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Old 11-10-2018, 02:07 PM   #1
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Bluetooth battery monitor and shut off switch.

I put a cutoff switch on my battery and also want the Bluetooth monitor

In what order should the cables be placed on the posts?

Do I just put the monitor on top? That would be way too easy.
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Old 11-10-2018, 02:28 PM   #2
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I put a cutoff switch on my battery and also want the Bluetooth monitor

In what order should the cables be placed on the posts?

Do I just put the monitor on top? That would be way too easy.
If you choose a "Bluetooth Monitor", consider a Victron 712. It uses a shunt that is installed in series with the ground cable from batteries to frame attachment point (usual connection point for RV's).

The shunt needs to be installed in negative/ground cable that is common to all batteries so ALL current in and out of the batteries has to pass through the shunt. Instructions will show where the cable to the batteries is to be connected to the shunt. If you get it backwards it will just show discharge on the monitor itself when the batteries are actually charging.
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Old 11-11-2018, 12:16 PM   #3
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I suspect the OP is referring to one of those small bluetooth "monitors" that simply clamps to both battery posts. Which would be a voltmeter.

While reading voltage alone may certainly meet the needs of some users, I myself consider true battery monitoring with a device capable of the following:
1) Sensing when battery is fully charged, and automatically setting that as the start point for the next discharge cycle
2) Measuring actual total capacity removed from the battery over time during discharge cycle
3) With the above two in hand, battery degradation can be monitored and accounted for each charge/discharge cycle

Unfortunately, the "battery post" monitor only shows voltage, so really does not "monitor" much. While resting battery voltage can be a general indicator of charge state of a LA battery, it is not particularly accurate (especially with some of the newer chemistries that maintain a steady voltage deep into discharge).

The Victor may not account for total system draw (according to an Amazon review their tech support confirmed it does not measure its own usage, also just the way it is wired up it looks like it could be true since a positive wire goes to the shunt, need to verify the negative lead goes to the battery or load side of the shunt). Also, the Victor cannot sense a full battery (user must enter guesstimate of remaining total battery capacity after being fully charged).
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Old 11-11-2018, 12:28 PM   #4
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The Victor may not account for total system draw (according to an Amazon review their tech support confirmed it does not measure its own usage, also just the way it is wired up it looks like it could be true since a positive wire goes to the shunt, need to verify the negative lead goes to the battery or load side of the shunt). Also, the Victor cannot sense a full battery (user must enter guesstimate of remaining total battery capacity after being fully charged).
The Victron 712 draws 1mA which turns out to be 0.7AH/month. Likely WAY lower than the battery's self discharge if you are using flooded lead acid.


The Victron does sense a full battery and adjusts the %charge remaining to 100% when it sees that voltage level/current combo. Can't always trust those Amazon reviews. A lot of non technical people providing poor advice. Kinda like what happens here a lot!
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Old 11-11-2018, 01:38 PM   #5
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The Victron 712 draws 1mA which turns out to be 0.7AH/month. Likely WAY lower than the battery's self discharge if you are using flooded lead acid.


The Victron does sense a full battery and adjusts the %charge remaining to 100% when it sees that voltage level/current combo. Can't always trust those Amazon reviews. A lot of non technical people providing poor advice. Kinda like what happens here a lot!
People also tend to not read or understand fully before responding.
1) My comment for Victron meters was in general, which can use up to 15ma if the battery gets below the 50% capacity remaining guesstimate. If a user forgets to unhook the device for storage, can definitely lead to trouble.
2) I agree don't trust Amazon reviews. Still in this case, the review in question had nothing to do with setting SOC, it did have to do with my stating Victron's may not include their own current usage (if you actually read the review, you will find it took some technical skill to find the condition, which a technical source did verify, and still I mentioned this needs to be verified to make sure it's true, and how to do it).
3) The very first step per Victron user manual is to manually enter the battery capacity.

Anyway, out and best, now into the garage to find out where to put my battery monitor in the a-frame .
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Old 11-11-2018, 01:57 PM   #6
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People also tend to not read or understand fully before responding.
1) My comment for Victron meters was in general, which can use up to 15ma if the battery gets below the 50% capacity remaining guesstimate. If a user forgets to unhook the battery for storage, can definitely lead to trouble.
2) I agree don't trust Amazon reviews. Still in this case, the review in question had nothing to do with setting SOC, it did have to do with my stating Victron's may not include their own current usage (if you actually read the review, you will find it took some technical skill to find the condition, which a technical source did verify, and still I mentioned this needs to be verified to make sure it's true, and how to do it).
3) The very first step per Victron user manual is to manually enter the battery capacity.

Anyway, out and best, now into the garage to find out where to put my battery monitor in the a-frame .
If you have the 712 monitor(I wouldn't buy any other model) you will find on their spec sheet that the draw is 1mA....not 10mA.


https://www.victronenergy.com/upload...2-Smart-EN.pdf


Yes you have to enter the battery capacity yourself which may or may not be an exact perfect number.
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Old 11-11-2018, 03:02 PM   #7
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Ok so I have a question for all those smarter than I. You have your trailer winterized the battery( s) are left in the RV the solar panels are still functioning and the solar charge controller is maintaining the battery! The battery disconnect switch is engaged to isolate the batteries from the RV. The battery are fully charged controller reads %100. This is no draw or very minimal draw on the battery, nor will there be.
Now lead acid battery (s) self discharge at approximately %5 per month. Your batteries capacity is 220 amp/ hour. The controller sees %100 there is no current flow through the shunt? After a couple of months 220 x %5 x 2 months = 22 amp/ hours is lost from the battery, how would this be replaced?
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Old 11-11-2018, 03:10 PM   #8
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Ok so I have a question for all those smarter than I. You have your trailer winterized the battery( s) are left in the RV the solar panels are still functioning and the solar charge controller is maintaining the battery! The battery disconnect switch is engaged to isolate the batteries from the RV. The battery are fully charged controller reads %100. This is no draw or very minimal draw on the battery, nor will there be.
Now lead acid battery (s) self discharge at approximately %5 per month. Your batteries capacity is 220 amp/ hour. The controller sees %100 there is no current flow through the shunt? After a couple of months 220 x %5 x 2 months = 22 amp/ hours is lost from the battery, how would this be replaced?
Pretty sure I'm not smarter than you, but put the shunt in front of the switch, directly on the battery post. The bluetooth connects to the shunt. The wire on the left goes to the battery post. The one on the right goes to the cutoff switch. The switch goes to the camper.

To the OP. You really need to specify what kind of monitor you want/have.
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Old 11-11-2018, 06:17 PM   #9
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Ok so I have a question for all those smarter than I. You have your trailer winterized the battery( s) are left in the RV the solar panels are still functioning and the solar charge controller is maintaining the battery! The battery disconnect switch is engaged to isolate the batteries from the RV. The battery are fully charged controller reads %100. This is no draw or very minimal draw on the battery, nor will there be.
Now lead acid battery (s) self discharge at approximately %5 per month. Your batteries capacity is 220 amp/ hour. The controller sees %100 there is no current flow through the shunt? After a couple of months 220 x %5 x 2 months = 22 amp/ hours is lost from the battery, how would this be replaced?
When you recharge. The monitor will not keep track of self discharge but will be accurate again once you complete a full charge.
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Old 11-11-2018, 06:37 PM   #10
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When you recharge. The monitor will not keep track of self discharge but will be accurate again once you complete a full charge.
Doesn't the "tail current" setting on the BMV-712 provide for this "lost current"? When the tail current drops to a given level which should be the same as the normal self discharge current, the monitor just shows zero current and 100% charge. Or does it?

If that is the case then it would be essential that that tail current setting be accurate. Also, the rest of the settings such as Peukert, Charge Efficiency %, and last but not least, a good "Zero Current" calibration. When I do the latter I just disconnect the ground cable from the frame so Zero current flows but the shunt is still in the circuit and providing power to the monitor.

On the Solar side, I have a Victron Smart Solar Controller (MPPT) and it "networks" with the Monitor. Voltage and battery temp is fed to the solar controller and the rest of the battery parameters are handled by the Monitor.
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Old 11-11-2018, 06:47 PM   #11
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Doesn't the "tail current" setting on the BMV-712 provide for this "lost current"? When the tail current drops to a given level which should be the same as the normal self discharge current, the monitor just shows zero current and 100% charge. Or does it?

If that is the case then it would be essential that that tail current setting be accurate. Also, the rest of the settings such as Peukert, Charge Efficiency %, and last but not least, a good "Zero Current" calibration. When I do the latter I just disconnect the ground cable from the frame so Zero current flows but the shunt is still in the circuit and providing power to the monitor.

On the Solar side, I have a Victron Smart Solar Controller (MPPT) and it "networks" with the Monitor. Voltage and battery temp is fed to the solar controller and the rest of the battery parameters are handled by the Monitor.
No...it doesn't.

Tail current is only used to determine if your battery is fully charged.
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Old 11-11-2018, 06:56 PM   #12
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No...it doesn't.

Tail current is only used to determine if your battery is fully charged.
Wasn't sure.

I do notice that the Kwh discharged versus Kwh charged varies with the charged always running higher. Is this where the self discharge current is "tallied"?
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Old 11-11-2018, 07:16 PM   #13
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Wasn't sure.

I do notice that the Kwh discharged versus Kwh charged varies with the charged always running higher. Is this where the self discharge current is "tallied"?
Possibly. Some gets lost due to heat loss due to battery internal resistance as well

Also not positive how Peukerts constant is involved here.
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Old 11-11-2018, 07:54 PM   #14
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Geez folks. The OP was simply asking how to connect his cutoff switch.
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Old 11-11-2018, 08:38 PM   #15
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Geez folks. The OP was simply asking how to connect his cutoff switch.


Thank you OYO. Didnít think I was going to get such a debate.
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Old 11-11-2018, 10:03 PM   #16
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Thank you OYO. Didnít think I was going to get such a debate.
Sorry mtmurphy56 didnít mean for this thread to go that way! But to answer your initial question. In your first post you mention you are looking for a Bluetooth battery monitor. If you really want to monitor your battery accurately you will want a battery monitor that uses a shunt for measurement. I have the trimetric but itís a hard wired device. You will probably want the victron unit which is Bluetooth capable. What this type of monitor does is actually measure amp flow in and out of the battery, much like the fuel gauge in your car. It will convert the amps into watts used or replaced or simply tell you percentage of power consumed. I have ours set in percentage because it makes it easy for my wife to understand. When it gets to 50% I tell her itís time to stop using power or start the generator. This is provided the solar panels are not receiving much sunlight. Not sure model victron you want but someone here can help.

As far as connecting wires Iím sure the monitor will include a schematic diagram for the install. There should only be 4 wires to connect so quite easy. Two for power 1 positive and 1 negative. The other two, one on each side of the shunt.
I hope this helped. Good luck.
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Old 11-12-2018, 08:53 AM   #17
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Sorry mtmurphy56 didnít mean for this thread to go that way! But to answer your initial question. In your first post you mention you are looking for a Bluetooth battery monitor. If you really want to monitor your battery accurately you will want a battery monitor that uses a shunt for measurement. I have the trimetric but itís a hard wired device. You will probably want the victron unit which is Bluetooth capable. What this type of monitor does is actually measure amp flow in and out of the battery, much like the fuel gauge in your car. It will convert the amps into watts used or replaced or simply tell you percentage of power consumed. I have ours set in percentage because it makes it easy for my wife to understand. When it gets to 50% I tell her itís time to stop using power or start the generator. This is provided the solar panels are not receiving much sunlight. Not sure model victron you want but someone here can help.



As far as connecting wires Iím sure the monitor will include a schematic diagram for the install. There should only be 4 wires to connect so quite easy. Two for power 1 positive and 1 negative. The other two, one on each side of the shunt.

I hope this helped. Good luck.


Thanks so much.
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Old 11-12-2018, 09:18 AM   #18
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The picture in post #8 is a Victron 712. The picture below shows the connections in the battery box. The wire labeled 'battery' goes to the post labeled 'B' in the 1st picture. The switch is on the top left of the battery box. The wire on top of the switch is coming from the right hand terminal of the shunt in the 1st picture. The wire on bottom of the switch is going to the camper.

I chose to switch the negative (earth) side of the battery. Which one to use is a debated subject. It seems either way works.

Pretty much everything I know about this subject came from this thread: http://www.forestriverforums.com/for...ml#post1683637


Good luck.
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Old 11-12-2018, 03:16 PM   #19
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I got a couple of inquiries about my battery box. It came from Batteries Plus. If you order anything online and pick up in store you get a 10% discount, even if it's in stock. Unless they've changed.

The box is nice. Plenty of room for cables, lid is secure and easy to remove.
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Old 11-12-2018, 03:28 PM   #20
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I chose to switch the negative (earth) side of the battery. Which one to use is a debated subject. It seems either way works.
Regardless of which, an open circuit is an open circuit.

If you have the Victron BMV-712 (as do I also) putting the shutoff for the batteries in the negative cable (between shunt and frame) makes it a piece of cake to perform a "Zero Current Calibration". Off with the switch, key the process on either monitor or smart phone, and when finished reconnect the switch.

Don't know how often that step is required but since it, and 100% charge sync, are both on the app with their own "buttons" apparently the manufacturer thinks it's needed enough that they provided an easy method to do it. With the switch it's a lot easier than disconnecting the ground cable from the frame (if you take it off at the battery it won't work as the shunt is now disconnected and monitor goes dead).
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