8/1 @ 10:00am 12.87

8/2 @ 10:00am 12.83

8/3 @ 10:30am 12.81 Plugged in cutoff switch. Everything off except LPGas Detector.

8/4 @ 9:30am 12.60

8/4 @ 12:00pm ran power jack several times (bummer for my tests, but the neighbor was spray painting his house and I had to move it.)

8/5 @ 9:15am 12.51

8/6 @ 10:45am 12.45

8/7 @ 9:45am 12.42

8/7 @ 10:10am plugged into 30A shore power

8/8 @ 9:00am unplugged from shore power

8/8 @ 9:45am 13.00

8/8 @ 2:43pm 12.93 turned on fridge on propane

8/9 @ 10:00am 12.60

8/9 @ 3:20pm 12.47

Old: 2014 177 HRE
2015 Tacoma V6 4x4 Double Cab
New: 2016 EVO ATS 200rd
2016 F150 4x4 Sport

CharlieM

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Posted: 09 Aug 2017 at 11:55pm

You are correctly measuring voltage and they seem reasonable for what you're doing. What we need are current measurements. You should disconnect the jumper between your two batteries and insert the multimeter in place of the jumper. With the jumper disconnected :

Plug the red test lead into the jack marked 10A on the multimeter
Plug the black test lead into the jack marked COM on the multimeter.
Set the multimeter range selector switch to 10A on the DCA section of the meter switch.
This is all described on page 5 of your instruction manual under "DC Current Measurements".
Be very careful with the following steps. An error here can destroy your multimeter.
Connect the positive (red) lead of the meter to the positive terminal of the battery that has its negative terminal connected to ground.
Connect the negative (black) lead of the meter to the negative of the battery that has its positive terminal connected to the camper.

The meter should read positive values for current flowing out (discharge) of the battery and negative values for current flowing into (charging) the battery. Start with everything off and the battery disconnect switch in the disconnected position. It should read zero. With everything off in the camper, close the disconnect switch and you should see a small value much less than 1A. Continue turning things on and recording the readings. Let us know what you find.

Charlie
Northern Colorado
OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD
PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD

GlueGuy

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Posted: 10 Aug 2017 at 12:36am

Originally posted by GLBCamper

Honestly I feel like an absolute idiot here, but I have a multimeter and not an ammeter, which should do the job, but I'm confused what you mean by "across the open battery cutoff."

In order to measure current, your meter must be in series with the batteries.

In your case, you have an easy way to do this. First, remove the wire/cable that runs between the two batteries. It will be connected to the (+) on one battery, and the (-) on the other battery.

Then put your meter into DCA (DC Amps) mode. based on what we've been seeing, you hopefully have a meter that can go to 20 amps (because I think that may be in the neighborhood of what your drain is). Set it to that mode (if it has it, or higher if necessary).

Now here is the tricky part. You want the meter to measure the flow of current. The meter will be polarity sensitive, so you want to connect the red (positive) lead to the (+) terminal on one battery, and the black (negative) lead to the (-) terminal on the battery. This is the same terminals that you removed the jumper in the first step.

At that point, your meter should be showing you the amps that are being drained. If your meter is not big enough, you may blow a fuse in the meter.

bp
2017 R-Pod 179 Hood River
2015 Ford F150 SuperCrew 4WD 3.5L Ecoboost

pgoelz

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Posted: 10 Aug 2017 at 8:04am

Originally posted by GLBCamper

I am using a CenTech multimeter model 98025. I have it set to DCV 20 and am touching the red lead to the positive on the battery with the positive line connected to it and the negative lead to the negative terminal on the other battery with the ground wire attached. Wrong? Here is my log: I'm not seeing a smoking gun yet.

Perhaps because there is none to find? It looks to me like your voltages imply (note that I said "imply") a fairly slow discharge after you burned off the surface charge. According to the discharge table I have, 12.65V is 100% charge. Assuming your meter is correctly calibrated, your batteries spent several days ABOVE that voltage. That would not be the case if there was any appreciable discharge current. And your voltages certainly do not show a full discharge overnight like I thought you initially were describing????

ONE MORE TIME..... merely measuring battery voltage DOES NOT help diagnose rapid battery discharge since we have no idea how healthy your batteries are. Too many variables in the equation. If you want to figure out what (if anything) is discharging your batteries MEASURE THE BATTERY CURRENT. At the batteries, and preferably between them, to eliminate any unexpected connections. Without that, all we can do is speculate. And speculation is not definitive.

Paul

GLBCamper

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Posted: 10 Aug 2017 at 11:06am

OK. Finally, we are getting somewhere! No thanks to me and ALL thanks to you.

I followed the above instructions exactly. Here are my results.

With battery bypass OUT reading 0.00 (as expected)

With battery bypass IN and all systems except LPGD off, reading fluctuated wildly between 0.30 & 0.80 (again, I believe as expected. But is it normal to have it bounce around wildly?)

I will now start adding things beginning with the fridge and will update later.

Like I said, even my passive "leave it on for 3 days and see what happens to the voltage" hasn't replicated the rapid draw down that I experienced while camping, so hopefully this will produce results.

Old: 2014 177 HRE
2015 Tacoma V6 4x4 Double Cab
New: 2016 EVO ATS 200rd
2016 F150 4x4 Sport

pgoelz

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Posted: 10 Aug 2017 at 11:32am

Originally posted by GLBCamper

With battery bypass OUT reading 0.00 (as expected)

With battery bypass IN and all systems except LPGD off, reading fluctuated wildly between 0.30 & 0.80 (again, I believe as expected. But is it normal to have it bounce around wildly?)

I will now start adding things beginning with the fridge and will update later.

Without knowing exactly what is connected to the battery (including any loads you don't know about), I can't comment on whether a variable load of 300-800 mA is normal or not. Off the top of my head, I don't think so. But I don't know how your LPGD works.... it might be heating a small sensor element.

Were you by chance connected to shore power? Any chance the charge controller was providing a float charge? It is also remotely possible that if you were connected to shore power, there was some AC leakage into the battery circuit that was confusing your ammeter. Switch your meter from DC to to AC amps and see if you see anything.... should be zero. If it is non-zero, that could explain the fluctuation.

Paul

CharlieM

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Posted: 10 Aug 2017 at 12:47pm

That degree of fluctuation is unusual but could have several causes. Common LP detectors typically draw ~0.1. Electronic thermostats have some draw and control boards in fridges will draw something even if "off". If the fluctuation is rapid and random I'd suspect the meter itself. Inexpensive meters can be flaky at the low end of their ranges. If the fluctuation appears more regular it might really be in the trailer.

We are assuming shore power is disconnected but that's a good thought.

The meter in use has no AC current capability.

Charlie
Northern Colorado
OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD
PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD

GLBCamper

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Posted: 10 Aug 2017 at 1:29pm

I'm definitely not connected to shore power.

It stabilized at 0.31 which, if you look at my original post is very close to the parasitic loads I already identified, so I'm not surprised. Here is my log from today:

Baseline 0.31 stable

+ fridge 0.86

- fridge + ALL interior LED lights 1.45 (When camping, I rarely use more than 1 for more than half hour)

- lights + furnace 3.29. (I couldn't get it to come on for long, hot today)

Now the INTERESTING thing: The water pump. First, switch on but no demand 0.31 (the baseline.) Then with demand 3.45. BUT after I turned off the faucet with the switch still on it jumped to 6.45 and stayed there. When camping, I try to remember to turn off the switch when not in use, but if I forget that could really add up. The pump is cool to the touch, even with demand.

But even MORE INTERESTING is that I noticed that when the water pump switch is on, the green light power indicator on the LP Gas detector goes out. On/off. Off/on. They are connected?!?

Old: 2014 177 HRE
2015 Tacoma V6 4x4 Double Cab
New: 2016 EVO ATS 200rd
2016 F150 4x4 Sport

pgoelz

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Posted: 10 Aug 2017 at 3:26pm

Originally posted by GLBCamper

Now the INTERESTING thing: The water pump. First, switch on but no demand 0.31 (the baseline.) Then with demand 3.45. BUT after I turned off the faucet with the switch still on it jumped to 6.45 and stayed there. When camping, I try to remember to turn off the switch when not in use, but if I forget that could really add up. The pump is cool to the touch, even with demand.

But even MORE INTERESTING is that I noticed that when the water pump switch is on, the green light power indicator on the LP Gas detector goes out. On/off. Off/on. They are connected?!?

Whoa, that IS interesting indeed! I would highly suspect something wrong with your water pump..... it should draw current when it is pumping but as soon as you close the tap and the pressure switch opens, it should stop altogether. My best guess is that your pressure switch is not opening when the tap is closed and the water pump either runs continuously or stalls against the pressure. Put the ammeter in series with just the pump and confirm.... the drain should be ZERO before AND AFTER it runs.

As for the LPG LED, can't say for sure. I wonder if it goes out if the voltage sags below some voltage. If it is tapped into the same feed as the water pump, I would look for under sized wiring or perhaps a loose connection.

Another possibility is that there is bad or undersized wiring somewhere between the battery and the water pump.... or the batteries themselves are bad. It may be that there is insufficient voltage to the pump and that it cannot pump the water system up far enough once a tap is closed to activate the pressure shutoff, so it keeps trying forever.

Go step by step..... measure the battery voltage at the battery terminals with the pump "stuck" drawing 6A.... does the voltage sag more than a couple tenths of a volt? If so, bad batteries. If not, check the voltage at the pump itself. If it more than (say) half a volt below the battery voltage with the pump "stuck" look for bad or undersized wiring somewhere.

Does the LPG LED go out when the pump runs when you are on shore power? That would tend to implicate your batteries.

We're getting somewhere....

Paul