Lithium Batteries
We build lots of custom lithium battery options — everything from gate opener packs to multi-pack Powerwalls for homes. New and used, off-the-shelf and custom.
LFP / LiFePO4: 3.2V/cell nominal — safer, longer life, preferred for off-grid
Li-ion: 3.7V/cell nominal — more energy-dense, used in EV modules
Remember: Energy storage is measured in kWh (kilowatt-hours).
To find the kWh capacity of a battery, multiply the nominal voltage by its amp hour (Ah) capacity.
Lead acid (12V): 12V × 100Ah = 1,200Wh = 1.2 kWh
Lithium (12.8V): 12.8V × 100Ah = 1,280Wh = 1.28 kWh
What Makes a Good Lithium Battery?
Not every pack on the market is built the same. Here's what we look for — and build to — before it goes on our shelf.
Cell Quality
Grade-A LiFePO4 cells with matched capacity and internal resistance across the pack — not mismatched reclaimed cells.
BMS Quality
A real battery management system with genuine over-charge, over-discharge, and short-circuit protection — not a bargain-bin board.
Mechanical Connection to the BMS
Properly gauged, torqued busbars between cells and BMS. Undersized wiring or weak crimps are where cheap packs fail first.
Cell Balancing
Active or passive balancing keeps every cell at the same voltage over hundreds of cycles, so the pack ages evenly.
Low-Temp Charge Protection
LiFePO4 cells can be damaged charging below freezing. A good BMS cuts charging — not just discharging — at low temps.
Bluetooth BMS
Bluetooth communication lets you watch individual cell voltages and pack health from your phone, not just guess.
Rugged for Mobile Use
A case and internal mounting that can take vibration, impact, and temperature swings in an RV, boat, or vehicle.
Warranty & Support
Backed by a shop that will actually test, diagnose, and stand behind the pack if something goes wrong.
See It In Your Pocket
Real screens from the Overkill Solar BMS app — live voltage, charge/discharge status, and per-cell settings, all over Bluetooth.
Home — live status
Settings — per-cell config
12V Lithium
U1 Lithium
LFP12.8V · 28Ah · 0.36 kWh
Clearance
$90
Valence U-Charge
LFP12.8V · 35Ah · 0.45 kWh
$110
Mac's 100Ah Bluetooth
LFP12.8V · 100Ah · Bluetooth BMS · 100A BMS · 1.28 kWh
$230
Mac's 170Ah Bluetooth
LFP12.8V · 170Ah · Bluetooth BMS · 150A BMS · 2.18 kWh
$360
Mac's 300Ah
LFP12.8V · 300Ah · Bluetooth BMS · 200A BMS · 3.84 kWh
$525
Mac's 330Ah
LFP12.8V · 330Ah · Bluetooth BMS · 200A BMS · 4.22 kWh
$600
24V Lithium
Mac's Custom 7S 285Ah Mach-E
Li-ion24V · 285Ah · Custom Bluetooth BMS · 200A BMS · ~7.4 kWh
$1,200
Mac's Custom 8S 285Ah Mach-E
Li-ion24V · 285Ah · Custom Bluetooth BMS · 200A BMS · ~8.4 kWh
$1,400
36V Lithium
Mac's Custom 10S 212Ah Mach-E
Li-ion36V · 212Ah · 200A Bluetooth BMS · ~7.8 kWh
Clearance
Mac's Golf Cart LFP
LFP36V · 100Ah · Bluetooth BMS · 200A BMS · 3.6 kWh
$1,000
48V Lithium — Powerwalls
Mac's Powerwall LFP
LFP48V · 150Ah · Bluetooth BMS · 200A BMS · 7.7 kWh
Clearance
14S Nissan Leaf Pack
Li-ion48V · 160Ah · Bluetooth BMS · 200A BMS · ~7.7 kWh
Clearance
$800
Mac's Golf Cart LFP
LFP48V · 100Ah · Bluetooth BMS · 200A BMS · ~5.1 kWh
$1,000
48V 280Ah DIY LFP Pack
LFP48V · 280Ah · 13.44 kWh · Bluetooth BMS · 200A BMS (JK v19 screen)
Our newest, smallest, most compact build for a 48V LiFePO4 battery system
$3,000
BMS Manuals
Battery Management System manuals for the units we sell and support. If you need to reset your BMS or configure settings, start here.
JK BMS
Manual for the JK Battery Management System. Covers wiring, Bluetooth app setup, cell balancing configuration, and protection settings.
Download JK BMS Manual (PDF)
Xiaoxiang BMS
Manual for the Xiaoxiang Battery Management System. Mac's modified version — a work in progress with notes from real-world use.
Download Xiaoxiang BMS Manual (PDF)Need Something Custom?
Don't see exactly what you need? We build custom packs of any size — from portable power to whole-home energy storage. Call or stop by to discuss your project.