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Old 07-28-2016, 09:55 PM   #1
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Parasite battery draw?

With new, fully charged coach batteries and the coach disconnect switch in the "Use" position my Thor ACE battery reserve drops to 12.1 volts in just 3 days. I have repeatedly combed through the interior and exterior compartments for any power draws and find nothing but the propane detector on. Could this single item draw the coach batteries down by one half in that short a time? BTW, my radio has the option to turn off the power-off display, so should not be the culprit. There is no battery drawdown in the "Store" switch position. I'm not inclined to try any dry camping until I figure what the heck is going on.
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Old 07-28-2016, 10:09 PM   #2
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THOR #3916
See the "Dead House batteries" thread, very good discussion there on parasite draws

http://www.thorforums.com/forums/f10...ries-3177.html
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Old 07-28-2016, 10:16 PM   #3
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Originally Posted by saddlesore View Post
See the "Dead House batteries" thread, very good discussion there on parasite draws

http://www.thorforums.com/forums/f10...ries-3177.html
Yes, interesting. Can measure battery state but don't really know how to measure battery current draw. Any suggestions, there? Thanks
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Old 07-28-2016, 10:29 PM   #4
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THOR #3552
Quote:
coach disconnect switch in the "store" position
When the disconnect switch in my coach is in "store", my propane detector is off. But the detector should not draw that much - one source estimate 2.4 amp-hours in a day.
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Old 07-28-2016, 10:35 PM   #5
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THOR #711
Disconnect your positive battery cable and hook your multi meter in series between the positive post and the cable end. I don't recall the amperage reading that is normal with no parasitic draw (possibly something like 5 milliamps). If higher amperage found, start pulling 12 volt fuses one at a time. When you find an amperage drop, you will have found your parasitic draw.
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Old 07-28-2016, 10:39 PM   #6
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Originally Posted by Cosmo View Post
When the disconnect switch in my coach is in "store", my propane detector is off. But the detector should not draw that much - one source estimate 2.4 amp-hours in a day.
Don't forget that there is a draw for dash/fridge/clocks & LP/Co2 monitors, and some inverters & auto levelrers everywhere that are not disconnected with the store switch. Otherwise you would have to re-set them each time you put switch to "use" settings.
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Old 07-28-2016, 11:48 PM   #7
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THOR #608
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Originally Posted by rskrbina View Post
Disconnect your positive battery cable and hook your multi meter in series between the positive post and the cable end. I don't recall the amperage reading that is normal with no parasitic draw (possibly something like 5 milliamps). If higher amperage found, start pulling 12 volt fuses one at a time. When you find an amperage drop, you will have found your parasitic draw.
Thanks for the elementary but so useful info. Actually sounds pretty easy!
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Old 07-29-2016, 12:09 AM   #8
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You are welcome. I hope you find what's causing the problem. Let us know.
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Old 07-30-2016, 04:53 PM   #9
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THOR #608
OK, armed with the advice and a new multimeter set to the 200 milliamp scale I have measured 0 milliamp battery draw with the disconnect sw. in "store" and a .2ma draw with the sw. in "use", which is inconsequential. So, I conclude that I either have 2 bad batteries or the very old multimeter with which I initially tested the batteries was inaccurate in showing me rapidly depleted battery states. I'm letting the freshly charged batteries sit for a week or so and will then retest their charge to confirm their condition. Thanks for contributing to the learning experience!
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Old 08-04-2016, 11:41 AM   #10
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THOR #3785
I had the EXACT same problem on my 2016 Challenger 37TB. It turned out to be the crappy no name batteries Thor uses. I changed them for interestate batteries and the problem went away. My mechanic tested it and found the problem, but I don't know what kind of meter he used.
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Old 08-04-2016, 07:05 PM   #11
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Thanks a lot for that insight. I wasn't aware that there were chronic problems with Thor's coach batteries so sounds like it's replacement time!
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Old 08-04-2016, 07:27 PM   #12
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Originally Posted by skyridez View Post
Thanks a lot for that insight. I wasn't aware that there were chronic problems with Thor's coach batteries so sounds like it's replacement time!
Yes. I finally found a mechanic who I believe knows what he is doing. Not a dealer though, so I had to fight a bit with Thor to use him for warranty. He said it was a "Bad Cell" and once he replaced both factory batteries there was no abnormal draw on the system.
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