Battery Connection

[Gunny]

I picked up my 6 volts today at Batteries plus, they had connections but they were 6 and 8 gauge, to me looked a little thin for the job. What gauge should be used?

Rob

 

[SternWake]

The correct answer would be determined by the maximum possible load placed on the batteries, or the largest charging source, but when in doubt, go fat.

Have this guy make custom top quality cables for you rather than investing in a hydraulic crimper and learning how to use it properly:

http://www.genuinedealz.com/custom-cables

Just figure out the lengths required beforehand.

 

[Spaceman Spiff]

I picked up my 6 volts today at Batteries plus, they had connections but they were 6 and 8 gauge, to me looked a little thin for the job. What gauge should be used?

Rob

I used 4 AWG from roof to controller to shunt to batteries, 1/0 between batteries (I had a short piece), and 8 AWG from shunt to fuse box.  4 AWG is a little overkill, but I wanted to wring out every amp I could out of my panels, leave room for expansion, and the cost difference with 6 AWG was not much.  My system runs well with 200W solar and 208 AH batteries.  I am almost always back to 100% by 1 PM.  I used 60 amp ANL fuses between solar and controller, and between the battery and everything.

A good circuit calculator will give correct wire sizes if you know the run lengths of the wire and maximum amps.  I went with 1% voltage drop because, again, I wanted the most efficiency out of my system.

http://circuitwizard.bluesea.com/#

 -- Spiff

 

[SternWake]

Spaceman.

Please note that a solar controller dropping from absorption to float does not mean the batteries are at 100%.

It can mean it, if the time at the proper absorption is met, but this must be verified with a hydrometer on flooded batteries, and an Ammeter when holding the batteries at absorption voltage for AGM batteries.

When AGMs can only accept 0.5% of their rated capacity at absorption voltage then they can be considered full.

As batteries age they require more and more time at absorption voltage. if they do not get this mnore and more, then they lose capacity faster and faster.

Also when discharging to 75%, the time required to be held at absorption voltage can be quite different than when discharged to 50%. Other factors in this are the rate at which the batteries are brought to absorption voltage and battery temperature and the phase of the moon and the position of jupiter and the possible presence of Locusts.

So verify, with a hydrometer, and or an ammeter, and be prepared to extend the absorption duration, if possible. It is a shame/crime when one has lots of solar wattage available and the whole afternoon, but the controller reverts prematurely to float voltage as it simply does not know any better.

 

[jimindenver]

Rob if 1/0 is thick enough, we got it covered. I still have plenty along with lugs and a 16 ton crimp tool.

 

[Optimistic Paranoid]

Rob, the only reason I could think of for needing bigger wires than 1/0 is if you were going to hook a really BIG inverter up, in which case the wire between the two batteries needs to be the same size as the wires feeding the inverter.  Here's a chart for that kind of stuff:

http://www.donrowe.com/power-inverter-faq-a/258.htm#hookup

 

[Gunny]

I don't need a big inverter, maybe 600 watts or so. Biggest thing I want to run is a direct tv dish for the days I feel crappy and don't get out much. I'll have a generator that I hope to not have to use too much. Jimindenver has been helping me plan it out. Thank you for the link OP.

Rob