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re: battery interconnect size
22 apr 2000
ron rosenfeld wrote:
>...i'm trying to understand how much power is actually going through
>an individual battery interconnect, and how much loss it would introduce
>to have, say, 2-0 instead of 4-0.
awg b&s 00 annealed copper wire (0.3468 in. diameter) has r = 0.00007793
ohms (george might say "amps" :-) per foot, and 0000 has 0.00004901, and
the instantaneous power loss is i^2r watts...
>the only reason this has come up is that my electrician as recommended
>2-0 battery interconnects saying that they are short lengths so the
>loss won't be much...
with a peak current i = 4kw/48v/2strings = 41.7 a, each foot of 00
wire loses 0.135 watts of peak power, vs 0.0851 watts for 0000 wire.
at i = 20 a, each foot of 00 wire loses 0.0312 watts.
>i'll have two 48v/820ah strings (6 batteries at 8v)...
if you collect 8 kwh/day of energy and budget 1% of it to 10 battery
jumpers over 8 hours, that's 10 watts, peak, at i = 1 kw/48v/2 strings
= 10.4 amps, so 1 watt = 10.4^2r, and r = 0.009216 ohms per foot, max;
12 gauge wire has r = 0.001588, making the loss less than 0.2%, with
a fusing current of 235 amperes. you might wrap it around the battery
connectors several times to ensure a nice low-resistance wire contact.
nick
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