Conversion guide

Lead-acid to LiFePO₄ conversion guide

Most 12 V LiFePO₄ conversions are a battery change plus a few checks around charging and protection. Your lights, pumps, fridge, switches and fuse panel usually stay where they are.

Checked Sep 11, 2026 · 12 V DC planning · your manual wins

What changes

Usually, less than you think.

Work outwards from the battery. Only the gear that charges, protects or measures the bank needs a second look. Everything else is just a load, and loads don't care what chemistry feeds them.

Replace

House battery

Pick enough usable capacity for the way you actually use the boat or van, and a BMS that can carry your biggest load without tripping. Take the old bank out rather than mixing chemistries. The two charge so differently that one of them is always being treated wrong.

Set or swap

Shore and solar charging

Take these one at a time. If a charger can match your battery maker's lithium settings, keep it and configure it. Compare the SmartSolar MPPT 100/50 battery/PV paths and the MultiPlus-II 12/3000 DC example (120 V AC model). Check the AC voltage of the actual shore unit in your boat, campervan or RV.

If connected

Alternator charging

If the alternator fed the house bank directly, review a current-limited DC–DC charger or managed regulator. The Orion XS 12/12-50A example shows the starter-to-house-bank paths. For a 4WD auxiliary bank or campervan B2B setup, compare the BCDC1240D and BCDC1250D installations. Use the DC-DC charger size calculator to check actual vehicle headroom and battery acceptance.

Check

Main cables and fuse

Review the largest charge and load currents, installed cable limits and whole-bank fault current. The Lynx Distributor example separates branch fuses from battery-feed protection. Use the fuse sizing and exact-part checker for the main fuse and holder, and the sizing methodology to understand the cable calculations. The wire size calculator compares ampacity with voltage drop for your one-way run.

Reset

Battery monitor

Reset capacity and lithium charge settings, then synchronize after a full charge. The SmartShunt 500 installation example shows the battery-negative and system-negative connections, including the fused supply lead. Keep all load and charging returns on the system side.

What usually stays

Most branch wiring and ordinary 12 V loads can stay. Keep them if they are in good condition, accept the new battery's voltage range, and were fused and sized properly to begin with. A run that was marginal before is still marginal now. The new battery doesn't fix that, so draw it and see.

Crimp

Draw what you know. Let Crimp ask for the rest.

You do not need model numbers, a finished parts list or exact cable measurements to begin.

Where Crimp takes over

A rough drawing is enough.

Add a generic LiFePO₄ battery, the charging paths you know about and your biggest loads. Connect them and type in rough cable lengths. Crimp follows the current through the drawing, suggests wire and fuse sizes, estimates voltage drop and flags anything that is overloaded or left unprotected.

Start with a blank canvas

Look things up only when needed

Keep using generic parts while the shape of the system is settling. Open a label or a manual when you decide to keep a charger, enter its final settings, or clear a warning that hinges on an exact rating. Crimp doesn't know how hot your engine bay gets or how the old cable was run, so those two calls stay with you.

Before power

Check four things, then switch on.

This is where the exact details matter: after the plan is clear and before the new bank is connected.

Charging settings
Every charging path that stays connected is set to numbers the new battery manual allows. Check each source as you commission it, not all of them before you have started planning.
Alternator path
If the alternator charges the house bank, its current and temperature are under control and it can stop safely when the BMS blocks charging. A BMS that opens under full alternator output can take the alternator's diodes with it.
Battery protection
The BMS, main fuse, disconnect and battery cables all cover the current you expect. Charging is blocked when the battery is colder than its manual allows.
First test
With power off, check polarity and terminal torque. Then bring up one charging source at a time and finish with the biggest load you own.

When you need a number

Use the manual for the part in front of you.

The battery manual and the manuals for the charging gear you plan to keep are enough. The references below show the kinds of limits you are confirming. They are not a reading list.

Battle Born BatteriesBB10012 100 Ah 12 V Battery ManualThe battery maker's own limits for charging, temperature, connections and protection. This is the manual that wins.Victron EnergyLithium Battery Smart: Technical dataVoltage, current, temperature and configuration limits for each model, so you can check a charger's settings against them.Victron EnergyLithium Battery Smart: System design and BMS selectionHow the BMS is wired in and how it tells chargers and loads to stop.BalmarLithium Battery Charge Programming service bulletinWhat to set on an alternator regulator for a lithium bank, and how to protect the alternator when the BMS disconnects.Victron EnergyOrion XS 12/12-50A manualSections 3.9–3.10 show how the BMS can switch the charger off (remote on/off, ATC, DVCC); section 4.1 covers engine-shutdown detection.Victron EnergySmartShunt: ConfigurationWhere to enter the new capacity and charged voltage so the state-of-charge reading means something.

Keep goingCheck the main battery fuseCheck its amp rating, DC voltage and interrupt capacity against the new bank. Those are three separate questions, and a fuse can pass two of them and still be wrong.