Why Does My F250 Have Two Batteries?

Why Does My F250 Have Two Batteries

The Ford F250 is a high-performance vehicle and as such, it has two batteries instead of one. But why does the Ford F250 have two batteries exactly, and how should you jumpstart it given this unusual set-up? The answers are all below.

Why does my Ford F250 have two batteries? Your F250 has two batteries because two battery systems are needed for trucks requiring a much larger resistance load to start. In other words, a diesel engine needs a higher power to start the engine than a gas engine needed.

A Ford F250 also has two batteries as it needs a double amount of energy to start compared to a smaller, less powerful vehicle. Dual batteries are good for trucks when hauling or even for smaller tasks like when you have a boosted stereo system and you want just one battery to supply power. Then the primary battery is used to start the F250.

Why does my F250 diesel have two batteries?

Ford F250 diesel trucks are designed with a high compression engine, meaning that they must have two batteries for smooth operation. The compression 15:1 or 23:1 ratio provides sustainably improved performance in these heavy-duty vehicles and is ideal if you plan on carrying heavier loads.

Tech features supported by the F250 two batteries system

  • Ford Co-Pilot360 system.
  • Backup Assist for trailer.
  • Tow Camera System for trailer.
  • Sway Control in trailer.
  • Ford Pass Connect.

When diesel trucks have two batteries, they can be configured in different ways. 

1. Parallel-linked battery

The parallel-linked battery is attached in a 12-volt engine system. In a parallel linked system, both the positive and the negative ends of each of the F250’s two batteries are connected to one another, which means when you see the wiring in that system it is interlinked. 

This arrangement of parallel batteries allows an increase in the rate of the current flowing with a regular and same voltage. By this I mean the performance of your truck will improve without any spill of charges. 

Other electrical parts of your truck are also protected by this connection. But it also comes with a set down because this type of battery set-up is used to avoid burnout, so these batteries will use a heavy-duty cable, which can be more expensive to reinstall. 

Because the load is too much it could burn the local one out. 

2. Series-linked battery

In this dual battery set-up, the power is kept the same by adding up the voltage of each battery. In series, circuit batteries are arranged in linear appearance and perfect for the truck which uses higher voltage than normal cars. 

However, this system could prove fatal if installed incorrectly in your truck, as it releases a high amount of voltage which can fry the entire electrical system of your truck.

How the F250 dual battery system works

The most common method to attach two batteries is a parallel-joined set-up. So yes, the Ford F250 also has parallel-connected batteries because one battery has a hard time charging grid heaters when it’s cold out among other things. 

While one would work, it has to work harder, so they were two in parallel.

In a parallel circuit, the current divides and makes two streams and only part of it flows through a single stream. The potential difference, or voltage, across each branch of a parallel circuit, is the same, but the currents changes. 

This means if you attach load with one end of the battery it will automatically drain the charge from both consecutively

Handy Hint: Here’s why your F250 has aux switches and what they can be used for.

Related questions

Now you know why your F250 have 2 batteries, here’s how you can make the most of them of fix any faults, including how to jumpstart dual battery set-ups.

How do you jumpstart a diesel with two batteries?

Jumper wires are a trucker’s best friend. If you have ever tried to start your diesel engine with only one battery, it can be difficult if not impossible because of the parallel-joined batteries that most modern trucks use for power supply systems (PSS). 

To get started on these types of vehicles simply attach both ends to someone else’s car battery – positive towards theirs and negative from their vehicle; then after ensuring there isn’t too much voltage difference between them wait about 30 seconds before trying to start your truck.

Which battery do I jump on F250 diesel?

You can jumpstart either of the two batteries on a Ford F150 diesel. As they are connected in parallel to each other it makes no difference. 

However, for safety reasons, jumpstart the battery on the passenger side of the F250 as this will keep you safer and away from moving traffic. 

What If one of the two F250 batteries dies?

There are many benefits to installing an isolator in your truck. The best part is that it will keep you from losing power when one of the batteries dies, and also helps with charging because both can be charged at once.

Why won’t diesel trucks start with the new batteries?

It is very common for diesel trucks not to start with new batteries. The main reason for this is that the new batteries are not properly charged. When you first get your new batteries, it is important to charge them fully before using them. 

Another reason your diesel truck won’t start with batteries maybe because the batteries are not properly connected. Check the battery terminals and make sure they are clean and free of corrosion. 

Also, check the connections to the starter and alternator. If these are loose, they can prevent the engine from starting. Finally, check the fuses and relays. If any of these are faulty, they can prevent the engine from starting.

Can you start a diesel truck on one battery?

It is possible to start a diesel truck on one battery, but it is not recommended. A single 12-volt battery can be used to start a diesel truck. If the battery is not powerful enough, it may not be able to start the engine. 

Additionally, if the battery is not properly connected, it can prevent the engine from starting. Finally, if the weather is cold, it can make it difficult or impossible to start the engine.

How many batteries are in an F250?

F250 trucks come with two batteries. The truck uses one battery to start the engine and the other battery powers the accessories.

What is the purpose of a diesel truck’s second battery?

The purpose of a diesel truck’s second battery is to power the accessories. This includes the lights, radio, heater, and air conditioner. 

The second battery also helps to start the engine if the first battery is not working. Additionally, the second battery can keep the truck running if the first battery dies.

How to properly charge f250 batteries?

To properly charge two batteries in parallel the negative clamp on your charger needs to go to the negative post on the battery that goes to the chassis ground. Thhe positive clamp will go to the positive battery post on the other battery, the battery where the positive clamp goes should go to your fuse box/main fuse.

When should you change batteries on a Ford F250?

Every truck is different but typically 3-5 years is the average lifespan for a battery. If your truck is older and you can’t remember ever changing the battery, you may want to schedule an appointment before you find yourself stranded on the side of the road. 

There are a few signs you can recognize as well when it comes to your battery losing power such as dim lighting, backfiring and slow crank.


All recent Ford F150 diesels come with two batteries as a standard feature. Due to how powerful they are, they need dual cranking amps to turn over the engine.

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Josh Henderson

Hi I'm Josh and I'm a huge pickup enthusiast. I started this website in 2018 in order to share all my projects and custom mod tips that I've done with my own Ford F-150.

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