I can't answer this question in terms of FAA requirements.gsontheimer wrote:The AMM states to replace the battery pack when the voltage is < 36 Volts. Now that there are two packs with a nominal voltage of 30 Volts and 36 Volts, what would be the "open current" voltage of the 30 Volt version? 30 Volts? 32 V? 36 V?
Practically speaking, this particular sub-type of Li-Ion cell (not a battery) starts out life at >=3.2 volts. The discharge curve is such that an open circuit voltage below 3.0 volts per cell would probably indicate a substantial loss of capacity. A much better test would be a momentary reading of the voltage under a 10% load. A 200 ohm resistor would create this load assuming that the cells are 1500 ma max continuous load rating. In this test, I would look for a voltage of >= 2.93 volts. This would suggest that you have >=95% remaining capacity. A 10% load voltage of >=2.9 volts would suggest that you have at least 50% capacity. All of this is approximate as the attached spec sheet will make this more clear. [If you conduct this test, make sure that the load resistor is large enough that it will not change temperature substantially. If it does, the resistance goes up, dropping the load. You can either run the test very quickly with a standard 1/4 or 1/2 watt resistor or, better still, use a 5 or 10 watt resistor and allow the load on the cells to stabilize for 30 seconds or so.]
A typical problem when you have 10 cells in a battery, one cell will have gone bad (maybe reading 2.0 volts) while the other nine are still fresh giving you an indication of an average loss of 0.1 volts per cell. Given the way Diamond sealed this pack, it is difficult to deal with the individual cells.
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