Lithium Cell Protection- H9 W+ K! E, ]+ E' a, u0 H6 y. Z
4.3.21. _1 z8 Q( b2 T) I2 z3 h
60950(ed.2)$ z/ O) f/ X f; ~
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Standard: IEC60950, 2nd Clause: 4.3.21 Sheet n. P384' y6 O5 K6 V9 |! \: e {
Page 1(1) 0 m7 U' s' h! T2 R% e& A0 gSubject: Lithium Cell Protection Key words:7 N% }( S4 Z- x* a: T2 H, o! j! t
-Lithium Cell 3 I& K# Q# v% ^: l* c& ]-Clearances 7 L7 q. P4 ? n1 T7 e- failure mode* @ `) `( X- o, B4 Z, i
Provisional Decision taken by ETF2 9 ~/ X4 V: ]& ` |and to be approved by CTL at its k& J! M' j; M& h$ m& r
38th meeting, in Toronto1 ?4 [5 o4 U: D* Z) z- t# ^
Question: 9 _6 b$ O- u) r+ ]# lClause 4.3.21 requires that two levels of protection are required to prevent forced or reversed charge ( m- U# a) A" ^or forced discharge if this would result in a hazard. Conventionally a combination of resistor, diode: s# W! L. ]7 `( N
or ic has been considered suitable and is for the series current path. However, a new consideration 6 D7 m1 ^+ R5 k3 J' ^: q- M8 H. h5 Khas been raised in respect of adjacent tracks, separated by no more than operational insulation, which, & a7 m4 M: A* G3 c9 Zunder s/c conditions will bypass the protective series components and provide charging current for . r- T$ Q$ Z0 G& ]3 B% H5 {! C/ W6 Meither chargeable or non-rechargeable batteries. Does this mean that there is therefore a requirement / i4 I6 Z6 x. a% i% ^2 S( V0 Zfor Reinforced separation?! G0 `; r/ ~5 ^2 m
If that is the case, then the controlling factor is the clearance of 0.8mm in Table 5 (circuits not subject8 E* f) Q# W2 G3 t3 X2 O
to transient over voltage). This is based on the fact that creepage cannot be less than clearance and( z! P6 Y: g5 [* E& Q1 ~; P/ \
creepage can be calculated to be, for example at +5V, 0.4mm (based on rounding up 0.12mm to# i: M& G$ |5 d) }, i3 U
0.2mm for Basic and doubling for reinforced. / s; C4 \7 s+ R+ f% A# u+ w7 h( E5 dDecision: * y4 P8 I6 `1 t; a# g4 w; T& M' I+ \Operational insulation is suitable taking into account 5.4.4 because there is no risk of electric shock.9 d: y$ t- X8 d- _) }
(see 1.2.9.1)+ R% X0 Y+ q. P+ b
Care should be taken by determining clearance and creepage distances which column of the table has 7 c4 r5 y' m3 W# T) u8 c- Bto be used.(Transients have to be taken into account)7 _8 ]0 m. }9 W
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DSH 384