Minimum battery voltage

[jamergamer]

Hi, We are rookie team 6323. Quick battery question...

Given that we can see the current battery voltage in the driver station, at what voltage should we swap batteries to ensure their longevity? Please consider the idle voltage vs driving full speed voltage.

[cgmv123]

To know for sure, check the battery with a Battery Beak, but ~12.3 volts idle seems good if you're trying to ensure longevity and have enough batteries to swap in and out.

[Billfred]

Originally Posted by jamergamer

Hi, We are rookie team 6323. Quick battery question...

Given that we can see the current battery voltage in the driver station, at what voltage should we swap batteries to ensure their longevity? Please consider the idle voltage vs driving full speed voltage.

At competitions: Before every match--you don't have enough matches to afford blowing one to a dead battery.

At home: As voltages start dipping close to or below 12V at rest, we swap them. (Under load, the robot will naturally dip below 12V as amp draws increase.) My team's process for this is far from scientific and we invariably run them a little long, so we tend to use our oldest batteries for practice first since they're already less likely to be the fittest battery for competition.

We (I) put some tips on the AndyMark website: http://www.andymark.com/battery-tips-s/615.htm.

(Full disclosure of the probably obvious: I work at AndyMark.)

[Gravity]

We usually swap our batteries at the high 11v idling. Consider your battery empty at the low 11v.

Refer to this:

[Ed Sparks]

Most 12V AGM batteries don't like to be discharged below 10.5V (1.75 Volts per cell). If you repeatedly do this, you will experience a noticeable decrease in the battery's capacity over a short period of time. Put another way, if you abuse the battery by over discharging, the battery won't hold as much charge during the next cycle and you'll start noticing that the battery discharges faster.

[messer5740]

I mean we had some battery issues and it ran about 11V, but I would take it out around then. Keep the batteries charged, and at comp, swap batteries every match.

[Ether]

I found the attached chart online.

Lead-Acid State of Charge vs Voltage, Richard Perez, Home Power #36, August/September 1993, Page 67

I can't vouch for the chart, but it says that if you let your at-rest battery voltage drop below 12 volts you've already discharged the battery by more than 75% (the State of Charge is less than 25%).

Last I checked, discharges no deeper than 50% (around 12.25 volts at rest) are recommended by FRC battery manufacturers.

[DonRotolo]

To emphasize: you really really need to swap out your battery for every match in competition.

[FrisbeeFunTime]

We usually swap out the batteries when testing at around 12 to 12.1 volts maybe a little more.