A slow battery swap once cost my team dearly. There’s no experience like watching your robot obviously run out of power because your drive team didn’t have time to both charge pneumatics and change battery…when you had to win that match to extend your season.
Okay, I’ll be the voice of caution here.
I once was mentoring a team that elected to put their battery mount upside down as you’re proposing, and we had an inspector who would not let it fly. I was involved in the decision for how to mount it, and I know it was rock solid. The whole depth of the battery was supported—basically five full faces of the prism surrounding the battery—it did not hang below the frame, and the bottom side was supported with two redundant straps. But nevertheless, our inspector didn’t like it and wanted it changed.
I’m not saying I think it’s a bad idea, but be prepared that some inspectors may not see it the same way.
At that point you probably should have gone to the LRI. If there wasn’t anything illegal about it, the inspector should have nothing to say. Only the LRI has the authority to declare something illegal due to a safety concern.
My usual method for inspecting the battery mounts’ security was to grab the loaded battery and try to shake and jostle it out of the mounts. If it moved more than a little bit, I would mention that, but I would phrase it as a suggestion (along with “This is really likely to come out on the field, and you don’t want that”). If it came out, the team had to fix it.
There seems to be two philosophies regarding battery mounting. One is to ensure that the battery is tightly held in place like @EricH describes. The other interpretation of “secure” is to drop the battery into a 5-sided box that prevents the battery from sliding around but there is no 6th side to prevent the battery from falling out if the robot flipped over. I have seen some pretty prominent teams doing it the second way.
In the second link you provided, it states that the battery terminal was driven into the battery. That can happen no matter what orientation the battery is mounted in, either by the battery shifting position or something moving and pushing against the terminal. If the battery was mounted sufficiently securely AND with adequate clearance around the terminals, the fire would not have happened.
The OP did not mention the battery being mounted upside down, had they I would have highly recommend against it.
There are two reason for this. First in the unlikely case your mounting method fails the battery would fall leads first which may cause a leak, short and/or fire. Secondly not all batteries are as sealed as others and you wouldn’t want acid leaking on your robot or the field.
I just re-read R37 and it specifically states that the battery “will not dislodge during vigorous ROBOT interaction including if the ROBOT is turned over or placed in any arbitrary orientation.” Emphasis is mine.
On teams I have worked with, we mount the battery securely enough that one can lift one end of the robot off the floor by grabbing the battery by the “handle” and lifting up.
By battery “handle” I assume you mean the leads, correct?
I’ll leave now…
My first thought when reading your post is that you are asking about mounting the battery under the robot. OIf that is the case, please reconsider your design.
I didn’t mean what you think I did. By “upside down,” and I guess I could have been more careful with my words, I meant what the OP was referring to—the direction of egress for the battery being downward, not the leads being on the bottom. That is why I phrased it as the mount being upside down, not the battery being upside down.
Or don’t! Assuming ample ground clearance, a 6-sided enclosure that hangs from a solid brainpan would be very legal and very cool. You’ll just have to tip your robot over to change it every time, but it’s workable.
I seem to recall a certain tiny vacuum robot winning a division last year with a bottom-mounted battery.
And seeded to pick at every event
Mounting a battery on the bottom of a robot in a game with high spots on the field is not a good choice. The same can be said for bottom mounting the PDP and other critical robot components. Please review Sec. 9-7 and R8. While something may not be covered by a specific rule, doesn’t mean it is a good design choice.
If it’s a 6 sided box, how does it matter which side opens up so long as your ground clearance is still safe and the opening side is still secured well? What is the functional difference between what is being proposed here and a team who installs their battery in the bent sheet metal back part of the AM14U3?
I can only offer advice based on a general description of the robot design. I have seen a lot of robots over the years, and only a handful that have used battery mounting under the robot effectively. We did it a long time ago and it didn’t work that well.
95 has used bottom mounted batteries in at least two robots in recent years, and maybe a pre-season build. Aside from the minor annoyance of having to tip the robot over to effect battery changes, it wasn’t a problem. We started last season with a battery mounted on the bottom, but ended up putting it on ‘top’ so we could move it around to manipulate CG. You can see the original mounting position in this photo:
The battery slid into part of the frame and was secured to the wood deck with a big honking velcro strap or two. It held on fine repeatedly driving off the Hab2 platform.
We’ve also done a couple of upside-down PDPs. I recall being concerned that the breakers might fall out under vibration, but it’s never turned out to be a real problem. If anything, having most of the electronics upside down and under the robot kept game pieces and robots from whacking them, and swarf and debris to fall out.
I have to remind everyone that there are a number of rules that specify visibility of components. In addition, if there is an issue with your robot on the field and the volunteers cannot easily determine the problem, you may be disabled and bypassed for that match.