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Old 15-06-2019, 16:17   #1
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Victron bmv 700-tally

On our victron bmv 700 the number of consumed Ah does not tally with the shown percentage of remaining battery capacity:
E.g it would show 23Ah consumed (230Ah bank) & 95% remaining capacity
The % is always higher than it should be according to the Ah consumed
Which value is correct?
Why donít they tally?
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Old 15-06-2019, 16:36   #2
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Re: Victron bmv 700-tally

Most likely because of Peukert factor. I've had a Link 2000 in for 15 years and never bothered with the small discrepancy, because it's not a discrepancy but rather a reality of battery performance.

AH out is a measure. The depth of discharge, i.e. 5A vs. 30A affects the remaining capacity. Higher the load eats more % of total for whatever time it is on.

At least that's my layman's language understanding of it.

Once you've lived with it and on board and regularly checking the numbers, and end up becoming intimately familiar with what you think they should be and confirm it only then by looking, it will become even less of an issue.

I even guess and write down what I think it will be when I arise the next morning.


Just talkin' operationally and management-wise, not evaluating the engineering.

Interestingly enough, just last week I made up a blank spreadsheet and wrote down time, V, A (instantaneous), AH, and what's on or not (fridge, phones, VHF, etc.). I didn't record the % 'cuz I never have used it since I zero in on V and AH. I do this periodically to check up on the condition of my house bank. I have 200 ah out of my 400 ah bank.

Good luck, I can't wait to hear the REAL reason! Great question, thanks.
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Old 15-06-2019, 16:43   #3
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Re: Victron bmv 700-tally

I Could understand if the percentage value were lower than the consumed Ah, but higher?
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Old 15-06-2019, 16:49   #4
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Re: Victron bmv 700-tally

Quote:
Originally Posted by double u View Post
I Could understand if the percentage value were lower than the consumed Ah, but higher?

Possible if the load is less than the 20 hour rate.
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Old 15-06-2019, 17:34   #5
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Re: Victron bmv 700-tally

Are you sure you've programmed it with an accurate Ah capacity?

You should also be reducing that as the bank ages.

https://marinehowto.com/programming-a-battery-monitor/
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Old 15-06-2019, 21:39   #6
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Re: Victron bmv 700-tally

There's also this, don't know if you've seen it:


For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Also read this one:

Programming a Battery Monitor (by Maine Sail)

https://marinehowto.com/programming-a-battery-monitor/
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Old 15-06-2019, 22:51   #7
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Re: Victron bmv 700-tally

Your 230ah bank is only 230ah at a 20h rate. ((11.5a) At higher rates I.e. 10h rate it’s less the 230. And vrs versa.

If if says -23 and 95%. Yiu were probably only drawing say 2.3a for 10h.

If you draw 11,5a for 2 hours it will say 90%

Both would say -23ah. Both are different % of battery cap. Both are correct.
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Old 16-06-2019, 15:33   #8
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Re: Victron bmv 700-tally

Thx guys, that’s it! C20 is 230Ah, but at our much lower discharge rate it is more
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