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Battery temperature sensor installation


saflyer
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I have a Magnum MS2012 inverter/charger connected to two SOK 12v batteries and a Victron solar controller. I’ve added a Magnum temperature sensor to connect to the inverter. Standard installation would be to mount the sensor on the negative terminal of one of the batteries. However, I read somewhere but can’t remember where, that when doing this it’s possible to fry the inverter instantly. Maybe because of a spark. Has anyone heard of this problem? Can I just hang or lay the sensor anywhere in the battery compartment?

Ed         
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No.  The temp sensor does not actually electrically connect to the battery.  

The issue is if you disconnect the main ground to the inverter it will try to ground through the remote and cause problems.  

Also the temp sensor is not even required.  

Edited by vito.a
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I know there has been debate about whether the temperature sensor is needed.  I think it's a good idea to read why Magnum is using a battery temperature sensor.

The purpose of this temperature sensor is to change absorb and float charge voltages depending on battery temperatures.  The idea is to extend battery life.  Below is a screen shot out of the Magnum manual. 

The coach owner can read the information and decide whether or not to install the BTS.  I have mine installed on the battery negative terminal.  It came from the factory that way and I never removed it.

Untitled10.thumb.jpg.ad92a035e8d40b033ed549329d04906c.jpg

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My bts didn't work. It was connected to the negative post. When I had to get a new magnum 2012 I don't remember if one came with it or if I bought one.

There was no way I could see to get the telephone wire from the inverter back to the batteries. I bought a phone wire splice and added it to the end of the old wire. Still doesn't work. Pretty sure I ended up unplugging it.

Have had no battery problems or charging problems though.

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12 hours ago, Frank McElroy said:

I know there has been debate about whether the temperature sensor is needed.  I think it's a good idea to read why Magnum is using a battery temperature sensor.

The purpose of this temperature sensor is to change absorb and float charge voltages depending on battery temperatures.  The idea is to extend battery life.  Below is a screen shot out of the Magnum manual. 

The coach owner can read the information and decide whether or not to install the BTS.  I have mine installed on the battery negative terminal.  It came from the factory that way and I never removed it.

Untitled10.thumb.jpg.ad92a035e8d40b033ed549329d04906c.jpg

How does having LiFePO4 batteries enter into this? I also have the Magnum battery monitor and, if I remember correctly, the system has a low temperature cutoff the batteries can’t charge below freezing temperatures. I believe I have mine set for 35°F. I think this restricts the MS2012 from charging the batteries below this temperature. The batteries also have low temperature charge protection built into their BMS.

vito.a’s point about the inverter trying to ground through the BTS is something to think about. I wondered if the hangar on the BTS was electrically connected or just that, a hangar. If so then I see no need to connect the BTS to the battery, just lay or hang it nearby.

 

 

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2 hours ago, saflyer said:

How does having LiFePO4 batteries enter into this? I also have the Magnum battery monitor and, if I remember correctly, the system has a low temperature cutoff the batteries can’t charge below freezing temperatures. I believe I have mine set for 35°F. I think this restricts the MS2012 from charging the batteries below this temperature. The batteries also have low temperature charge protection built into their BMS.

vito.a’s point about the inverter trying to ground through the BTS is something to think about. I wondered if the hangar on the BTS was electrically connected or just that, a hangar. If so then I see no need to connect the BTS to the battery, just lay or hang it nearby.

 

 

Some random thoughts and I discussed with Frank so we are on the same page.  The BTS, at some time, was not connected to the Negative post,  it was glued or afixed to the battery case.  I wondered if it would be OK by merely taping the housing to the outside sheath of the rear negative cable…with the actual temperature probe not grounded or touching the cable or post.  The Magnum write up says “around” the battery.  The BTS temp can be read from the Tech button,  Frank checked his in his barn.  Remote says 77 dF…but the ambient inside the shed was 70 dF…he was going to test with a laser later on.

My point, from Magnum, was that when the temp sensor goes “crazy”, there is a multitude of codes and garbage.  We had a member get readings or 60 VDC.  The only solution was a soft reset.  That cured it.  I called Magnum and the tech said….maybe bad BTS.  Unplug it.  He did and all is still well. M&M in February 2015 at our Gathering, during a Q&A, cautioned about the issues they were seeing with the BTS on the Negative post and recommend unplugging.  I ran mine that way for a long time.  Then reconnected it.  Later on, my Remote was acting up….and was defective.  I now wonder.  I might pull mine and Gorilla tape to the cable with the probe near the post.  

This is a personal decision…but Magnum says, if you have some funky issues, do the Soft Reset….and leave off the BTS….and see if it works.  If you leave all the 3 cables off and do the soft reset, then the Magnum is set to all the internal defaults that most 4 house battery rigs need.  Then you can plug in the Remote and monitor…..then late the AGS.  Then the BTS….if the funky conditions come back after the BTS….you know the problems.

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Spoke to magnum tech support. Was told temp sensor is if no use with lithium batteries. Just remove it. As Frank McEkroy’s post indicates it’s only useful to modify charging of lead acid batteries.

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  • 2 weeks later...
On 9/13/2022 at 8:00 PM, vito.a said:

No.  The temp sensor does not actually electrically connect to the battery.  

The issue is if you disconnect the main ground to the inverter it will try to ground through the remote and cause problems.  

Also the temp sensor is not even required.  

Thanks Vito. I spoke to Magnum and they confirmed what you said, with lithium batteries the temp sensor is of no use.

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