Power calculation

	nom Power	max Power	nom current discharge	max current discharge	nom current charge (drive)	max current charge (drive)	nom current charge (Idel)	max current charge (idel)
Battery			0	0	0	0	0	0
Charger Interface		3300	0		0	0	-21.82539683	-21.82539683
Motor 1	2000	5000	15.28350909	40.21976077	-15.28350909	-40.21976077	0	0
Motor 2	2000	5000	15.28350909	40.21976077	-15.28350909	-40.21976077	0	0
Solar	-592.5	-1185	0	0	-4.527739569	-9.055479138	-4.527739569	-9.055479138
Pre-charger				2.1	0	0	0	0
DC DC	36	278	0.275103164	2.124407764	0	0	0	0
motor controller		18446.4
motor controller		18446.4

		Total current	30.84212135	84.66392931	-35.09475776	-89.49500068	-26.35313639	-30.88087596

Fuse calculation

IEC ampacity (A/m2)	1.3	cyclic load	1.3	alt(min)	2500	alt(max)	2600	Kx	0.8
	current	Kt(min) (T=60C)	Kt(max) (T=60C)	Kt(max) (T=45C)	Wire diameter	Cross sectional area	100% cable area	% cable used	Ke	Kv	Ka(min)	Ka(max)	I(rating) max	I rating min	wire current rating	maxium fuse
Battery fuse	84.66392931	0.845	0.9		6.15	29.70572204	65.12609947	0.456126227	0.95	1	0.975	0.97	165.0368992	144.8198791	255	191.25	EXRAD-XLX-4X
Charger fuse	21.82539683	0.9	0.9	0.95	2.58826	5.261452847	16.78876679	0.313391264	0.91	1	0.975	0.97	42.07710975	38.9739229	73	54.75	Awg 8
Motor fuse 1	40.21976077	0.845	0.9		4.95	19.2442185	30.93827752	0.622019713	0.95	1	0.975	0.97	78.40109312	68.79695922	155	116.25	EXRAD-XLX-6X
Motor fuse 2	40.21976077	0.845	0.9		4.95	19.2442185	30.93827752	0.622019713	0.95	1	0.975	0.97	78.40109312	68.79695922	155	116.25	EXRAD-XLX-6X
Solar fuse	9.055479138	0.845	0.9		1.62814	2.081964757	6.965753183	0.298885806	0.9	1	0.975	0.97	18.63267312	16.35017067	32	24	Awg 14
Pre-charger fuse	2.1	0.845	0.9		1.02362	0.82293855	1.615384615	0.50943815	0.95	1	0.975	0.97	4.093567251	3.592105263	16	12	Awg 18
DC DC fuse	2.124407764	0.845	0.9		1.02362	0.82293855	1.634159818	0.503585109	0.95	1	0.975	0.97	4.141145739	3.633855386	16	12	Awg 18

Thermal derating (Kt)

Thermal connection derating (Ke)

Recomendation

	Fuse	current rating
battery fuse	XEV25-175	175
Charger fuse	XEV10-50	50
Motor fuse 1	XEV20-80	80
Motor fuse 2	XEV20-80	80
Solar fuse	XEV10-20	20
Pre-charger fuse	XEV10-5	5
DC DC fuse	XEV10-5	5

For the lower-current fuses (Solar, Pre-charger, DC-DC), we will be using the axial bolt-on type.

Power calculation excel doc

Fuse calculation excel doc

Alternate Sources for fuses (since COVID happened and Eaton was not going to sponsor for a while)

Note On Interrupting Rating:

Fuses on our HV system should be able to project against a short circuit condition on the cables they are connected to. So what's the short circuit current?

The max current available from our batteries will be at their highest voltage, since a short circuit is just a resistive load. Maximum condition calculations will assume that the external short is 0mOhm, and the only thing limiting the current is the battery's internal resistance. This is a reasonable estimation as it will ensure an adequate safety factor for our fuses. Since our modules are in series, we only need to do the calculation for 1 module.

Voltage: 4.2V

Internal Impedance (using AC since a short circuit is a transient event, and AC IR is lower than DC IR typically): 25mOhm (ish - rough value of what was observed)

Short circuit current per cell (Iscc) = 4.2/0.025 = 168A

Short circuit current per module = 168A * 25 cells = 4200A = 4.2kA.

So all of our fuses must be rated to break a minimum of around 4.2kA.

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