question

boekel avatar image
boekel asked

feature request - storage mode (battery life?) for Lithium batteries

As the world is slowly moving from Lead-Acid to Lithium batteries, it would be nice if some of the functions to improve battery life for Lead-acid's were to be available for Lithium battery users.

Lots of systems are not used full-time, like boats, off grid cabins, campervans, etc.
Where a LA battery is happy being fully charged, a Lithium battery lives longest around 50-60% SOC

If a function would be available to keep the SOC between a set range, this would help many systems to gain a longer life from the batteries.

For the systems I install, I've made a 'storage mode' switch on the BMS, where the BMS sends a lower 'charged' voltage to the system, this works very well, but it's not a function on other BMS's as far as I know, and it's not remotely settable (although I could use a relay output from the Venus)

For systems with DVCC enabled a setting in the Venus to keep battery SOC between a range in SOC would be a very helpful addition.

Lithium Battery
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4 Answers
ben avatar image
ben answered ·

Also, for this feature (which would be great), if the battery has its own BMS, managing to its estimate might be okay. But if the system is deriving SOC from a BMV, it may drift over time, and under a static/no load it would probably be best to be able to specify instead a holding (float) voltage ,rather than SOC.

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boekel avatar image boekel ♦ commented ·

Correct, my BMS also uses voltage to calculate SOC btw.

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benm avatar image benm boekel ♦ commented ·

Which BMS you mean, it is a custom made only for your own use or availible for sale.

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boekel avatar image boekel ♦ benm commented ·

Custom made for use with Second Life EV batteries

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geomz avatar image
geomz answered ·

I would very much second this and had been trying to derive a homebrew solution to do the same. What I came up with was to set a charge current assistant (on the Quattro/multi) triggered by a physical switch that I use to set charge Amps to 0. I then let the batteries discharge to 50% (using powerassist with a low input rate limit) and then flip the switch to set the Amps to 0.

Kinda klunky, but it works well enough when the rig is plugged into shore power and will be so for more than a couple of weeks.


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boekel avatar image boekel ♦ commented ·

smart!
you can also use this to give connected solar panels priority over shore power (and flip the switch if you want a full charge)

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geomz avatar image geomz boekel ♦ commented ·

I also use that to downspin my genset to idle, out in the field. I don't like just powering it off while it's still cranking out 3Kw (charging) :)

And I rarely let the batteries top above 90%.

It would be awesome if Victron could allow us more access to "Virtual" switches/triggers within CCCGX to simulate this functionality, but this works well enough for now.

I'd considered using the genstart script, but I'm saving that script for when I eventually get my lazy a## to doing auto genstart :)


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boekel avatar image boekel ♦ geomz commented ·

have a look here:

https://community.victronenergy.com/questions/549/feature-request-scheduled-virtual-switch-for-venus.html

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gs-nz avatar image
gs-nz answered ·

If you want this feature, then please log in, and then click on the green up arrow on top of this page to upvote this idea.

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nebulight avatar image
nebulight answered ·

I would also like to see this. I have a camper van that can sit for a month at a time. I'd like to keep things online and powered, but would also like to keep SOC at around 50% for long term health of the lifepo4 cells. Using DVCC would be a great idea as it's not plugged in, but keeping charged with the MPPT.

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