I do not have enough batteries to power all my robots. Is there a way to plug a brain into a wall charger?
Not without DIYing, no. In theory you should be able to power the brain with any 12-14v power supply with a sufficient current rating (20+ amps), and at that point you would just have to build an adapter for actually plugging that power supply into the brain.
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Would a Vex battery charger work? Cut the plug that goes into the battery and use those leads to a modified battery to brain cable?
From memory a charger for a V5 batter has an output voltage of 16V, which would be higher than what the brain is rated for. Additionally, I believe that the current output provided by the charger would not be sufficient to run motors. Therefore, I don’t think you can safely use a charger to directly power the brain.
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I would highly recommend just buying more batteries as you might permanently damage the brain by modding it.
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The “smart battery” acts as sort of a voltage regulator for the “dumb charger”. It has been reported by VEX a couple years ago (you’ll need to search the forums if you want to see the post) that you can operate a brain just fine with the battery being actively charged. You cannot bypass the battery though. In our organization, we have three batteries per team…it’s just something you’ll need to buy to support your program.
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Unfortunately, this isn’t really possible at the moment, as the V5 battery is backordered.
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That what I have been trying to do, but there are no batteries to be found anywhere.
Did you check third party sellers?
If this was just an engineering problem, I would try to use a liberated ATX computer power supply. Most of those PSUs build in the last decade could supply motherboard and video cards with plenty (20A+) of current on the 12V rails.
ATX PSUs are very easy to use outside of a computer (just connect “Power On” green wire to GND), have an automatic overcurrent protection on their rails, and could be connected to the V5 power cable without any wire cutting and with minimal effort. Just pull two +12V and GND wires from one of the connectors and adjust their size to fit with V5 cable.
However, there are safety and legal concerns. In addition to +12V and GND lines, V5 power cable has two data wires that V5 brain uses to communicate with the battery and inquire its charge status, temperature, and error codes.
It would be an interesting experiment to see if V5 brain firmware was designed to shutdown for the safety reasons, if it couldn’t communicate with V5 battery and read a valid packet with status data out of the battery.
It would, also, be very nice for VEX to open up that communication protocol to allow students to experiment with such alternative power delivery methods.
However, I don’t think VEX legal department would appreciate any educational benefits that such openness would bring.
I guess, your best bet would be to contact VEX support to see if they have an emergency stash of the batteries to support your school engineering class, or try to coordinate borrowing some batteries from another school in your region.
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I have to agree with most people it would be smarter and cheaper to buy another battery instead of taking the risk of damaging the brain
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