This graph shows the voltage (multiplied by 10, so 65=6.5 volts, and 50 = 5.0 volts) batteries 1-6 of my electric pickup while accelerating. My first battery (blue) is consistently 0.1 volt below the others, so I am keeping an eye on it. But this graph shows that although it is a 1/10th of a volt lower, it does not sink lower than the other batteries under load, so it appears to be holding up well so far.
The graph also shows off my new (to me) Pak Trakr system. The Pak Trakr system connects to each battery in your pack with small remotes that daisy chain together. Each remote monitors six batteries and transmits the voltage levels once a second to a display and optional serial data logger.
Does the first battery run the 12 volt accessories, by chance?
If not, perhaps it just needs a little more charge to bring it in line with the rest of the string. When was the string last balanced?
The 12v auxiliary system is powered by a DC-DC converter off of the main pack. I charged battery 1 individually after a full pack charge but after removing the charger and waiting a bit it was down to 0.1v less than the other batteries again (at 6.3…most others are at 6.4). As it is able to keep up with the heavy current demand when driving, I’ve decided it can’t be too bad off yet. I plan on keeping an eye on it, but I’m hoping its voltage is just naturally a bit low.