miya avatar image
miya asked

Smart BMS / Smart Lithium / MultiPlus II - Strange Spike in Charge Profile

Hi All

This may be nothing to worry about - but I have a strange spike in the charge profile - as just after Absorption - when the V is dropping down to Float. See graph -


The Amps jump us, only for a few minutes, to 11A, when they should be dropping to NIL, and the V on batteries increase to 13.35v for a short time.

There are no loads or charging sources attached. Nothing.

Anything to worry about why this happens ? It always happens on very charge.

Thoughts ?



Multiplus-IIBMSsmart lithium
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Trevor Bird avatar image Trevor Bird commented ·
Hello @Miya Interesting observation. You mention no charging sources?? Surely a charging source must be connected to have such a charge profile?? I wonder what the charger is?



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miya avatar image miya Trevor Bird commented ·
Hi Trevor

Well spotted... sorry... was typing this in a rush. It should have said "no other charging sources other than the MultiPlus II".

Thanks, Tim

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1 Answer
Stefanie avatar image
Stefanie answered ·


To me it looks like a load has been calling for power and the Multi is taking some time (it's really only seconds and looks more dramatic than it really is on the graph) to regulate the extra power (beyond what is needed for the charger). I've seen that on my system as well, but not on a regular basis e.g. on every full charge. Nothing to worry about.

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miya avatar image miya commented ·

Hi Stefanie

Yes - that would explain it to me too - if a load was on, switched off, the Amps would jump before the Multi could reduce Amps to compensate. The only load connected it the Cerbo & Touch (attached directly via AUX power to Lynx Smart BMS).

Very odd - this happens every charge cycle. With no loads attached.

I am probably worrying too much about the magic absorption value of 14.2v. If you say it's OK to go to 14.35v for a few minutes - I'll forget about this spike and stop worrying.

Thanks Stefanie.



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Stefanie avatar image Stefanie ♦♦ miya commented ·

Hi Tim,

There's definitely nothing wrong with worrying. I would also worry if something isn't the way it's supposed to be.

It should be 14.20V. But as I said before, regulation sometimes takes a little time.

One way to get to the bottom of the matter would be to download the log for the relevant period via VRM Advanced menu and take a closer look. The time intervals in the log are much shorter than those in the graph.

Another option is to monitor the cell voltages of the lithiums during the higher charge voltage to see if there are any significant readings above 3.55V for one or more cells.

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miya avatar image miya Stefanie ♦♦ commented ·
Wow !!! I have never looked at the detail download data before - that's amazing detail.

Its shows the V went up to 14.29v for 2 minutes - then dropped to 14.20v in next 5 minutes. Amazing detail :-) thanks ! So nothing to worry about.

I will check the cells next time I do a charge.

As always - great support and advice Stefanie.


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