Battery power source

Discussion in 'On the Road' started by KO4CPR, May 15, 2021.

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  1. KO4CPR

    KO4CPR Ham Member QRZ Page

    Just installed a new Yaesu FTM-400XDR in my pickup truck. Connected power directly to my only power source, the cranking battery. I realize it will drain that battery really quickly if the engine+alternator is not running. Someday soon I will invest into a dual battery setup with an AGM deep cycle battery as my secondary power source.

    Any concerns with the radio connected to the starting battery? Will it cause any damage or drain issues during normal / heavy road use while driving?
    KO4ESA likes this.
  2. AG6QR

    AG6QR Premium Subscriber QRZ Page

    From a power consumption perspective, no problem. It's the way most people power their mobile radios. I have two vehicles wired that way, for almost a decade, with no issues. I do recommend turning on the radio's APO (auto power off) menu option, to shut the radio off automatically after about an hour, in case you forget to turn it off when leaving the vehicle.

    There are also potential issues around safety and fusing. Any wire that goes directly to the battery, whether the positive or negative terminal, must have a properly rated fuse as close to the battery as possible. I don't recommend running a negative lead back to the battery, but instead, using the chassis as the negative power path, just like the factory does for every other electrical item on the vehicle.
    K0UO, WA7ARK, KO4ESA and 1 other person like this.
  3. KO4CPR

    KO4CPR Ham Member QRZ Page

    Good tip about APO, thanks. Already got two fuses at the battery for each + - connection. Might move that to a seat bolt for shorter ground, but it seems to be working perfectly as is wired directly to battery now.
    KO4ESA likes this.
  4. W7HV

    W7HV Ham Member QRZ Page

    FWIW: The normal and best thing to do is to hook the negative lead to the same point the battery negative lead attaches to the chassis. That keeps the radio chassis at the same potential as the vehicle chassis irrespective of any voltage that develops across the battery's negative lead due to high current draw, particularly when starting.
    KY4GD, K0UO and KO4ESA like this.
  5. W9WQA

    W9WQA Ham Member QRZ Page

    seat bolt is fine...
    K0UO and KO4ESA like this.
  6. W7HV

    W7HV Ham Member QRZ Page

    Seat bolt is probably OK, but you're still subject to whatever resistance exists between that point and the where the battery connects to the chassis.
    KO4ESA likes this.
  7. KD4UPL

    KD4UPL Ham Member QRZ Page

    While driving your alternator is supposed to be supplying power, not the battery. You can operate for days on end if the engine is running. With the engine off you should still have no real concern. The vast majority of hams have their radios connected to the starting battery. Very few install separate dedicated radio batteries. I often leave my FTM-400 on for a 8 or 10 hour workday with the engine off. I often have the rig in cross band repeat mode so it's transmitting periodically throughout the day. I've never had it run down my starting battery where the truck wouldn't start. I've had similar rigs in other vehicles for nearly 30 years. Most were just a starting battery and I never killed one.
    K0UO and KO4ESA like this.
  8. W9WQA

    W9WQA Ham Member QRZ Page

    just dont leave the dome lite oh...
    K0UO and KO4ESA like this.
  9. W9WQA

    W9WQA Ham Member QRZ Page

    could be luck
    KO4ESA likes this.
  10. KO4ESA

    KO4ESA Ham Member QRZ Page

    Ten Mile Tennessee and I just purchased an ic705 to use as a portable radio. Mostly during trips and car shows.

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