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Old 06-21-2019, 04:28 PM   #1
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Question Why the strong Power drain on my Forester TS 2391 when turned off.

Getting fairly well up on the learning curve on our Motor Home.


We have a power monitor, and with the main 12V switch Turned OFF, when we connect the battery, we can get a drain of up to 5 Amps! Fortunatly the drain seems to reduce after a while, and eventually reaches close to zero.



I know the Smoke detector Should be making a drain, and it seems the Truma Milti heater also gets power at least for the themostat, BUT what else might be Pulling back that much power when the Mootrhome is parked.



Paranoid me is always wondering about heat being generated by that Much power. with the Voltage pot out by the Lithium Battery in this model, 5 amps darw is almost 70 watts.


Anyone else noticed this and knows what is going on. The wiring harness is not friendly to trace the wiring on these things, with random colour wires running all over.
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Old 06-21-2019, 04:42 PM   #2
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12v entertainment system? Co/Propane sensor. Have to search and find all of the systems powered even if the battery disconnect is turned on.
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Old 06-21-2019, 05:23 PM   #3
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You mentioned the "drain" tapers off to almost nothing when you connect the battery. Are you sure you are measuring "Drain" or could it be charging current. That is the usual behavior when charging a battery. Current flow that diminishes as the battery gets closer and closer to fully charged.

Depending on the monitor it could be that if showing a minus sign before number, while the battery is actually charging, the shunt that sends the current signal to the monitor "brains" is merely installed backwards.

Only other drains I can think of that taper to nothing after a while would be "delayed off" lights lie headlights, puddle lights, step light, etc.
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Old 06-21-2019, 05:42 PM   #4
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Hi Titan Mike, the monitor is a Vectron, and as my co-pilot is a retired electrical engineer I believe her when she sees the result as a "drain" when we got the vectron she tried all the functions in a test setup on her desk over the winter. (including running a incandescent 60 watt Bulb off an inverter to plot the charge and discharge curves on the battery.) And she charges the battery with a lithium rated charger before bringing it out to the motorhome.

There is no a source of charging current when we connect the battery, (engine and generator off- shore power unplugged)
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Old 06-21-2019, 06:13 PM   #5
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Quote:
Originally Posted by cmacd View Post
Hi Titan Mike, the monitor is a Vectron, and as my co-pilot is a retired electrical engineer I believe her when she sees the result as a "drain" when we got the vectron she tried all the functions in a test setup on her desk over the winter. (including running a incandescent 60 watt Bulb off an inverter to plot the charge and discharge curves on the battery.) And she charges the battery with a lithium rated charger before bringing it out to the motorhome.

There is no a source of charging current when we connect the battery, (engine and generator off- shore power unplugged)

Who can argue with an Engineer?

My guess is that somewhere you have a circuit or device that is "charging up" or turns on when the battery is connected and if not actually used it just powers down. Since it's a Motor Home I would suspect it's something chassis related. Other item mentioned before could be entertainment center that behaves as I suggested.

One way to diagnose would be to pull the fuse for a suspect device, turn on battery switch, then look for the usual drain. If it stops after pulling a fuse, that's the culprit.

Without knowing your specific vehicle and all the accessories it's hard to be certain but just check the usual suspects like stereo, refrigerator (even Propane refrigerators draw power from battery), clocks, TV amplifier, even a water pump that is left turned on and runs to build up pressure when the power is switched on. Mine is pretty quiet and I could see it being that kind of problem if it wasn't for the big blue light showing me it's switched on.

Fuse by fuse might be your best bet unless you want to start disconnecting anything that might be drawing power.
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Old 06-21-2019, 06:54 PM   #6
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Does it have one of those control panels that connects with you phone by on board WiFi? That possibility could explain a draw then drop off.
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Old 06-22-2019, 12:51 PM   #7
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Here's a systematic process

Quote:
Originally Posted by TitanMike View Post
Who can argue with an Engineer?

Fuse by fuse might be your best bet unless you want to start disconnecting anything that might be drawing power.
Here's a more systematic process.

--Set your inexpensive multimeter on the 10 Amp (10 A) scale. Plug the black lead into the Common (COM) jack and the red lead into the 10 amp (10A) jack.

For each fuse on the 12v distribution board:
--Remove the fuse
--Plug the multimeter leads into the two fuse connectors. (They will fit nicely into the "curls" at the edges.) Polarity doesn't matter. Current might be shown with a "-" sign. For this purpose it doesn't matter.
--Record the current and fuse number
--Replace the fuse

Also try this with all the devices that have inline fuses connected directly to the battery, bypassing the distribution board.

It's likely that you will discover something silly like the antenna booster amplifier you forgot to turn off.

You may also be surprised by some of the intentional loads like the propane detector and settings maintenance current for control panel and A/V entertainment center.

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Old 06-22-2019, 12:56 PM   #8
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That sounds like typical behavior of a modern vehicle that has many electronic devices. When I had my shop and we were trying to measure parasitic draw (the current required to keep alive the electronics) it was not unusual for it to take 15 or 20 minutes for everything to go to sleep, before the current would settle out at the minimum.

My Flagstaff TV and stereo will drain my battery in just a couple of days. Any electronic device that has a remote control has a current draw when it is off. .
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