Peter,
The 210-amp rating is probably for a 105°C insulation temperature in
free air. For comparison, #2 THHN (90°C) copper in free air is rated for
190 amps. Not sure that it makes sense to use a free-air rating in a
small closed box. For outside use a temperature de-rating for ambient
temperature, maybe around -10%, should be included too.
It looks like Cotek recommends a minimum cable size of 1/0, so out of
fear of starving the inverter of enough voltage, I wouldn't use any smaller.
Kent Osterberg
Blue Mountain Solar
On 8/11/2020 3:18 PM, peter...@pobox.com wrote:
I have been designing a off-grid system that can fit in an
outside-accessible compartment with an approximate 24" square
footprint and space above about 18" - 24".
I am using two Battle Born LiFePO4 batteries rated at 24 V / 50 Ah, a
Cotek pure sine wave inverter with an output power of 4,000 VA , a
MorningStar TS-MPPT-60 charge controller, a Victron BMV-712 "coulomb
counter" and a Battle Born surge limiter CL500.
The current limiter limits the current to 120 continuous, and 200 A
for 30 sec.
I have been able to fit everything in and I am designing the cabling,
and here is my problem.
I have one vendor that recommends Ancor brand Tinned Marine Grade
Battery Cable. It is "resistant to salt water, battery acid, oil,
gasoline, heat, abrasion and ultra-violet radiation. Exceeds UL 1426,
ABYC and US Coast Guard Charter boat (CFR Title 46) standards. Highest
quality ultra-flexible (Type 3) tinned copper stranding. Vinyl
insulation. -50 deg-C to 105 deg-C." 2 AWG is composed of 665 ea 30
AWG stands.
The same vendor has "welding cable" with an EPDM insulation rated at
600 V, water/chemical/grease/abrasion resistant, -50 deg-C to 105
deg-C, "marine grade". Not UL listed. 624 ea 30 AWG strands.
Roughly comparable pricing.
They claim both 2 AWG cables are rated at 210 A. Not sure if this is
continuous duty or whether I should derate this for what will be
continuous duty.
This is new territory for me, and any help would be appreciated.
Peter T. Parrish, Ph.D.
President, California Solar Engineering
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