Battery cable layout

Discussion in 'Freightliner Forum' started by Cedric62, Dec 23, 2024.

  1. Cedric62

    Cedric62 Bobtail Member

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    A friend of mine is an owner operator who has been off the road for several years due to cancer, and his truck has been sitting. Also, earlier in my own life I had workd as an automotive smog mechanic during the 1990s, so this friend of mine asked me to to help him to take a look at a charging issue he was having on his truck. It turned out to be that the remote sense wire on his alternator was completely corroded, and after cleaning that and a few other connections around the alternator, the guage in his dash was once again reading 14.25 after things settled down. However, it appears that his batteries had gone bad during the two or three years that his truck sat, and now they will no longer hold a charge over night, and I'm fairly certain that it is not a problem with a parastic draw, or a minor short somewhere. Additionally, in the meanwhile, someone else came along and helped him to take the batteries out of his box, in order to get replacements, but this other person did not help him put the new batteries back into the box, and when they took the old batteries out, they unnessarily dissassembled all of the battery connecting cables, and hardware, and this friend of mine is afraid to put the new batteries back in their until we find an official diagram from Freightliner. - I understand the concept of connection batteries in parallel, and I can tell by the wear marks on the old connecting brackets how they were connected, but he still doesn't want to put them back in, eventhough I put the cable hardware back together. I cannot seem to find anything other than partially obscured photos on the internet, but from looking at these photos I drew up the attached picture of how I believe that his batteries should be connected. If someone could take a look at the attached picture I made in Paintbursh and let me know, I would greatly appreciate it. Also, the truck in question is a 2016 Freightliner Cascadia, and it has the DD15 motor. Battery_Connectors_X1.jpg
     
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  3. Rideandrepair

    Rideandrepair Road Train Member

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    Looks good. As long as they’re all tied together. I like the way your diagram is, because it’s easy to disconnect one battery should it short out. On my Truck 2 positives go to battery, one negative to frame. Looks like you have 2 neg. I’m guessing the 3rd set pos/neg on your diagram are for a apu or inverter maybe? If inverter, the pos should be fused at the battery. There’s also a set of smaller pos/neg wires that power the ecm. The pos. has an inline fuse to protect the ecm. The neg goes to the frame like the others. Very important to have a good ground at frame. The connection often gets corroded, same with pos inline fuse. It can get corroded or blow out from a bad installation or jump starting with loose connections, shorted battery or accidental reversing polarity (hooking up batteries or jumpers backwards) Done that before.
     
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  4. xsetra

    xsetra Road Train Member

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    Call a Freightliner dealer and ask them for a schematic. They can send it to you in an email. They will ask for the last 6 numbers or letters of the VIN.
     
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  5. Cedric62

    Cedric62 Bobtail Member

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    Good information. Thank you.
     
  6. Cedric62

    Cedric62 Bobtail Member

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    I'm not certain, but I think that the second negative cable, on the right hand side is going back towards the trailer somewhere. Not sure about that though. The smaller guage red wire attached directly to the positive battery seems to be powering the inverter inside the cab. Also, you are right, all of the negative ground connection to the frame were severly corroded, but we have since fixed that. It looks like he might have driven it through some sort of extra heavy duty road salt, and didn't rinse it off afterwards. Thinking to put white lithium grease on some of these connections in order to prevent future corrosion issues.

    The Freightliner dealership probably isn't going to be able to help us with a schematic until after the holidays, so I was wondering if anyone might happen to have a clearer photograph showing how the batteries are connected inside the box? Or maybe a picure of a schematic from a manual? If not, it can wait until after the dealership people get back from the holidays.
     
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  7. Rideandrepair

    Rideandrepair Road Train Member

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    All the positives go together. Often the two hots are just connected to any two positive. They both run to the same post on the starter. Sometimes the original cables have an extra post on two of them. The result is same as your design. Grounds are usually just to the frame. Then there’s another short ground from frame to starter. Looks like yours has a ground directly from battery to starter. Probably also have a backup ground cable from frame to starter The end result is the same. Look for an inverter in the Truck. Leave it disconnected at the battery, if anything for now. There’s a positive and a negative cable for inverters. Especially if there’s no big fuse or resetting breaker at the battery. Sometimes they put a resetting breaker or a fuse in the bunk for convenience. That’s dangerous and can lead to a fire. Needs to be at the battery. Inverter might be the source of a draw if any. Tape the ends up and zip tie them safely away from terminals for now if you’re not sure how it’s fused. You can always hook it up later with a proper fuse or breaker. Surely you can follow the third set of cables and see where they go. Inverter or apu? I don’t know how APUs are wired. I’m guessing directly from the batteries The ecm power and ground wires are very small gauge. Any grease will work. A tube of dielectric grease is ideal. Put it on the frame post and ground wires before connecting them.
     
    Last edited: Dec 24, 2024
  8. Rideandrepair

    Rideandrepair Road Train Member

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    Why not post a pic of what you’re looking at? Sometimes one battery is isolated against parasitic draw when Trucks not running, to allow starting. I think it’s done using a solenoid. I don’t know how that works. Post a pic. Maybe someone else can tell you more. All I know is how my Trucks wired.
     
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  9. SmallPackage

    SmallPackage Road Train Member

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    On Freightliners they ground batteries straight to frame. I recommend running one set of batteries ground cable straight to starter and leave the other set to frame. Being direct is Much better for starter.
     
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  10. SmallPackage

    SmallPackage Road Train Member

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    Part of the corrosion they get is from arching. FL welds a threaded lug on the frames for grounds. They work loose all the time. I have seen many that were cracked at weld and not easily noticeable but getting bad connection. I seen them sometimes spark at night when hitting start button trying to jumpstart in the dark. That is why I recommend running a set of batts straight to starter ground lug and leave the other factory grounds as they are. Check the lugs often to make sure they are tight and if they corrode the cables at that point the attachment point on frame rail may be broke.
     
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  11. Cedric62

    Cedric62 Bobtail Member

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    Well, I can confirm that the red wire going to the inverter has some sort of an inline fuse installed on it, and since the owner didn't mention any issues with APU, I guess I have to assume that they are wired and installed correctly. Also, I guess you're right, leaving the inverter disconnected during the initial startup with new batteries makes sense.
     
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