SmartLithium 330Ah deep-discharge recovery: is 0.5C essential

DIY
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1

Unfortunately through a series of failures I’m trying to recover severely discharged SmartLithium 330Ah batteries on my boat, one battery at a time.

Equipment:

  • SmartLithium 330Ah, 12V system
  • Victron PMP122200102 MultiPlus 12/2000/80-50 120V VE.Bus, UL 458 (80A charger; current/non-Compact model)
  • VE.Bus BMS V2
  • Cerbo GX
  • Balmar XT170 (170 Amp) alternator with MC-618 external regulator

The batteries were drained for a few days and read 2.5V at the terminals. I know, very bad.

I’m using the recovery procedure here:

  1. DONE Initial 0.1A recovery until the lowest cell reaches 2.5V. This took about a day.
  2. CURRENTLY: MultiPlus fixed charging at 13.8V and 0.1C (33A for one 330Ah battery).
  3. NEXT: Once terminal voltage reaches 13.8V, increase to 14.2V and 0.5C (165A), followed by the six-hour charge/balance check and prescribed rest checks.

My PMP122200102 MultiPlus can supply only 80A/0.24C. My only other charging source is the Balmar. I would prefer to keep this recovery as simple and controlled as possible rather than add a running engine unless it is genuinely necessary.

Questions:

  1. Is 0.5C a necessary recovery condition, or a recommended current limit/target? Is 14.2V with an 80A current limit acceptable for this stage, allowing current to taper normally?
  2. If additional current is necessary, is simultaneous charging with the MultiPlus and BMS-controlled Balmar acceptable for the later stage? My understanding of the MC-618 programming is I can try and get close at a constant RPM but not guaranteed.

Thanks all - appreciate any tips and good luck I can get here

2

You don’t need to increase the current, you can continue with 0.1C until 100%.
IMO it’s better to charge slowly.