I am designing an advanced driver station for our team, and I was wondering if a car battery would be allowed as a power source. I would use a shunt connected to the mcu to monitor the battery conditions and see if it would be safe. Are car batteries allowed at the competition if they are not on the robot? If anyone is interested in the project, the homepage is at: http://devstuff.no-ip.biz:890
From previous Q&A:
I believe there are available power strips or individual sockets at each of the driver stations on all fields. I’m pretty sure they are available at all venues, if you need power.
I was wanting the cart to be portable, and I wanted two BAG motors aboard to help reduce the weight of many batteries; otherwise, the 15 amp outlet would be the best solution
I believe there are connectors for the KOP driver station computers, however teams not running that computer can not benefit from them.
We wound up connecting a 12v robot battery to a 120v inverter, and powered the laptop charger directly. This saved us on a number of occasions, going into matches only to find that the driver station battery was about to die as we were setting up.
I am talking about a 2000 watt inverter connected to a car battery, breakered and fused. I am willing to place every safety feature possible, like current watch and temp watch. In my current schematic, I am having 250 amp MOSFETs powering everything so if too high of a current is detected, an automatic shutdown of that component for a set amount of time. It will also have a display and a usb-serial plug to the driver station and control EVERYTHING, even the power TO the motor drivers (victors)
EDIT: I am also thinking of placing the battery inside an ABS holder, because of it’s resistance to acid spills. We would smell a spill before it becomes too late.
Who is going to carry this monster?
A robot battery and one of these should suffice.
This is kind of overkill, but this is what I was looking at. However, the price tag isn’t the prettiest. However, we could start out with a small inverter to just start off with and if we decide to do something like charging robot batteries on the fly, maybe upgrading to something similar to this would be feasible. However, the inverter that Gregor linked to was the first one that I looked at. BTW, has anyone visited the site that I posted and think something is impractical?
Use solid state relays not MOSFETs.
Still not really sure why you have such high current requirements.
Propeller input + voltage divider = 5V tolerant input
This response was for a time when power was not supplied in the driver’s station and this became the FRC recommendation for that year.
We are very concerned about safety in all areas of the competition and moving a heavy, liquid acid battery and high voltage source pushes the envelope on that precept. Additionally, there is very little floor space in the driver’s station to place your equipment. There is no substitute to having the laptop battery charged before you come to the field. And while nice, most teams find there is no substitute for charging batteries in the pit prior to coming to the field.
More likely to be invoked is this…
The OPERATOR CONSOLE must not exceed 60 in. long by 12 in. deep (excluding any items that are held or worn bythe DRIVERS during the match). There is a 54 in. long by 2 in. wide strip of hook-and-loop tape (“loop” side) along the center of the PLAYER STATION support shelf that may be used to secure the OPERATOR CONSOLE to the shelf. See Section2.2.9 for details.
In 2011 Team 11 was given an approval to use batteries in flashlights at the driver’s station
However I agree this seems extreme and of course rules change. Those flashlights would not exceed the driver’s station dimensions but we scraped it early on. It was for a camera tracking system we did not need.
Considering that a laptop charger is usually < 150W and < 30V.
I do not understand why anyone would need the sorts of current listed at the link.
If you must charge a laptop from a battery why not get a universal laptop car charger and put an Anderson Power connector on the end for a FIRST approved robot battery?
At least then you should have plenty of opportunities to charge that robot battery.
Plus handling the robot batteries is typical for this competition.
Plus a laptop charger meant to work in the car will not put out wall socket voltages.
So there’s much less risk of some unusual accident.
Plus 150W max is no worse that 2 CIMs dragging on that battery.
Finally the custom electronics power supply on the robot would work at the driver’s station (with less issues).
Course again it is entirely at FIRST’s discretion if they allow this in future years.
I will also add that in past years while in various volunteer positions I’ve had the crazed experience of trying to help a team find a replacement laptop battery at a competition (laptop batteries are not cheap and the software just takes hours to install). Lucky for those that got one I have several friends with computer stores and piles of questionable laptops they can part for a used spare. Usually my friends have been good enough to just give them the battery which is generous considering it’s a zero notice demand and sometimes they’ve even delivered it (hey that was not 30 minutes or less :)).
I myself have a universal car charger with an Anderson power connector and a few tails just in case something like this happens. I come prepared (I even lately bring a spare dual core laptop suitable as a driver’s station with most of the software and updates installed) and the mess stops with me. However I would never offer this up as a solution without confirming with the field crew they understand what is going on (even if the rules might allow it in any given year).
We have always plugged our laptop in the pits between matches. We have had close calls. Especially in the finals when you do not go back to the pits between matches. We are looking at putting power on our cart for this reason.
The FRC legal battery with a small inverter will keep your lap top charged. Since it is the same battery as the robot, you get a spare robot battery or you can use an older robot battery that doesn’t have the umph for competition. A lot less likely to raise a flag with the safety people since there are 100s in the building already.
you could also use a computer that has the same power requirements as the classmate.
Our Lenovo x61 laptop-tablet computer has a power adapter that uses the same connection just before the power brick.
Please don’t plan on unplugging parts of the field at your whim.
The field provides a barrel connector for a Classmate. It doesn’t provide any other plugs.
I am changing my design a bit. We want our laptop to be able to come off the cart, so I thought of designing a docking station. Are supercapacitors allowed in the driver station? They could probably hold power for use in a little time, and they would charge in no time! Also, I am thinking of dropping the idea of to car battery. Something safer might be better. Also, the team doesn’t want the two CIMs because of safety issues. That means that a 6.6 volt LiFePO4 battery at 5000 mAH should suffice. I am expecting the control panel to draw a maximum of 500 mAH, monitoring all batteries, highest PLL and display on highest brightness. BTW, if anyone has been on my website, http://devstuff.no-ip.info, please tell me any concerns or ideas for my ‘advanced driver station’. Also, does anyone know how to model a hinge in inventor? I want the drive station to have a little of stashing space!
Regardless of legality in FRC:
Per the other topic where I mentioned supercapacitors please be sure to consider internal resistance when you consider this.
The better capacitors from DigiKey are much lower ESR.
Also along with that ‘charging in no time’ consider what your in-rush currents will actually be for whatever large capacitance you are considering.
I’m still not quite sure what you are powering with all this.
Netbooks and laptops generally have internal batteries.
LiFePO4 at 5 AH? If you’re only doing the monitoring, you can probably get away with that. (Barring safety, which I’ll get to.) But if you’re charging batteries, I’d use something with a lot more charge capacity, say the car battery or maybe a deep-cycle battery.
LiFePO4 batteries are known to need care. Shipping: You can drive 'em, but if you’re going to ship 'em you need someone certified to do so at both ends; if you’re going to fly 'em, you really mean you’re going to drive 'em. No joke. They are a bit less flammable than LiPO… but that’s not saying much. Gotta take care of 'em. Oh, and they’re not cheap.
–Display panel is OK, but why does it need to integrate with the driver’s station? Make it separate–use an ancient laptop or something similar. The DS doesn’t need to know that stuff
–You’re asking for trouble with the magnets, particularly. Do it just right, you’re OK–MAYBE. Do it wrong and the least you can expect is a pinched finger or ten depending on how many are caught between the driver station and the cart. Maybe a bit of a shock, delivered to a person. Maybe some electromagnetic interference. You get the picture.
–No power switch to cut ALL power is listed; that’s probably a good idea in case something goes down.
If I were you, I’d stick with a car battery, and use PowerPole connections for all power to the driver’s station laptop charger–no magnets whatsoever–and have another means of lockdown. Or, seeing as you’re thinking of having an outlet on the cart, just use that.
The REAL question is, Why are you NOT using your laptop’s INTERNAL battery, and just charging that?
Thank you for the feedback. I think I may have forgotten to put on my site that the current draw will be monitored. If the current draw ever goes too high in some part, an automatic shutdown of that part will happen. Also, the battery cart, as my team is saying, if typically going to be plugged in. About the display, the Propeller chip, what I am currently wanting to work with should be very easy to interface. I want the battery cart to think for itself…Monitoring battery charge levels, and selecting the perfect battery for the next match. (our team likes to switch out batteries almost every match). Also, we are using the laptop internal battery. However, incidents where it doesn’t charge are often so this is to limit that. The small battery will be just to power the control panel. Also, I did chose LiFePO4 because we do not have very high space constraints currently. They are also a lot safer than LiPolys, especially because I probably will 3D print a perfectly fitting mount for the battery. Because of the want for simplicity, I would like everything to dock together, and the magnets won’t be way too strong to hurt someone. We probably have more dangers around the power tools than we would have with these magnets. Just to make it clear to me, the team and anyone else wondering, The magnets will conduct, not induct. If that won’t work, I will put metal sheets and brushes for the contacts.
Theory is a nice place… I suggest having one point with a big, easy-to-hit button or switch to shut down the whole thing. If that current draw happens to be in the monitoring circuit… This is just for extra safety, mind you. Also to keep the safety folks happy. It’s easier to put it in now, during design, than to add it later.
Also, the battery cart, as my team is saying, if typically going to be plugged in.
Bear in mind that if the cart comes out to the competition floor, power drops may or may not be available. Most regionals, probably not; Championships typically does have something.
Also, we are using the laptop internal battery. However, incidents where it doesn’t charge are often so this is to limit that.
I think there might be something funny with the laptop charging system. If that’s the case, maybe putting a new charge system to get to the laptop isn’t going to help. That, or you still have to remember to charge it (AKA plug it in/put the station on the cart).
Also, I did chose LiFePO4 because we do not have very high space constraints currently. They are also a lot safer than LiPolys, especially because I probably will 3D print a perfectly fitting mount for the battery.
True–but remember to take care of them. The 12V LiFePO4s I’ve had experience with would take up the exact same space as the 12V SLAs used on an FRC robot. Matter of fact, the LiFePO4 vs SLA debate hinged on weight and voltage drop pattern. (LiFePO4 won both categories, despite losing cost.) A perfectly-fitting mount does virtually nothing for battery safety, BTW–I’ve seen the effects of overcharging a LiPo when a good mount would have done nothing. I’ve seen SLAs spark while charging on a normal charger–I think there was something funny about the setup, but what escapes me. Can’t say I’ve seen anything with LiFePO4s, but I’ve heard about the hazards. Note the transit comments earlier–LiPos, IIRC, have similar constraints unless they’re in a special container, and maybe even then.
Because of the want for simplicity, I would like everything to dock together, and the magnets won’t be way too strong to hurt someone. We probably have more dangers around the power tools than we would have with these magnets.
Again, just take care with the strength. I know I’ve had a project designed for rare-earth magnets where I had to make it clear that nobody but nobody was to put their hand between the magnet carrier and anything metal. Admittedly, 20+ magnets in a small steel disc can easily be way different than 4-5 spread out over an operator console–but will those 4-5 actually hold the console on the cart when it goes over a bump?
Just to make it clear to me, the team and anyone else wondering, The magnets will conduct, not induct. If that won’t work, I will put metal sheets and brushes for the contacts.
Just for safety’s sake, please please make it darn near impossible for anything that ISN’T the driver’s station to contact both magnets–or whatever the contacts are–at once. Maybe have a cap over one or more when the station is off–on both the station and the cart. (I’d say impossible… but then someone would find a way to connect both through him/herself. It’s a law of nature.)