Turd Furguson
it's a funny name.
- Joined
- Jan 27, 2020
- Messages
- 64
I'm sitting here charging my 2p4s bank that I drew down to 11-ish volts while (still) awaiting my BMS ... Impatience to start some low-risk capacity testing has kicked in. My bench charger is currently set to 14v, 5amp max. It's been pegged on CC all day although sometimes dipping to CV and then back... interesting.
What's also interesting is the voltages across parallel banks. Voltage at the positive lead is fluctuating between 3.5-3.6v. Voltages for downstream banks drop progressively to 3.3-3.4v at the negative terminal. When I turn off my supply, voltages for these 4 parallel banks are dead even at (currently) 3.3x volts.
Prior to this, I assumed that voltage readings would always be even across parallel banks while charging/discharging balanced cells... I'm seeing a 'waterfall effect' for voltage while connected to a charge source and haven't seen this referenced before.
Naturally this leads to some questions:
What's also interesting is the voltages across parallel banks. Voltage at the positive lead is fluctuating between 3.5-3.6v. Voltages for downstream banks drop progressively to 3.3-3.4v at the negative terminal. When I turn off my supply, voltages for these 4 parallel banks are dead even at (currently) 3.3x volts.
Prior to this, I assumed that voltage readings would always be even across parallel banks while charging/discharging balanced cells... I'm seeing a 'waterfall effect' for voltage while connected to a charge source and haven't seen this referenced before.
Naturally this leads to some questions:
- Since cell voltages match at rest, is current is being distributed in an equal fashion?
- How does a BMS monitor these packs... do they just trip a HVD when a cell hits the datasheet spec (i.e. Daly lists 3.75v), or is there further intelligence to sense charge/discharge?
- Is there risk of a single cell going over 3.65v when charging/floating at anything under 14.6v?
