Robot Battery Placement
 

Hello CD,
Traditionally, my team has always mounted our batteries upright in our chassis. However, this year we are considering mounting it horizontally. Are there any safety risks/harm that comes with mounting it horizontally? Thanks. :)

Re: Robot Battery Placement
 

They can be mounted flat. No problem.

Re: Robot Battery Placement
 

None other than secure mounting. These are sealed lead acid batteries. If you were using a standard lead acid car battery (spillable, also not FRC legal), then you would have to make sure it is upright.

Re: Robot Battery Placement
 

One thing that could be worth noting is changing the battery - it could be harder (probably not significantly, but maybe if there are a lot of other mechanisms near it) to change the battery between matches if it's placed weirdly.

Re: Robot Battery Placement
 

The only time orientation matters is charging. You shouldn't charge the batteries upside down, as overcharging can generate hydrogen, and the vents at the top of the battery need to release said hydrogen.

Re: Robot Battery Placement
 

Make sure battery terminals don't hit any metal parts, especially when robot bumps into obstacles. The location should be easy to access and replace.

Re: Robot Battery Placement
 

Thanks for all your help! :)

Re: Robot Battery Placement
 

Huh. I've never heard that. Is charging batteries on their side still ok? Is the hydrogen still able to vent in that orientation?

Re: Robot Battery Placement
 

They shouldn't be able to. Keep all your battery terminals covered, all the time. Electrical tape is the natural choice to put over the ring terminals and bolts on the battery leads. If you get new batteries and aren't able to put leads on them right away, cover the terminals with tape or caps. It's a really small amount of effort to do, and there's just no sense in taking the risk of shorting a battery on anything.

Re: Robot Battery Placement
 

Most of the stuff I see says anything but upside down is fine. The issue is that when you're charging lead acid batteries the charging voltage is causing water electrolysis at the same time as the normal charging chemical reaction. A slow charge lets the H and O recombine at the same rate it's generated. Extremely rapid charging and overcharging create H and O faster than it can recombine, so pressure builds up and has to be vented through a pressure regulated valve. There shouldn't be much or any liquid electrolyte in an SLA battery, but charging it upside down would concentrate it at the valve, where it could leak if the valve ever has to release pressure.

So it's an unlikely problem, but completely avoidable by just not charging them upside down.

Re: Robot Battery Placement
 

If you have the terminals somewhere they could run into something outside the robot, most plastic coverings won't save you. For instance, imagine a battery horizontal underneath a robot last year with the terminals down instead of up. Electrical tape isn't going to stay an insulator long in those conditions. It's only protection against momentary incidental contact, not violent contact or repeated rubbing.

Re: Robot Battery Placement
 

I am not sure how many teams charge their batteries on the robot, we never did. We chose to replace battery for every match, so ease of replacing was on top of the priority list. We used electrical tape over the heat shrink rap on terminals as cushion (after our run into mysterious issue), so terminals were protected. Electrical tape doesn't have to come out or get loose to cause problems. When battery jumps as a result of robot bumps, if terminals hits metal tubing electrical tape gets hairline cut, it's hard to notice, which may cause short during next bump.

Re: Robot Battery Placement
 

Well sure. You shouldn't design your robot in a way that allows the battery to be subjected to repeated hard impacts, but you also shouldn't leave the terminals exposed in case something ever happens. I think Tungrus meant that the battery would shift within the robot, not come into contact with the outside world. But think, for instance, of a piece of your robot breaking off and landing inside the chassis. It shouldn't short the battery if the two come into momentary contact. Likewise around the shop. Don't handle batteries in an aggressive or unsafe way, but I'd rather have some insulation on the terminals than none.

Re: Robot Battery Placement
 

We mounted our battery vertical our first four years, and last year we used the AM battery mounting kit for the kit chassis, which mounts the battery horizontally. It was in there quite securely (better than most of our home brew solutions), and only required pulling a single bungee off to remove it from the bracket, but it did require moving some other components out of the way to get to the battery. I'm about 98% certain we're going vertical again this year.

Re: Robot Battery Placement
 

Is there a way to mount the AM mounting kit vertical on a kit chasis?

Re: Robot Battery Placement
 

Only if you have enough end sheet left, and then it still wouldn't be convenient. The AM kit takes advantage of the 3" width of the "C" on the end sheet being very slightly larger than the battery thickness, and secures the battery in that space.