24 volts is how many amperes? We understand electrical parameters for cars and equipment

Why the question “24V - how many amperes?” is incorrect, and how to set it correctly

At first glance, the question “how many amperes are in 24 volts?” seems logical - especially if you deal with the electrical work of trucks, boat batteries or industrial equipment. However, from a physics point of view, this is the same as asking: “how many kilometers are in 5 liters?” Volts (V) and amperes (A) are different units of measurement., and it is impossible to directly translate one into another without additional data.

To find the current (amps) at a voltage of 24V, you need to know at least one of the parameters:

• 🔋 Power consumer or source (watts, W)
• 🔌 Resistance circuits (ohms, Ω)
• ⚡ Load type (active, reactive, direct/alternating current)

Without this data, the answer will be approximate or even impossible. For example, battery 24V 100Ah can deliver from 0.1A to hundreds of amperes - depending on the connected load. Next, we’ll figure out how to correctly calculate the current for different situations.

Ohm's law: basic formula for calculating amperes at 24V

If you remember your school physics course, then Ohm's law - your main assistant. The formula connects three key quantities:

I = U / R
where:
I - current strength (amps, A)
U - voltage (volts, V)
R - resistance (ohms, Ω)

Example: you have heating element resistance 4.8 Ohm, connected to a 24V source. The current in the circuit will be:

I = 24V / 4.8Ω = 5A

But what if the resistance is unknown? Then the formula through power:

I = P / U
where P is power (watts, W)

Let's say you connect to 24V LED spotlight power 120W. The current will be:

I = 120W / 24V = 5A

Table: Current at 24V for typical loads in cars and equipment

In order not to count every time, we have prepared a table with calculations for common devices. Please note: values are given for DC (DC), which is used in most battery systems.

Important: actual current may differ by 10–15% due to device efficiency and wire losses. For example, cheap Chinese inverters often have an efficiency below 80%, which increases current consumption.

24V in the truck’s on-board network: how many amperes does the generator produce?

In trucks (for example, Volvo FH, Scania R450, MAZ or KrAZ) standard on-board voltage is 24V. But how many amps can such a vehicle's generator produce?

Modern truck generators have a current rating of 80 to 150A, depending on the model and number of consumers. For example:

• 🚛 Bosch 14V 120A (28V) - actually produces ~100A at 24V due to losses
• 🔋 Delco Remy 36SI - up to 140A at full load
• ⚡ Generators Europe GE28150 — 150A (installed on DAF XF)

At the same time maximum current the generator produces only at high engine speeds (usually from 2000 rpm). At idle, its power drops to 30–50% of the nominal value.

How to calculate the capacity of a 24V battery in ampere hours (Ah)?

Whether you're choosing a battery for a boat, solar power system, or power backup, it's important to understand how long it will last at a given current. The formula is simple:

Operating time (h) = Capacity (Ah) / Load current (A)

Example: you have battery 24V 200Ah, and you connect a 10A load. The operating time will be:

200Ah / 10A = 20 hours

But there are nuances:

• 🔋 Deep discharge reduces battery life. For lead-acid batteries, it is not recommended to discharge below 50%.
• ⚡ Temperature affects capacity: at -10°C, actual capacity can drop by 30–40%.
• 🔄 If the batteries are connected in series (to obtain 24V from two 12V), their capacity does not add up.

Check the production date (lead batteries lose 1-2% of capacity per month during storage)

Make sure that the open circuit voltage is not lower than 25.2V (for Li-ion - 25.8V)

Inspect the housing for bulges or cracks

Ask the seller to check the cold cranking current (for starter batteries) -->

Dangerous errors when working with 24V systems

Even low voltage circuits can be dangerous if not handled correctly. Here are typical mistakes that lead to breakdowns or fires:

⚠️ Attention: Never use wires with a cross-section of less than 1.5 mm² for currents exceeding 10A at 24V. The resistance of thin wires causes heat and a risk of fire. For currents of 50A+, a cross-section of at least 10 mm² is required.

Other critical points:

• 🔌 Short circuit 24V can melt battery terminals in seconds. Always disconnect the power supply before starting work.
• 🔋 Pereplyusovka when charging Li-ion batteries 24V leads to an explosion. Use BMS boards with protection.
• ⚡ Connecting 12V devices directly to 24V without a converter will burn them instantly.

Case Study: Owner GAZon Next I connected the 12V radio to 24V through a resistor “to save money.” The result is that not only the radio tape recorder burned out, but also the fuse box.

FAQ: Frequently asked questions about 24 volts and amperes

I = 2400W / 24V = 100A