Something to think about

Discussion in 'Mobile Radio Systems' started by K0BG, Jan 21, 2019.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    Yeah I already knew the Hall Effect Sensor was a line of crap. However what I suggest you give a try is is remove the Negative of the radio from the battery term post, shorten it and terminate on the Chassis hard point. Under the dash or under one of the kick boards on either passenger or drivers side. There are two good reasons for doing that that revolve around Equipotential Ground Plane.

    1. Should make the Negative return DC power path lower resistance which results in lower voltage loss thus a few more watts on TX. You want to limit voltage losses as much as practical.
    2. A Equipotential Ground plane significantly reduces impedance between any two points on the Ground Plane. So all the gizmos and gadgets have the same exact reference point which reduces/eliminates noise. In other words reduces interference between the various sensitive electronics used in modern vehicles.

    It may or may not be noticeable, but no harm in trying.
  2. N4MU

    N4MU Ham Member QRZ Page

    Now that'w worth doing and I understand the benefit of less loss (is that proper grammar?). When we get closer to hamfest day (read: spending $$$) I will definitely give it a try...perhaps a good time to do that would be just before I enlarge existing wiring as a matter of fact. Also, by doing this (using body bond for neg) shouldn't that take care of the dreaded load sensor issue? Thanks for all your info! Too bad you're not much closer. I'd be happy to let "you show me how to do it"! LOL Thanks! BTW, there's no way in Hell I could ever find the main grounding point! It's pretty "dark" down there. You used to be able to see the pavement if you looked through the engine compartment...LOL again.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Me no care, me getit.

    In your application with dual batteries, not going to been seen by the sensor, at least not all of the current. The Sensor will only be on one of the Negative battery cables. So pop the hood, look at both batteries, and count how many wires are on each battery Negative Post. On one side I bet you see only 1 going straight to chassis and no sensor on it. On the other, one heavy conductor going to the engine block for the starter, one to the chassis, and maybe another going to the Fuse Distribution Block or alternator with a sensor.

    What the Hall Effect sensor is there for is the BMS to monitor charge current so as to tell the alternator to reduce voltage when the battery is charged up. When you start the vehicle, the alternator voltage is turned up to 14.2 to 14.2 volts to force as much current into the battery as the alternator can provide. Once that current tapers off tells the BMS the battery is charged and will reduce the Alternator voltage to around 13.2 to 13.6 volts and floats the battery so it does not over charge.

    So no worries about the sensor. Go back to what I said earlier, all the auto manufactures universally say about law enforcement radios; Bond the Negative Radio Cable to the nearest chassis hard point. Makes the sensor a moot point as it may or may not see the radio current. Like Ford told you the car BMS does not care.
  4. N4MU

    N4MU Ham Member QRZ Page

    THANKS and you just gave me a new definition for BMS...a familiar one with a new twist. I'll let you know when I do the voltage drop thing...old cable and new cable to chassis.
    BTW, yes...driver side battery as NO additional wires, pass side battery has additional wire with "something" wrapped very close -AND- a whole slew of smaller gauge wires that simply jump to firewall ground point.
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    That tells you immediately the BMS cannot monitor all the currents. To be able to monitor all the currents would require there to be only one cable, or a bundle with the sensor around the bundle making it act like a single cable. Otherwise you have parallel circuits the sensor cannot monitor.

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