Quote:
Originally Posted by Fej
My team has been having a big problem with dying batteries. I'll cut right to the chase - is there any benefit to charging the batteries more slowly?
|
Yes, definitely. Charging the batteries slower prolong their life. Here are a few tips that I've been told over the years:
(1) Do not deep-cycle the batteries if possible. By "Deep Cycle", I mean don't drain the battery until it's near-dead. Batteries don't ever really fully-recover from being run until they're basically dead, a couple of times of doing this and your battery will never get back to full charge. Fun Fact: Lithium Ion batteries like to explode if you completely drain them and then try to recharge them, so many batteries have a "suicide switch" in them that will prevent the battery from recharging if they get below a set level.
(2) Do not charge batteries while hot. It's best to pull the battery off the robot and just set them aside INSTEAD of immediately putting them on the charger. Give the batteries about 30 minutes to cool, and then put them on charge. You'll get a much better charge on the battery that way. Interesting fact: The difference between a fast charge (charging in 2-4 hours @ 6A or 10A) versus a slow charge (charging in 8-10 hours @ 2A) is heat and gas buildup. Charging a battery quicker causes the battery to heat up quicker while charging, which damages the battery. It can cause hydrogen gas to build up inside the battery and if the gas isn't vented properly can cause a dangerous situation.
(3) If you think your batteries aren't charging properly, check the voltage on the charger itself. It must be charging at a voltage higher than the battery itself in order for the battery to get a good charge. You can detect a dying battery charger by checking its charging voltage.
(4) Never trust the voltage off a recently-charged battery. If you merely test the voltage with a voltmeter, you will be seeing what's known as a "surface charge", you won't actually know how "good" a battery really is. My team really likes a product known as a
Battery Beak from Cross the Road Electronics. The bugger is $150, but well worth it. It tests the battery at various power draws, and can show you what the REAL level of the battery is.
(5) If your battery doesn't seem to be charging properly and you've ruled out a bad charger, check the terminals going to the battery. I've seen WAY too many batteries that didn't have a SOLID connection between the wires and the battery terminals, and that can lead to loss of power in charging. I've even seen the connection corroded (rust), that's never good!
(6) Last but not least, never leave a battery on a charger unattended. I've been witness to too many batteries exploding while on charge. Fortunately none of them at FIRST events, but unfortunately the worse ones were at various robotics competitions (mainly BEST Robotics).
Happy Trails.
-Danny