DON'T LET YOUR BATTERY FAIL YOU!The battery is one of the most important parts of your robot. A failing battery can slow or stop you on the field at best, and create a serious safety hazard at worst. While every battery will eventually need to be retired and recycled, we've compiled some tips and advice to help FIRST Robotics Competition teams get the most from their batteries.
ASSEMBLY PREP BEFORE USEEvery battery will need a cable. We offer a battery cable (am-0009) with connectors crimped in place with a 6-ton pneumatic crimping tool for high security. If you want to use cables that aren't terminated like those that usually come in the Kit of Parts, you can crimp on your own terminals or use a floating tongue lug that screws into place. (We don't recommend the floating tongue lugs because they can come undone, but a poor termination job of any sort is not good!)
When attaching your cable to the battery, use a #10 star washer between the connector and the terminal on the battery. This will cut through any surface crud on both sides that can increase resistance and ensure a solid mechanical connection between them. Once attached, nothing in the connection should wiggle or move. If it can move now, it will move more once on the robot--and that's how things get undone.
After your terminals are connected solidly, you need to insulate both terminals until none of the metal is showing. Use plenty of quality electrical tape or heat shrink.
We've started including stickers with our batteries to let you mark when a battery was purchased and its identifier within your team. (Some teams use the year and a letter to identify batteries, some use Greek letters, and others just start naming them random things. It's your call, as long as you can tell them apart!)
CHARGINGThe charger that comes in the Kit of Parts, as well as our 1-bank (am-2555) and 3-bank (am-2026)chargers, are all smart chargers. It's okay to charge at the 6A setting on all of them because the charger will modulate the charge current to adapt to the battery's actual needs. If you're looking at other chargers, be sure to check that!
The battery chargers we sell come with the Anderson SB-50A connectors attached. If yours doesn't have it, you're going to need it! We sell it separately (am-0546), or you can use a cable from the Kit of Parts. When attaching your connectors, follow good wiring practices, triple-check your polarity before finishing assembly, and don't forget some strain relief if you're splicing cables together.
Charge your batteries upright and with ventilation, so gases that develop during charging can vent through the top as designed. And while everything should be okay, you shouldn't leave your batteries unattended on a charger--just in case something goes wrong.
It is wise to invest in a battery spill kit in the event a battery does start leaking. Industrial gloves, baking soda to neutralize acid, and a strong plastic container to hold the leaking battery are better than nothing, but purpose-built spill kits can be obtained from industrial supply companies for $100-150.
CARE AND HANDLINGThe first things to instill in anyone handling batteries is simple: never, ever carry a battery by its cable. This damages the solder joints inside the battery, increasing resistance which will both hamper its performance and increase the chances of a failure.
Dropping a battery onto the ground can dislodge the lead plates inside, causing individual cells to fail. This sometimes only manifests itself under discharge, when the heat makes components expand and contacts loosen just enough for a cell to go bad (causing a noticeable voltage drop) but then contract back together after it cools.
If either happens, the battery should be considered suspect and tested thoroughly. Depending on your tolerance for risk, the battery should be removed from competition use or recycled.
BEFORE YOUR MATCHBefore you put your battery on the robot for a match, it's important to do a few checks:
- Inspect for damage, bulging, or leaking. If you see signs of any of them, stop using the battery and put it in a sturdy plastic bin, and take it to be recycled.
- Make sure the connection between the battery cable and the battery doesn't move at all. If it does move, take the time to repeat the assembly steps from the start. Most of the time, this means you need to use a different battery for the upcoming match.
- We recommend one more charge check using a Battery Beak (am-0995). This plugs directly into your battery connector and displays your state of charge, internal resistance, and the battery voltage at different current draws. There are more thorough tests of battery health you can do at home, but a Battery Beak is a useful spot-check to ensure neither you nor your partners go on the field with an obviously bad battery.
- Secure the robot and battery SB-50A connectors together. Velcro wrap or zip ties will ensure they don't come apart during a collision.
- Secure the battery in place on the robot. How you do this will depend on your robot's design, but many teams use a bracket or a wide strap. We also sell a Battery Mount Kit (am-3964a) that fits the AM14U series of frames. Your battery should stay in place even if the robot is on its side or upside-down.
AFTER YOUR MATCHSome robots can theoretically run multiple matches on a single battery charge, but that's a big risk to take. Avoid disappointment and use a fresh battery every match. Here are the steps to take once your robot gets back to the pits:
- Inspect again for damage, bulging, or leaking. If you see signs of any of them, stop using the battery, put it in a sturdy plastic bin and take it to be recycled.
- Inspect the battery terminal connection again. If it does move, take the time to repeat the assembly steps from the start.
- Wait 30 minutes before recharging. The chemical reactions that happen inside the battery to power your robot also create heat. Allowing the battery's internal components to cool back down will allow the battery to last longer.
RETIREMENT RECYCLINGYour battery provides power created in a chemical reaction. Charging the battery reverts the process, but it will never get 100% of the capacity back. Over time, this means the battery's capacity will diminish. Manufacturers will often specify the capacity a battery will retain after a number of charges and discharge cycles, but experience shows that most batteries lose their competitive edge after 1-2 seasons depending on how many matches the robot runs and how much current the robot draws. Heavy pushing situations and high-traction drive systems like pneumatic tires or treads will accelerate this process.
Even if a battery is unfit for competition use, it can be useful to your team for many things:
- Driver practice
- Demonstration events
- Powering a testbed for the electrical or programming teams
- Charging phones and laptops in the stands at competitions with a 120V inverter, available at many hardware and auto parts stores.
When it's time for new batteries, we have you covered. We sell 2-packs of Power Patrol SLA1116 batteries (am-3062) at great prices that are ready to ship to your door!