I have a 2015, F250 diesel super duty truck. It has two batteries.
I have never owned a vehicle that uses two batteries. can someone tell me why the truck has two batteries?

 

the compression ratio's are 20:1 which requires a large current draw to crank over. Add in additional cranking amps to turn over a cold engine with cold fluids. the current draw of glow plugs and def tank heaters add to battery load. Then consider that cold temperature reduce battery capacity.


One battery isn't enough.


when battery testing is required the battieries must be isolated from each other or they will test as one big battery.

 

Thank you for the reply,

So the two batteries are in parallel?

 

Yes they are.

 

And remember...You have to replace them in pairs.

 

I was thinking that they would have to be replaced in pairs.

Owning this type of vehicle is a new experience for me. But I sure do like it

 

If you follow the manufacturer's recommendations you should get very good service from a diesel.

 

What is the wattage of the alternator/regulator on the 2015 F250?

I wonder if it could handle the output of a 100watt amateur radio transceiver, that is made to operate from a 13.8volt DC supply.

 

the draw would be around 10amps


I've wondered about the ecm controlled alternators... if you draw power from the battery and the current is not measured by the amp clamp on the main battery cables...will the charging system account for the draw?

 

Ford has a voltage sensing circuit that is controlled by the PCM. If it senses a voltage drop it communicates this info to the PCM which in turn will increase output to maintain that 80% charge state.
I believe GM uses the clamp in the cable to determine draw and issues necessary instructions to the charging system to increase output.