Any suggestions on new batteries and a better battery charger? One of the batteries in our KOP doesn’t hold a charge and the charger doesn’t charge fast.
We bought two of thesefrom AndyMark. It charges up to three batteries then automatically switches to float, so you can leave the batteries on the charger off-season when you might be out of the shop for a couple of weeks at a stretch. They also have SB50As built in. They also sell a single charger.
And since Gus has already started the plugs for us, I’ll finish the job:
MK Battery 2-packs: MK ES17-12 12V SLA Battery (Set of 2) - AndyMark, Inc
Power Patrol 2-packs: Interstate SLA1116 12V SLA Battery (Set of 2) - AndyMark, Inc
Assembled battery cable: http://www.andymark.com/12-inch-robot-battery-cable-p/am-0009.htm
SB-50A connectors if you’d rather roll your own: SB50 Anderson Powerpole Connector with Contacts - AndyMark, Inc
Burndy 6 AWG compression lug connectors for the other end if you’d rather roll your own: 6 Gauge Compression Lug Connector 1/4 Stud Hole BURNDY #: YAZV6CTC14FX - AndyMark, Inc
Battery Beak battery checker: Battery Beak - AndyMark, Inc
Even if I wasn’t working for AndyMark (but I do), I would say no team should be without at least 3-4 good batteries (and that’s a minimum; Iron Kings will be bringing about 6 to events, and I’ve seen some high-end teams with double that) and ideally a Battery Beak to check them before going out for a match*. The cables and Battery Beak are a little more specific to FRC, but you can probably find batteries from a local supplier at varying prices. (And if you can get that local supplier to sponsor you, bonus!)
You want a fresh battery for every match, and you want a battery to cool for about 30 minutes after the match before recharging. You’ll be playing 8-12 qualification matches across a day and a half before playoffs, so you can imagine that 3-4 is still scraping by…but only having 1-2 is really playing with fire.
Over time, batteries will age and need to be retired from competition (first demoted to practice or demos, then maybe to power a programming test bed or inverter, then eventually sent for recycling). 1-2 seasons from a battery before demotion is par for the course. On Iron Kings, we’ve started logging the Battery Beak reading for internal resistance of our newly-assembled batteries (because the factory internal resistance figures don’t account for the connectors and 6 AWG wire), and we plan to demote a battery once it starts reading 150% of that figure. (We’re pulling that figure from this article (PDF); they deal in backup systems, but many of the concepts are similar. It’s something we’re trying new this year, so we may adjust that 150% figure depending on what we see from the Beak’s other measurements.)
*2815 first bought one in 2012 or 2013 when I worked with them. I showed it to 1293, my high school team, which historically has a small budget and does a lot of scrounging in their parts bins. A year later, we were talking to a new team and 1293’s coach shows them their Battery Beak. He then tells them “If we paid retail for something, it’s worth it!”
Check out Batteries Plus. Last time my team needed some new batteries, I was able to create a “corporate account” and get a pretty good discount!
It also has some holes for mounting, so you can build a custom charging shelf easily.
Since you appear to be a rookie and likely are asking about KOP batteries, I have to ask a few questions. Are you sure that the battery is wired properly? When wired backwards, some chargers are likely to discharge the battery instead of charging. Second, are you sure that the terminals are tight on the battery? Loose terminals will confuse most chargers. Finally, has the battery been dropped? Check the corners for a flat spot. When batteries are dropped the event will cause some evidence of the drop. When dropped, it is possible for parts of the internals to become disconnected.