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    Disclaimer: Lithium power packs are potentially dangerous. Never tamper with them. Never leave any lithium power pack, or any device containing lithium batteries charging in the house over night, especially not in the bedroom. There are many poorly constructed cells on the market that are unsafe. Be wary of unreasonable capacity claims of some lithium power packs. You should also always make sure that the USB cable you are using can handle the current you are going to pass through it!

    As you may have seen in some of my posts, I’ve been using USB power packs to power my Crumble projects. So I thought I would say something about these power packs which hopefully will be of use to Crumble users.

    The standard 3 primary cell power pack for the Crumble is ok, but it has limitations. It is only 4.5V and many modules require 5 V to function correctly. If connecting sparkles and motors to the Crumble, the voltage level can quickly drop too low. I have found this to be a particular problem with the ultrasonic measuring device. Then of course, the primary cells do not last very long and they have to be replaced. This is expensive and is bad for the environment.

    The Crumble in standby mode also draws about 6 mA, which doesn’t sound much, but it does mean that primary cells are not great for projects left running 24/7.

    NiMH cells are not suitable, so what to do?

    I have had a look at a range of different USB lithium power packs. They output 5 V, they are regulated overload protected and, they can be recharged up to 500 times, simply by plugging them into a USB port.

    This post turned out a lot longer than I expected, so I’ll make it into a PDF and post it 🙂


    Here is the full post as a PDF 🙂


    Had a look at the battery current draw when one of the Poundland £1 1200 mAh USB power packs is not being used to power anything.

    I had a pack where the cell inside had died and I had a spare cell, so before soldering it in I put a multimeter in the circuit.

    It measured 1.5 mA from the cell to the DC/DC converter board, without any USB device connected. So that should give you an idea of how long one will last in standby mode.

    Terry ONeill

    Why not use a cell phone USB charger and connect a USB-A cable to the + and – pins on the crumble?

    Shaun Lewis

    Is there an easy way of finding out whther a given USB power block has a sleep mode or not?

    Airlines Updates


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