question

ashdash avatar image
ashdash asked

Smart BMS CL 12/100 shows 7% charging when battery is disconnected. [SOLVED]

With 125A fuse fitted and correctly set in Bluetooth app settings, unit limits alternator charging current to about 70A as reported by Smart BMV-712 and confirmed by clamp meter. App indicates charging is 100% at this current. With 125A fuse link fitted and entered into settings, unit should be able to charge at 100A.

With the Victron Smart 160aH disconnected completely and just the fuse link in place 7% (seven percent) charging is indicated in app. Does the CL 12/100 have a fault to be indicating charging current when there is none and limiting charging current to 70A? Or is there a zero amp calibration or factory reset required? Latest firmware loaded.

BMS
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ashdash avatar image ashdash commented ·
[SOLVED]

Feel free to roll around on the floor laughing if you choose. I solved the problem of the lower than expected charge current as follows:


I buffed and thoroughly cleaned with alcohol the tabs of the fuse links, studs on the BMS and cable lugs. After that I got the charging current I had been expecting with both 100A and 125A fuse links.

I had changed fuse links (new units) several times, updating the fuse capacity within settings of the Bluetooth app. I had tightened the connections. They definitely were not loose. And every time the current was less than expected.

So the knowledge I would like to pass onto others is that the cleanliness and integrity of the connections to the fuse link for this type of BMS, that uses the fuse link as a current sensing shunt, are paramount. Even a few millivolts dropped at either connection will make the BMS current limit prematurely.

There is still an offset in the current percentage reported in the Bluetooth app. I don't know if this is the app or BMS. On this unit zero charge current is reported as 6 or 7% and current increases above 100%.

Best regards.
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3 Answers
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Mike Dorsett answered ·

Hi, You shouln't disconnect the battery when solar input is present. If you want to check the zero current on charging, please disconnect the PV+ input. The &% may be self consumption of the MPPT.

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Mike Dorsett avatar image Mike Dorsett commented ·
typo : &% should read 7%!!
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ashdash avatar image
ashdash answered ·

No solar or MPPT charging involved. Alternator connected to cranking battery and input of CL 12/100. Output of CL 12/100 connected to Victron 160Ah smart lithium. This is the same as the simplest example in the CL 12/100 manual.


With 125A fuse fitted, CL 12/100 should be able to charge at 100A, but is only achieving 70A. Bluetooth app indicates that at 70A this is 100%. Looks like unit is measuring voltage across the fuse link incorrectly (too high) and is therefore limiting current and would explain why with battery disconnected, and no possibility of current, that it still indicates seven percent charging.

But it also has the feel that maybe something needs resetting or zeroing if such a thing is possible.

Seven percent must be some language issue because it reads correctly at my end.

Thanks for the interest.

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ashdash answered ·

[SOLVED] See comments appended to original post.

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