Where This 24V LiFePO4 Build Guide Comes From
Every fact in this article comes from one source video — DIY Solar Power with Will Prowse’s Dirt Cheap 24V Preassembled LiFePO4 Battery: Beginner Friendly Tutorial!, which has been watched more than 226,000 times. In the video, Will takes a preassembled 8S LiFePO4 block — eight 100Ah cells already welded into a 2.5 kWh pack — and finishes it into a working 24V battery by adding a BMS, the way a first-time builder would. If you would rather watch the wiring before reading the breakdown, the video is right here:
What You Get: A 2.5 kWh Pack Without a BMS
The starting point is a pre-assembled lithium iron phosphate battery: eight cells in series, each rated at 100 ampere-hours, which gives you a 24-volt battery with 2.5 kilowatt-hours of energy. The main stages of assembly are already done — the cells are locked in place with holders and secured with a strap, and the busbars are welded to the terminals. What is missing is the BMS, the circuit board that manages the cells, and that is the part this video installs in a few minutes of wiring.
Will describes it as almost like an EG4 server battery cut in half — no BMS and, it seems, no warranty. There is a 5-year warranty on the pack, but the product page gives few details on what it covers, and the video is blunt about the trade-off: if you mess up this thing or use the wrong BMS, that is on you, and you most likely will not get a replacement if you break it. That is why the video recommends some beginners simply buy a server battery with a BMS already installed — the BMS you add yourself will not have all the cool features of a server-grade EG4. But it is cheap: two of these units cost around $1,000 for 5 kWh, and adding a $100 BMS gives you a lot of capacity for a very low price.
Tools and Parts You Need Before You Start
The video keeps the parts list short. You need an 8S BMS — the one shown has a Bluetooth module, and the balance harness is easy to connect to the cells. If you plan to run two of these blocks in series for a 48V system, you need a 16S BMS instead. You also need ring terminals for the BMS balance wires, ring terminals for the main connections, a wire stripper, a proper crimping tool, and a few screws — the pack does not come with screws for the busbars.
On the BMS itself, one side has two blue wires and the other has two black wires, marked B− and C−. The blue wires connect to the battery's main negative terminal; the black wires go to your inverter, solar controller, or charger. The BMS also carries a Bluetooth module and a connector that links to each individual cell to monitor voltage and manage the pack, plus two temperature sensors for protection against overheating. The last piece is the charger: a 24V charger, because this pack charges as a 24V battery.
Preparing the Balance Wires and Ring Terminals
Before anything connects to the cells, the ends of the BMS balancing cable wires need terminal lugs. The factory ends look terrible — bare conductor showing and badly cut — so the video cuts them off and re-makes them. A stripper removes the insulation, and the wire is stated to be 8 gauge, so the matching ring terminal is 8 AWG. Cheap sets of these terminals are available on Amazon, and they fit the terminal holes on the cells.
Then comes the crimping lesson, and this is the part beginners get wrong. Use a real crimping tool — not pliers. The tool is designed to make a secure mechanical connection, which is better than a soldered connection. Crimp, then check the joint is sturdy: if the wire pulls out, redo it. If you have heat shrink, slide it over the ring terminal. For the main BMS connections you add your own ring terminals too, matching the size of the hole you are connecting to.
Sizing the Screws and Main-Terminal Lugs
The pack's busbars have threaded holes and no screws included, so you have to source them. The video measured them at the hardware store: you need M5-0.8 screws. The smallest ones available were still too long — tightened fully they would hit the cell underneath and could damage it. The fix is a nut, or a stack of washers, to take up the extra thread. The rule the video emphasizes: the ring terminal must sit flush against the busbar, and the nut must not end up on the other side — it has to fully touch the busbar for a good connection.
For the main terminals, the red wire needs your own conductor added to power chargers and loads — typically a 2/4 gauge cable attached to the terminal. Some of the screws on the battery side are a different size (M6 in Will's case), and Signature Solar should arguably have included the mount, but you can find them at a hardware store. Do not over-tighten with washers stacked too high: if there is not enough thread, you can rip the terminals right off the cells.
Wiring the BMS: Where Each Balance Wire Goes
Before connecting anything, the video sends beginners to the Overkill website to study the wiring diagram, because getting the order wrong is how batteries smoke. The rule is simple once you see it: every balancing wire goes to the positive terminal of its cell — except the black one. The black wire connects to the main negative of the battery, which is the negative of the first cell. Then the next wire is the positive of the first cell, the next is the positive of the second cell, and so on up to the positive of the eighth and last cell.
Most people start with the first cell's negative connection, which is also where the BMS main wires land — all three of the B− connections share the main negative terminal, and the pack is labeled on the side. When you connect the balance wires to the cells, they should fit snugly and evenly against the terminal. It is a fiddly job — the balance cables are inconvenient and hard to keep neat — and the BMS mounting position decides how you measure and cut them. Will ties his with cable ties and leaves them long, since he reuses the BMS across batteries, but you can make them very neat if you want.
Mounting, First Power-Up and Charging to 100%
The BMS can be double-sided taped to the metal of the pack, as long as the battery contacts do not touch that metal, or mounted on a plastic box secured to the side. Most builders will put the whole pack in a plastic enclosure anyway. The two main outputs — main positive and main negative — come out to the terminals, and the BMS is activated by plugging in its connector last. In the video the indicator light comes on, and the pack reads 26V — comfortably above the 24V nominal voltage, which is exactly what a freshly assembled LiFePO4 pack should show.
Then the video connects a 24V charger, positive to positive and negative to negative, and the pack charges at 35 amps on the way to 100%. For solar or an inverter, the same main terminals feed the system. Will's honest note: the most difficult part of this build is creating a housing where you can attach the positive and negative terminals — special battery terminals for this exact job are available on Amazon, and they make the finish much cleaner.
Safety Warnings and Series Connections
The video closes the build with the warnings that matter. If you strip a thread in these cells, you will have to Heli-Coil it — drilling into a battery cell where there is electrolyte is genuinely dangerous, and it is the kind of mistake that ruins a pack. That is why the video's honest recommendation is that beginners should buy a ready-made battery, and only experienced builders should consider this route.
If you do run two of these blocks in series for a 48V bank, they must each be charged to full with their own 24V charger and BMS first, and only then connected in series — otherwise the two packs will not be balanced. For experienced users building a large system, these blocks are a great foundation: instead of many small BMSes and a pile of parallel wiring, a big pack built from these preassembled blocks with quality BMSes can be a very cheap, very powerful system.
Who Should Build This Pack — and Who Shouldn’t
The verdict from the video is a straight cost-benefit call. For a beginner, a ready-made 24V server-rack battery is the safer buy: the BMS is installed, tested, and carries features this DIY BMS lacks, and you do not risk damaging cells with a wiring mistake. For the experienced builder who wants capacity at a ridiculous price — 5 kWh for about $1,100 including the two BMSes — the preassembled block route is hard to beat, and the video shows it really is only minutes of wiring once the prep is done.
If you would rather skip the DIY entirely and order the battery as a finished product — a 24V or 48V LiFePO4 pack at your exact capacity, with a quality BMS, low-temperature protection and the right enclosure — 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 battery guides. Tell us your voltage, capacity and compartment size, and the pack is engineered to fit — BMS, terminals and all.
What Viewers Are Asking (Top Comments on the Video)
Where the creator replied, we quote his answer verbatim; where he didn’t, we give our own practical answer — the way we’d answer a customer on the shop floor. We kept only comments with real practical value and dropped the pure thank-you notes.
Source video: DIY Solar Power with Will Prowse — “Dirt Cheap 24V Preassembled LiFePO4 Battery: Beginner Friendly Tutorial!” (youtube.com/watch?v=AiEmhC8f9lo). Comment excerpts are quoted verbatim from the video’s top comments; creator replies are quoted where they exist, and unanswered threads carry Dajiu Energy’s own answers. 226K+ views. An 8S 100Ah block finished into a working 24V battery with a beginner-friendly BMS install.