Low insertion force connector

[Foxxz]

I am helping modify a power wheelchair for a disabled family member. The charging port on their wheelchair has been a source of frustration for them and they'd like to move it and replace it with an easier to use connector.

I am looking for a 2-terminal connector to handle 24v @ 25a that has low insertion and disconnect force and is water resistant when not in use (it will be mounted low on the wheelchair and get splashed). Something like a spring loaded cover flap would be fine. But having to screw on or unscrew a cover would be difficult. While charging the port on the wheelchair does not need to maintain any water resistance.

I appreciate the recommendations

[Foxxz]

Your links (specifically the electric vehicle connectors) gave me an idea. Maybe a plug like the 7 pin towing connector on trucks. The receptacle on the vehicle commonly has a door on it to keep out debris when not in use.

The XLR connectors would also be a good idea. Looks like there is a 4 pin variant. If they can handle the power rating and a little bit of weather proofing (like the spring loaded door) then that might be ideal.

Thank you. Please keep the ideas flowing.

[free_electron]

why a connector ? inductive charging. It doesn't need to be complicated. take a simple ac transformer and cut the core in half one coil in the wheel chair, one in the charger. bring both cores together . microswitch engages driving coil when they are in range.

[inse]

@free_electron
...and how do you transfer 24V DC without designing an entirely new charger?

[Gyro]

You might want to look at the Neutrik Powerconn series... https://www.neutrik.com/en/products/power The audio versions are often used on PA stacks, stage monitors and the like.

They are pretty robust and have a low insertion force slide-in and followed by twist operation which may or may not be easier for your family member to handle. Both the plug and the socket have concealed contacts, so you wouldn't have any difficulty with live end short circuits.

If you look in the accessories section, you will find things like sealing gaskets, waterproof flaps, covers etc.


EDIT: Actually, as it isn't a mains application, you could also use the Speakon speaker connectors, they are rated to 40A continuous, 50A peak... https://www.neutrik.com/en/product/nl2fx

[Gyro]

Yes, I saw the no power and mains use on the Speakon connectors. This may be an operating environment thing though - you don't want the possibility of connecting DC power or mains into a speaker cabinet. I really don't know though, they have pretty rugged contacts, in addition to being cheap to replace.

The no breaking on the Powercon is potentially an issue though.

Generally, looking at switch / relay contact ratings, you normally see specifications of 24V DC / 240V AC to account for the lack of zero-crossings. I think It's going to be tough to find an easily insertable connector that is officially rated for hot making (contact weld) / breaking (arc) high current DC, even the vehicle ones. One thought is that the connector is only likely to be removed once the battery is charged, and so is only carrying minimal current.

[free_electron]

@free_electron
...and how do you transfer 24V DC without designing an entirely new charger?

i'm assuming the charger is in the wheelchair and only needs 24v dc. so a simple bridge rectifier is needed. the transformer runs on regular line AC. no need for inverters.

[Foxxz]

I will add a more detail from the questions I see being asked.

About the disabled gentleman... He is in his 30s and tries to live a normal life as much as the rest of us - friends, outings, conventions. One limb is a leg + foot. His other foot is attached to his hip - he can use a computer mouse with it. He has one arm which is just a stub about 4 inches long he uses to manipulate the wheelchair joystick.

The wheelchair uses 2 lead acid gel batteries for 24v @ ~70ah which tend to fade out over the course of 2 years of daily cycling. I am (ahem) "upgrading" it to 105ah LiFePO4 batteries (could probably fit double that but $$$). You can bet on a busy day he can run his current batteries dead quickly and then the charger takes something like 8 hours to recharge it.

The present charger uses something akin to an XLR connector with no latch. It is an external DC charger that connects directly to the battery via that plug. The problem is it plugs into the joystick controller that is mounted up high at shoulder level where he can manipulate the joystick with his "arm". Therein lies one problem. He can sit on the floor and yank the plug out of the controller by the wire or grip the cord between his shoulder and cheek and unplug it but can not plug the charger back in. I have looked at the cabling on the controller and charger and it is only 16ga wire so I don't think it can handle higher current anyway.

Given the gentleman's disability; he can not manipulate something like a latch while simultaneously holding an object.  His options are:
Using his foot/toes to hold an object while sitting on the floor - hence a low mounted charge port that may be subjected to splashing while rolling across wet pavement, shallow puddles, and snow.
Clasping an object between his shoulder and cheek - he could reach a charging port mounted up higher, it'd probably need to be a larger connector for his to be able to grip and align properly.
In both situations it might be difficult to apply much insertion force.


So after talking with him the requirements were:
Longer battery life
Faster charge up time
Make the charging port usable for him - low insertion force, no latch, no indexing if possible


Sorry I was trying to keep things simple initially but I thought a more detailed explanation of the "why" might help.

[BrokenYugo]

A more detailed "why" is usually beneficial.

Having a picture of the problem in my head now, if I'm understanding correctly, I'm thinking something similar to the current high mount arrangement. Just add a length of some rigid lightweight tubing to the plug, so he may see the plug and easily align it with the tube held between his shoulder and cheek. If that cannot give enough force/grip a protrusion could be added to catch somewhere on the front of the shoulder area to let him lean on it a little, same goes for yanking it out.

[inse]

@free_electron
Many years ago I repaired several chargers for golf caddies,12V SLA, and the carging circuit was in the power supply.

[tooki]

Does the chair need to be movable while charging? If not, I’d ponder whether it’s possible to create a “drive-in” charging bay where the mere act of parking the chair enables charging.

What about a magnetically-mated charging port, kinda like a giant MagSafe?


(In all of these cases, I’d use use some kind of load switch so that power doesn’t flow until the physical connection is made.)