Repack cells from Eco Worthy 12V battery to 48V box

Been down this rabbit hole myself. Worth flagging a few things before you crack those cases open.

First — the cells inside Eco Worthy packs are notoriously inconsistent. Capacities vary batch to batch and even cell to cell within the same pack. If you're repacking into a 48V configuration you really want matched cells, otherwise your BMS is going to have a nightmare balancing them and you'll lose usable capacity.

Second, what BMS are you planning to use? Going from 12V to 48V means you're looking at 16S if they're LiFePO4 cells (which they should be). A half-decent 16S BMS isn't cheap — by the time you've bought one worth trusting, you might want to revisit whether this project actually saves you money vs just buying a proper 48V Fogstar Drift or similar.

That said, I've done similar repacks on my boat — pulled cells from a couple of knackered packs and reconfigured them. Key things I'd check:

• Individual cell voltage before assembly
• Internal resistance — anything wildly out of spec, bin it
• Physical condition — swelling is an immediate no

What capacity are you actually aiming for with the 48V pack? And how many Eco Worthy batteries are you starting with? The maths might work out fine, just want to make sure you're not building a headache for yourself.

Anyone else here done Eco Worthy cell repacks? Curious whether the quality has improved on their newer batches.

@HollyBaker raises a solid point about the cell inconsistency — I'd add that before you even think about repacking, do a proper capacity test on each individual cell once you've got them out. A cheap capacity tester off Amazon will save you a world of grief later.

The other thing worth mentioning is that if you're jumping from 12V to a 48V configuration, your cell count needs careful thought. Assuming the standard 3.2V LiFePO4 cells, you're looking at 16S for a nominal 48V pack. Getting that many matched cells from a handful of budget 12V batteries is optimistic at best.

Honestly, buying quality Grade A cells separately and starting fresh might work out cheaper once you factor in your time.

Tried something similar a couple of years back. Ended up with a 48V pack that had the energy density of a disappointed sigh and the consistency of British weather.

Genuine practical point though — if you're paralleling cells from different batches before series-ing them up, capacity matching matters a lot more than voltage matching at rest. Your BMS will thank you

@HollyBaker is right but honestly the bigger headache is finding a BMS that'll actually talk to those cells properly once you've repacked them. I've got a Fogstar Drift 48V in the motorhome and the difference in cell matching quality vs budget repacks is night and day.

If you're dead set on doing it — at minimum get a proper cell tester before you even start pulling anything apart. Mixing cells with even slightly different internal resistance will make your BMS work overtime and you'll get early cutoffs constantly.

Blunt truth: by the time you buy a halfway decent 48V BMS, spend time testing and balancing, and factor in the risk of cooking the whole lot — just buy a proper 48V pack from the start.

Great thread. One thing nobody's mentioned yet — check your cell groups are physically compatible before you commit to a 48V enclosure. Eco Worthy packs often mix cylindrical formats internally, and I've seen people discover mid-build that their cells won't sit sensibly in a standard 16S arrangement without some creative (read: dodgy) bus bar work.

Also worth thinking about thermal management. Four 12V packs' worth of cells crammed into a single 48V box generates heat differently than the original configuration was designed for. @DownsCruiser's BMS point is well taken — make sure whatever BMS you choose has adequate temperature sensing inputs, not just voltage balancing. A decent 48V LiFePO4 BMS with NTC inputs doesn't cost a fortune from the usual suppliers. Don't skimp there.

Good points all round. One thing I'd add from my static caravan setup — if you're planning to use this for EV charging at any point, cell inconsistency becomes a much bigger problem than it might seem on paper.

A 48V pack built from mismatched cells will sag badly under the sustained draw that even a basic EVSE demands. I found this out the hard way before I switched to purpose-built Fogstar Drift cells.

A few practical questions worth answering before you proceed:

• What's your target capacity in kWh?
• Do you have a cell tester that can measure internal resistance, not just voltage?
• Which BMS are you considering — something like a Daly or JK with active balancing?

@DownsCruiser raises a valid concern about BMS compatibility. JK units tend to handle unknown cell chemistries more gracefully in my experience, worth investigating.