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Thread: power chair batteries

  1. #21
    Quote Originally Posted by wheelin 48 View Post
    its an on board charger do i check it somewere on the charger itself or at the joystick
    Ideally, you want to check on the battery POSTS to eliminate the effects of cable, connector and connection resistance (as magnified by any load passing through those potential problem points).

    You can check at the "charger port" (often near your joystick controller; its on the battery pack itself, for some chairs/scooters) by probing between the two diametrically opposed connector pins (i.e., the two that are farthest apart, "across" from each other). The third (middle) pin is an "inhibit" signal that prevents the chair from moving while connected to a charger (disables the motors). I'd wager that while on the "onboard charger", you can't engage the motors (if you COULD, then you could examine the meter built into that charger to see what's happening to the battery "under load")

    But, this assumes there are "decent" connections in the wiring harness all the way from the battery to the charger port; and, that there is negligible load on the battery through that portion of the wiring harness. Any bad/loose connections/connectors increase the resistance of the cable. As the load (amperage) through the cable increases, that resistance causes a "voltage drop" to manifest.

    It's surprising how SLIGHT of a "bad connection" can make a meaningful difference in voltage available. For example, if you can wiggle the wires at the battery terminals (loose connection), you're probably losing a great deal of voltage ("potential" in technospeak) before you've made it more than an inch from the battery, itself!

    [I serviced a faulty battery cable on a forklift a few weeks back. Attempts to start the truck resulted in wisps of smoke coming from one of the battery terminals -- caused by the HEAT generated in that poor connection vaporizing some oil that had spilled on it!]

    As a gross check of the integrity of your wiring AND the state of the battery pack, you would monitor the voltage at some point "off" the battery as well as directly ON the battery posts. Then, apply a hefty load (like turning the motors on).

    If the voltage at the battery posts sags significantly, then either you've got a bad battery pack OR a defective/shorted load.

    If the voltage at the battery posts does NOT sag -- but the voltage at the remote/off point does, then you probably have a bad connection somewhere between the battery posts and that remote measurement point.

    Note that the charger pumps juice into the battery possibly through that same faulty connection! So, there will be "charging losses"...

  2. #22
    Quote Originally Posted by wheelin 48 View Post
    these are under warranty but ill keep those on the back burner
    You'd need to plan for a different charger, as well!

  3. #23
    Senior Member Andy's Avatar
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    Jun 2003
    Chicago IL
    Quote Originally Posted by automation View Post
    You'd need to plan for a different charger, as well!
    Makers of Lithium Iron battery alternatives usually add a CMB (charging management board) to the pack they build, which allows your typical 12V lead acid charger to be used. Of course with bizarroville medical equipment design, who knows what sort of weird shit they designed into that wheelchair's electronics. Hopefully it just supplies DC current to the battery and doesn't try to get fancy, lol

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