dh68 wrote: ↑
Dec 04 2017 5:46am
I have put together 13S5P battery with Sanyo/Panasonic NRC18650GA cells with smart bluetooth BMS. The BMS arrived with basic settings already there (see picture). this is fine, but I would like to change this seetings to achive longer cycle life of the pack and to adjuts the BMS to the GA cells. I was thinking to limit useful voltage between 3,1 to 4,1 V? Which parameters should I change? I am not very familiar with this, so I would apperiate your help very much.
The BMS voltage limits should be set outside the normal operating range. Normally, the charge termination voltage should be determined by the charger, and the low-voltage cutoff should be handled by the controller. If you implement these limits in the BMS, it will shut down charging before actually reaching the desired voltage (due to excess voltage across the battery's internal resistance), and it will disconnect from the controller while there's still capacity in the battery, as the voltage dips when you apply the throttle. It looks like you can partly avoid the second problem in this BMS by adjusting the "Delay" parameters, but it's still not ideal.
Usually it's possible to adjust the termination voltage of even inexpensive chargers. The controller LVC may not be adjustable, so in this case you'd need to have some sort of display so you can keep an eye on the voltage. Read the voltage when the throttle has been at zero for several seconds, to allow the battery time to recover from being loaded.
The function of the BMS is to protect the battery from conditions outside normal operation. For example, a runaway charger that doesn't stop at the termination voltage, an out-of-balance cell group that hits its termination voltage before the rest of the pack, a short circuit, or a load (e.g. lights) that's inadvertently left connected when the bike is in the garage.
All that said, whatever limits you decide on, the CellOVP, CellUVP, PackOVP, and PackUVP are the relevant parameters. If it were me, I'd just rely on the cell-level protection and set the pack levels to something the pack would never reach, but in some cases there may be legitimate reasons to use these.
See also my post about 5 back regarding balancing.