What size lithium battery replaces a Group 24 80Ah lead-acid?

A Group 24 80Ah lead-acid only delivers about 40Ah usable at 50 percent depth of discharge, so the energy equal lithium is roughly 50Ah. The easiest drop-in is a 100Ah lithium built in the same Group 24 case, which fits the existing tray and gives about 2.5 times the usable energy.

Will a lithium battery fit my existing battery tray?

Many LiFePO4 batteries are built to match BCI Group 24, 27 and 31 footprints, so a same group lithium is a true drop-in. Always check the exact model dimensions, as some are slightly taller or use different terminals.

Can I charge a lithium battery below freezing?

LiFePO4 should not be charged below 0 C without harm. Choose a self heating pack or add a heater pad if you will charge in sub freezing conditions. Discharging in the cold is fine.

Lead to Lithium: find the lithium battery that replaces your 12V lead-acid

The tool

Find your lithium match

Tell us the 12V battery you run now. We show the lithium that replaces it, the weight you save, and whether it drops into your tray. Free, and built by a battery engineer.

Enter what you know. Group size is optional and only used to check the physical fit.

Capacity (Ah)

Chemistry

Group size (optional)

Or start with a common setup

Best match

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Before you swap

Some lithium drops straight in. Some needs a few changes.

A lithium battery that fits your tray is not automatically plug and play. Here is what matters before you buy.

Your charger

AGM and gel charger profiles usually suit lithium. Plain flooded and desulfation modes run too high and can trip the battery management system. Use a lithium profile where you can.

Learn more in the guide

Alternator charging

Never wire lithium straight to a vehicle or engine alternator. Fit a DC to DC charger. It protects the alternator and applies the correct lithium charge profile.

Learn more in the guide

Solar controller

Set your MPPT to the lithium voltage, around 14.4V for a 12V pack, and turn float off. Lead-acid float settings keep a lithium pack at the wrong voltage.

Learn more in the guide

Fusing and wiring

Lithium delivers far more current than lead. Check your cable gauge is up to it and fit a correctly rated main fuse close to the battery.

Learn more in the guide

A battery monitor

Lithium holds a flat voltage, so you cannot read charge from voltage alone. A shunt based monitor on the negative lead gives you a true state of charge.

Learn more in the guide

Do not mix

Never run lithium in parallel with lead-acid. Every battery in a bank should be the same type, size and age. Keep your engine start battery separate.

Learn more in the guide

Charging below freezing needs a self heating pack or a heater pad. Lithium is sealed, so it can mount any way up and does not need venting. Read about cold weather charging.

Read the full Knowledge guide FAQ

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The plan

Your swap, step by step

Eight steps from the battery you run now to a lithium bank that is sized, charged and wired correctly.

Audit the existing bank. Note the battery type, amp-hours or group size, how many, and the wiring.
Decide the approach. A like-for-like swap, or a redesign around your real loads.
Size the lithium pack. Use the tool above, then round up to a real product.
Check the chargers. Shore or mains charger, solar MPPT and alternator each need a lithium profile. Add a DC-DC charger for the alternator.
Plan cold weather. A self-heating pack or heat pad if charging below 0C is possible.
Add monitoring. A shunt for true state of charge.
Re-fuse and wire. Lithium supports higher currents, so verify cable gauge and fuse ratings.
Commission. Set charge voltages, 14.2 to 14.6 bulk and 13.6 or no float, and confirm the BMS.