Where This Guide Comes From
Every step in this article comes from one source video — Will Prowse’s build log Quickly Balance and Build a 48V LiFePO4 Battery w/ Cells from Different Suppliers, which has been watched more than 127,000 times. In it, he takes 280 Ah LiFePO4 prismatic cells from four different suppliers — Current Connected, Docan Power and EEL Battery — and assembles them into one 16S (51.2V nominal) battery bank. Because the cells arrived at different states of charge, his first job is a fast top balance done in 4S groups, then a snake-configuration pack with a single JBD 150A BMS. If you would rather watch the build before reading the breakdown, the video is right here:
Why Different Suppliers Means Different States of Charge
When you buy cells from a single supplier, they usually sit at a similar state of charge because they came off the same production and testing line at roughly the same time. Mix cells from two or three different suppliers and that assumption disappears. In the video, the 280 Ah cells on the table came from Current Connected, Docan Power and EEL Battery; some of the packs had been through capacity tests, others had never been touched. Their resting voltages were all over the place, which is exactly the condition where a top balance earns its keep.
The risk is not cosmetic. If you wire mismatched cells into series and let the BMS do its best, the pack is only ever as strong as its weakest cell. One cell that starts low will hit its low-voltage cutoff early on discharge and its high-voltage cutoff early on charge, throttling the whole battery and shortening that cell’s life. Charging every cell group to 100% before assembly is the way to remove that variable before it becomes a problem.
When a Top Balance Is Actually Required
Will is unusually blunt about this: for brand-new cells from a trusted supplier, a top balance is “completely pointless”. New cells track each other closely, and if the finished pack pulls full capacity, you simply leave it alone. His advice is to build, connect, then do a capacity test — if the pack delivers what the cells are rated for, no balancing gymnastics were needed.
The exceptions are where the top balance becomes mandatory. Grade B cells should be top-balanced no matter what, because their internal resistance and capacity spread is large enough that they will drift badly under load. And when you mix suppliers, as in this build, you have no shared history to lean on, so balancing is the safe default even if the cells look pristine. If you are unsure which category your cells fall into, balance them — it costs a few hours of charging and removes the largest unknown in a DIY battery.
The Fast 4S Group Charging Method
A full 16S pack is 51.2V nominal, and charging it to 100% as one unit needs a 48V charger with real output. Will’s shortcut is to treat the pack as four independent 4S groups first: each group of four cells gets a 4S (12V) BMS, is charged all the way up with a high-amperage 12V charger, then the BMS moves to the next group. Because 12V chargers with serious current are cheap and everywhere, this is dramatically faster than waiting on a small bench power supply.
In the video, the charging rig uses a JBD 150A BMS wired so that two chargers can feed one pack at once — charger one at 72 amps, then charger two for another 72 amps, for about 144 amps total into the battery. A 16S pack of 280 Ah cells charged at that rate reaches full in roughly two hours. The B- terminal connects to the battery negative and to the chargers or loads, and the balance leads ride on top.
The Snake Configuration and 16S BMS
Once every 4S group is topped off, the pack is laid out in a snake (S-shaped) configuration instead of the more common rows. The cells do not touch each other, the balance wires are easy to organize, and the layout has worked so well in Will’s shop that friends have started copying it. Instead of two separate 8S BMS units, the build uses a single 16S BMS that supervises the whole series string.
A note from the build that matters for anyone replicating it: the JBD 150A BMS survived having its balance leads on cell one and cell three accidentally switched during setup. Most BMS units — and especially active balancers — would be destroyed by that mistake. It is not an excuse to be careless, but it is a useful data point on how much fault tolerance the JBD units have.
Bus Bars for Cells with Different Terminal Placement
The build hits a real-world snag that every mixed-cell builder will meet: the EVE cells from Current Connected have their terminals closer together than the other suppliers’ cells. The stock bus bars did not reach. Rather than fabricating custom bars, Will simply bolts two bus bars together end to end for those positions — a quick, mechanical fix that works without fuss.
This is also where the snake layout earns its keep. The case of a LiFePO4 prismatic cell is bonded to one of its terminals, so a full chain of cells has a theoretical short path from the first cell’s case to the last cell’s case. With cells in the snake layout, that short path cannot happen — there is no case-to-case contact to begin with — and the cells can expand and contract freely without stressing the terminal-to-case bond. Some builders add foam or fiberboard between cells in row layouts for the same reason; the snake arrangement makes it unnecessary.
Mounting the BMS for Heat Dissipation
The BMS in the finished pack is mounted standing off from everything, touching nothing, with open air around it. Will copied the design from an earlier Grade B pack: it is ugly, but it dissipates heat without issue and keeps the balance board away from any conductive surface. If something were to overheat, the first failure would be wire insulation or the board itself, not the cells — an acceptable order of failure for a DIY system.
The whole bank also sits behind its own circuit breaker, isolating it from the rest of the system. A pack-level breaker is a cheap component that turns a catastrophic short into a tripped handle, and it is one of the few non-negotiable parts in a battery this size.
Capacity Test: The Only Proof That Matters
With the new pack added, Will’s shop system came to about 91.6 kWh across all connected batteries — enough to charge a Tesla Model S Plaid from 10% to 100% in one cycle, run GPU miners, or power air conditioning through a hot summer. But the number only matters if it is real, so the final step is a capacity test: charge to 100%, change the settings on the Victron shunt, and run one complete discharge cycle to zero. Only then do you know the new pack is actually pulling its rated capacity.
Build Sequence You Can Copy
Pulling the video together into a repeatable order:
- Sort cells by supplier and note their resting voltages; keep each 4S group to cells from the same source where possible.
- Connect a 4S BMS to each group and charge to 100% with a 12V charger. Repeat for all four groups.
- Lay out the pack in a snake configuration with the terminals facing the bus-bar plane; verify no cell-to-cell case contact.
- Fit the 16S BMS and double-check every balance lead against the measured cell voltage before applying power.
- Assemble bus bars; where terminal spacing differs, join two bars rather than forcing a single one.
- Mount the BMS clear of everything, add the pack-level breaker, then charge the finished pack.
- Run a full capacity cycle through a calibrated shunt and record the result.
That sequence works for a 16S bank, a 12V drop-in, or any mixed-cell project in between. The philosophy is the same at any scale: remove the unknown of mismatched state of charge before assembly, protect with a real BMS, and verify with a capacity test. Those three habits are exactly what we bake into every custom LiFePO4 pack we ship, and the same principles show up throughout our buying guides.
When DIY Beats Buying — and When It Does Not
The appeal of this build is obvious: assembling cells yourself lets you choose the exact capacity, footprint and BMS, and it is frequently cheaper than a prebuilt 48V server-rack battery. It is also genuinely easy — as Will puts it, you buy good cells, slap a BMS on, keep anything combustible away, and you are done.
But DIY is not the right answer for everyone. It requires time, confidence with high-current wiring, and the willingness to own the risk. A manufactured pack arrives with matched cells, a tested BMS, an enclosure and a warranty. If your project timeline or skill set does not comfortably include top balancing and bus-bar assembly, the smarter move is a factory-built battery at your voltage and capacity — which is exactly what we build at Dajiu Energy when customers need a specific pack without doing the assembly themselves.
And if you are not hunting for a consumer brand but need the battery itself — a custom LiFePO4 pack at a specific voltage and capacity, an OEM or ODM project, or wholesale supply for your own power station line — that is what we do. Dajiu Energy is a Chinese manufacturer building LiFePO4 batteries for RVs, homes, golf carts and portable applications since 2017. Our product range covers LiFePO4 drop-in replacement batteries, EV and golf cart batteries, wall-mounted home storage, portable power stations, commercial energy storage and battery swap cabinets — explore the full lineup in our product center, or browse more buying guides. Tell us your voltage, capacity and size, and we’ll engineer the pack to hit it.
What Viewers Are Asking (Top Comments on the Video)
These are the most useful of the video’s top comments, with our practical answers. Where the creator replied, we quote his response; where he did not, we give our own answer written the way we would answer a customer on the shop floor. Thanks-only comments were left out on purpose; these are the ones with actual information in them.
Source video: DIY Solar Power with Will Prowse — "Quickly Balance and Build a 48V LiFePO4 Battery w/ Cells from Different Suppliers" (youtube.com/watch?v=vSYoai8BhIE). Comment excerpts are quoted verbatim from the video’s top comments; creator replies are marked as Will’s reply. Build figures are transcribed from the video’s measurements.