question

miya avatar image
miya asked

Lithium - Repeated Absorption

Hi All

Is it bad for Lithium batteries to be going in to bulk / absorption daily - when they probably don't need to ?

Situation is....

  • yacht in marina
  • connected shore power
  • the Multiplus has the batteries in float
  • small 12v loads are being covered by the Multiplus
  • Sun rises everyday - and the MPPTs go to Bulk, then Absorption
  • The multi reduces the Amps as the MPPTs start to provide
  • the result in the batteries are full
  • and the MPPTs are going in to Bulk, then Absorption, every day

Thanks

Tim

battery chargingLithium Battery
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2 Answers
seb71 avatar image
seb71 answered ·

As a precautionary measure, you could set all chargers to some lower voltages.


Such as: absorption 3.40V ... 3.45V (LiFePO4 cell voltages).


Float voltage should be about 3.35V even now.

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miya avatar image miya commented ·

Arhh.... I see... good idea.

Do you know if it is bad for the MPPTs to going in to bulk / absorption every day ?

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seb71 avatar image seb71 miya commented ·

Well, worse than if you keep them in their box, unopened. :)


Should be fine, assuming they were sized properly.

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miya avatar image miya seb71 commented ·

:-) like it.... Thanks Seb71.

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rslifkin avatar image
rslifkin answered ·

I've got AGMs, not lithium, but with my MPPTs set to end absorb based on tail current, it doesn't seem to be an issue. It's usually no more than 5 minutes from the point where the MPPTs are making enough power to push the voltage up to the point where they hit absorb voltage, sense the low current and immediately drop to float, allowing the voltage to fall back to float voltage. So the batteries aren't getting held at higher voltage for very long every morning.

That said, it would be nice if DVCC had a way to send the MPPTs right to float if SOC = 100% and the multiplus is on shore power and currently in float.

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