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.
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.
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. ::safety::
Here’s My project Synopsis:
Curious - Are you planning on using chargers that can also desulfate?
That is a great idea . However, aren’t chargers with the ability to desulfate fairly expensive, and often quite heavy?:rolleyes: Weight may not be too much of a problem is a motorized drive used (using motors like window motors!)::safety::
Window motors aren’t very powerful whatsoever
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.
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.
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.
You seem to be confusing power and torque.
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!
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.
Team 1293 used window motors for their drive in 2003:
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:
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:
However it all depends on your resources. I look forward to seeing the results.
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.
Yeah…I guess that I overestimated window motors! Their gear ratio seems better than it actually is
It’s not about the gear ratio, it is about the power. Any motor can be geared down so that you have enough torque, however speed will obviously suffer. Therefor you need a motor with adequate power so that you have enough torque AND speed.
What do you think about BAG motors? They have a nice torque and their RPM is high! Gearing it down shall allow it to do weight lifting, shoudn’t it?
What’s wrong with pushing a battery cart? Seriously our teams costco runs for snack and drinks is way more then 200 lbs. Pushing that stuff is not hard. yeah a bag motor may work with the right gearing but is it worth it? I much rather investing that time to make sure the ergonomics of the rack nice.
Kinda steering this back to the original poster’s question. We are tinkering with a battery rack this year that is ergonomic and organized. We want to have the charger display next to its corresponding battery and all the wiring tied to the frame. We will have a power strip inside so we will only have one plug to deal with. We may make it modular to the racks can be divided into smaller chunks. 3 rack with 4 batteries each may be more manageable.
I think its more better to go through a design matrix and hone the battery cart to practical design specs. I don’t think self propulsion is high on that list. having good ergonomics, ease of battery removal, locking casters, durable frame and clean wiring are much more important features to consider. I think this is a good lesson for students to think about ergonomics, something I see often as an afterthought in manufacturing.
The BAG motors are designed more for a high speed, low torque application. When thinking about what kinds of motors to use you should be looking at their specifications. For example the BAG motor has a free speed of 14,000+ RPM’s, a stall current draw of 41A, and a stall torque of only .4N•m. Compare this to the CIM Motor which has a free speed of 5,310 RPM’s, a stall current draw of 133A and a stall torque of 2.42N•m. The CIM motor is a work horse motor much better suited for a drive application. Keep the BAG motors and RS-series motors in more suitable applications for their specs, such as an intake, flywheel, etc.
I agree, all this talk about motorized and/or remote controlled toolboxes, robot carts, and charging stations, why not just push it the old fashion way. Besides adding motors and controls and such only adds weight, time, and money. Which could be spent on better things like the robot.
I also am not a big fan of the idea of motorized drive. A castor can easily make it possible to push the load. However, I am guessing that I may reach 400 pounds or more! At that weight, an assisting system will help. I want it so the motor doesn’t push, but just aids the person pushing the cart!