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camperclark avatar image
camperclark asked

Time to go not changing

I just installed a BVM 712. I set the battery capacity and everything appears to be working but the time to go does not change. i ran every light and the fridge for over 12 hours last night and this morning the time to go is at 240 H which is the same as it was last night prior to running these things. The battery charge percentage came down from 100% to 93% so it seems to me that the time to go should have changed as well. What am I missing?

Venus GX - VGX
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@Camperclark

Can you take a screenpic or list your settings so we can take a look?

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9 Answers
Alexandra avatar image
Alexandra answered ·

@Camperclark


It may have been that the system was already charging up again from solar, but not enough to counter the load so the discharge time to go would be increased calculated at the battery draw at that point.

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camperclark avatar image
camperclark answered ·

2c6c0f79-d8f2-4d79-bba8-1ea2ba4d80ea.jpeg93fec35b-fe8e-4f8e-803e-0d0f80a58fe2.jpegd9ce299b-7d2a-4c33-a5ab-e941460b3384.jpeg14beffea-9556-4a5c-8653-d020f600dc58.jpeg694af083-2a4f-4de1-bc36-6272fb3a8270.jpega10e5cb4-36cc-424d-b316-d7fa94d57e91.jpeg

The part that puzzles me is that I start with 240 H (Which I assume is the time to go number) even after running 3 fans and every light for 5 or 6 hours without any charge going in, the voltage drops and battery charge percentage drops but the 240 H number does not change. I feel that I must be missing something.


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Use the VictronConnect app make some screenshots of your settings.
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rmaddy avatar image
rmaddy answered ·

240 hours (10 days) is the max that the BMV will show even if your batteries will last longer than that. Once the combination of current draw and battery capacity drops below 240 actual hours remaining then you will see the value begin to go down.

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But if I am using 64 amp hours and have a total of 2000 amp hours available between both batteries shouldn’t the time to go reading come down after 5 or 6 hours of this load? It still remains at 240. 64 into 2000 is 31.25 amp hours not 240.0.
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How are you measuring the 64Ah? And over what time period? There is a unit mismatch here. 2000Ah / 64Ah is just 31.25, not 31.25Ah. If you have a constant 64A draw then yes, the 2000Ah would last only 31.25 hours. But in one of the pictures you posted you are pulling 4.89A. If you have a steady 4.89A draw then the 2000Ah battery will last 409 hours.

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Thank you for the clarification. I appreciate the help.
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camperclark avatar image
camperclark answered ·

Thank you

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camperclark avatar image
camperclark answered ·

We went on a 7 night camping trip with no hook ups. The bottom line is that my new batteries worked flawlessly and we never ran out of power. My question is I started with 100% charge, 13.2 volts and 240 hours to go. I ended with 97.2% charge, 12.1 volts and still 240 hours to go. Does the hours to go calculate how many hours until I have 0% charge and 0 voltage? If so can this be changed? Since from zero to about 11.5 volts is really unusable power can a setting be changed that shows me let’s say 11.8 volts as the lowest i would want to go which would still run my fridge etc.?

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JohnC avatar image
JohnC answered ·

Hi @Camperclark

The Time to Go is determined to the set Discharge Floor. It's a % of max SOC. You really need the manual.. https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE.pdf

I'm intrigued over your 2 batts totalling 2000Ah. They must be massive. Are you sure of this? If they were 200Ah then your observations would make more sense..

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camperclark avatar image
camperclark answered ·

Thank you. Boy, now I feel stupid. You are correct in that they are 100 amp hours each hooked in parallel. This makes perfect sense. I don’t know where I came up with the 1000 amp hours each. I will reset the battery monitor and then run some tests at home. Thank you for your help.

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garyartista avatar image
garyartista answered ·

The manual should state that the maximum time to go is 240. I have been puzzled by this reading.

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Kevin Windrem avatar image
Kevin Windrem answered ·

Time to go is calculated from the remaining battery charge (in amp-hours) and the current value of the discharge current averaged over the preset time period. The discharge floor is factored in: if the SOC is 60% and the discharge floor is 40% then the usable available SOC is 20%. Multiply that by the battery bank AH setting. So for a 200 AH bank, you have 40 AH remaining. Then if the current average draw is 5 amps, then you have 8 hours remaining.

With the battery bank set to 2000 AH and the discharge floor is set to 0%, then a constant current of 8 amps or less would register 240 hours which may explain why you were not seeing a drop.

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