Why are loop keys female?

DubP

10 mW
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Mar 31, 2020
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I'm about to add a loop key and I thought I would make the removable key male and the part attached to the bike female. This way the side with power all the time is female and thus more protected from shorting. This makes sense to me but I just noticed that every loop key on the internet seems to have the removable side female. Does anyone know why or am I overthinking this?
 
For only a few bucks, you can get a power disconnect switch with a removable key, and insulate it to your heart's content.
 
Because the resistor can be replaced quickly with another loop key. At least that's how I do it with Antispark loop keys.
 
Unless you have space restrictions or some other reason to require a loop key instead of some other disconnect type, then like Chalo I'd recommend a keyed battery disconnect, like some of the ones shown here
I've been using one of the cheap several-dollar ones on SB Cruiser for several years (2016? 2017?) without problems.

Regarding loop keys, though:

I I just noticed that every loop key on the internet seems to have the removable side female.
The ones made using Anderson Powerpoles aren't, because they're genderless. ;)

(the SB series makes a good key because they even have T-handles and such available for them, and panel mounts and caps etc for the bike side; PP versions can also be and have been used).

Why the ones you found use female on the key, I don't know. I'd have to see your search terms and try them, then sort thru the results to see the specific usages.


This way the side with power all the time is female and thus more protected from shorting.
Not really something to worry about with a loop key's plug...shorting it's contacts does the same thing the key does, so it's not going to damage anything, unlike a power connector that has both + and - available to it. ;)
 
This tutorial seems to back up what eee291 said:
Do note that the female connector has a green L on the connector. It’s a resistor that kinda acts as a fuse as well in case you decided to mess up your battery polarity yea that happened to me
Good thing is that the loop key and male connector will be the one that pops, and hopefully everything else will be fine. Do not use a female XT90 without the resistor as a loop key.

So putting the resistor in the key makes it easy to replace by making a new key.

Which is interesting. I knew about anti-spark connectors with resistors built in that are connected first to prevent sparks on connection. Never considered they might be a fuse for saving stuff when connecting the polarity wrong too.
 
I guess it depends on what you are using the loop key for.

If you are only using it for a key, as specified in it's name, then it is just a wire from one contact to the other, such that removing it removes part of the connection from battery to controller (or whatever circuit it is part of). Can be used as a safety (like on racing motorcycles that require a lanyard to pull a disconnect if the rider comes off the bike, etc), or antitheft (pull the key off and the bike/etc is harder to use without the same kind of connector, if it's not a simple round-contact type you can stick a wire loop into). This is the most common usage I've seen here on ES, for instance.

If you're using it as a precharge key, that's a separate thing, and would also require a second key that gets plugged in either in place of it or in parallel with it to do the job of the other key, or a switch across the precharge key, etc. (but a switch would be silly since it's much better, cheaper, smaller, and more failsafe to use the switch for the precharge and the key for the conductor section). It wouldn't matter if the key was male or female for how easy or hard it would be to put a resistor into the contacts of the key, since that would go in the back of the key, where wires would have normally gone, and those should be the same for male or female or genderless types.

If it's for some other purpose, you'd need to define that to figure out why one way is used more than another.


BTW, the precharge resistor in an antispark connector can't protect against wrong polarity, unless you stop plugging it in before the main contacts touch.
 
It wouldn't matter if the key was male or female for how easy or hard it would be to put a resistor into the contacts of the key, since that would go in the back of the key, where wires would have normally gone, and those should be the same for male or female or genderless types.
Definitely not true for XT90 loop keys with resistors in them for anti-spark/pre-charge. I've only seen female ones with the resistor off the shelf, the resistor is in the front, and you only need one key, not two.
1634935093954.png
Resistor in the back doesn't make a lot of sense since you need to connect with the resistor first, and then only after that, add a connection without it which is done by pushing the connectors farther together and mating an additional set of contacts inside the barrel. Using the off the shelf female connector is definitely easier.
 
Yeah, there isn't room in a male for the resistor and extra contact. There are some other plug types that make this work...

2023-05-06 09_21_32-Amazon.com_ Amass AS150 and XT150 Male Female Anti Spark Connector Set for...png
Like this "XT150 AS" plug, the concept is the same. The top part of the connector is only attached to the lower with that plastic bit and, internally, there is a resistor from the top to the bottom so that as you make the connection you get the resistor portion first.

The biggest problem I've had with these (and a reason they suggest you make the "key" the AS part) is that the resistors tend to be TINY and can easily fry after a few plug/unplug. This is especially true as you go higher voltage. Where it got really popular in the eskate ecosystem, it's rare to go past 10-12s, so it didn't happen a ton, but if you make your bikes in the 14-20s realm (20s all day long for me) then you can fry these little resistors in as few as 2 plug cycles (glares at pile of dead XT90S' in the bin....).

You can make your own, if you get creative, but you end up needing two, one for the pre-charge and then you swap to one which is just a plain copper pass through:

2022-12-01 16.50.13.jpg
Plain copper bypass and one with a big chonker resistor that will survive longer than me.
 
Thanks for all the advice. I should have mentioned I was planning to use an XT90 with the anti spark resistor and the application is an on-off key. I'm only running 13S so less likely to blow up the precharge resistor. I had not heard that they die quick at higher voltage but it makes sense now that I think about it. I guess I'll follow the trend and use the female as the key. I do like that it's a lot smaller than the male side.
 
Here's what I'm going with. XT90 male bulkhead and female w/precharge resistor. I think it's rad.

Screenshot_20230516-003356.png
 
I finally got my bike set back up with all (ok most) of the updates I am planning. Here's how the loop key looks installed (still working cleanup to do please don't judge lol). I'm using it for an on/off switch. Only running 48V so no expected issues with the precharge resistor life.PXL_20230806_022608732.jpg
 

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