Battery Charging Station

[Valcore]

For an Engineering Design and Development class, my partner and I have decided to make a new battery charging station for our senior project, since the one that we made last year ended up breaking on us. We were wondering if any of you guys had any ideas you'd like to share or suggestions of what to include in our project.

[*Oz*]

It would also be very helpful to fill out this survey. It will help us identify more constraints and help result in a better cart.

https://docs.google.com/forms/d/1o2H...ZP8Oo/viewform

-Thanks

[yash101]

For my design, I am aiming at simplicity of use, and functional. My battery cart shall be able to run on it's own without an external power source, to charge robot batteries.
Here's My project Synopsis:
http://devstuff.no-ip.biz:890/?page_id=58

[MysterE]

Curious - Are you planning on using chargers that can also desulfate?

[yash101]

That is a great idea . However, aren't chargers with the ability to desulfate fairly expensive, and often quite heavy? Weight may not be too much of a problem is a motorized drive used (using motors like window motors!)

[MichaelBick]

Originally Posted by yash101

(using motors like window motors!)

Window motors aren't very powerful whatsoever

[MysterE]

We just got a charger/constant desulfator from BatteryMinder. http://batteryminders.com/details.php?prod=2012

We just got it in but it charges well. We will be running tests with an old battery and BatteryBeak to confirm how well it works.

[yash101]

They are geared down quite a bit, so four of these window motors are quite some power! I can imagine a team using window motors for their drivetrain!

[EricH]

Originally Posted by yash101

They are geared down quite a bit, so four of these window motors are quite some power! I can imagine a team using window motors for their drivetrain!

To speak for Billfred and FRC1293: Never again! (If I'm wrong, fellas, let me know...)

Devyash, I think you need to do some study of the spec sheets. Yes, the window motors have some power--but if you look, they're weak, with a capital "weak". Compared to the CIM especially. Looking at the FRC official specs, the Densos only put out 23W--at MAX power. The CIMs? 337W, or more than 10x the window motors. The only motor weaker than the Denso window motors is the other Denso motor (18W), or the VEX motors (4W).

You've been fooled by their non-backdriveability. The worm gears in their transmissions (which, IIRC, are ruled integral to the motor) keep them from going backwards when loaded. That said, having that sort of thing--with a proper clutch to allow the cart to move without power applied--does have its advantages (follow the link below).


Now, an anecdote to explain my earlier comment about "never again"... There WAS a team that used window motors in their drivetrain, about a decade ago.
http://www.chiefdelphi.com/media/photos/19905 for pictures and reason--original thread seems to have been deleted.

[Jon Stratis]

Originally Posted by yash101

They are geared down quite a bit, so four of these window motors are quite some power! I can imagine a team using window motors for their drivetrain!

No, they really aren't. Each window motor has 23W of power - 4 of them would be 92W. In comparison, a single CIM motor has 337W of power. Correctly geared, a CIM motor is both faster (speed) and stronger (torque) than a window motor.

http://www.usfirst.org/sites/default...nformation.pdf

[Ether]

Originally Posted by yash101

They are geared down quite a bit, so four of these window motors are quite some power! I can imagine a team using window motors for their drivetrain!

You seem to be confusing power and torque.

[yash101]

Sorry for the confusion. I mean high torque, low speed!

Also, another up on those window motors is that they will automatically brake because they consist of a worm drive!

If you guys are wondering about my power ideas, currently, I am planning marine batteries. Has anyone used those WInston LIS batteries? They seem too good to be true. Hopefully you guys have google translate. That site is in Chinese!

[BurkeHalderman]

Originally Posted by yash101

Also, another up on those window motors is that they will automatically brake because they consist of a worm drive!

No. Just no.

A worm gear will not break under a drivetrain application if used properly. In fact AndyMark offers a worm gear gearbox to be used for various applications such as lifting and drive. The advantage for using a worm gear is the anti-backdrive properties. Yes the KOP windows motors are breakable, but not all worm drives are made from cheaper plastic such as the KOP denso window motors. And if you break the worm gear a window motor then chances are some re-designing should be done.

AndyMark WormBox:
http://www.andymark.com/product-p/am-0917.htm

Team 1293 used window motors for their drive in 2003:
http://www.chiefdelphi.com/forums/sh...ad.php?t=33926

Basically why use window motors in a drivetrain application when much more suitable options are available.

Back to the OP's question, what I look for in a battery charging station is how many batteries it can hold, how many it can charge at once, maneuverability, and it's footprint. I'd recommend that your charging station should hold a minimum of six batteries, any less and you run a chance of not having fully charged batteries late in the competition (this is based off of my own experiences). As far as charging I'd get a 3-battery charger from AM:
http://www.andymark.com/Battery-Char...-p/am-2026.htm
We used one of for the last two seasons and they are great.
The charging station should be fairly maneuverable, and like everything in your pit should have a small footprint. The more room in your pit to work on the robot the better.

Here's an example of what I would consider the perfect cart:
http://www.chiefdelphi.com/forums/sh...ht=pwnage+cart

However it all depends on your resources. I look forward to seeing the results.

[MichaelBick]

Originally Posted by yash101

Sorry for the confusion. I mean high torque, low speed!

Just with 12 batteries you are looking at 156 lbs. Add in 35 for chargers and frame you are at 190 lbs. Just looking at the batteries you mention you need to add another 40 lbs. With window motors on a 4:1 so that you get reasonable current draw you are at .5fps. That is insanely slow. CIMs would likely be the much better fit here as they have a relatively low RPM, are high power, and are built like tanks.

[yash101]

Yeah...I guess that I overestimated window motors! Their gear ratio seems better than it actually is