Although we never had it untill this day I am concerned about someday someone might connect battery backwards. I don’t think components on the robot have reverse voltage protection. Making the necesarry warnings to team will avoid from happening to some point but team can be tired after working for hours and might not realize it is connected backwards. So is there anything we can implement into our battery changing procedure or any electrical/mechanical fail-safe to prevent it from happening?
Enforce red-red, black-black connections everywhere on the robot. (Or your equivalent.)
Ensure that red is + and black is -.
Visually check all connections before powering on.
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Check your battery connectors during assembly. Once they’re assembled everything is polarized appropriately, but until they are that’s a risk…
Fortunately, the main 120a breaker will happily open and prevent damaging currents flow through the Rev PDH and associated falcons and SparkMax. We, uh, “experimentally determined” this recently when we went too fast reassembling a battery connector. So it’s not actually a huge issue as long as your stuff is correct downstream and you’re using a main breaker.
It’s a lot easier to damage individual components (SparkMax is particularly vulnerable) where the main distribution is correctly polarized but a single device is backwards.
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As part of the team’s procedure to install wires and an Anderson connector to a battery, add a step to test the battery with a CTR battery beak BEFORE the battery can be connected to a robot. A beak is protected against reverse polarity. If the beak will not light up, the polarity of the battery connector should be checked and fixed if needed.
For connecting motors to controllers and controllers to a PDH, we use insulated male/female spade connectors from TE Connectivity. We have a standard for which color wire gets which half of the connector pair (e.g. controller input red gets male, black gets female; PDH output red gets female, black gets male). This would not stop someone from putting a red wire in a black Wago connector on the PDH, but it does stop someone from connecting the controller wires to the PDH wires with the wrong polarity.
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I wouldn’t rely on this – the main breaker may limit the time that a very large current can flow, but there is still a very large amount of energy involved. If this is all going through only a few devices (simple robot, robot with mostly motor controllers that are reverse-polarity protected, etc.) it will very likely not save the day. Even if the current is high enough to trip fairly quickly and spread over many devices, it will still cause considerable stress and could fry individual parts.
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It was not an intentional situation. Luckily we didn’t appear to fry anything. the fact that I did not end up with a $2,000 scrap pile is solace to OP’s anxiety, not a recommendation to try it.
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