3amp USB Wall Charger and Battery

I've got a niche piece of equipment that's powered by a USB barrel jack. It requires up to 3 amps of power, and I'm having stability issues with both wall chargers and batteries.

I find it hard to discern which USB batteries and wall chargers will be good for my purposes, any recommendations?

Further info:
It's a portable PCR-like testing machine that can test for assorted diseases using pre-packaged cassettes. It uses a little heater to keep the cassette at a configured temperature and a sensor to detect whatever you're looking for, taking about 40 minutes.

The heater spends periods of time on and off, with the device consuming next to zero power while off. Long enough that a battery might go into a low power state. If the battery doesn't respond quickly enough when the heater comes on, the voltage drops and either bluetooth drops (inconvenient, recoverable) or controller restarts (collect new sample, start all over).

A poor design IMO, surely the heater's high power draw could've been isolated from the rest of the machine, but they're scientists not electrical engineers I guess.

I need a battery and wall charger that will be rock solid so I stop losing tests. Any suggestions of how to choose a good product are very welcome.

Comments

  • I am having trouble both with the terms you are using, and your diagnosis of the problem. What is a "USB barrel jack"? Batteries don't go into low power states and take time to respond.

    If I had the problem you seem to be describing, that when the heater goes on, the voltage to the electronics dips, I'd go get a supercapacitor and wire it across the input so that for that short period of time it was supplying the current needed.

    • It's a cable with USB-A on one end, and a barrel jack on the other end. Here's an example.

      It's called Trickle Charging Mode where the battery assumes the connected device is a low-power device that still wants to sip power. Normally when the connected device starts sipping power very slowly the battery assumes it's fully charged and turns itself off. I wondered if something about this low power mode changed the way the batteries behave.

  • +1

    You're not referring to a device sold to you by Elizabeth Holmes by any chance are you?

    • Lol no, this is normal medical product from a reputable company. They do something similar to PCR by selectively amplifying DNA you are interested in detecting the presence of. Where PCR requires temperature cycles to replicate the DNA sequences, this uses a different method (that I'm no expert on) that is faster but has fewer useful applications. This is the device.

  • USB barrel jack?
    Do you mean like this USB to ‘barrel’?
    It won’t do 3A, but this 240V to ‘barrel’ should

  • Make/model/power requirements would all be helpful in offering suggesstions

    • This is the device. The data sheet isn't very helpful. DC5V, 3A, centre positive.

      I've tried two of these and two of these. Both specifically say they support 3A+ via the USB-A port, but I understand devices are supposed to negotiate additional power for anything over about 1-2A. It could be that since this is a simple barrel jack there's no negotiation so the battery isn't prepared to deliver 3A loads.

      Maybe my particular batteries are detecting the extended period of trickle charging as the connected device being fully charged so it switches off, or maybe it's assuming it's a low-current device and again isn't prepared for a sudden 3A load. Or maybe it's nothing like this, I dunno.

      I've tried a 5V 3A mains PSU w barrel jack, which still had a bluetooth connection issue. I've ordered a USB-C/barrel jack cable that's pre configured to negotiate 5V 3A+ loads which I'm hoping will solve it, but if the issue is the battery just turning itself off thinking the device is charged I'm not sure where to go.

      I've got an iron in the fire which is a

      • Didn’t it come with a power supply?
        Get it working off a mains PSU before stuffing around with a powerbank. If it doesn’t work, check your PSU is ok with a multimeter. There is no point stuffing around with a complex solution (powerbank) when the simple solution (mains PSU) isn’t working.
        Dunno what Bluetooth has to do with the PSU.
        Are you sure about it’s 5V?

        • Came w a psu, not a good one and has a euro plug so using with an adapter. The power hasn't dropped on wall charge just bluetooth.

          Dunno what Bluetooth has to do with the PSU.

          Seems the circuit wasn't designed super well – heater's draw isn't isolated from the main controller or bluetooth chip. If the voltage drops then apparently can cause bluetooth chip to reset.

          Are you sure about it’s 5V

          Written on the box and the unit

          • @ozrobert: Because you haven’t explained this very well, I’m guessing this device provides results to a phone app using Bluetooth, but the Bluetooth to said phone app sometimes disconnects resulting in a loss of results, and you think that Bluetooth disconnection relates to a possible voltage drop to the Bluetooth chip, possibly triggered by the PCR device turning on its internal heater.
            Is that the situation?

            Noting(LOL),

            the device comes with a reliable portable smart charging station

            I doubt your theory, especially since this is pseudo ‘medical equipment’, but regardless, your options seem to be:
            * Talk to the supplier
            * Google other people’s experiences
            * Monitor your PSU voltage & current, including as heater turns on & off
            * Look into a higher current PSU
            * Get a hardware engineer to diagnose the circuitry
            * If it’s for commercial use, buy a commercial grade device. They must’ve dropped a lot in price post COVID

Login or Join to leave a comment