diy solar

diy solar

BigBattery 170 Concerns

Hey syspig - so I have had the same concerns - I'm a career solar engineer - 40 years - so can provide some insight. First switches don't tend to fail but they do tend to get accidentally switched off - but I'm planning on just mounting so that can't happen - not a major concern. But as for cable size - Yes as a licensed electrician I'm amazed that all the battery companies use such skimpy cable sizes. It's the age-old interface between electronics folks and power folks - sure you can get by with cranking 200 amps through two 200ºC insulation rated 6 AWGs for short periods for a few inches but to supply 6 AWG output cables on a battery that's supposed to be 175 Amps continuous to me is outright criminal besides being dangerous. However you also don't need to go to 2/0 if you get quality 90ºC or better UL cable. I won't go into the fullness of how to calculate temp derates from NEC table 310.15(b)(16) but suffice it to say that if you are paralleling batteries you can figure the max amps your inverter or other loads will draw from the whole pack - divide that by how many paralleled batteries you have so you are looking at the max amperage each battery will see in your setup. So if you have a 2 KW inverter on 2 BB 170s at 12 volts - the total inverter amperage is on the order of 165 Amps but if you have two batteries in parallel each one will only see 83 Amps max. So the parallel cables can get by with like 2 AWG cables (in my book - still NOT 6 AWG) and the final pack cable set should be at least 1/0 (which does fit in the 175 A Anderson connector). Hope that helps!
Hi there, when you say "final pack cable" are you referring to the cables on the inside of the box or just the last run to the anderson plug on the outside? I've in the exact same boat as OP except one big difference is I only have 1 12v battery-evo (big battery) pack, so nothing to split the load with.

I'm trying to pull as close to 2500w as I can out of the battery, but cannot figure out if it's possible and with what awg wire to use! I want to run from the sb175 anderson plug to a busbar and then to 2500w inverter and various other DC loads.
 
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