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Old 10-06-2016, 02:16 PM   #1
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Victron Energy BMV-702 Battery Monitor

Anybody using the BMV-702 and what settings are you using?

I recently had two 100 GoPower flex panes installed on my 19' International. I used the GoPower solar controller. I may swap out the GoPower solar controller for a Victron Energy Solar controller in the future. I really like being able to use an app while outside the AS or while in my TV to check my readings. I use an iPad as my dedicated backup camera and battery monitor.

I added a Victron Energy BMV-702 battery monitor with shunt and bluetooth dongle. I couldn't be happier with the results. In the last 3 weeks of having solar and the BMV-702, I have come to realize that simply measuring the voltage of the battery can be off as much as 20%. Depending on the load (high amp draw vs low amp draw) seems to greatly affect the available amp hours. I am attaching a photo of the GoPower controller reading my batteries are at 75% charged based on voltage whereas my iPad with Victron Energy app shows my battery at 95% charged based on amp usage.

I have two 6V batteries ran in series. My battery capacity is 225 Ah

My question is; what charge voltage should be used? Victron Energy recommends 13.2V. There is an engineer on YouTube who recommends lowering the voltage by .2V below the float voltage. Does this mean I should set the charge voltage to 13.0V?

He also recommended changing the tail current to 3% and increasing the time to 10 minutes. Does anybody else agree with this or have other input?
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Old 10-06-2016, 09:49 PM   #2
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The BMV-702 will sync the SOC (State Of Charge) over time so it will learn what 100% is, you can also set the SOC manually.

If the BMV-702 isn't showing the correct SOC it might be that your actual battery capacity is lower than their rating because they are old. The only accurate way to know your batteries capacity is to do a 20hr load test, but that's a lot of work.

Also the Peukerts and Charge Effeciency Factor values in the monitor settings should match your battery, the correct value should be available from the battery manufacturer.
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Old 10-07-2016, 01:50 AM   #3
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Quote:
Originally Posted by Mgieselman View Post
The BMV-702 will sync the SOC (State Of Charge) over time so it will learn what 100% is, you can also set the SOC manually.

If the BMV-702 isn't showing the correct SOC it might be that your actual battery capacity is lower than their rating because they are old. The only accurate way to know your batteries capacity is to do a 20hr load test, but that's a lot of work.

Also the Peukerts and Charge Effeciency Factor values in the monitor settings should match your battery, the correct value should be available from the battery manufacturer.
I set the SOC manually when the batteries were fully charged. The BMV-702 is incredibly accurate. I was just mentioning how inaccurate the GoPower charge controller is. In the photo the GoPower display was reading 75% full, based on the voltage reading which coincided with the See Level display. After removing the load by turning off the lights/fans/pump/radio/heater the voltage began to rise. I really like how the BMV-702 actually measures Ah used and stored.

I just wanted to make sure my settings were all correct.
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Old 10-14-2016, 05:00 PM   #4
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I am finding the BMV 702 a total waste of money. When disconnected from shore power after 3 days it still reads 100 battery charge at 12.3 Volts.

Either it is faulty or ??. Might as well use the built in meter in the trailer.
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Old 10-14-2016, 11:51 PM   #5
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I am finding the BMV 702 a total waste of money. When disconnected from shore power after 3 days it still reads 100 battery charge at 12.3 Volts.

Either it is faulty or ??. Might as well use the built in meter in the trailer.
That seems very odd. Is it reading 12.3 volts under a heavy load? How many Ah are consumed? Is it reading 100% after no usage or after boonidocking?

Has it ever worked properly? Can you take it back to the place you had it installed?

Sorry for so many questions but I'm sure there is a reasonable explanation for why it's not reading correctly. Our friends also have the same BMV702 and find it incredibly accurate too.

I'm sure this forum's collective minds can help resolve this dilemma.

Jon
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Old 10-15-2016, 09:49 AM   #6
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Thanks Tin

I have not had a chance to use the meter as it was intended ie, consumed amp hrs etc. The reading of 12.3V was after sitting with no use. Did not check amp hrs consumed.

I had returned from camping with full utilities and then left the trailer unhooked from shore power for three days. The only item drawing power would be the detector.

I assumed the battery would show something other than 100%.

I have a PD4655 charger and after leaving it back on shore power over night it is back to charging in normal mode of 13.6 volts.

I will let it charge till it reaches its 13.2 storage mode then I will disconnect shore power and turn on some lights for a few hours and see what happens.

If you or others have any other suggestions they are welcomed.

Dave
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