One of the functions of the battery is to supply a stable voltage, without allowing it to change rapidly. As such, you should NEVER see it changing it's voltage rapidly unless severely stressed, by excessive loads or excessive charging. You cannot positively determine if your battery can be overcharged in a 2 second test, particularly if you haven't established what the current SOC (State of Charge) is for the battery installed.
Lithium batteries operate at a different voltage basis than the lead acid types the original charging system.
Battery SOC for a lead acid is 12.7 V full (static) and 11.9V empty. Lower voltages are somewhat tolerable without damage. And, provided voltages up to 14.7V can be absorbed.
LiFEPO4 batteries are 14.4V full and 12.8 empty, with further voltage drops due to loading causing irreparable damage. The same is true for over voltage application with slightly less severity for damage.
Further, your present battery has 8 cells, meaning 4 pairs of cells, 2 ea wired in parallel and then the 4 pairs wired in series. With cells wired in parallel, there is no way to monitor cell imbalance from the battery posts. Better quality LiFEPO4 batteries will have an extra connector for connecting to individual cells for balance purposes.
Once the cells are imbalanced, you cannot balance them from the battery posts, which all automotive and motorcycle charging systems have as the only means of charge. Charging from the posts only results in some cells being overcharged, while others are undercharged. Overcharging damages the technology, as well as over discharge of an only partially charged cell within the battery assembly.
Your bike can put very large loads on the battery, particularly during starting operation. 210 cranking amps is common for a starting battery. Your charging system can put out 14 to 15 Amps maximum.
So when you electric start the bike, the battery cannot be at 100% charge, and it will take 10 times longer to restore the energy taken from it by the alternator. Simple numbers, 2 seconds to electric start, 20 seconds or more to restore, IF nothing else on the bike is taking power from the alternator like headlights ignitions, etc. Most SOHC4s draw about 10 amps whenever the key is switched on. That only leaves 4 amps to restore whatever was sucked out of it during electric start. It's never going to happen in 2 seconds.
If you EVER run a LiFEPO4 battery below its minimum, it must then be charged with a balance charger to equalize the cells, or risk damage to the battery pack.
The next issue is what the MC voltage regulator instructs the charging system to do to the battery. LiFEPO4 batteries demand that charge current be curtailed when the voltage reaches 14.4 V. This voltage indicates that the battery has been charged to it's full capacity. Further charge current damages at least some of the internal cells. If your charger continues to provide 1-2 amps above the voltage where the battery is fully charged, you guessed it, damage.
So, your present goal to ensure future batteries aren't damaged by your bike's charging system, is to find out what it supplies to your battery posts when you know the battery's state of charge is topped up to peak.
