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Old 03-25-2018, 07:21 AM   #1
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Question regarding Victron BMV-712

Hi,

Installed a Victron 712 battery monitor recently and am on my first trip with it. I am currently sitting at 86% according to the battery monitor but my voltage is only 12.36. Does that make sense? I would think the depletion % would be more. I am using the stock Interstate batteries and saw various amp-hour capacity ratings on one when I was setting up the system. Currently, Iím using 168 Ah for my setup.

Thanks,
Bill
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Old 03-25-2018, 07:39 AM   #2
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Your reading may be fairly close. 12.4 volts is about 80%.

When you programmed the BMV-712 what amp hour capacity did you use? Perhaps your older batteries don't hold their rated capacity any more. Temperature is also a factor, have you accounted for that?
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Old 03-25-2018, 10:20 AM   #3
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Your reading may be fairly close. 12.4 volts is about 80%.

When you programmed the BMV-712 what amp hour capacity did you use? Perhaps your older batteries don't hold their rated capacity any more. Temperature is also a factor, have you accounted for that?


Batteries are brand new....just replaced under warranty by Interstate. Iím using 168 Ah for the two batteries.
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Old 03-25-2018, 10:29 AM   #4
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What temperature is it outside?

Lower temperature causes a lower voltage reading even though there is higher capacity available.

Thatís the beauty of the bmv- if wired correctly it measures all loads and energy to/from the battery to provide an accurate guage of current capacity.
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Old 03-25-2018, 10:30 AM   #5
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In FL at the moment so temps were in the high 60ís when I looked this morning.
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Old 03-25-2018, 10:38 AM   #6
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Did you ensure that all negative side of the loads in the trailer are wired to the shunt? Inverter, propane detector, sub woofer, etc?
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Old 03-26-2018, 06:45 AM   #7
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Question regarding Victron BMV-712

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Originally Posted by wulfraat View Post
Did you ensure that all negative side of the loads in the trailer are wired to the shunt? Inverter, propane detector, sub woofer, etc?


I believe so! I basically spliced the two negative battery cables that go from the battery box to the trailer...one for the house system and one for the inverter. I also retired the Zamp connection to be on the load side of the shunt.
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Old 03-26-2018, 12:26 PM   #8
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How many Amp-hrs does the meter show consumed since that last discharge? Also, I think you may need to discharge and charge the batteries a few times for the Victron meter to calibrate.
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Old 03-26-2018, 01:42 PM   #9
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Have not set up a BMV yet, but is that 168Ah configured as total at full charge or available at full charge? That number makes sense for total, but with lead-acid batteries you can only use half that value.
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Old 03-27-2018, 12:01 PM   #10
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Have not set up a BMV yet, but is that 168Ah configured as total at full charge or available at full charge? That number makes sense for total, but with lead-acid batteries you can only use half that value.
I'm going by memory from when I set mine up last fall, there is a 2nd configuration element that corresponds to % of capacity that is available hidden in a configuration menu for a relay. By default, IIRC, it is ~50% as I couldn't figure out why it was so far off for my 100Ah lithium battery...and then realized that the relay % sets the consumption curves.
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Old 03-27-2018, 01:30 PM   #11
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The Victron BMV-712 manual says this:

"Battery capacity (preferably use the 20 hour capacity rating (C20))"

In other words, for a new battery, use the battery's rated amp-hour capacity. (For an older battery, the rule of thumb I've heard is to deduct 8-10% for every year of use.)
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Old 03-27-2018, 01:34 PM   #12
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Ok, so if I had a BMV712 right now, I'd set it for 200 AH, because I have a pair of Group 27 flooded lead-acid batteries. I imagine that somewhere I'd also tell it that I could only use 50% of that capacity. Cool.
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Old 03-27-2018, 06:56 PM   #13
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Have not set up a BMV yet, but is that 168Ah configured as total at full charge or available at full charge? That number makes sense for total, but with lead-acid batteries you can only use half that value.


Agree....168Ah is the total. When it gets to 50% it must be charged. I was just surprised that it was showing 80+% at 12.4 volts.
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Old 03-27-2018, 07:01 PM   #14
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I'm going by memory from when I set mine up last fall, there is a 2nd configuration element that corresponds to % of capacity that is available hidden in a configuration menu for a relay. By default, IIRC, it is ~50% as I couldn't figure out why it was so far off for my 100Ah lithium battery...and then realized that the relay % sets the consumption curves.


Iím not sure I understand this?? Why would the meter need to know that I can only use a % of the total capacity? If I am using wet cell batteries and they should be recharged by 50% capacity remaining, what difference does that make to the monitor?
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