SmartLithium absorption time: How much is too much?

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brendanmitchell asked Feb 19, '24

SmartLithium absorption time: How much is too much?

Hello all,

I am configuring a mobile power system based on two LFP 25.6V 100Ah batteries with a third party charger (MeanWell DBU-3200-48 if it matters). Because the system is mobile, the end-user will have the ability to power the charger on and off at will, meaning that a new charging curve could be started several times per day.

I've read that Victron "recommends a minimum absorption time of 2 hours per month for lightly cycled systems, such as backup or UPS applications and 4 to 8 hours per month for more heavily cycled (off-grid or ESS) systems. This allows the balancer enough time to properly balance the cells" (manual, chapter 5).

Currently, our charger is configured to provide 2 hours of absorption time after every bulk phase. My question is, can an excess of absorption time cause issues with the battery? If so, how much is too much? Should we be adding safeguards to ensure that the system doesn't go into its 2 hour absorption phase too often? (Again, in the current configuration this could be as often as several times a day).

Many thanks!

battery charging lifepo

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Answer 1 · 2024-02-19T17:47:57Z

Alexandra answered · Feb 19 at 05:47 PM

@BrendanMitchell

Interesting question with no definite answer since the answer depends on the battery (manufacturer recommendations) and the type of balance system it has in it. It is mostly there for cell balancing in lifepo4.

You can see repeat absorption interval on the inverter. Adaptive charging will also vary the length of time in absorption based on depth of discharge.

What Victron components do you have exactly?

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brendanmitchell commented · Feb 19 at 06:23 PM

Batteries: Victron SmartLithium 25.6V, 100Ah
Charger: MeanWell DBU-3200-48
BMS: VE.Bus BMS V2

We have other Victron stuff too (Cerbo S GX, MultiPlus II inverters, SmartShunt) but battery charging is handled entirely by the DBU-3200. The BMS can shut it down if it needs to.

But really, my question is only about the batteries. I can configure our charger to do what it needs to do, but I need to know if there is an upper limit on how much time batteries should be spending in absorption mode.

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