While I know the most effective determination of battery health is something like a CBAIV, the Battery Beak is accepted as a very good way to check on a battery when you can’t discharge it.
Given the data from a Beak, how do you determine the ideal next battery? State of charge? Internal resistance? V0/V1/V2? Any attempt to balance out match cycles? This thread had a lot of good information, but not quite that information.
Assuming all batteries are in good status, we will take batteries at 115% and over to be “charged” and good for a match. If I recall correctly, 130% on the Battery Beak is a fully charged battery off of the charger.
Do you take any steps to address the batteries surface charge when “ranking the batteries”
The surface charge should be indicated by the “130%” fresh off the 3-bank charger (AM-2026). If we have a battery sitting around, it will be around 115% fully-charged normally. We do not do anything special to address surface charge.
We put all of our batteries through a battery test at a testing facility, so we know the batteries we have are good.
I haven’t experienced the battery beak before, but what info does it give to you? Does it just say “This battery is good” or does it give other info like battery voltage and other pieces of information?
http://www.crosstheroadelectronics.com/Beak.html
The Battery Beak has an onboard 18A load test that will give a Good/Fair/Bad rating on the battery based. It will give also give a %-charge and Voltage.
May I ask, what kind of test?
The CBA4 is great for overall battery health, but not readiness for a match.
Internal resistance indicates the maximum current the battery can deliver, the lower the resistance the higher the current.
State of charge tells you, with some small inaccuracies, how fully charged a battery is, meaning is it ready to do its thing.
V0/V1/V2 tells you what kind of use you can get from the battery at different current draws, and for FRC the 18A value is the most useful. These values are somewhat related to internal resistance.
To determine which is the next battery to use in a match, we check SoC only, if it is OK we go with it, otherwise find another battery to check.
We do rank our batteries on internal resistance, the lower (better) ones get more play time.
Eventually all batteries go bad - then we recycle them…
We used an industry standard constant current discharge test. We also recorded voltage during this time and identified any batteries that showed signs of bad cells.
Yes. The internal resistance is a big thing. When you suddenly push the joystick all the way forward, you will notice a voltage drop. The higher the battery internal resistance, the greater the drop will be. E=I/R is what Ohm’s law says. That means, if I am right, that the voltage drop will be the current draw divided by the internal resistance of the battery! That makes me think, Ohm’s law will allow me to find out how many amps are flowing through the battery at any time!
^^Darn it! Why didn’t I remember that at vegas? That would have given us the problem solution within a couple minutes instead of a couple hours^^
Also, that may be why our battery wires were starting to melt a little!
Sounds like the right thing to do. Not to be a pest, but what industry standard did you use? i.e. How much current and what cutoff voltage?
So it seems simple: the legal charged battery with the lowest internal resistance?
I’m imagining a side task for our electrical and programming crew using an Arduino/RasPi/whatever they feel like, where the Battery Beak reading is taken off the charger, the battery is stored, and The Next Battery is lit up automatically so we don’t have to think before grabbing a battery. The trick would be determining what data to use, and that seems like a jumping off point.
Short version, we used an Aircraft Battery Tester. 10A constant current discharge with a cutoff of 10V. We found that good batteries were typically producing 14Ah under these conditions. The 10A was chosen as that is approximately the 1-hour rate according to the spec sheets. It appears the new batteries were quite a bit better than we anticipated.
I’m considering purchasing a battery tester that was mentioned on CD last year. It’s supposed to provide the constant current discharge & voltage logging.
Thank you. That is useful information.
Nope. The voltage drop is the current multiplied by the resistance: E=I*R
Actually, Watt’s law caused that: P=I*E, so as current and voltage increased, power also increased, expressed as heat.