[RE-wrenches] 12V loads

[R Ray Walters]

On Aug 11, 2012, at 6:43 AM, Drake wrote:

> Ray,
> 
> If golf cart batteries can't surge over 2000 amps, then it would seem that the fuse in line with the QO can be deleted in some cases.  Is the 2000 A surge for one 6 volt battery or 2 in series?

Current stays the same, just voltage changes in series.

> 
> Fuses can be put in the QO enclosure ahead of the loads and DC rated Class T fuses can be bolted to battery terminals (code questionable, but a good method for safety).  In the old days we often had a DC system with a few lights and maybe a Sunfrost.  That way, if the inverter went down, the home wouldn't be left in the dark. DC was tricky code wise, but not impossible.

I don't think DC is not code compliant, it just doesn't make financial sense.  Actually another reason I don't like DC loads, is that after the inverter shuts off, a DC light left for emergencies as you suggested will rain the batteries into reverse polarity (negaitve voltage)  At least an inverter shuts off at about 80% DOD.  Believe me, my first off grid house had half the lights on 12 vdc, but I slowly brought it over to AC.    Between the expensive wiring, switches, nd bulbs, volt drop, lights that put out significantly less lumens when the battery voltage dropped, etc. its just more trouble than benefit.

Ray


> 
> Thanks
> 
> Drake
> 
> 
> At 08:03 PM 8/10/2012, you wrote:
>> The QO breaker has an AIC of 5000 amps.  The usual golf cart batteries have a short circuit current of about 2000 amps, so you could do a set of 4 golf cart batteries at 12v, without worrying about the extra fuse.
>> Once again, if the system gets any bigger, they should just go to an inverter based design.
>> Also, to be clear, I don't risk my license installing ATC fused systems on permanent structures.  (strictly RVs, and portable set ups)
>> As soon as I'm doing an install covered by the code, it's going to be code compliant, and it's going to be inverter based.
>> Take a look at Midnite's Mini DC panel wired to Magnum's smallest inverter.  You'd be surprised how cheap you can do a code compliant inverter based system, and how much money you can waste trying to do a code compliant DC only system.
>> 
>> Ray Walters
>> NABCEP certified since 2004
>> 
>> On Aug 10, 2012, at 4:35 PM, Drake wrote:
>> 
>> > I second using QO load centers.  You will want to put a fuse, like an FRN-R, between the battery and the load center, as the QO breakers don't have a high AIC rating. 12 V systems can be wired as easily as a regular AC system.
>> >
>> >
>> > At 05:05 PM 8/9/2012, you wrote:
>> >> Hello,
>> >>
>> >> I've been looking at a lot of hunting shacks, fish houses and other 12V loads setups and was wondering how people go about setting these up? What are people using for load termination, fusing?
>> >>
>> >> I'd like to keep all disconnects and fusing in one "box".
>> >>
>> >> Jesse
>> >>
>> >> Sent from my iPhone
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