144vdc charging [RE-wrenches]

[Robert Warren]

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Nick,
 I see you got a couple responses to your charger question, but not 
about the fuses. (I do question the idea of Outback charge controllers 
in series, though.) 
Quite a few UL listed Uninterruptible Power Supplies (UPS) have class T 
fuses bolted driectly to the positive terminal of the battery, just like 
you described. The only thing is, these are sealed batteries, so it is 
quite unlikely that there will be any flammable gases around. When a 
fuse burns, the flash is usually contained within the silica contained 
in its jacket. But on the off chance that the fire shoots out beond this 
(and I have seen this happen), fuse holders are normally required by NEC 
to be inside either a metallic or a non flammable box. A UPS case 
satisfies them as far as UPS manufacturers are concerned. 
 On matters of safety, I believe it is our responsibilty to put our foot 
down and in no uncertain terms, let the customer know that the fuse 
holder box is a requirement. It is a real dis-service (and a potential 
liabiltiy later on) if there is ever a fire due to battery outgassing 
(in combination with a blown fuse). Just think about this:  an internal 
short inside a battery bank, causing a battery fuse to blow while 
charging will have certainly created some outgassing in the process of 
getting overcharged. It is precisely at times of heavy charging that 
gases are created in profusion. It isn't the PV charge controller we 
have to worry about, it is the charger running on the generator. 
 In short, for sealed batteries, OK, but for wet cells, use a fuseholder 
with a cover, a bit further away from the batteries.
Regards,
Robert Warren 

Nick Lucchese wrote:
> 
>
>   Another unrelated question regarding class-T fuses. From time to 
> time (usually on temporary systems) I'll bolt the fuse directly to 
> the battery and then run a bolt through the other side to hold the 
> inverter cables. Also from time to time a customer does not want to 
> fork out $50-$70 for the fuse with the block. So, is this method 
> acceptable if it's in a battery box or must it be installed on the 
> block with the protective sleeve? Are there issues with arching to 
> the other side of a blown fuse with a 48v system. Where might the NEC  
> stand on this?
> 
> Sorry to hit the list with so many questions, always appreciate the 
> collective intelligence,
> 
> Nick A Lucchese
> 
> 
Check out my website on making your own fuel: 
http://running_on_alcohol.tripod.com 
robertwarren at mail.com

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