still have to meet or exceed this:
In lieu of the requirements of 14 CFR 25.1353(c)(1) through (c)(4), the following special conditions apply. Lithium ion batteries must be designed and installed as follows:
(1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system not shown to be extremely remoteimprobable. The lithium ion battery installation must preclude explosion in the event of those failures. (working group to refine).
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure. (this may be met with requirement (1) - working group to refine).
(3) No explosive or toxic gases emitted by any lithium ion battery in normal operation, or as the result of any failure of the battery charging system, monitoring system, or battery installation not shown to be extremely remoteimprobable, may accumulate in hazardous quantities within the airplane. (this may be redundant with (1)).
(4) Installations of lithium ion batteries must meet the requirements of 14 CFR 25.863(a) through (d). (may also need to include parts 23, 27, & 29).
(5) No corrosive fluids or gases that may escape from any lithium ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition, in accordance with 14 CFR 25.1309(b) (also 23, 27, & 29) and applicable regulatory guidance. We may want to give other means of compliance such as venting gases off-board, containment enclosure, etc.
(6) Each lithium ion battery installation must have provisions to prevent any hazardous effect on structure or essential systems caused by the maximum amount of heat the battery can generate during a short circuit of the battery or of its individual cells. NOTE: Need to add a requirement to report maximum temperature reached during the RTCA/DO-311 Short circuit test. The equivalent UN 38.3 short circuit test states that testing occur at 55 deg C. DO-311 2.3.12 – External Short Circuit With Protection Disabled: states to report maximum temperature.
Test is run at 23 deg C. (7) Lithium ion battery installations systems must have a system means to control the charging
rate of the battery automatically, so as to prevent battery overheating or overcharging, and,
(i) A battery temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over- temperature condition, or,
(ii) A battery failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.
(8) Any lithium ion battery installationsystem whose function is required for safe operation of the airplane must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state of charge of the batteries has fallen below levels considered acceptable for dispatch of the airplane. (this is a new requirement that is applicable to Li-ion batteries/systems).
(9) The Instructions for Continued Airworthiness required by 14 CFR 25.1529 must contain maintenance requirements for measurements of battery capacity at appropriate intervals to ensure that batteries whose function is required for safe operation of the airplane will perform their intended function as long as the battery is installed in the airplane. The Instructions for Continued Airworthiness must also contain procedures for the maintenance of lithium ion batteries in spares storage to prevent the replacement of batteries whose function is required for safe operation of the airplane with batteries that have experienced degraded charge retention ability or other damage due to prolonged storage at a low state of charge. (this requirement is already required to meet compliance to 1529).