Why Does a 12V LTO Battery Show 13.8V, 9V and 17.4V? Nominal and Cut-off Voltages Explained

Short answer: 13.8V, 9V and 17.4V are the same three cell numbers multiplied by six. 13.8V is the nominal voltage, 9V is where discharging must stop, and 17.4V is the highest voltage the cells may be charged to. The last one is a limit for the cells, not a voltage your 12V audio gear is designed to run at.

Where the three numbers come from

A 12V LTO pack is six lithium titanate cells in series (6S). Series connection adds voltage, so every pack figure is the cell figure times six. The pack figures below are the ones on our product listing, and the per-cell figures are those divided by six.

• Nominal voltage is the label value. Real voltage moves above and below it.
• Discharge cut-off is where discharging stops. Going lower can damage the cells.
• Charge cut-off is where charging stops. It is the most the cell should be charged to.

For comparison, Battery University describes LTO as having a nominal cell voltage of 2.40V and charging to 2.85V. Times six, that is 14.4V nominal and 17.1V at full charge. These are close to our listing but not identical, because cell makers use slightly different figures. Always check the datasheet of the cell in the pack you are buying.

What the cell maker publishes

Gree Altairnano, the cell maker formerly known as Yinlong, publishes reference data for its 40Ah and 45Ah 66160 cells on its official product page. Both cells are listed there at a nominal voltage of 2.3V, which matches the figure above. The page does not list charge or discharge cut-offs, so the 2.9V and 1.5V per cell on our listing are listing figures, not the maker's. The maker describes its figures as reference data, with the product specification taking precedence, so check the specification supplied with the cells you receive.

Why a car charges it only part way

Take an alternator that holds about 14.4V. Divided by six cells, that is 2.4V per cell, which is 0.5V below the 2.9V charge cut-off. A vehicle's charging system is designed around a 12V system, so it stops well short of what these cells accept.

We do not have a manufacturer figure for how much capacity an LTO cell holds at 2.4V, so we do not give a percentage. What the numbers do show is that an alternator on its own is unlikely to take the pack to its listed full charge. Measure the voltage at the battery terminals with the engine running, and plan your capacity around that. Our LTO vs AGM guide covers the same point in the context of choosing a battery.

Why 17.4V is a problem for 12V equipment

Car audio amplifiers are built for the 12V system in a vehicle, and their manuals state a voltage range. Two examples:

• The Rockford Fosgate R250-2 Prime lists an operating voltage of 9–16V DC.
• The Kicker KX 5-channel amplifier manual refers to a 10–16 volt operating range, and says voltage outside that range can make the amplifier shut down.

A pack charged all the way to 17.4V is above both ranges. That does not mean every charge ends at 17.4V. A charger does not have to push the pack that far, and the voltage of a cell is higher while it is being charged than after the charger is removed. It does mean the charge cut-off and the equipment's voltage range are two separate things, and you need to check both.

Before you buy or charge

• Find the charge cut-off and discharge cut-off in the pack's listing. Ours are 17.4V and 9V.
• Find the operating voltage range in the manual of each amplifier or other device on the pack.
• Ask what voltage your charger holds the pack at. If it can reach the charge cut-off, check that everything connected can accept that voltage, or disconnect the loads while charging.
• Measure the alternator voltage at the battery terminals, engine running.
• Do not run the pack below the 9V discharge cut-off. Our 12V packs and kits have no BMS to stop discharge for you, so watch the voltage yourself.

Next steps

See our 12V LTO battery packs, or read how to size an LTO battery for your system.

Sources

• Battery University, BU-409: Charging Lithium-ion (LTO nominal cell voltage and charge voltage)
• Gree Altairnano, 40Ah/45Ah LTO cylindrical cells (reference data, read 10 November 2026; nominal voltage)
• Rockford Fosgate, R250-2 Prime amplifier manual (operating voltage)
• Kicker, KX 5-channel amplifier manual (operating range)

Last reviewed 11 November 2026. AURINET figures come from our product listings. This guide is general information, not installation advice.