BMV-702 wont SYNC - LiFeYPO4

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question

sebastian-w asked Oct 28, '20

BMV-702 wont SYNC - LiFeYPO4

First - Sorry
I know it has been asked before, but I can’t seem to find a solution to the earlier posts from other users. So, therefore, I allowed myself to ask.

Setup: My battery is a DIY (Winston 200AHA) project, a 12V system. 8cells in total. Two parallel and series.

From the last cell, the negative terminal is connected to the shunt for the BMV-702 (on the battery side of the shunt), from the load side of the shunt there is a 100A copper bar connected with all the negative connections to loads.

So that must be correct.

Problem: The BMV-702 won’t do the regular automatic synchronization.

Settings of the BMV-702:
01. 400Ah
02. 13.90V (.30 under the absorptions as recommended)
03. 02.0%
04. 01

I know that 03 and 04 normally are 4% and 3 minutes, it didn’t work, so I tried to make them smaller.

Have tried to sync when the battery is fully charged manually, it hasn’t helped.

Here are some screenshots from the settings:

BMV Battery Monitor SOC error

skærmbillede-2020-10-28-kl-180536.png (783.1 KiB)

skærmbillede-2020-10-28-kl-180236.png (813.8 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2020-10-28T17:31:14Z

Justin Cook answered · Oct 28, 2020 at 05:31 PM

@Sebastian W., just to double-check: your post says 200Ah battery bank but your settings are 400Ah... if both of those are true at the same time, then that's why your SOC isn't calculating properly!

I'll also note, just as a general operational thing, that automatic synchronization happens at the top of a completed charge cycle, and for the BMV to register a charge cycle, the battery bank should be drawn down to ~65-75% SOC and then recharged. "Micro-cycles" won't register as charge cycles, and indeed this can cause SOC drift over time... but I don't think that's the condition you're reporting in this case. From what I can tell, it looks simply like you have it programmed for 2x your actual capacity.

Please confirm your battery bank capacity?

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sebastian-w commented · Oct 28, 2020 at 07:17 PM

I try to turn off the shore power tonight then I will post an update in the morning.

0 ·

marekp commented · Oct 28, 2020 at 09:24 PM

The capacity is OK.

There are 8 cells 200Ah each connected into 12V pack.

0 ·

Answer 2 · 2020-10-30T09:12:04Z

sebastian-w answered · Oct 30, 2020 at 09:12 AM

Update: after yesterdays discharge to 65%. It has now SYNC automatically and the count is now saying "1".
But why is "Total charge cycles" or "Number of full discharges" not up with "1"?

skærmbillede-2020-10-30-kl-100304.png

skærmbillede-2020-10-30-kl-100304.png (723.5 KiB)

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Answer 3 · 2020-11-01T13:33:29Z

sebastian-w answered · Nov 01, 2020 at 01:33 PM

After some years of trying, it now work 100% :D
skærmbillede-2020-11-01-kl-142103.png

skærmbillede-2020-11-01-kl-142103.png (798.2 KiB)

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