Crimp

Conversion field guide

Lead-acid to LiFePO₄ conversion guide

A 12 V LiFePO₄ battery is not automatically a drop-in replacement for a 12 V lead-acid bank. Audit every charging source, the alternator path, BMS, loads, cables, fuses and cold-weather behavior against the exact battery manual.

Reviewed Aug 28, 2026Scope 12 V DC planningRule Exact manuals win
01Audit

Start with manuals and current paths.

Do not buy the replacement battery first and discover the charging system later. Record exact models, ratings and wiring before deciding what stays.

  1. 01

    Name the exact batteries

    Record the existing and proposed make, model, quantity, voltage and series/parallel topology. Capture the proposed BMS continuous, surge, charge and temperature limits.Stop here
  2. 02

    Inventory every charger

    List the AC charger or inverter/charger, solar controller, alternator regulator and DC–DC equipment. A menu label that says lithium is not enough; verify its actual voltage, duration and temperature behavior.Stop here
  3. 03

    Add simultaneous charge current

    Sum every source that can charge at the same time. Compare that total with the battery, BMS, conductors, busbars, disconnects and terminal limits—not just with each charger in isolation.Stop here
  4. 04

    Trace the alternator path

    Identify alternator rating, regulator, cable, VSR/ACR and starter battery. Lithium charge acceptance can hold an alternator near maximum output, so the path needs documented current limiting or temperature control.Stop here
  5. 05

    Measure load and surge

    Use the inverter and other load manuals, not battery capacity, to establish continuous and surge current. Compare both with the bank, BMS, disconnect, busbar, cable and fuse limits.
  6. 06

    Define BMS actions

    Document what stops charging, what disconnects loads and how temperature protection acts. Plan essential loads and alternator shutdown so a BMS opening does not create a second hazard.
  7. 07

    Record the coldest battery

    Use the temperature at the cells, not the cabin. If charging can occur below the selected manual limit, add manufacturer-approved sensing, heating or charge inhibition.Stop here
  8. 08

    Audit conductors and protection

    Record conductor material, gauge, length, insulation, routing and current protection. Recalculate ampacity, voltage drop, fuse rating, DC voltage rating and interrupt rating for the new fault source.Stop here
  9. 09

    Verify the physical installation

    Check battery restraint, permitted orientation, dry/IP requirements, clearance and cooling, cable strain relief, and whether the structure can carry the changed weight at the installed location.Stop here
  10. 10

    Reset the monitor

    Review shunt capacity, charged voltage, tail current, Peukert exponent and charge efficiency. Keep all load and charge returns on the system side of the shunt.

Fail closed

Stop the design if the proposed battery manual is unknown, any charger cannot be identified, a direct alternator path has unknown limits, cold charging is possible without approved protection, load or surge exceeds the BMS, chemistries share a bank, or the cable and fuse data is incomplete.

02Before / after

Draw the retrofit as two systems.

The before drawing is an inventory. The after drawing makes the changed DC power paths and main BMS isolation boundary visible. Toggle the live canvas to inspect the topology—not final wire or fuse sizes.

Control wiring omitted

Crimp does not draw battery communication, allow-to-charge, allow-to-discharge, remote-enable or alternator-shutdown signal leads in this example. Add and verify those paths from the exact battery, BMS, charger and load manuals. The live canvas intentionally hides cable sizes and fuse ratings because the required installation and fault-current evidence is not part of this example.

Before — typical lead-acid layout
AlternatorVSR / ACRAGM bankDC distribution

A direct relay path can expose the alternator to lithium charge acceptance.

After — controlled lithium layout
Starter batteryFused DC–DCLiFePO₄ + BMSMain protection

DC topology only; required BMS control wiring, exact cable sizes and verified protection are not shown.

Live Crimp canvas

Pan through the before and after systems.

03Decision ledger

Keep, configure, replace or add.

These are decisions to verify, not universal parts. The exact equipment manuals decide whether a specific component belongs in each column.

replace

Replace the AGM house bank

The LiFePO4 bank is a different chemistry and capacity, not a drop-in setting change.

replace

In this example, replace the combiner with DC-DC charging

A current-limited DC-DC charger is one common retrofit. A documented regulated-alternator and BMS-control design may be valid instead; the exact equipment decides.

reconfigure

Reconfigure compatible charge sources

Set the solar charger for the installed battery maker's LiFePO4 limits and connect its supported remote-control path to the BMS as the manuals require.

replace

Replace an uncontrolled shore charger

This example replaces the NOCO with a programmable Phoenix Smart IP43 whose remote input can be controlled by the BMS. A lithium mode alone is not enough.

reconfigure

Reset the battery monitor

Update capacity, charged voltage, tail current, and state of charge after the new bank is commissioned.

keep

Keep serviceable distribution and loads

The starter battery, disconnect, bus bars, fused branches, solar panel, fridge, and lighting remain in place after their ratings and condition are checked.

add

Add the battery-management layer

The external BMS must be compatible with the exact battery and able to stop charging and loads at the battery limits. This power-path canvas omits its communication and allow-to-charge/discharge signal wiring.
Example manufacturer charge settings showing why exact manuals are required
Example manualAbsorptionFloatCharge temperature
Victron Lithium Smart14.2 V13.5 V5–50 °C
Battle Born BB1001214.2–14.6 V13.4–13.8 V0–55 °C

Two current manuals, two different limits. These values illustrate why “a LiFePO₄ profile” is not a specification; use the values printed for the exact battery and charger.

04Commission

Prove each protection path before service.

Commission methodically, with the installation isolated whenever wiring is touched. If the system is on a boat, vehicle or fixed site, apply the standards and inspection rules for that installation.

  1. 01

    Inspect before energizing

    Verify polarity, strain relief, over-current protection placement, holder ratings, cable support and every manufacturer torque value.
  2. 02

    Configure one source at a time

    Apply the exact battery profile to shore and solar charging. Disable equalization or temperature compensation only where the selected manuals require it.
  3. 03

    Load-test the alternator path

    Confirm DC–DC current, alternator temperature and voltage at idle and cruising speed. Verify the alternator is shut down safely before a BMS charge disconnect.
  4. 04

    Test BMS boundaries

    Prove charge inhibit, load disconnect and low-temperature behavior without relying on a destructive fault. Confirm essential circuits reach their intended safe state.
  5. 05

    Measure under real load

    Run the largest expected continuous load and documented surge. Check voltage drop, conductor and terminal temperature, fuse-holder heating and BMS headroom.
  6. 06

    Document the finished system

    Save the schematic, settings, fuse part numbers, torque record and manuals with the installation. Label disconnects and update the emergency procedure.

Capacity is not equivalence.

“One lithium battery replaces two AGMs” is not a design rule. Compare usable energy, required continuous and surge power, temperature, reserve policy, parallel topology and the BMS current limits. A bank can have enough amp-hours and still be unable to start or sustain the load.

05Sources

The manuals behind this guide.

Manufacturer instructions are model-specific and change. Open the current document for every part you actually install; a summary page cannot replace it.

01Battle Born BatteriesBB10012 100 Ah 12 V Battery ManualManufacturer limits for charging, temperature, connections and protection.02Victron EnergyLithium Battery Smart: OperationCharge, discharge and low-temperature operating behaviour.03Victron EnergyLithium Battery Smart: Technical dataModel-specific voltage, current, temperature, configuration and physical limits.04Victron EnergyLithium Battery Smart: InstallationMounting, battery-bank, BMS, cabling, fuse and commissioning instructions.05Victron EnergyLithium Battery Smart: System design and BMS selectionBMS topology and control of charge sources and loads.06BalmarLithium Battery Charge Programming service bulletinAlternator regulation and load-dump precautions for lithium banks.07Victron EnergyLynx Smart BMS: InstallationExact BMS and contactor installation used in the worked conversion.08Victron EnergyPhoenix Smart IP43 charger manualCharge settings, DC wiring and remote on/off control for the worked example.09Victron EnergySmartSolar MPPT 75/10–100/20: FeaturesVE.Direct remote on/off support and charger behavior for the example solar controller.10Victron EnergyOrion XS 12/12-50A manualSections 3.9–3.10 cover remote on/off and BMS ATC/DVCC control; section 4.1 covers engine-shutdown detection.11Victron EnergySmart BatteryProtect: Installation and wiring examplesDirectional power wiring and external-BMS load-disconnect control.12Victron EnergySmartShunt: ConfigurationBattery-capacity, charged-voltage and state-of-charge monitor setup.
Next referenceCheck a LiFePO₄ fuse candidateSeparate the amp rating from the interrupt rating, and see which missing inputs prevent a safe result.