HD Series lead-acid replacement LiFePO4 battery, 1.28–4.02 kWh

The replacement market is bigger than the new-build market

Most lithium sold into golf carts, RVs, boats and street lights is not bought as lithium — it is bought as a replacement for a lead-acid block that has died. The HD series is built for that purchase: standard plastic case sizes, bolt terminals, and a BMS inside the case so the customer's existing wiring and fuse remain valid.

The engineering difference is the cells. A 12.8 V 100 Ah block uses four 3.2 V 100 Ah prismatic cells in series, capacity- and resistance-matched, with a balancing BMS. The same case in AGM would weigh 30 kg; the HD weighs 10 kg, which matters when the block is lifted into a battery box on a boat.

What "drop-in" does and does not cover

It covers dimensions, terminal layout and discharge behaviour. It does not cover charging. A lead-acid charger holds a float voltage that leaves a lithium block at 80–85 % state of charge, and an equalisation cycle will trip the BMS on over-voltage. Before fitting, check the charger for a lithium setting or a programmable profile: 14.2–14.6 V absorption per 12.8 V block, float at 13.5 V, no equalisation.

Where the charger cannot be changed, the block still works but delivers less usable capacity — a fact worth stating in the quotation rather than discovering at commissioning.

Where the 25.6 V blocks fit

Two blocks in series make a 25.6 V battery for 24 V systems: trolling motors, small off-grid inverters, mobility scooters and floor scrubbers. Using one 25.6 V block instead of two 12.8 V blocks halves the number of busbars and removes one set of terminals from the maintenance list.